[PATCH V5] Add support for BTRFS raid5/6 to GRUB

[PATCH V5] Add support for BTRFS raid5/6 to GRUB

[Goffredo Baroncelli]

Hi All,

the aim of this patches set is to provide support for a BTRFS raid5/6
filesystem in GRUB.

The first patch, implements the basic support for raid5/6. I.e this works when
all the disks are present.

The next 5 patches, are preparatory ones.

The 7th patch implements the raid5 recovery for btrfs (i.e. handling the
disappearing of 1 disk).
The 8th patch makes the code for handling the raid6 recovery more generic.
The last one implements the raid6 recovery for btrfs (i.e. handling the
disappearing up to two disks).

I tested the code in grub-emu, and it works both with all the disks,
and with some disks missing. I checked the crc32 calculated from grub and
from linux and these matched. Finally I checked if the support for md raid6
still works properly, and it does (with all drives and with up to 2 drives
missing)

Comments are welcome.

Changelog
v1: initial support for btrfs raid5/6. No recovery allowed
v2: full support for btrfs raid5/6. Recovery allowed
v3: some minor cleanup suggested by Daniel Kiper; reusing the
    original raid6 recovery code of grub
v4: Several spell fix; better description of the RAID layout
    in btrfs, and the variables which describes the stripe
    positioning; split the patch #5 in two (#5 and #6)
v5: Several spell fix; improved code comment in patch #1, small
    clean up in the code


BR
G.Baroncelli
--
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

[PATCH 1/9] btrfs: Add support for reading a filesystem with a RAID 5 or RAID 6 profile.

[Goffredo Baroncelli]

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/fs/btrfs.c | 70 ++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index be195448d..4d418859b 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -119,6 +119,8 @@ struct grub_btrfs_chunk_item
 #define GRUB_BTRFS_CHUNK_TYPE_RAID1         0x10
 #define GRUB_BTRFS_CHUNK_TYPE_DUPLICATED    0x20
 #define GRUB_BTRFS_CHUNK_TYPE_RAID10        0x40
+#define GRUB_BTRFS_CHUNK_TYPE_RAID5         0x80
+#define GRUB_BTRFS_CHUNK_TYPE_RAID6         0x100
   grub_uint8_t dummy2[0xc];
   grub_uint16_t nstripes;
   grub_uint16_t nsubstripes;
@@ -764,6 +766,74 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 	      stripe_offset = low + chunk_stripe_length
 		* high;
 	      csize = chunk_stripe_length - low;
+	      break;
+	    }
+	  case GRUB_BTRFS_CHUNK_TYPE_RAID5:
+	  case GRUB_BTRFS_CHUNK_TYPE_RAID6:
+	    {
+	      grub_uint64_t nparities, stripe_nr, high, low;
+
+	      redundancy = 1;	/* no redundancy for now */
+
+	      if (grub_le_to_cpu64 (chunk->type) & GRUB_BTRFS_CHUNK_TYPE_RAID5)
+		{
+		  grub_dprintf ("btrfs", "RAID5\n");
+		  nparities = 1;
+		}
+	      else
+		{
+		  grub_dprintf ("btrfs", "RAID6\n");
+		  nparities = 2;
+		}
+
+	      /*
+	       * Below is an example of a RAID 6 layout and the meaning of the
+	       * variables. The same applies to RAID 5. The only differences is
+	       * that there is only one parity disk instead of two.
+	       *
+	       * A RAID 6 layout consists of several stripes spread
+	       * on the disks, following a layout like the one below
+	       *
+	       *   Disk1  Disk2  Disk3  Ddisk4
+	       *
+	       *    A1     B1     P1     Q1
+	       *    Q2     A2     B2     P2  
+	       *    P3     Q3     A3     B3
+	       *  [...]
+	       *
+	       *  Note that the placement of the parities depends on row index.
+	       *  In the code below:
+	       *  - stripe_nr is the stripe number not considering the parities
+	       *    (A1=0, B1=1, A2 = 2, B2 = 3, ...),
+	       *  - high is the row number (0 for A1...Q1, 1 for Q2..P2, ...),
+	       *  - stripen is the column number (or disk number),
+	       *  - off is the logical address to read (from the beginning of
+	       *    the chunk space),
+	       *  - chunk_stripe_length is the size of a stripe (typically 64k),
+	       *  - nstripes is the number of disks,
+	       *  - low is the offset of the data inside a stripe,
+	       *  - stripe_offset is the offset from the beginning of the chunk
+	       *    disks physical address,
+	       *  - csize is the "potential" data to read. It will be reduced to
+	       *    size if the latter is smaller.
+	       */
+	      stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);
+
+	      /*
+	       * stripen is evaluated without considering
+	       * the parities (0 for A1, A2, A3... 1 for B1, B2...).
+	       */
+	      high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
+
+	      /*
+	       * stripen now considers also the parities (0 for A1, 1 for A2,
+	       * 2 for A3....). The math is performed modulo number of disks.
+	       */
+	      grub_divmod64 (high + stripen, nstripes, &stripen);
+
+	      stripe_offset = low + chunk_stripe_length * high;
+	      csize = chunk_stripe_length - low;
+
 	      break;
 	    }
 	  default:
-- 
2.17.1

[PATCH 2/9] btrfs: Add helper to check the btrfs header.

[Goffredo Baroncelli]

This helper will be used in a few places to help the debugging. As
conservative approach, in case of error it is only logged. This is
because I am not sure if this can change something in the error
handling of the currently existing code.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/fs/btrfs.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 4d418859b..669c49301 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -77,7 +77,8 @@ struct btrfs_header
 {
   grub_btrfs_checksum_t checksum;
   grub_btrfs_uuid_t uuid;
-  grub_uint8_t dummy[0x30];
+  grub_uint64_t bytenr;
+  grub_uint8_t dummy[0x28];
   grub_uint32_t nitems;
   grub_uint8_t level;
 } GRUB_PACKED;
@@ -286,6 +287,25 @@ free_iterator (struct grub_btrfs_leaf_descriptor *desc)
   grub_free (desc->data);
 }
 
+static grub_err_t
+check_btrfs_header (struct grub_btrfs_data *data, struct btrfs_header *header,
+                    grub_disk_addr_t addr)
+{
+  if (grub_le_to_cpu64 (header->bytenr) != addr)
+    {
+      grub_dprintf ("btrfs", "btrfs_header.bytenr is not equal node addr\n");
+      return grub_error (GRUB_ERR_BAD_FS,
+			 "header bytenr is not equal node addr");
+    }
+  if (grub_memcmp (data->sblock.uuid, header->uuid, sizeof(grub_btrfs_uuid_t)))
+    {
+      grub_dprintf ("btrfs", "btrfs_header.uuid doesn't match sblock uuid\n");
+      return grub_error (GRUB_ERR_BAD_FS,
+			 "header uuid doesn't match sblock uuid");
+    }
+  return GRUB_ERR_NONE;
+}
+
 static grub_err_t
 save_ref (struct grub_btrfs_leaf_descriptor *desc,
 	  grub_disk_addr_t addr, unsigned i, unsigned m, int l)
@@ -341,6 +361,7 @@ next (struct grub_btrfs_data *data,
 
       err = grub_btrfs_read_logical (data, grub_le_to_cpu64 (node.addr),
 				     &head, sizeof (head), 0);
+      check_btrfs_header (data, &head, grub_le_to_cpu64 (node.addr));
       if (err)
 	return -err;
 
@@ -402,6 +423,7 @@ lower_bound (struct grub_btrfs_data *data,
       /* FIXME: preread few nodes into buffer. */
       err = grub_btrfs_read_logical (data, addr, &head, sizeof (head),
 				     recursion_depth + 1);
+      check_btrfs_header (data, &head, addr);
       if (err)
 	return err;
       addr += sizeof (head);
-- 
2.17.1

[PATCH 3/9] btrfs: Move the error logging from find_device() to its caller.

[Goffredo Baroncelli]

This is a preparatory patch. The caller knows better if this
error is fatal or not, i.e. another disk is available or not.


Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/fs/btrfs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 669c49301..9b3a22772 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -604,9 +604,6 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id, int do_rescan)
     grub_device_iterate (find_device_iter, &ctx);
   if (!ctx.dev_found)
     {
-      grub_error (GRUB_ERR_BAD_FS,
-		  N_("couldn't find a necessary member device "
-		     "of multi-device filesystem"));
       return NULL;
     }
   data->n_devices_attached++;
@@ -902,6 +899,9 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 		dev = find_device (data, stripe->device_id, j);
 		if (!dev)
 		  {
+		    grub_dprintf ("btrfs",
+				  "couldn't find a necessary member device "
+				  "of multi-device filesystem\n");
 		    err = grub_errno;
 		    grub_errno = GRUB_ERR_NONE;
 		    continue;
-- 
2.17.1

[PATCH 5/9] btrfs: Move logging code in grub_btrfs_read_logical()

[Goffredo Baroncelli]

A portion of the logging code is moved outside of internal for(;;). The part
that is left inside is the one which depends by the internal for(;;) index.
This is a preparatory patch: in the next one it will be possible to refactor
the code inside the for(;;) in an another function.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/fs/btrfs.c | 25 ++++++++++++++-----------
 1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index b64b692f8..e2baed665 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -867,6 +867,18 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 	for (j = 0; j < 2; j++)
 	  {
+	    grub_dprintf ("btrfs", "chunk 0x%" PRIxGRUB_UINT64_T
+			  "+0x%" PRIxGRUB_UINT64_T
+			  " (%d stripes (%d substripes) of %"
+			  PRIxGRUB_UINT64_T ") \n",
+			  grub_le_to_cpu64 (key->offset),
+			  grub_le_to_cpu64 (chunk->size),
+			  grub_le_to_cpu16 (chunk->nstripes),
+			  grub_le_to_cpu16 (chunk->nsubstripes),
+			  grub_le_to_cpu64 (chunk->stripe_length));
+	    grub_dprintf ("btrfs", "reading laddr 0x%" PRIxGRUB_UINT64_T "\n",
+			  addr);
+
 	    for (i = 0; i < redundancy; i++)
 	      {
 		struct grub_btrfs_chunk_stripe *stripe;
@@ -879,20 +891,11 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
 
-		grub_dprintf ("btrfs", "chunk 0x%" PRIxGRUB_UINT64_T
-			      "+0x%" PRIxGRUB_UINT64_T
-			      " (%d stripes (%d substripes) of %"
-			      PRIxGRUB_UINT64_T ") stripe %" PRIxGRUB_UINT64_T
+		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
 			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-			      grub_le_to_cpu64 (key->offset),
-			      grub_le_to_cpu64 (chunk->size),
-			      grub_le_to_cpu16 (chunk->nstripes),
-			      grub_le_to_cpu16 (chunk->nsubstripes),
-			      grub_le_to_cpu64 (chunk->stripe_length),
 			      stripen, stripe->offset);
 		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-			      " for laddr 0x%" PRIxGRUB_UINT64_T "\n", paddr,
-			      addr);
+			      "\n", paddr);
 
 		dev = find_device (data, stripe->device_id);
 		if (!dev)
-- 
2.17.1

[PATCH 6/9] btrfs: Refactor the code that read from disk

[Goffredo Baroncelli]

Move the code in charge to read the data from disk in a separate
function. This helps to separate the error handling logic (which depend by
the different raid profiles) from the read from disk logic.
Refactoring this code increases the general readability too.

This is a preparatory patch, to help the adding of the RAID 5/6 recovery
code.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/fs/btrfs.c | 76 ++++++++++++++++++++++++++------------------
 1 file changed, 45 insertions(+), 31 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index e2baed665..9cdbfe792 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -625,6 +625,47 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
   return ctx.dev_found;
 }
 
+static grub_err_t
+btrfs_read_from_chunk (struct grub_btrfs_data *data,
+		       struct grub_btrfs_chunk_item *chunk,
+		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
+		       int redundancy, grub_uint64_t csize,
+		       void *buf)
+{
+
+    struct grub_btrfs_chunk_stripe *stripe;
+    grub_disk_addr_t paddr;
+    grub_device_t dev;
+    grub_err_t err;
+
+    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+    /* Right now the redundancy handling is easy.
+       With RAID5-like it will be more difficult.  */
+    stripe += stripen + redundancy;
+
+    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+
+    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
+		  " maps to 0x%" PRIxGRUB_UINT64_T "\n",
+		  stripen, stripe->offset);
+    grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T "\n", paddr);
+
+    dev = find_device (data, stripe->device_id);
+    if (!dev)
+      {
+	grub_dprintf ("btrfs",
+		      "couldn't find a necessary member device "
+		      "of multi-device filesystem\n");
+	grub_errno = GRUB_ERR_NONE;
+	return GRUB_ERR_READ_ERROR;
+      }
+
+    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+			  csize, buf);
+    return err;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 			 void *buf, grub_size_t size, int recursion_depth)
@@ -638,7 +679,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
       grub_err_t err = 0;
       struct grub_btrfs_key key_out;
       int challoc = 0;
-      grub_device_t dev;
       struct grub_btrfs_key key_in;
       grub_size_t chsize;
       grub_disk_addr_t chaddr;
@@ -881,36 +921,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 	    for (i = 0; i < redundancy; i++)
 	      {
-		struct grub_btrfs_chunk_stripe *stripe;
-		grub_disk_addr_t paddr;
-
-		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
-		/* Right now the redundancy handling is easy.
-		   With RAID5-like it will be more difficult.  */
-		stripe += stripen + i;
-
-		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
-
-		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
-			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-			      stripen, stripe->offset);
-		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-			      "\n", paddr);
-
-		dev = find_device (data, stripe->device_id);
-		if (!dev)
-		  {
-		    grub_dprintf ("btrfs",
-				  "couldn't find a necessary member device "
-				  "of multi-device filesystem\n");
-		    err = grub_errno;
-		    grub_errno = GRUB_ERR_NONE;
-		    continue;
-		  }
-
-		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
-				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
-				      csize, buf);
+		err = btrfs_read_from_chunk (data, chunk, stripen,
+					     stripe_offset,
+					     i,     /* redundancy */
+					     csize, buf);
 		if (!err)
 		  break;
 		grub_errno = GRUB_ERR_NONE;
-- 
2.17.1

[PATCH 7/9] btrfs: Add support for recovery for a RAID 5 btrfs profiles.

[Goffredo Baroncelli]

Add support for recovery fo a RAID 5 btrfs profile. In addition
it is added some code as preparatory work for RAID 6 recovery code.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/fs/btrfs.c | 180 +++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 175 insertions(+), 5 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 9cdbfe792..c8f034641 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -29,6 +29,7 @@
 #include <minilzo.h>
 #include <grub/i18n.h>
 #include <grub/btrfs.h>
+#include <grub/crypto.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -666,6 +667,157 @@ btrfs_read_from_chunk (struct grub_btrfs_data *data,
     return err;
 }
 
+struct raid56_buffer {
+  void *buf;
+  int  data_is_valid;
+};
+
+static void
+rebuild_raid5 (char *dest, struct raid56_buffer *buffers,
+	       grub_uint64_t nstripes, grub_uint64_t csize)
+{
+  grub_uint64_t i;
+  int first;
+
+  i = 0;
+  while (buffers[i].data_is_valid && i < nstripes)
+    ++i;
+
+  if (i == nstripes)
+    {
+      grub_dprintf ("btrfs", "called rebuild_raid5(), but all disks are OK\n");
+      return;
+    }
+
+  grub_dprintf ("btrfs", "rebuilding RAID 5 stripe #%" PRIuGRUB_UINT64_T "\n",
+	        i);
+  first = 1;
+  for (i = 0; i < nstripes; i++)
+    {
+      if (!buffers[i].data_is_valid)
+	continue;
+
+      if (first)
+	grub_memcpy(dest, buffers[i].buf, csize);
+      else
+	grub_crypto_xor (dest, dest, buffers[i].buf, csize);
+
+      first = 0;
+    }
+}
+
+static grub_err_t
+raid56_read_retry (struct grub_btrfs_data *data,
+		   struct grub_btrfs_chunk_item *chunk,
+		   grub_uint64_t stripe_offset,
+		   grub_uint64_t csize, void *buf)
+{
+
+  struct raid56_buffer *buffers = NULL;
+  grub_uint64_t nstripes = grub_le_to_cpu16 (chunk->nstripes);
+  grub_uint64_t chunk_type = grub_le_to_cpu64 (chunk->type);
+  grub_err_t ret = GRUB_ERR_NONE;
+  grub_uint64_t i, failed_devices;
+
+  buffers = grub_zalloc (sizeof(*buffers) * nstripes);
+  if (!buffers)
+    {
+      ret = GRUB_ERR_OUT_OF_MEMORY;
+      goto cleanup;
+    }
+
+  for (i = 0; i < nstripes; i++)
+    {
+      buffers[i].buf = grub_zalloc (csize);
+      if (!buffers[i].buf)
+	{
+	  ret = GRUB_ERR_OUT_OF_MEMORY;
+	  goto cleanup;
+	}
+    }
+
+  for (i = 0; i < nstripes; i++)
+    {
+      struct grub_btrfs_chunk_stripe *stripe;
+      grub_disk_addr_t paddr;
+      grub_device_t dev;
+      grub_err_t err2;
+
+      stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+      stripe += i;
+
+      paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+      grub_dprintf ("btrfs", "reading paddr %" PRIxGRUB_UINT64_T
+                    " from stripe ID %" PRIxGRUB_UINT64_T "\n", paddr,
+                    stripe->device_id);
+
+      dev = find_device (data, stripe->device_id);
+      if (!dev)
+	{
+	  buffers[i].data_is_valid = 0;
+	  grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " FAILED (dev ID %"
+			PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
+	  continue;
+	}
+
+      err2 = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+			     paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+			     csize, buffers[i].buf);
+      if (err2 == GRUB_ERR_NONE)
+	{
+	  buffers[i].data_is_valid = 1;
+	  grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " Ok (dev ID %"
+			PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
+	}
+      else
+	{
+	  buffers[i].data_is_valid = 0;
+	  grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T
+			" FAILED (dev ID %" PRIxGRUB_UINT64_T ")\n", i,
+			stripe->device_id);
+	}
+    }
+
+  failed_devices = 0;
+  for (i = 0; i < nstripes; i++)
+    if (!buffers[i].data_is_valid)
+      ++failed_devices;
+  if (failed_devices > 1 && (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5))
+    {
+      grub_dprintf ("btrfs",
+		    "not enough disks for RAID 5: total %" PRIuGRUB_UINT64_T
+		    ", missing %" PRIuGRUB_UINT64_T "\n",
+		    nstripes, failed_devices);
+      ret = GRUB_ERR_READ_ERROR;
+      goto cleanup;
+    }
+  else
+    {
+      grub_dprintf ("btrfs",
+                    "enough disks for RAID 5 rebuilding: total %"
+		    PRIuGRUB_UINT64_T ", missing %" PRIuGRUB_UINT64_T "\n",
+                    nstripes, failed_devices);
+    }
+
+  /* if these are enough, try to rebuild the data */
+  if (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5)
+    rebuild_raid5 (buf, buffers, nstripes, csize);
+  else
+    grub_dprintf ("btrfs", "called rebuild_raid6(), NOT IMPLEMENTED\n");
+
+cleanup:
+
+  if (buffers)
+    {
+      for (i = 0; i < nstripes; i++)
+	if (buffers[i].buf)
+	  grub_free(buffers[i].buf);
+      grub_free(buffers);
+    }
+
+  return ret;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 			 void *buf, grub_size_t size, int recursion_depth)
@@ -743,6 +895,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 	grub_uint16_t nstripes;
 	unsigned redundancy = 1;
 	unsigned i, j;
+	int is_raid56;
+
+	is_raid56 = !!(grub_le_to_cpu64 (chunk->type) &
+		       GRUB_BTRFS_CHUNK_TYPE_RAID5);
 
 	if (grub_le_to_cpu64 (chunk->size) <= off)
 	  {
@@ -919,17 +1075,31 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 	    grub_dprintf ("btrfs", "reading laddr 0x%" PRIxGRUB_UINT64_T "\n",
 			  addr);
 
-	    for (i = 0; i < redundancy; i++)
+	    if (!is_raid56)
+	      {
+		for (i = 0; i < redundancy; i++)
+		  {
+		    err = btrfs_read_from_chunk (data, chunk, stripen,
+						 stripe_offset,
+						 i,     /* redundancy */
+						 csize, buf);
+		    if (!err)
+		      break;
+		    grub_errno = GRUB_ERR_NONE;
+		  }
+	      }
+	    else
 	      {
 		err = btrfs_read_from_chunk (data, chunk, stripen,
 					     stripe_offset,
-					     i,     /* redundancy */
+					     0,     /* no mirror */
 					     csize, buf);
-		if (!err)
-		  break;
 		grub_errno = GRUB_ERR_NONE;
+		if (err != GRUB_ERR_NONE)
+		  err = raid56_read_retry (data, chunk, stripe_offset,
+					   csize, buf);
 	      }
-	    if (i != redundancy)
+	    if (err == GRUB_ERR_NONE)
 	      break;
 	  }
 	if (err)
-- 
2.17.1

[PATCH 8/9] btrfs: Make more generic the code for RAID 6 rebuilding

[Goffredo Baroncelli]

The original code which handles the recovery of a RAID 6 disks array
assumes that all reads are multiple of 1 << GRUB_DISK_SECTOR_BITS and it
assumes that all the I/O is done via the struct grub_diskfilter_segment.
This is not true for the btrfs code. In order to reuse the native
grub_raid6_recover() code, it is modified to not call
grub_diskfilter_read_node() directly, but to call an handler passed
as an argument.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/disk/raid6_recover.c | 52 ++++++++++++++++++++++------------
 include/grub/diskfilter.h      |  9 ++++++
 2 files changed, 43 insertions(+), 18 deletions(-)

diff --git a/grub-core/disk/raid6_recover.c b/grub-core/disk/raid6_recover.c
index aa674f6ca..0cf691ddf 100644
--- a/grub-core/disk/raid6_recover.c
+++ b/grub-core/disk/raid6_recover.c
@@ -74,14 +74,26 @@ mod_255 (unsigned x)
 }
 
 static grub_err_t
-grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
-                    char *buf, grub_disk_addr_t sector, grub_size_t size)
+raid6_recover_read_node (void *data, int disknr,
+				    grub_uint64_t sector,
+				    void *buf, grub_size_t size)
+{
+    struct grub_diskfilter_segment *array = data;
+
+    return grub_diskfilter_read_node (&array->nodes[disknr],
+				      (grub_disk_addr_t)sector,
+				      size >> GRUB_DISK_SECTOR_BITS, buf);
+}
+
+grub_err_t
+grub_raid6_recover_gen (void *data, grub_uint64_t nstripes, int disknr, int p,
+			    char *buf, grub_uint64_t sector, grub_size_t size,
+			    int layout, raid_recover_read_t read_func)
 {
   int i, q, pos;
   int bad1 = -1, bad2 = -1;
   char *pbuf = 0, *qbuf = 0;
 
-  size <<= GRUB_DISK_SECTOR_BITS;
   pbuf = grub_zalloc (size);
   if (!pbuf)
     goto quit;
@@ -91,17 +103,17 @@ grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
     goto quit;
 
   q = p + 1;
-  if (q == (int) array->node_count)
+  if (q == (int) nstripes)
     q = 0;
 
   pos = q + 1;
-  if (pos == (int) array->node_count)
+  if (pos == (int) nstripes)
     pos = 0;
 
-  for (i = 0; i < (int) array->node_count - 2; i++)
+  for (i = 0; i < (int) nstripes - 2; i++)
     {
       int c;
-      if (array->layout & GRUB_RAID_LAYOUT_MUL_FROM_POS)
+      if (layout & GRUB_RAID_LAYOUT_MUL_FROM_POS)
 	c = pos;
       else
 	c = i;
@@ -109,8 +121,7 @@ grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
         bad1 = c;
       else
         {
-          if (! grub_diskfilter_read_node (&array->nodes[pos], sector,
-					   size >> GRUB_DISK_SECTOR_BITS, buf))
+	  if (!read_func(data, pos, sector, buf, size))
             {
               grub_crypto_xor (pbuf, pbuf, buf, size);
               grub_raid_block_mulx (c, buf, size);
@@ -128,7 +139,7 @@ grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
         }
 
       pos++;
-      if (pos == (int) array->node_count)
+      if (pos == (int) nstripes)
         pos = 0;
     }
 
@@ -139,16 +150,14 @@ grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
   if (bad2 < 0)
     {
       /* One bad device */
-      if ((! grub_diskfilter_read_node (&array->nodes[p], sector,
-					size >> GRUB_DISK_SECTOR_BITS, buf)))
+      if (!read_func(data, p, sector, buf, size))
         {
           grub_crypto_xor (buf, buf, pbuf, size);
           goto quit;
         }
 
       grub_errno = GRUB_ERR_NONE;
-      if (grub_diskfilter_read_node (&array->nodes[q], sector,
-				     size >> GRUB_DISK_SECTOR_BITS, buf))
+      if (read_func(data, q, sector, buf, size))
         goto quit;
 
       grub_crypto_xor (buf, buf, qbuf, size);
@@ -160,14 +169,12 @@ grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
       /* Two bad devices */
       unsigned c;
 
-      if (grub_diskfilter_read_node (&array->nodes[p], sector,
-				     size >> GRUB_DISK_SECTOR_BITS, buf))
+      if (read_func(data, p, sector, buf, size))
         goto quit;
 
       grub_crypto_xor (pbuf, pbuf, buf, size);
 
-      if (grub_diskfilter_read_node (&array->nodes[q], sector,
-				     size >> GRUB_DISK_SECTOR_BITS, buf))
+      if (read_func(data, q, sector, buf, size))
         goto quit;
 
       grub_crypto_xor (qbuf, qbuf, buf, size);
@@ -190,6 +197,15 @@ quit:
   return grub_errno;
 }
 
+static grub_err_t
+grub_raid6_recover (struct grub_diskfilter_segment *array, int disknr, int p,
+                    char *buf, grub_disk_addr_t sector, grub_size_t size)
+{
+  return grub_raid6_recover_gen (array, array->node_count, disknr, p, buf,
+				     sector, size << GRUB_DISK_SECTOR_BITS,
+				     array->layout, raid6_recover_read_node);
+}
+
 GRUB_MOD_INIT(raid6rec)
 {
   grub_raid6_init_table ();
diff --git a/include/grub/diskfilter.h b/include/grub/diskfilter.h
index d89273c1b..8deb1a8c3 100644
--- a/include/grub/diskfilter.h
+++ b/include/grub/diskfilter.h
@@ -189,6 +189,15 @@ typedef grub_err_t (*grub_raid6_recover_func_t) (struct grub_diskfilter_segment
 extern grub_raid5_recover_func_t grub_raid5_recover_func;
 extern grub_raid6_recover_func_t grub_raid6_recover_func;
 
+typedef grub_err_t (* raid_recover_read_t)(void *data, int disk_nr,
+					   grub_uint64_t addr, void *dest,
+					   grub_size_t size);
+
+extern grub_err_t
+grub_raid6_recover_gen (void *data, grub_uint64_t nstripes, int disknr, int p,
+			    char *buf, grub_uint64_t sector, grub_size_t size,
+			    int layout, raid_recover_read_t read_func);
+
 grub_err_t grub_diskfilter_vg_register (struct grub_diskfilter_vg *vg);
 
 grub_err_t
-- 
2.17.1

[PATCH 9/9] btrfs: Add RAID 6 recovery for a btrfs filesystem.

[Goffredo Baroncelli]

Add the RAID 6 recovery, in order to use a RAID 6 filesystem even if some
disks (up to two) are missing. This code use the md RAID 6 code already
present in grub.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/fs/btrfs.c | 50 ++++++++++++++++++++++++++++++++++++++------
 1 file changed, 44 insertions(+), 6 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index c8f034641..0b6557ce3 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -30,6 +30,7 @@
 #include <grub/i18n.h>
 #include <grub/btrfs.h>
 #include <grub/crypto.h>
+#include <grub/diskfilter.h>
 
 GRUB_MOD_LICENSE ("GPLv3+");
 
@@ -706,11 +707,35 @@ rebuild_raid5 (char *dest, struct raid56_buffer *buffers,
     }
 }
 
+static grub_err_t
+raid6_recover_read_buffer (void *data, int disk_nr,
+			   grub_uint64_t addr __attribute__ ((unused)),
+			   void *dest, grub_size_t size)
+{
+    struct raid56_buffer *buffers = data;
+
+    grub_memcpy(dest, buffers[disk_nr].buf, size);
+
+    grub_errno = buffers[disk_nr].data_is_valid ? GRUB_ERR_NONE :
+		 GRUB_ERR_READ_ERROR;
+    return grub_errno;
+}
+
+static void
+rebuild_raid6 (struct raid56_buffer *buffers, grub_uint64_t nstripes,
+               grub_uint64_t csize, grub_uint64_t parities_pos, void *dest,
+               grub_uint64_t stripen)
+
+{
+  grub_raid6_recover_gen (buffers, nstripes, stripen, parities_pos,
+                          dest, 0, csize, 0, raid6_recover_read_buffer);
+}
+
 static grub_err_t
 raid56_read_retry (struct grub_btrfs_data *data,
 		   struct grub_btrfs_chunk_item *chunk,
-		   grub_uint64_t stripe_offset,
-		   grub_uint64_t csize, void *buf)
+		   grub_uint64_t stripe_offset, grub_uint64_t stripen,
+		   grub_uint64_t csize, void *buf, grub_uint64_t parities_pos)
 {
 
   struct raid56_buffer *buffers = NULL;
@@ -791,6 +816,15 @@ raid56_read_retry (struct grub_btrfs_data *data,
       ret = GRUB_ERR_READ_ERROR;
       goto cleanup;
     }
+  else if (failed_devices > 2 && (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID6))
+    {
+      grub_dprintf ("btrfs",
+		    "not enough disks for raid6: total %" PRIuGRUB_UINT64_T
+		    ", missing %" PRIuGRUB_UINT64_T "\n",
+		    nstripes, failed_devices);
+      ret = GRUB_ERR_READ_ERROR;
+      goto cleanup;
+    }
   else
     {
       grub_dprintf ("btrfs",
@@ -803,7 +837,7 @@ raid56_read_retry (struct grub_btrfs_data *data,
   if (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5)
     rebuild_raid5 (buf, buffers, nstripes, csize);
   else
-    grub_dprintf ("btrfs", "called rebuild_raid6(), NOT IMPLEMENTED\n");
+    rebuild_raid6 (buffers, nstripes, csize, parities_pos, buf, stripen);
 
 cleanup:
 
@@ -896,9 +930,11 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 	unsigned redundancy = 1;
 	unsigned i, j;
 	int is_raid56;
+	grub_uint64_t parities_pos = 0;
 
-	is_raid56 = !!(grub_le_to_cpu64 (chunk->type) &
-		       GRUB_BTRFS_CHUNK_TYPE_RAID5);
+        is_raid56 = !!(grub_le_to_cpu64 (chunk->type) &
+		       (GRUB_BTRFS_CHUNK_TYPE_RAID5 |
+		        GRUB_BTRFS_CHUNK_TYPE_RAID6));
 
 	if (grub_le_to_cpu64 (chunk->size) <= off)
 	  {
@@ -1043,6 +1079,8 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 	       * 2 for A3....). The math is performed modulo number of disks.
 	       */
 	      grub_divmod64 (high + stripen, nstripes, &stripen);
+	      grub_divmod64 (high + nstripes - nparities, nstripes,
+			     &parities_pos);
 
 	      stripe_offset = low + chunk_stripe_length * high;
 	      csize = chunk_stripe_length - low;
@@ -1097,7 +1135,7 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 		grub_errno = GRUB_ERR_NONE;
 		if (err != GRUB_ERR_NONE)
 		  err = raid56_read_retry (data, chunk, stripe_offset,
-					   csize, buf);
+					   stripen, csize, buf, parities_pos);
 	      }
 	    if (err == GRUB_ERR_NONE)
 	      break;
-- 
2.17.1

Re: [PATCH 1/9] btrfs: Add support for reading a filesystem with a RAID 5 or RAID 6 profile.

[Daniel Kiper]

On Sun, Jun 03, 2018 at 08:53:40PM +0200, Goffredo Baroncelli wrote:
> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
> ---
>  grub-core/fs/btrfs.c | 70 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 70 insertions(+)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index be195448d..4d418859b 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -119,6 +119,8 @@ struct grub_btrfs_chunk_item
>  #define GRUB_BTRFS_CHUNK_TYPE_RAID1         0x10
>  #define GRUB_BTRFS_CHUNK_TYPE_DUPLICATED    0x20
>  #define GRUB_BTRFS_CHUNK_TYPE_RAID10        0x40
> +#define GRUB_BTRFS_CHUNK_TYPE_RAID5         0x80
> +#define GRUB_BTRFS_CHUNK_TYPE_RAID6         0x100
>    grub_uint8_t dummy2[0xc];
>    grub_uint16_t nstripes;
>    grub_uint16_t nsubstripes;
> @@ -764,6 +766,74 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>  	      stripe_offset = low + chunk_stripe_length
>  		* high;
>  	      csize = chunk_stripe_length - low;
> +	      break;
> +	    }
> +	  case GRUB_BTRFS_CHUNK_TYPE_RAID5:
> +	  case GRUB_BTRFS_CHUNK_TYPE_RAID6:
> +	    {
> +	      grub_uint64_t nparities, stripe_nr, high, low;
> +
> +	      redundancy = 1;	/* no redundancy for now */
> +
> +	      if (grub_le_to_cpu64 (chunk->type) & GRUB_BTRFS_CHUNK_TYPE_RAID5)
> +		{
> +		  grub_dprintf ("btrfs", "RAID5\n");
> +		  nparities = 1;
> +		}
> +	      else
> +		{
> +		  grub_dprintf ("btrfs", "RAID6\n");
> +		  nparities = 2;
> +		}
> +
> +	      /*
> +	       * Below is an example of a RAID 6 layout and the meaning of the
> +	       * variables. The same applies to RAID 5. The only differences is
> +	       * that there is only one parity disk instead of two.
> +	       *
> +	       * A RAID 6 layout consists of several stripes spread
> +	       * on the disks, following a layout like the one below
> +	       *
> +	       *   Disk1  Disk2  Disk3  Ddisk4

Numbering seems confusing to me. I think that it should be
                   Disk0  Disk1  Disk2  Disk3

> +	       *
> +	       *    A1     B1     P1     Q1
> +	       *    Q2     A2     B2     P2
> +	       *    P3     Q3     A3     B3
> +	       *  [...]
> +	       *
> +	       *  Note that the placement of the parities depends on row index.
> +	       *  In the code below:
> +	       *  - stripe_nr is the stripe number not considering the parities
> +	       *    (A1=0, B1=1, A2 = 2, B2 = 3, ...),

Please be consistent. A1 = 0, B1 = 1, A2 = 2, B2 = 3, ...

> +	       *  - high is the row number (0 for A1...Q1, 1 for Q2..P2, ...),

Ditto. Please always use "..." not "..".

> +	       *  - stripen is the column number (or disk number),

AIUI starting from 0. Right? If yes then I think that
drawing above requires disks/columns renumbering.

> +	       *  - off is the logical address to read (from the beginning of
> +	       *    the chunk space),

s/chunk space/chunk/?

> +	       *  - chunk_stripe_length is the size of a stripe (typically 64k),
> +	       *  - nstripes is the number of disks,
> +	       *  - low is the offset of the data inside a stripe,
> +	       *  - stripe_offset is the offset from the beginning of the chunk
> +	       *    disks physical address,

I am not sure that I understand. Could clarify this?

> +	       *  - csize is the "potential" data to read. It will be reduced to
> +	       *    size if the latter is smaller.
> +	       */
> +	      stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);

OK.

> +	      /*
> +	       * stripen is evaluated without considering
> +	       * the parities (0 for A1, A2, A3... 1 for B1, B2...).
> +	       */
> +	      high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);

OK.

> +	      /*
> +	       * stripen now considers also the parities (0 for A1, 1 for A2,
> +	       * 2 for A3....). The math is performed modulo number of disks.
> +	       */
> +	      grub_divmod64 (high + stripen, nstripes, &stripen);

OK.

> +	      stripe_offset = low + chunk_stripe_length * high;

Hmmm... I am confused. What does it mean?

Daniel

Re: [PATCH 2/9] btrfs: Add helper to check the btrfs header.

[Daniel Kiper]

On Sun, Jun 03, 2018 at 08:53:41PM +0200, Goffredo Baroncelli wrote:
> This helper will be used in a few places to help the debugging. As
> conservative approach, in case of error it is only logged. This is

s/, in case of error it/ the error/

> because I am not sure if this can change something in the error
> handling of the currently existing code.

s/code/code or not/

Otherwise LGTM.

Daniel

Re: [PATCH 3/9] btrfs: Move the error logging from find_device() to its caller.

[Daniel Kiper]

On Sun, Jun 03, 2018 at 08:53:42PM +0200, Goffredo Baroncelli wrote:
> This is a preparatory patch. The caller knows better if this
> error is fatal or not, i.e. another disk is available or not.

Please make first sentence last one in separate line.
The same applies to other patches.

Otherwise LGTM.

Daniel

Re: [PATCH 5/9] btrfs: Move logging code in grub_btrfs_read_logical()

[Daniel Kiper]

On Sun, Jun 03, 2018 at 08:53:44PM +0200, Goffredo Baroncelli wrote:
> A portion of the logging code is moved outside of internal for(;;). The part
> that is left inside is the one which depends by the internal for(;;) index.

s/depends by/depends on/

> This is a preparatory patch: in the next one it will be possible to refactor

s/: in the next one it will be possible to/. The next one will/

> the code inside the for(;;) in an another function.

s/in/into/

> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
> ---
>  grub-core/fs/btrfs.c | 25 ++++++++++++++-----------
>  1 file changed, 14 insertions(+), 11 deletions(-)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index b64b692f8..e2baed665 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -867,6 +867,18 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>
>  	for (j = 0; j < 2; j++)
>  	  {
> +	    grub_dprintf ("btrfs", "chunk 0x%" PRIxGRUB_UINT64_T
> +			  "+0x%" PRIxGRUB_UINT64_T
> +			  " (%d stripes (%d substripes) of %"
> +			  PRIxGRUB_UINT64_T ") \n",

s/") \n"/")\n"/

Otherwise LGTM.

Daniel

Re: [PATCH 6/9] btrfs: Refactor the code that read from disk

[Daniel Kiper]

On Sun, Jun 03, 2018 at 08:53:45PM +0200, Goffredo Baroncelli wrote:
> Move the code in charge to read the data from disk in a separate

s/in a/into a/

> function. This helps to separate the error handling logic (which depend by

s/depend by/depends on/ Please fix this here and in other patches too.

> the different raid profiles) from the read from disk logic.
> Refactoring this code increases the general readability too.
>
> This is a preparatory patch, to help the adding of the RAID 5/6 recovery
> code.
>
> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
> ---
>  grub-core/fs/btrfs.c | 76 ++++++++++++++++++++++++++------------------
>  1 file changed, 45 insertions(+), 31 deletions(-)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index e2baed665..9cdbfe792 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -625,6 +625,47 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
>    return ctx.dev_found;
>  }
>
> +static grub_err_t
> +btrfs_read_from_chunk (struct grub_btrfs_data *data,
> +		       struct grub_btrfs_chunk_item *chunk,
> +		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
> +		       int redundancy, grub_uint64_t csize,
> +		       void *buf)
> +{
> +

Please drop this empty line.

> +    struct grub_btrfs_chunk_stripe *stripe;
> +    grub_disk_addr_t paddr;
> +    grub_device_t dev;
> +    grub_err_t err;
> +
> +    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
> +    /* Right now the redundancy handling is easy.
> +       With RAID5-like it will be more difficult.  */
> +    stripe += stripen + redundancy;
> +
> +    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
> +
> +    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
> +		  " maps to 0x%" PRIxGRUB_UINT64_T "\n",
> +		  stripen, stripe->offset);
> +    grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T "\n", paddr);

Could you put this into one grub_dprintf() call?

> +
> +    dev = find_device (data, stripe->device_id);
> +    if (!dev)
> +      {
> +	grub_dprintf ("btrfs",
> +		      "couldn't find a necessary member device "
> +		      "of multi-device filesystem\n");
> +	grub_errno = GRUB_ERR_NONE;
> +	return GRUB_ERR_READ_ERROR;

Why grub_errno = GRUB_ERR_NONE and then return GRUB_ERR_READ_ERROR?
If you do things like that I think that you should add a few words
of comment before such code. Otherwise it is confusing.

Daniel

Re: [PATCH 7/9] btrfs: Add support for recovery for a RAID 5 btrfs profiles.

[Daniel Kiper]

On Sun, Jun 03, 2018 at 08:53:46PM +0200, Goffredo Baroncelli wrote:
> Add support for recovery fo a RAID 5 btrfs profile. In addition

s/fo /for /

> it is added some code as preparatory work for RAID 6 recovery code.
>
> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
> ---
>  grub-core/fs/btrfs.c | 180 +++++++++++++++++++++++++++++++++++++++++--
>  1 file changed, 175 insertions(+), 5 deletions(-)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index 9cdbfe792..c8f034641 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -29,6 +29,7 @@
>  #include <minilzo.h>
>  #include <grub/i18n.h>
>  #include <grub/btrfs.h>
> +#include <grub/crypto.h>
>
>  GRUB_MOD_LICENSE ("GPLv3+");
>
> @@ -666,6 +667,157 @@ btrfs_read_from_chunk (struct grub_btrfs_data *data,
>      return err;
>  }
>
> +struct raid56_buffer {
> +  void *buf;
> +  int  data_is_valid;
> +};
> +
> +static void
> +rebuild_raid5 (char *dest, struct raid56_buffer *buffers,
> +	       grub_uint64_t nstripes, grub_uint64_t csize)
> +{
> +  grub_uint64_t i;

grub_uint64_t i = 0;
int first = 1;

> +  int first;
> +
> +  i = 0;

Then you can drop this assignment.

> +  while (buffers[i].data_is_valid && i < nstripes)
> +    ++i;
> +
> +  if (i == nstripes)
> +    {
> +      grub_dprintf ("btrfs", "called rebuild_raid5(), but all disks are OK\n");
> +      return;
> +    }
> +
> +  grub_dprintf ("btrfs", "rebuilding RAID 5 stripe #%" PRIuGRUB_UINT64_T "\n",
> +	        i);

This can be in one line.

> +  first = 1;

And you can drop this assignment too.

> +  for (i = 0; i < nstripes; i++)
> +    {
> +      if (!buffers[i].data_is_valid)
> +	continue;
> +
> +      if (first)
> +	grub_memcpy(dest, buffers[i].buf, csize);
> +      else
> +	grub_crypto_xor (dest, dest, buffers[i].buf, csize);

I am not sure why at first you use grub_memcpy() and
then move to grub_crypto_xor(). Could you explain this?
Why do not use grub_crypto_xor() in all cases?

> +
> +      first = 0;
> +    }
> +}
> +
> +static grub_err_t
> +raid56_read_retry (struct grub_btrfs_data *data,
> +		   struct grub_btrfs_chunk_item *chunk,
> +		   grub_uint64_t stripe_offset,
> +		   grub_uint64_t csize, void *buf)
> +{
> +

Please drop this empty line. I have asked about that earlier.

> +  struct raid56_buffer *buffers = NULL;
> +  grub_uint64_t nstripes = grub_le_to_cpu16 (chunk->nstripes);
> +  grub_uint64_t chunk_type = grub_le_to_cpu64 (chunk->type);
> +  grub_err_t ret = GRUB_ERR_NONE;
> +  grub_uint64_t i, failed_devices;
> +
> +  buffers = grub_zalloc (sizeof(*buffers) * nstripes);

How often this function is called? Maybe you should consider
doing memory allocation for this function only once and free
it at btrfs module unload.

> +  if (!buffers)
> +    {
> +      ret = GRUB_ERR_OUT_OF_MEMORY;
> +      goto cleanup;
> +    }
> +
> +  for (i = 0; i < nstripes; i++)
> +    {
> +      buffers[i].buf = grub_zalloc (csize);

Ditto.

> +      if (!buffers[i].buf)
> +	{
> +	  ret = GRUB_ERR_OUT_OF_MEMORY;
> +	  goto cleanup;
> +	}
> +    }
> +
> +  for (i = 0; i < nstripes; i++)
> +    {
> +      struct grub_btrfs_chunk_stripe *stripe;
> +      grub_disk_addr_t paddr;
> +      grub_device_t dev;
> +      grub_err_t err2;
> +
> +      stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
> +      stripe += i;
> +
> +      paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
> +      grub_dprintf ("btrfs", "reading paddr %" PRIxGRUB_UINT64_T
> +                    " from stripe ID %" PRIxGRUB_UINT64_T "\n", paddr,
> +                    stripe->device_id);
> +
> +      dev = find_device (data, stripe->device_id);
> +      if (!dev)
> +	{
> +	  buffers[i].data_is_valid = 0;
> +	  grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " FAILED (dev ID %"
> +			PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
> +	  continue;
> +	}
> +
> +      err2 = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
> +			     paddr & (GRUB_DISK_SECTOR_SIZE - 1),
> +			     csize, buffers[i].buf);
> +      if (err2 == GRUB_ERR_NONE)
> +	{
> +	  buffers[i].data_is_valid = 1;
> +	  grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " Ok (dev ID %"
> +			PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
> +	}
> +      else
> +	{
> +	  buffers[i].data_is_valid = 0;
> +	  grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T
> +			" FAILED (dev ID %" PRIxGRUB_UINT64_T ")\n", i,
> +			stripe->device_id);
> +	}
> +    }
> +
> +  failed_devices = 0;
> +  for (i = 0; i < nstripes; i++)

for (failed_devices = i = 0; i < nstripes; i++)

> +    if (!buffers[i].data_is_valid)
> +      ++failed_devices;
> +  if (failed_devices > 1 && (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5))
> +    {
> +      grub_dprintf ("btrfs",
> +		    "not enough disks for RAID 5: total %" PRIuGRUB_UINT64_T
> +		    ", missing %" PRIuGRUB_UINT64_T "\n",
> +		    nstripes, failed_devices);
> +      ret = GRUB_ERR_READ_ERROR;
> +      goto cleanup;
> +    }
> +  else
> +    {
> +      grub_dprintf ("btrfs",
> +                    "enough disks for RAID 5 rebuilding: total %"
> +		    PRIuGRUB_UINT64_T ", missing %" PRIuGRUB_UINT64_T "\n",
> +                    nstripes, failed_devices);
> +    }
> +
> +  /* if these are enough, try to rebuild the data */
> +  if (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5)
> +    rebuild_raid5 (buf, buffers, nstripes, csize);
> +  else
> +    grub_dprintf ("btrfs", "called rebuild_raid6(), NOT IMPLEMENTED\n");
> +
> +cleanup:

Space before the label please.
I have asked about earlier.

> +

Please drop this empty line.

Daniel

Re: [PATCH 9/9] btrfs: Add RAID 6 recovery for a btrfs filesystem.

[Daniel Kiper]

On Sun, Jun 03, 2018 at 08:53:48PM +0200, Goffredo Baroncelli wrote:
> Add the RAID 6 recovery, in order to use a RAID 6 filesystem even if some
> disks (up to two) are missing. This code use the md RAID 6 code already
> present in grub.
>
> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
> ---
>  grub-core/fs/btrfs.c | 50 ++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 44 insertions(+), 6 deletions(-)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index c8f034641..0b6557ce3 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -30,6 +30,7 @@
>  #include <grub/i18n.h>
>  #include <grub/btrfs.h>
>  #include <grub/crypto.h>
> +#include <grub/diskfilter.h>
>
>  GRUB_MOD_LICENSE ("GPLv3+");
>
> @@ -706,11 +707,35 @@ rebuild_raid5 (char *dest, struct raid56_buffer *buffers,
>      }
>  }
>
> +static grub_err_t
> +raid6_recover_read_buffer (void *data, int disk_nr,
> +			   grub_uint64_t addr __attribute__ ((unused)),
> +			   void *dest, grub_size_t size)
> +{
> +    struct raid56_buffer *buffers = data;
> +
> +    grub_memcpy(dest, buffers[disk_nr].buf, size);
> +
> +    grub_errno = buffers[disk_nr].data_is_valid ? GRUB_ERR_NONE :
> +		 GRUB_ERR_READ_ERROR;
> +    return grub_errno;

      if (!buffers[disk_nr].data_is_valid)
          return GRUB_ERR_READ_ERROR;

      grub_memcpy(dest, buffers[disk_nr].buf, size);

      return GRUB_ERR_NONE;

Daniel

Re: [PATCH V5] Add support for BTRFS raid5/6 to GRUB

[Daniel Kiper]

Hi Goffredo,

On Sun, Jun 03, 2018 at 08:53:39PM +0200, Goffredo Baroncelli wrote:
>
> Hi All,
>
> the aim of this patches set is to provide support for a BTRFS raid5/6
> filesystem in GRUB.
>
> The first patch, implements the basic support for raid5/6. I.e this works when
> all the disks are present.
>
> The next 5 patches, are preparatory ones.
>
> The 7th patch implements the raid5 recovery for btrfs (i.e. handling the
> disappearing of 1 disk).
> The 8th patch makes the code for handling the raid6 recovery more generic.
> The last one implements the raid6 recovery for btrfs (i.e. handling the
> disappearing up to two disks).
>
> I tested the code in grub-emu, and it works both with all the disks,
> and with some disks missing. I checked the crc32 calculated from grub and
> from linux and these matched. Finally I checked if the support for md raid6
> still works properly, and it does (with all drives and with up to 2 drives
> missing)
>
> Comments are welcome.

In general I am happy that you are doing this work. However, I have just
realized that in some cases you are agreeing with my comments and then
you do not incorporate the changes which I was asking for. So, I would
be more happy if you instead of saying OK just do requested changes.
Otherwise you lose your and my time. Hence, I would like ask you to
check carefully all my comments for v4 and v5 (at least), apply all
requested changes with which you agree and then post v6.

Sorry for being blunt.

Daniel

Re: [PATCH V5] Add support for BTRFS raid5/6 to GRUB

[Goffredo Baroncelli]

On 06/14/2018 03:21 PM, Daniel Kiper wrote:
> Hi Goffredo,
> 
> On Sun, Jun 03, 2018 at 08:53:39PM +0200, Goffredo Baroncelli wrote:
>>
>> Hi All,
>>
>> the aim of this patches set is to provide support for a BTRFS raid5/6
>> filesystem in GRUB.
>>
>> The first patch, implements the basic support for raid5/6. I.e this works when
>> all the disks are present.
>>
>> The next 5 patches, are preparatory ones.
>>
>> The 7th patch implements the raid5 recovery for btrfs (i.e. handling the
>> disappearing of 1 disk).
>> The 8th patch makes the code for handling the raid6 recovery more generic.
>> The last one implements the raid6 recovery for btrfs (i.e. handling the
>> disappearing up to two disks).
>>
>> I tested the code in grub-emu, and it works both with all the disks,
>> and with some disks missing. I checked the crc32 calculated from grub and
>> from linux and these matched. Finally I checked if the support for md raid6
>> still works properly, and it does (with all drives and with up to 2 drives
>> missing)
>>
>> Comments are welcome.
> 
> In general I am happy that you are doing this work. However, I have just
> realized that in some cases you are agreeing with my comments and then
> you do not incorporate the changes which I was asking for. So, I would
> be more happy if you instead of saying OK just do requested changes.

This is not good. I apologize,  If this happened it was a my mistake. 
When I put OK, this means that I agree with your reviews and I incorporate them. 
Now I am reviewing your old comments 

> Otherwise you lose your and my time. Hence, I would like ask you to
> check carefully all my comments for v4 and v5 (at least), apply all
> requested changes with which you agree and then post v6.
> 
> Sorry for being blunt.
> 
> Daniel
> 


-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

Re: [PATCH 1/9] btrfs: Add support for reading a filesystem with a RAID 5 or RAID 6 profile.

[Goffredo Baroncelli]

On 06/14/2018 01:17 PM, Daniel Kiper wrote:
> On Sun, Jun 03, 2018 at 08:53:40PM +0200, Goffredo Baroncelli wrote:
>> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
>> ---
>>  grub-core/fs/btrfs.c | 70 ++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 70 insertions(+)
>>
>> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
>> index be195448d..4d418859b 100644
>> --- a/grub-core/fs/btrfs.c
>> +++ b/grub-core/fs/btrfs.c
>> @@ -119,6 +119,8 @@ struct grub_btrfs_chunk_item
>>  #define GRUB_BTRFS_CHUNK_TYPE_RAID1         0x10
>>  #define GRUB_BTRFS_CHUNK_TYPE_DUPLICATED    0x20
>>  #define GRUB_BTRFS_CHUNK_TYPE_RAID10        0x40
>> +#define GRUB_BTRFS_CHUNK_TYPE_RAID5         0x80
>> +#define GRUB_BTRFS_CHUNK_TYPE_RAID6         0x100
>>    grub_uint8_t dummy2[0xc];
>>    grub_uint16_t nstripes;
>>    grub_uint16_t nsubstripes;
>> @@ -764,6 +766,74 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>>  	      stripe_offset = low + chunk_stripe_length
>>  		* high;
>>  	      csize = chunk_stripe_length - low;
>> +	      break;
>> +	    }
>> +	  case GRUB_BTRFS_CHUNK_TYPE_RAID5:
>> +	  case GRUB_BTRFS_CHUNK_TYPE_RAID6:
>> +	    {
>> +	      grub_uint64_t nparities, stripe_nr, high, low;
>> +
>> +	      redundancy = 1;	/* no redundancy for now */
>> +
>> +	      if (grub_le_to_cpu64 (chunk->type) & GRUB_BTRFS_CHUNK_TYPE_RAID5)
>> +		{
>> +		  grub_dprintf ("btrfs", "RAID5\n");
>> +		  nparities = 1;
>> +		}
>> +	      else
>> +		{
>> +		  grub_dprintf ("btrfs", "RAID6\n");
>> +		  nparities = 2;
>> +		}
>> +
>> +	      /*
>> +	       * Below is an example of a RAID 6 layout and the meaning of the
>> +	       * variables. The same applies to RAID 5. The only differences is
>> +	       * that there is only one parity disk instead of two.
>> +	       *
>> +	       * A RAID 6 layout consists of several stripes spread
>> +	       * on the disks, following a layout like the one below
>> +	       *
>> +	       *   Disk1  Disk2  Disk3  Ddisk4
> 
> Numbering seems confusing to me. I think that it should be
>                    Disk0  Disk1  Disk2  Disk3
> 
>> +	       *
>> +	       *    A1     B1     P1     Q1
>> +	       *    Q2     A2     B2     P2
>> +	       *    P3     Q3     A3     B3
>> +	       *  [...]
>> +	       *
>> +	       *  Note that the placement of the parities depends on row index.
>> +	       *  In the code below:
>> +	       *  - stripe_nr is the stripe number not considering the parities
>> +	       *    (A1=0, B1=1, A2 = 2, B2 = 3, ...),
> 
> Please be consistent. A1 = 0, B1 = 1, A2 = 2, B2 = 3, ...
> 
>> +	       *  - high is the row number (0 for A1...Q1, 1 for Q2..P2, ...),
> 
> Ditto. Please always use "..." not "..".
> 
>> +	       *  - stripen is the column number (or disk number),
> 
> AIUI starting from 0. Right? If yes then I think that
> drawing above requires disks/columns renumbering.
right
> 
>> +	       *  - off is the logical address to read (from the beginning of
>> +	       *    the chunk space),
> 
> s/chunk space/chunk/?
> 
>> +	       *  - chunk_stripe_length is the size of a stripe (typically 64k),
>> +	       *  - nstripes is the number of disks,
>> +	       *  - low is the offset of the data inside a stripe,
>> +	       *  - stripe_offset is the offset from the beginning of the chunk
>> +	       *    disks physical address,
> 
> I am not sure that I understand. Could clarify this?
- stripe_offset is the offset (in bytes) from the beginning of the chunk portion 
  stored on disk.

You can think "stripe_offset" as the "row" in the drawing, but measured in bytes.

> 
>> +	       *  - csize is the "potential" data to read. It will be reduced to
>> +	       *    size if the latter is smaller.
>> +	       */
>> +	      stripe_nr = grub_divmod64 (off, chunk_stripe_length, &low);
> 
> OK.
> 
>> +	      /*
>> +	       * stripen is evaluated without considering
>> +	       * the parities (0 for A1, A2, A3... 1 for B1, B2...).
>> +	       */
>> +	      high = grub_divmod64 (stripe_nr, nstripes - nparities, &stripen);
> 
> OK.
> 
>> +	      /*
>> +	       * stripen now considers also the parities (0 for A1, 1 for A2,
>> +	       * 2 for A3....). The math is performed modulo number of disks.
>> +	       */
>> +	      grub_divmod64 (high + stripen, nstripes, &stripen);
> 
> OK.
> 
>> +	      stripe_offset = low + chunk_stripe_length * high;
> 
> Hmmm... I am confused. What does it mean?
> 
> Daniel
> 
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> https://lists.gnu.org/mailman/listinfo/grub-devel
> 


-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

Re: [PATCH 7/9] btrfs: Add support for recovery for a RAID 5 btrfs profiles.

[Goffredo Baroncelli]

On 06/14/2018 03:03 PM, Daniel Kiper wrote:
> On Sun, Jun 03, 2018 at 08:53:46PM +0200, Goffredo Baroncelli wrote:
>> Add support for recovery fo a RAID 5 btrfs profile. In addition
> 
> s/fo /for /
> 
>> it is added some code as preparatory work for RAID 6 recovery code.
>>
>> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
>> ---
>>  grub-core/fs/btrfs.c | 180 +++++++++++++++++++++++++++++++++++++++++--
>>  1 file changed, 175 insertions(+), 5 deletions(-)
>>
>> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
>> index 9cdbfe792..c8f034641 100644
>> --- a/grub-core/fs/btrfs.c
>> +++ b/grub-core/fs/btrfs.c
>> @@ -29,6 +29,7 @@
>>  #include <minilzo.h>
>>  #include <grub/i18n.h>
>>  #include <grub/btrfs.h>
>> +#include <grub/crypto.h>
>>
>>  GRUB_MOD_LICENSE ("GPLv3+");
>>
>> @@ -666,6 +667,157 @@ btrfs_read_from_chunk (struct grub_btrfs_data *data,
>>      return err;
>>  }
>>
>> +struct raid56_buffer {
>> +  void *buf;
>> +  int  data_is_valid;
>> +};
>> +
>> +static void
>> +rebuild_raid5 (char *dest, struct raid56_buffer *buffers,
>> +	       grub_uint64_t nstripes, grub_uint64_t csize)
>> +{
>> +  grub_uint64_t i;
> 
> grub_uint64_t i = 0;
> int first = 1;
> 
>> +  int first;
>> +
>> +  i = 0;
> 
> Then you can drop this assignment.

I prefer to tie the assignment to the place where it is used.

> 
>> +  while (buffers[i].data_is_valid && i < nstripes)
>> +    ++i;
>> +
>> +  if (i == nstripes)
>> +    {
>> +      grub_dprintf ("btrfs", "called rebuild_raid5(), but all disks are OK\n");
>> +      return;
>> +    }
>> +
>> +  grub_dprintf ("btrfs", "rebuilding RAID 5 stripe #%" PRIuGRUB_UINT64_T "\n",
>> +	        i);
> 
> This can be in one line.
> 
>> +  first = 1;
> 
> And you can drop this assignment too.
> 
>> +  for (i = 0; i < nstripes; i++)
>> +    {
>> +      if (!buffers[i].data_is_valid)
>> +	continue;
>> +
>> +      if (first)
>> +	grub_memcpy(dest, buffers[i].buf, csize);
>> +      else
>> +	grub_crypto_xor (dest, dest, buffers[i].buf, csize);
> 
> I am not sure why at first you use grub_memcpy() and
> then move to grub_crypto_xor(). Could you explain this?
> Why do not use grub_crypto_xor() in all cases?

This avoid to require that dest has to be initialized to zero.

> 
>> +
>> +      first = 0;
>> +    }
>> +}
>> +
>> +static grub_err_t
>> +raid56_read_retry (struct grub_btrfs_data *data,
>> +		   struct grub_btrfs_chunk_item *chunk,
>> +		   grub_uint64_t stripe_offset,
>> +		   grub_uint64_t csize, void *buf)
>> +{
>> +
> 
> Please drop this empty line. I have asked about that earlier.
> 
>> +  struct raid56_buffer *buffers = NULL;
>> +  grub_uint64_t nstripes = grub_le_to_cpu16 (chunk->nstripes);
>> +  grub_uint64_t chunk_type = grub_le_to_cpu64 (chunk->type);
>> +  grub_err_t ret = GRUB_ERR_NONE;
>> +  grub_uint64_t i, failed_devices;
>> +
>> +  buffers = grub_zalloc (sizeof(*buffers) * nstripes);
> 
> How often this function is called? Maybe you should consider
> doing memory allocation for this function only once and free
> it at btrfs module unload.

This is only needed in case of recovery. Which should happen no too often. Usually, this function is never called.
> 
>> +  if (!buffers)
>> +    {
>> +      ret = GRUB_ERR_OUT_OF_MEMORY;
>> +      goto cleanup;
>> +    }
>> +
>> +  for (i = 0; i < nstripes; i++)
>> +    {
>> +      buffers[i].buf = grub_zalloc (csize);
> 
> Ditto.
> 
>> +      if (!buffers[i].buf)
>> +	{
>> +	  ret = GRUB_ERR_OUT_OF_MEMORY;
>> +	  goto cleanup;
>> +	}
>> +    }
>> +
>> +  for (i = 0; i < nstripes; i++)
>> +    {
>> +      struct grub_btrfs_chunk_stripe *stripe;
>> +      grub_disk_addr_t paddr;
>> +      grub_device_t dev;
>> +      grub_err_t err2;
>> +
>> +      stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
>> +      stripe += i;
>> +
>> +      paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
>> +      grub_dprintf ("btrfs", "reading paddr %" PRIxGRUB_UINT64_T
>> +                    " from stripe ID %" PRIxGRUB_UINT64_T "\n", paddr,
>> +                    stripe->device_id);
>> +
>> +      dev = find_device (data, stripe->device_id);
>> +      if (!dev)
>> +	{
>> +	  buffers[i].data_is_valid = 0;
>> +	  grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " FAILED (dev ID %"
>> +			PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
>> +	  continue;
>> +	}
>> +
>> +      err2 = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
>> +			     paddr & (GRUB_DISK_SECTOR_SIZE - 1),
>> +			     csize, buffers[i].buf);
>> +      if (err2 == GRUB_ERR_NONE)
>> +	{
>> +	  buffers[i].data_is_valid = 1;
>> +	  grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T " Ok (dev ID %"
>> +			PRIxGRUB_UINT64_T ")\n", i, stripe->device_id);
>> +	}
>> +      else
>> +	{
>> +	  buffers[i].data_is_valid = 0;
>> +	  grub_dprintf ("btrfs", "stripe %" PRIuGRUB_UINT64_T
>> +			" FAILED (dev ID %" PRIxGRUB_UINT64_T ")\n", i,
>> +			stripe->device_id);
>> +	}
>> +    }
>> +
>> +  failed_devices = 0;
>> +  for (i = 0; i < nstripes; i++)
> 
> for (failed_devices = i = 0; i < nstripes; i++)

Nice
> 
>> +    if (!buffers[i].data_is_valid)
>> +      ++failed_devices;
>> +  if (failed_devices > 1 && (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5))
>> +    {
>> +      grub_dprintf ("btrfs",
>> +		    "not enough disks for RAID 5: total %" PRIuGRUB_UINT64_T
>> +		    ", missing %" PRIuGRUB_UINT64_T "\n",
>> +		    nstripes, failed_devices);
>> +      ret = GRUB_ERR_READ_ERROR;
>> +      goto cleanup;
>> +    }
>> +  else
>> +    {
>> +      grub_dprintf ("btrfs",
>> +                    "enough disks for RAID 5 rebuilding: total %"
>> +		    PRIuGRUB_UINT64_T ", missing %" PRIuGRUB_UINT64_T "\n",
>> +                    nstripes, failed_devices);
>> +    }
>> +
>> +  /* if these are enough, try to rebuild the data */
>> +  if (chunk_type & GRUB_BTRFS_CHUNK_TYPE_RAID5)
>> +    rebuild_raid5 (buf, buffers, nstripes, csize);
>> +  else
>> +    grub_dprintf ("btrfs", "called rebuild_raid6(), NOT IMPLEMENTED\n");
>> +
>> +cleanup:
> 
> Space before the label please.
> I have asked about earlier.

The line before the label is already a space; Am I missing something ?

> 
>> +
> 
> Please drop this empty line.
> 
> Daniel
> 


-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

Re: [PATCH 7/9] btrfs: Add support for recovery for a RAID 5 btrfs profiles.

[Goffredo Baroncelli]

On 06/14/2018 09:05 PM, Goffredo Baroncelli wrote:
>>> +
>>> +cleanup:
>> Space before the label please.
>> I have asked about earlier.
> The line before the label is already a space; Am I missing something 

I think that now I understand: are you requiring a space before the label *on the same line* ?
I found this style in some grub code, but this is not used everywhere (ntfs.c and nilfs dont have the space, but xfs has it ).

-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

Re: [PATCH 1/9] btrfs: Add support for reading a filesystem with a RAID 5 or RAID 6 profile.

[Goffredo Baroncelli]

On 06/14/2018 08:55 PM, Goffredo Baroncelli wrote:
>>> +	       *  - stripe_offset is the offset from the beginning of the chunk
>>> +	       *    disks physical address,
>> I am not sure that I understand. Could clarify this?
> - stripe_offset is the offset (in bytes) from the beginning of the chunk portion 
>   stored on disk.
> 
> You can think "stripe_offset" as the "row" in the drawing, but measured in bytes.
> 

After some thoughts, I will update this description as:

-              *  - stripe_offset is the offset from the beginning of the chunk
-              *    disks physical address,
+              *  - stripe_offset is the disk offset from the beginning
+              *    of the disk chunk mapping start,

-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

Re: [PATCH 7/9] btrfs: Add support for recovery for a RAID 5 btrfs profiles.

[Daniel Kiper]

On Mon, Jun 18, 2018 at 08:12:22PM +0200, Goffredo Baroncelli wrote:
> On 06/14/2018 09:05 PM, Goffredo Baroncelli wrote:
> >>> +
> >>> +cleanup:
> >> Space before the label please.
> >> I have asked about earlier.
> > The line before the label is already a space; Am I missing something
>
> I think that now I understand: are you requiring a space before the
> label *on the same line* ?

Yep!

> I found this style in some grub code, but this is not used everywhere
> (ntfs.c and nilfs dont have the space, but xfs has it ).

I know but I prefer label with space before it.

Daniel

[PATCH 6/9] btrfs: Refactor the code that read from disk

[Goffredo Baroncelli]

From: Goffredo Baroncelli <kreijack@inwind.it>

Move the code in charge to read the data from disk into a separate
function. This helps to separate the error handling logic (which depends on
the different raid profiles) from the read from disk logic.
Refactoring this code increases the general readability too.

This is a preparatory patch, to help the adding of the RAID 5/6 recovery
code.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/btrfs.c | 75 ++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 31 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index dde0edd03..ea97f0502 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -625,6 +625,46 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
   return ctx.dev_found;
 }
 
+static grub_err_t
+btrfs_read_from_chunk (struct grub_btrfs_data *data,
+		       struct grub_btrfs_chunk_item *chunk,
+		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
+		       int redundancy, grub_uint64_t csize,
+		       void *buf)
+{
+    struct grub_btrfs_chunk_stripe *stripe;
+    grub_disk_addr_t paddr;
+    grub_device_t dev;
+    grub_err_t err;
+
+    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+    /* Right now the redundancy handling is easy.
+       With RAID5-like it will be more difficult.  */
+    stripe += stripen + redundancy;
+
+    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+
+    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
+		  " maps to 0x%" PRIxGRUB_UINT64_T
+		  ". Reading paddr 0x%" PRIxGRUB_UINT64_T "\n",
+		  stripen, stripe->offset, paddr);
+
+    dev = find_device (data, stripe->device_id);
+    if (!dev)
+      {
+	grub_dprintf ("btrfs",
+		      "couldn't find a necessary member device "
+		      "of multi-device filesystem\n");
+	grub_errno = GRUB_ERR_NONE;
+	return GRUB_ERR_READ_ERROR;
+      }
+
+    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+			  csize, buf);
+    return err;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 			 void *buf, grub_size_t size, int recursion_depth)
@@ -638,7 +678,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
       grub_err_t err = 0;
       struct grub_btrfs_key key_out;
       int challoc = 0;
-      grub_device_t dev;
       struct grub_btrfs_key key_in;
       grub_size_t chsize;
       grub_disk_addr_t chaddr;
@@ -884,36 +923,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 	    for (i = 0; i < redundancy; i++)
 	      {
-		struct grub_btrfs_chunk_stripe *stripe;
-		grub_disk_addr_t paddr;
-
-		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
-		/* Right now the redundancy handling is easy.
-		   With RAID5-like it will be more difficult.  */
-		stripe += stripen + i;
-
-		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
-
-		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
-			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-			      stripen, stripe->offset);
-		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-			      "\n", paddr);
-
-		dev = find_device (data, stripe->device_id);
-		if (!dev)
-		  {
-		    grub_dprintf ("btrfs",
-				  "couldn't find a necessary member device "
-				  "of multi-device filesystem\n");
-		    err = grub_errno;
-		    grub_errno = GRUB_ERR_NONE;
-		    continue;
-		  }
-
-		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
-				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
-				      csize, buf);
+		err = btrfs_read_from_chunk (data, chunk, stripen,
+					     stripe_offset,
+					     i,     /* redundancy */
+					     csize, buf);
 		if (!err)
 		  break;
 		grub_errno = GRUB_ERR_NONE;
-- 
2.19.1

[PATCH 6/9] btrfs: Refactor the code that read from disk

[Goffredo Baroncelli]

From: Goffredo Baroncelli <kreijack@inwind.it>

Move the code in charge to read the data from disk into a separate
function. This helps to separate the error handling logic (which depends on
the different raid profiles) from the read from disk logic.
Refactoring this code increases the general readability too.

This is a preparatory patch, to help the adding of the RAID 5/6 recovery
code.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/btrfs.c | 75 ++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 31 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index dde0edd03..ea97f0502 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -625,6 +625,46 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
   return ctx.dev_found;
 }
 
+static grub_err_t
+btrfs_read_from_chunk (struct grub_btrfs_data *data,
+		       struct grub_btrfs_chunk_item *chunk,
+		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
+		       int redundancy, grub_uint64_t csize,
+		       void *buf)
+{
+    struct grub_btrfs_chunk_stripe *stripe;
+    grub_disk_addr_t paddr;
+    grub_device_t dev;
+    grub_err_t err;
+
+    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+    /* Right now the redundancy handling is easy.
+       With RAID5-like it will be more difficult.  */
+    stripe += stripen + redundancy;
+
+    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+
+    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
+		  " maps to 0x%" PRIxGRUB_UINT64_T
+		  ". Reading paddr 0x%" PRIxGRUB_UINT64_T "\n",
+		  stripen, stripe->offset, paddr);
+
+    dev = find_device (data, stripe->device_id);
+    if (!dev)
+      {
+	grub_dprintf ("btrfs",
+		      "couldn't find a necessary member device "
+		      "of multi-device filesystem\n");
+	grub_errno = GRUB_ERR_NONE;
+	return GRUB_ERR_READ_ERROR;
+      }
+
+    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+			  csize, buf);
+    return err;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 			 void *buf, grub_size_t size, int recursion_depth)
@@ -638,7 +678,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
       grub_err_t err = 0;
       struct grub_btrfs_key key_out;
       int challoc = 0;
-      grub_device_t dev;
       struct grub_btrfs_key key_in;
       grub_size_t chsize;
       grub_disk_addr_t chaddr;
@@ -884,36 +923,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 	    for (i = 0; i < redundancy; i++)
 	      {
-		struct grub_btrfs_chunk_stripe *stripe;
-		grub_disk_addr_t paddr;
-
-		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
-		/* Right now the redundancy handling is easy.
-		   With RAID5-like it will be more difficult.  */
-		stripe += stripen + i;
-
-		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
-
-		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
-			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-			      stripen, stripe->offset);
-		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-			      "\n", paddr);
-
-		dev = find_device (data, stripe->device_id);
-		if (!dev)
-		  {
-		    grub_dprintf ("btrfs",
-				  "couldn't find a necessary member device "
-				  "of multi-device filesystem\n");
-		    err = grub_errno;
-		    grub_errno = GRUB_ERR_NONE;
-		    continue;
-		  }
-
-		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
-				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
-				      csize, buf);
+		err = btrfs_read_from_chunk (data, chunk, stripen,
+					     stripe_offset,
+					     i,     /* redundancy */
+					     csize, buf);
 		if (!err)
 		  break;
 		grub_errno = GRUB_ERR_NONE;
-- 
2.19.1

[PATCH 6/9] btrfs: Refactor the code that read from disk

[Goffredo Baroncelli]

From: Goffredo Baroncelli <kreijack@inwind.it>

Move the code in charge to read the data from disk into a separate
function. This helps to separate the error handling logic (which depends on
the different raid profiles) from the read from disk logic.
Refactoring this code increases the general readability too.

This is a preparatory patch, to help the adding of the RAID 5/6 recovery
code.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/btrfs.c | 75 ++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 31 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index a82211ccc..899dc32b7 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -625,6 +625,46 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
   return ctx.dev_found;
 }
 
+static grub_err_t
+btrfs_read_from_chunk (struct grub_btrfs_data *data,
+		       struct grub_btrfs_chunk_item *chunk,
+		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
+		       int redundancy, grub_uint64_t csize,
+		       void *buf)
+{
+    struct grub_btrfs_chunk_stripe *stripe;
+    grub_disk_addr_t paddr;
+    grub_device_t dev;
+    grub_err_t err;
+
+    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+    /* Right now the redundancy handling is easy.
+       With RAID5-like it will be more difficult.  */
+    stripe += stripen + redundancy;
+
+    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+
+    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
+		  " maps to 0x%" PRIxGRUB_UINT64_T
+		  ". Reading paddr 0x%" PRIxGRUB_UINT64_T "\n",
+		  stripen, stripe->offset, paddr);
+
+    dev = find_device (data, stripe->device_id);
+    if (!dev)
+      {
+	grub_dprintf ("btrfs",
+		      "couldn't find a necessary member device "
+		      "of multi-device filesystem\n");
+	grub_errno = GRUB_ERR_NONE;
+	return GRUB_ERR_READ_ERROR;
+      }
+
+    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+			  csize, buf);
+    return err;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 			 void *buf, grub_size_t size, int recursion_depth)
@@ -638,7 +678,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
       grub_err_t err = 0;
       struct grub_btrfs_key key_out;
       int challoc = 0;
-      grub_device_t dev;
       struct grub_btrfs_key key_in;
       grub_size_t chsize;
       grub_disk_addr_t chaddr;
@@ -884,36 +923,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 	    for (i = 0; i < redundancy; i++)
 	      {
-		struct grub_btrfs_chunk_stripe *stripe;
-		grub_disk_addr_t paddr;
-
-		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
-		/* Right now the redundancy handling is easy.
-		   With RAID5-like it will be more difficult.  */
-		stripe += stripen + i;
-
-		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
-
-		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
-			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-			      stripen, stripe->offset);
-		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-			      "\n", paddr);
-
-		dev = find_device (data, stripe->device_id);
-		if (!dev)
-		  {
-		    grub_dprintf ("btrfs",
-				  "couldn't find a necessary member device "
-				  "of multi-device filesystem\n");
-		    err = grub_errno;
-		    grub_errno = GRUB_ERR_NONE;
-		    continue;
-		  }
-
-		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
-				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
-				      csize, buf);
+		err = btrfs_read_from_chunk (data, chunk, stripen,
+					     stripe_offset,
+					     i,     /* redundancy */
+					     csize, buf);
 		if (!err)
 		  break;
 		grub_errno = GRUB_ERR_NONE;
-- 
2.19.1

[PATCH 6/9] btrfs: Refactor the code that read from disk

[Goffredo Baroncelli]

From: Goffredo Baroncelli <kreijack@inwind.it>

Move the code in charge to read the data from disk into a separate
function. This helps to separate the error handling logic (which depends on
the different raid profiles) from the read from disk logic.
Refactoring this code increases the general readability too.

This is a preparatory patch, to help the adding of the RAID 5/6 recovery
code.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/btrfs.c | 75 ++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 31 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 179a2da9d..554f350c5 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -625,6 +625,46 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
   return ctx.dev_found;
 }
 
+static grub_err_t
+btrfs_read_from_chunk (struct grub_btrfs_data *data,
+		       struct grub_btrfs_chunk_item *chunk,
+		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
+		       int redundancy, grub_uint64_t csize,
+		       void *buf)
+{
+    struct grub_btrfs_chunk_stripe *stripe;
+    grub_disk_addr_t paddr;
+    grub_device_t dev;
+    grub_err_t err;
+
+    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+    /* Right now the redundancy handling is easy.
+       With RAID5-like it will be more difficult.  */
+    stripe += stripen + redundancy;
+
+    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+
+    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
+		  " maps to 0x%" PRIxGRUB_UINT64_T
+		  ". Reading paddr 0x%" PRIxGRUB_UINT64_T "\n",
+		  stripen, stripe->offset, paddr);
+
+    dev = find_device (data, stripe->device_id);
+    if (!dev)
+      {
+	grub_dprintf ("btrfs",
+		      "couldn't find a necessary member device "
+		      "of multi-device filesystem\n");
+	grub_errno = GRUB_ERR_NONE;
+	return GRUB_ERR_READ_ERROR;
+      }
+
+    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+			  csize, buf);
+    return err;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 			 void *buf, grub_size_t size, int recursion_depth)
@@ -638,7 +678,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
       grub_err_t err = 0;
       struct grub_btrfs_key key_out;
       int challoc = 0;
-      grub_device_t dev;
       struct grub_btrfs_key key_in;
       grub_size_t chsize;
       grub_disk_addr_t chaddr;
@@ -885,36 +924,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 	    for (i = 0; i < redundancy; i++)
 	      {
-		struct grub_btrfs_chunk_stripe *stripe;
-		grub_disk_addr_t paddr;
-
-		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
-		/* Right now the redundancy handling is easy.
-		   With RAID5-like it will be more difficult.  */
-		stripe += stripen + i;
-
-		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
-
-		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
-			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-			      stripen, stripe->offset);
-		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-			      "\n", paddr);
-
-		dev = find_device (data, stripe->device_id);
-		if (!dev)
-		  {
-		    grub_dprintf ("btrfs",
-				  "couldn't find a necessary member device "
-				  "of multi-device filesystem\n");
-		    err = grub_errno;
-		    grub_errno = GRUB_ERR_NONE;
-		    continue;
-		  }
-
-		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
-				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
-				      csize, buf);
+		err = btrfs_read_from_chunk (data, chunk, stripen,
+					     stripe_offset,
+					     i,     /* redundancy */
+					     csize, buf);
 		if (!err)
 		  break;
 		grub_errno = GRUB_ERR_NONE;
-- 
2.19.0

[PATCH 6/9] btrfs: Refactor the code that read from disk

[Goffredo Baroncelli]

From: Goffredo Baroncelli <kreijack@inwind.it>

Move the code in charge to read the data from disk into a separate
function. This helps to separate the error handling logic (which depends on
the different raid profiles) from the read from disk logic.
Refactoring this code increases the general readability too.

This is a preparatory patch, to help the adding of the RAID 5/6 recovery
code.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 grub-core/fs/btrfs.c | 75 ++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 31 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index ee134c167..5c1ebae77 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -625,6 +625,46 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
   return ctx.dev_found;
 }
 
+static grub_err_t
+btrfs_read_from_chunk (struct grub_btrfs_data *data,
+		       struct grub_btrfs_chunk_item *chunk,
+		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
+		       int redundancy, grub_uint64_t csize,
+		       void *buf)
+{
+    struct grub_btrfs_chunk_stripe *stripe;
+    grub_disk_addr_t paddr;
+    grub_device_t dev;
+    grub_err_t err;
+
+    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+    /* Right now the redundancy handling is easy.
+       With RAID5-like it will be more difficult.  */
+    stripe += stripen + redundancy;
+
+    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+
+    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
+		  " maps to 0x%" PRIxGRUB_UINT64_T
+		  ". Reading paddr 0x%" PRIxGRUB_UINT64_T "\n",
+		  stripen, stripe->offset, paddr);
+
+    dev = find_device (data, stripe->device_id);
+    if (!dev)
+      {
+	grub_dprintf ("btrfs",
+		      "couldn't find a necessary member device "
+		      "of multi-device filesystem\n");
+	grub_errno = GRUB_ERR_NONE;
+	return GRUB_ERR_READ_ERROR;
+      }
+
+    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+			  csize, buf);
+    return err;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 			 void *buf, grub_size_t size, int recursion_depth)
@@ -638,7 +678,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
       grub_err_t err = 0;
       struct grub_btrfs_key key_out;
       int challoc = 0;
-      grub_device_t dev;
       struct grub_btrfs_key key_in;
       grub_size_t chsize;
       grub_disk_addr_t chaddr;
@@ -877,36 +916,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 	    for (i = 0; i < redundancy; i++)
 	      {
-		struct grub_btrfs_chunk_stripe *stripe;
-		grub_disk_addr_t paddr;
-
-		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
-		/* Right now the redundancy handling is easy.
-		   With RAID5-like it will be more difficult.  */
-		stripe += stripen + i;
-
-		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
-
-		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
-			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-			      stripen, stripe->offset);
-		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-			      "\n", paddr);
-
-		dev = find_device (data, stripe->device_id);
-		if (!dev)
-		  {
-		    grub_dprintf ("btrfs",
-				  "couldn't find a necessary member device "
-				  "of multi-device filesystem\n");
-		    err = grub_errno;
-		    grub_errno = GRUB_ERR_NONE;
-		    continue;
-		  }
-
-		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
-				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
-				      csize, buf);
+		err = btrfs_read_from_chunk (data, chunk, stripen,
+					     stripe_offset,
+					     i,     /* redundancy */
+					     csize, buf);
 		if (!err)
 		  break;
 		grub_errno = GRUB_ERR_NONE;
-- 
2.19.0

Re: [PATCH 6/9] btrfs: Refactor the code that read from disk

[Daniel Kiper]

On Tue, Jun 19, 2018 at 07:39:53PM +0200, Goffredo Baroncelli wrote:
> Move the code in charge to read the data from disk into a separate
> function. This helps to separate the error handling logic (which depend on

s/depend/depends/

> the different raid profiles) from the read from disk logic.
> Refactoring this code increases the general readability too.
>
> This is a preparatory patch, to help the adding of the RAID 5/6 recovery
> code.
>
> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>

Otherwise, Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

Daniel

[PATCH 6/9] btrfs: Refactor the code that read from disk

[Goffredo Baroncelli]

Move the code in charge to read the data from disk into a separate
function. This helps to separate the error handling logic (which depend on
the different raid profiles) from the read from disk logic.
Refactoring this code increases the general readability too.

This is a preparatory patch, to help the adding of the RAID 5/6 recovery
code.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/fs/btrfs.c | 75 ++++++++++++++++++++++++++------------------
 1 file changed, 44 insertions(+), 31 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 15ed59151..fa5bf56e0 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -625,6 +625,46 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
   return ctx.dev_found;
 }
 
+static grub_err_t
+btrfs_read_from_chunk (struct grub_btrfs_data *data,
+		       struct grub_btrfs_chunk_item *chunk,
+		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
+		       int redundancy, grub_uint64_t csize,
+		       void *buf)
+{
+    struct grub_btrfs_chunk_stripe *stripe;
+    grub_disk_addr_t paddr;
+    grub_device_t dev;
+    grub_err_t err;
+
+    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+    /* Right now the redundancy handling is easy.
+       With RAID5-like it will be more difficult.  */
+    stripe += stripen + redundancy;
+
+    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+
+    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
+		  " maps to 0x%" PRIxGRUB_UINT64_T
+		  ". Reading paddr 0x%" PRIxGRUB_UINT64_T "\n",
+		  stripen, stripe->offset, paddr);
+
+    dev = find_device (data, stripe->device_id);
+    if (!dev)
+      {
+	grub_dprintf ("btrfs",
+		      "couldn't find a necessary member device "
+		      "of multi-device filesystem\n");
+	grub_errno = GRUB_ERR_NONE;
+	return GRUB_ERR_READ_ERROR;
+      }
+
+    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+			  csize, buf);
+    return err;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 			 void *buf, grub_size_t size, int recursion_depth)
@@ -638,7 +678,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
       grub_err_t err = 0;
       struct grub_btrfs_key key_out;
       int challoc = 0;
-      grub_device_t dev;
       struct grub_btrfs_key key_in;
       grub_size_t chsize;
       grub_disk_addr_t chaddr;
@@ -881,36 +920,10 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 	    for (i = 0; i < redundancy; i++)
 	      {
-		struct grub_btrfs_chunk_stripe *stripe;
-		grub_disk_addr_t paddr;
-
-		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
-		/* Right now the redundancy handling is easy.
-		   With RAID5-like it will be more difficult.  */
-		stripe += stripen + i;
-
-		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
-
-		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
-			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-			      stripen, stripe->offset);
-		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-			      "\n", paddr);
-
-		dev = find_device (data, stripe->device_id);
-		if (!dev)
-		  {
-		    grub_dprintf ("btrfs",
-				  "couldn't find a necessary member device "
-				  "of multi-device filesystem\n");
-		    err = grub_errno;
-		    grub_errno = GRUB_ERR_NONE;
-		    continue;
-		  }
-
-		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
-				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
-				      csize, buf);
+		err = btrfs_read_from_chunk (data, chunk, stripen,
+					     stripe_offset,
+					     i,     /* redundancy */
+					     csize, buf);
 		if (!err)
 		  break;
 		grub_errno = GRUB_ERR_NONE;
-- 
2.18.0.rc2

Re: [PATCH 6/9] btrfs: refactor the code that read from disk

[Goffredo Baroncelli]

On 05/30/2018 01:07 PM, Daniel Kiper wrote:
> On Wed, May 16, 2018 at 08:48:16PM +0200, Goffredo Baroncelli wrote:
>> This is a preparatory patch, to help the adding of the RAID 5/6 recovery
> 
> Please move "This is a preparatory patch" sentence below...
> 
>> code. In case of availability of all disks, this code is good for all the
>> RAID profiles. However in case of failure, the error handling is quite
>> different. Refactoring this code increases the general readability.
> 
> s/readability/readability too/?
> 
> You can put "This is a preparatory patch" in separate line here.
> Same for the other patches.

What about
----
btrfs: Refactor the code that read from disk

Move the code in charge to read the data from disk in a separate
function. This helps to separate the error handling logic (which depend by 
the different raid profiles) from the read from disk logic.
Refactoring this code increases the general readability too.

This is a preparatory patch, to help the adding of the RAID 5/6 recovery
code. 

----


> 
>> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
>> ---
>>  grub-core/fs/btrfs.c | 85 +++++++++++++++++++++++++-------------------
>>  1 file changed, 49 insertions(+), 36 deletions(-)
>>
>> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
>> index 51f300829..63651928b 100644
>> --- a/grub-core/fs/btrfs.c
>> +++ b/grub-core/fs/btrfs.c
>> @@ -625,6 +625,47 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
>>    return ctx.dev_found;
>>  }
>>
>> +static grub_err_t
>> +btrfs_read_from_chunk (struct grub_btrfs_data *data,
>> +		       struct grub_btrfs_chunk_item *chunk,
>> +		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
>> +		       int redundancy, grub_uint64_t csize,
>> +		       void *buf)
>> +{
>> +
>> +    struct grub_btrfs_chunk_stripe *stripe;
>> +    grub_disk_addr_t paddr;
>> +    grub_device_t dev;
>> +    grub_err_t err;
>> +
>> +    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
>> +    /* Right now the redundancy handling is easy.
>> +       With RAID5-like it will be more difficult.  */
>> +    stripe += stripen + redundancy;
>> +
>> +    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
>> +
>> +    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
>> +		  " maps to 0x%" PRIxGRUB_UINT64_T "\n",
>> +		  stripen, stripe->offset);
>> +    grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T "\n", paddr);
>> +
>> +    dev = find_device (data, stripe->device_id);
>> +    if (!dev)
>> +      {
>> +	grub_dprintf ("btrfs",
>> +		      "couldn't find a necessary member device "
>> +		      "of multi-device filesystem\n");
>> +	grub_errno = GRUB_ERR_NONE;
>> +	return GRUB_ERR_READ_ERROR;
>> +      }
>> +
>> +    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
>> +			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
>> +			  csize, buf);
>> +    return err;
>> +}
>> +
>>  static grub_err_t
>>  grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>>  			 void *buf, grub_size_t size, int recursion_depth)
>> @@ -638,7 +679,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>>        grub_err_t err = 0;
>>        struct grub_btrfs_key key_out;
>>        int challoc = 0;
>> -      grub_device_t dev;
>>        struct grub_btrfs_key key_in;
>>        grub_size_t chsize;
>>        grub_disk_addr_t chaddr;
>> @@ -879,42 +919,15 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>>
>>  	    for (i = 0; i < redundancy; i++)
>>  	      {
>> -		struct grub_btrfs_chunk_stripe *stripe;
>> -		grub_disk_addr_t paddr;
>> -
>> -		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
>> -		/* Right now the redundancy handling is easy.
>> -		   With RAID5-like it will be more difficult.  */
>> -		stripe += stripen + i;
>> -
>> -		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
>> -
>> -		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
>> -			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
>> -			      stripen, stripe->offset);
>> -		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
>> -			      "\n", paddr);
>> -
>> -		dev = find_device (data, stripe->device_id);
>> -		if (!dev)
>> -		  {
>> -		    grub_dprintf ("btrfs",
>> -				  "couldn't find a necessary member device "
>> -				  "of multi-device filesystem\n");
>> -		    err = grub_errno;
>> -		    grub_errno = GRUB_ERR_NONE;
>> -		    continue;
>> -		  }
>> -
>> -		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
>> -				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
>> -				      csize, buf);
>> -		if (!err)
>> -		  break;
>> -		grub_errno = GRUB_ERR_NONE;
> 
> If you drop this line then you change behavior of this function.
> I have a feeling that this should stay as is. At least for now.
> If you need this change then probably it should be a part of the
> other patch.
OK
> 
>> +		err = btrfs_read_from_chunk (data, chunk, stripen,
>> +					     stripe_offset,
>> +					     i,     /* redundancy */
>> +					     csize, buf);
>> +		if (err == GRUB_ERR_NONE)
>> +		    break;
>>  	      }
>> -	    if (i != redundancy)
>> -	      break;
>> +	    if (err == GRUB_ERR_NONE)
>> +		break;
OK
> 
> Ditto.
> 
> Daniel
> 


-- 
gpg @keyserver.linux.it: Goffredo Baroncelli <kreijackATinwind.it>
Key fingerprint BBF5 1610 0B64 DAC6 5F7D  17B2 0EDA 9B37 8B82 E0B5

Re: [PATCH 6/9] btrfs: refactor the code that read from disk

[Daniel Kiper]

On Wed, May 16, 2018 at 08:48:16PM +0200, Goffredo Baroncelli wrote:
> This is a preparatory patch, to help the adding of the RAID 5/6 recovery

Please move "This is a preparatory patch" sentence below...

> code. In case of availability of all disks, this code is good for all the
> RAID profiles. However in case of failure, the error handling is quite
> different. Refactoring this code increases the general readability.

s/readability/readability too/?

You can put "This is a preparatory patch" in separate line here.
Same for the other patches.

> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
> ---
>  grub-core/fs/btrfs.c | 85 +++++++++++++++++++++++++-------------------
>  1 file changed, 49 insertions(+), 36 deletions(-)
>
> diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
> index 51f300829..63651928b 100644
> --- a/grub-core/fs/btrfs.c
> +++ b/grub-core/fs/btrfs.c
> @@ -625,6 +625,47 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
>    return ctx.dev_found;
>  }
>
> +static grub_err_t
> +btrfs_read_from_chunk (struct grub_btrfs_data *data,
> +		       struct grub_btrfs_chunk_item *chunk,
> +		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
> +		       int redundancy, grub_uint64_t csize,
> +		       void *buf)
> +{
> +
> +    struct grub_btrfs_chunk_stripe *stripe;
> +    grub_disk_addr_t paddr;
> +    grub_device_t dev;
> +    grub_err_t err;
> +
> +    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
> +    /* Right now the redundancy handling is easy.
> +       With RAID5-like it will be more difficult.  */
> +    stripe += stripen + redundancy;
> +
> +    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
> +
> +    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
> +		  " maps to 0x%" PRIxGRUB_UINT64_T "\n",
> +		  stripen, stripe->offset);
> +    grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T "\n", paddr);
> +
> +    dev = find_device (data, stripe->device_id);
> +    if (!dev)
> +      {
> +	grub_dprintf ("btrfs",
> +		      "couldn't find a necessary member device "
> +		      "of multi-device filesystem\n");
> +	grub_errno = GRUB_ERR_NONE;
> +	return GRUB_ERR_READ_ERROR;
> +      }
> +
> +    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
> +			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
> +			  csize, buf);
> +    return err;
> +}
> +
>  static grub_err_t
>  grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>  			 void *buf, grub_size_t size, int recursion_depth)
> @@ -638,7 +679,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>        grub_err_t err = 0;
>        struct grub_btrfs_key key_out;
>        int challoc = 0;
> -      grub_device_t dev;
>        struct grub_btrfs_key key_in;
>        grub_size_t chsize;
>        grub_disk_addr_t chaddr;
> @@ -879,42 +919,15 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
>
>  	    for (i = 0; i < redundancy; i++)
>  	      {
> -		struct grub_btrfs_chunk_stripe *stripe;
> -		grub_disk_addr_t paddr;
> -
> -		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
> -		/* Right now the redundancy handling is easy.
> -		   With RAID5-like it will be more difficult.  */
> -		stripe += stripen + i;
> -
> -		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
> -
> -		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
> -			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
> -			      stripen, stripe->offset);
> -		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
> -			      "\n", paddr);
> -
> -		dev = find_device (data, stripe->device_id);
> -		if (!dev)
> -		  {
> -		    grub_dprintf ("btrfs",
> -				  "couldn't find a necessary member device "
> -				  "of multi-device filesystem\n");
> -		    err = grub_errno;
> -		    grub_errno = GRUB_ERR_NONE;
> -		    continue;
> -		  }
> -
> -		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
> -				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
> -				      csize, buf);
> -		if (!err)
> -		  break;
> -		grub_errno = GRUB_ERR_NONE;

If you drop this line then you change behavior of this function.
I have a feeling that this should stay as is. At least for now.
If you need this change then probably it should be a part of the
other patch.

> +		err = btrfs_read_from_chunk (data, chunk, stripen,
> +					     stripe_offset,
> +					     i,     /* redundancy */
> +					     csize, buf);
> +		if (err == GRUB_ERR_NONE)
> +		    break;
>  	      }
> -	    if (i != redundancy)
> -	      break;
> +	    if (err == GRUB_ERR_NONE)
> +		break;

Ditto.

Daniel

[PATCH 6/9] btrfs: refactor the code that read from disk

[Goffredo Baroncelli]

This is a preparatory patch, to help the adding of the RAID 5/6 recovery
code. In case of availability of all disks, this code is good for all the
RAID profiles. However in case of failure, the error handling is quite
different. Refactoring this code increases the general readability.

Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
---
 grub-core/fs/btrfs.c | 85 +++++++++++++++++++++++++-------------------
 1 file changed, 49 insertions(+), 36 deletions(-)

diff --git a/grub-core/fs/btrfs.c b/grub-core/fs/btrfs.c
index 51f300829..63651928b 100644
--- a/grub-core/fs/btrfs.c
+++ b/grub-core/fs/btrfs.c
@@ -625,6 +625,47 @@ find_device (struct grub_btrfs_data *data, grub_uint64_t id)
   return ctx.dev_found;
 }
 
+static grub_err_t
+btrfs_read_from_chunk (struct grub_btrfs_data *data,
+		       struct grub_btrfs_chunk_item *chunk,
+		       grub_uint64_t stripen, grub_uint64_t stripe_offset,
+		       int redundancy, grub_uint64_t csize,
+		       void *buf)
+{
+
+    struct grub_btrfs_chunk_stripe *stripe;
+    grub_disk_addr_t paddr;
+    grub_device_t dev;
+    grub_err_t err;
+
+    stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
+    /* Right now the redundancy handling is easy.
+       With RAID5-like it will be more difficult.  */
+    stripe += stripen + redundancy;
+
+    paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
+
+    grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
+		  " maps to 0x%" PRIxGRUB_UINT64_T "\n",
+		  stripen, stripe->offset);
+    grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T "\n", paddr);
+
+    dev = find_device (data, stripe->device_id);
+    if (!dev)
+      {
+	grub_dprintf ("btrfs",
+		      "couldn't find a necessary member device "
+		      "of multi-device filesystem\n");
+	grub_errno = GRUB_ERR_NONE;
+	return GRUB_ERR_READ_ERROR;
+      }
+
+    err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
+			  paddr & (GRUB_DISK_SECTOR_SIZE - 1),
+			  csize, buf);
+    return err;
+}
+
 static grub_err_t
 grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 			 void *buf, grub_size_t size, int recursion_depth)
@@ -638,7 +679,6 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
       grub_err_t err = 0;
       struct grub_btrfs_key key_out;
       int challoc = 0;
-      grub_device_t dev;
       struct grub_btrfs_key key_in;
       grub_size_t chsize;
       grub_disk_addr_t chaddr;
@@ -879,42 +919,15 @@ grub_btrfs_read_logical (struct grub_btrfs_data *data, grub_disk_addr_t addr,
 
 	    for (i = 0; i < redundancy; i++)
 	      {
-		struct grub_btrfs_chunk_stripe *stripe;
-		grub_disk_addr_t paddr;
-
-		stripe = (struct grub_btrfs_chunk_stripe *) (chunk + 1);
-		/* Right now the redundancy handling is easy.
-		   With RAID5-like it will be more difficult.  */
-		stripe += stripen + i;
-
-		paddr = grub_le_to_cpu64 (stripe->offset) + stripe_offset;
-
-		grub_dprintf ("btrfs", "stripe %" PRIxGRUB_UINT64_T
-			      " maps to 0x%" PRIxGRUB_UINT64_T "\n",
-			      stripen, stripe->offset);
-		grub_dprintf ("btrfs", "reading paddr 0x%" PRIxGRUB_UINT64_T
-			      "\n", paddr);
-
-		dev = find_device (data, stripe->device_id);
-		if (!dev)
-		  {
-		    grub_dprintf ("btrfs",
-				  "couldn't find a necessary member device "
-				  "of multi-device filesystem\n");
-		    err = grub_errno;
-		    grub_errno = GRUB_ERR_NONE;
-		    continue;
-		  }
-
-		err = grub_disk_read (dev->disk, paddr >> GRUB_DISK_SECTOR_BITS,
-				      paddr & (GRUB_DISK_SECTOR_SIZE - 1),
-				      csize, buf);
-		if (!err)
-		  break;
-		grub_errno = GRUB_ERR_NONE;
+		err = btrfs_read_from_chunk (data, chunk, stripen,
+					     stripe_offset,
+					     i,     /* redundancy */
+					     csize, buf);
+		if (err == GRUB_ERR_NONE)
+		    break;
 	      }
-	    if (i != redundancy)
-	      break;
+	    if (err == GRUB_ERR_NONE)
+		break;
 	  }
 	if (err)
 	  return grub_errno = err;
-- 
2.17.0