[PATCH 0/3] readmirror feature

[PATCH 0/3] readmirror feature

[Anand Jain]

These patches are tested to be working fine.

Function call chain  __btrfs_map_block()->find_live_mirror() uses
thread pid to determine the %mirror_num when the mirror_num=0.

This patch introduces a framework so that we can add policies to determine
the %mirror_num. And adds the devid as the readmirror policy.

The property is stored as an extented attributes of root inode
(BTRFS_FS_TREE_OBJECTID).
User provided devid list is validated against the fs_devices::dev_list.

 For example:
   Usage:
     btrfs property set <mnt> readmirror devid<n>[,<m>...]
     btrfs property set <mnt> readmirror ""

   mkfs.btrfs -fq -draid1 -mraid1 /dev/sd[b-d] && mount /dev/sdb /btrfs
   btrfs prop set /btrfs readmirror devid1,2
   btrfs prop get /btrfs readmirror
    readmirror=devid1,2
   getfattr -n btrfs.readmirror --absolute-names /btrfs
    btrfs.readmirror="devid1,2"
   btrfs prop set /btrfs readmirror ""
   getfattr -n btrfs.readmirror --absolute-names /btrfs
    /btrfs: btrfs.readmirror: No such attribute
   btrfs prop get /btrfs readmirror

RFC->v1:
  Drops pid as one of the readmirror policy choices and as usual remains
  as default. And when the devid is reset the readmirror policy falls back
  to pid.
  Drops the mount -o readmirror idea, it can be added at a later point of
  time.
  Property now accepts more than 1 devid as readmirror device. As shown
  in the example above.

Anand Jain (3):
  btrfs: add inode pointer to prop_handler::validate()
  btrfs: add readmirror property framework
  btrfs: add readmirror devid property

 fs/btrfs/props.c   | 120 +++++++++++++++++++++++++++++++++++++++++++--
 fs/btrfs/props.h   |   4 +-
 fs/btrfs/volumes.c |  25 +++++++++-
 fs/btrfs/volumes.h |   8 +++
 fs/btrfs/xattr.c   |   2 +-
 5 files changed, 150 insertions(+), 9 deletions(-)

Anand Jain (2):
  btrfs-progs: add helper to create xattr name
  btrfs-progs: add readmirror policy

 props.c | 75 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 68 insertions(+), 7 deletions(-)
-- 
2.20.1 (Apple Git-117)

[PATCH 1/3] btrfs: add inode pointer to prop_handler::validate()

[Anand Jain]

In preparation to add the readmirror property, pass inode in the
prop_handler::validate() function vector, so that it can fetch
corresponding fs_devices.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/props.c | 12 +++++++-----
 fs/btrfs/props.h |  4 ++--
 fs/btrfs/xattr.c |  2 +-
 3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
index ca2716917e37..5c1fccc32b43 100644
--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -17,7 +17,7 @@ static DEFINE_HASHTABLE(prop_handlers_ht, BTRFS_PROP_HANDLERS_HT_BITS);
 struct prop_handler {
 	struct hlist_node node;
 	const char *xattr_name;
-	int (*validate)(const char *value, size_t len);
+	int (*validate)(struct inode *inode, const char *value, size_t len);
 	int (*apply)(struct inode *inode, const char *value, size_t len);
 	const char *(*extract)(struct inode *inode);
 	int inheritable;
@@ -55,7 +55,8 @@ find_prop_handler(const char *name,
 	return NULL;
 }
 
-int btrfs_validate_prop(const char *name, const char *value, size_t value_len)
+int btrfs_validate_prop(struct inode *inode, const char *name,
+			const char *value, size_t value_len)
 {
 	const struct prop_handler *handler;
 
@@ -69,7 +70,7 @@ int btrfs_validate_prop(const char *name, const char *value, size_t value_len)
 	if (value_len == 0)
 		return 0;
 
-	return handler->validate(value, value_len);
+	return handler->validate(inode, value, value_len);
 }
 
 int btrfs_set_prop(struct btrfs_trans_handle *trans, struct inode *inode,
@@ -252,7 +253,8 @@ int btrfs_load_inode_props(struct inode *inode, struct btrfs_path *path)
 	return ret;
 }
 
-static int prop_compression_validate(const char *value, size_t len)
+static int prop_compression_validate(struct inode *inode, const char *value,
+				     size_t len)
 {
 	if (!value)
 		return 0;
@@ -353,7 +355,7 @@ static int inherit_props(struct btrfs_trans_handle *trans,
 		 * This is not strictly necessary as the property should be
 		 * valid, but in case it isn't, don't propagate it futher.
 		 */
-		ret = h->validate(value, strlen(value));
+		ret = h->validate(inode, value, strlen(value));
 		if (ret)
 			continue;
 
diff --git a/fs/btrfs/props.h b/fs/btrfs/props.h
index 40b2c65b518c..5b1e39136f7f 100644
--- a/fs/btrfs/props.h
+++ b/fs/btrfs/props.h
@@ -13,8 +13,8 @@ void __init btrfs_props_init(void);
 int btrfs_set_prop(struct btrfs_trans_handle *trans, struct inode *inode,
 		   const char *name, const char *value, size_t value_len,
 		   int flags);
-int btrfs_validate_prop(const char *name, const char *value, size_t value_len);
-
+int btrfs_validate_prop(struct inode *inode, const char *name,
+			const char *value, size_t value_len);
 int btrfs_load_inode_props(struct inode *inode, struct btrfs_path *path);
 
 int btrfs_inode_inherit_props(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/xattr.c b/fs/btrfs/xattr.c
index 46ad7b5cf209..4e4f0edd4968 100644
--- a/fs/btrfs/xattr.c
+++ b/fs/btrfs/xattr.c
@@ -378,7 +378,7 @@ static int btrfs_xattr_handler_set_prop(const struct xattr_handler *handler,
 	struct btrfs_root *root = BTRFS_I(inode)->root;
 
 	name = xattr_full_name(handler, name);
-	ret = btrfs_validate_prop(name, value, size);
+	ret = btrfs_validate_prop(inode, name, value, size);
 	if (ret)
 		return ret;
 
-- 
2.20.1 (Apple Git-117)

[PATCH 2/3] btrfs: add readmirror property framework

[Anand Jain]

Function call chain  __btrfs_map_block()->find_live_mirror() uses
thread %pid to determine the %mirror_num for the read when mirror_num=0
in the argument.

This patch introduces a framework so that readmirror is a configurable
parameter, with default set to pid.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/props.c   | 41 +++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/volumes.c |  9 ++++++++-
 fs/btrfs/volumes.h |  6 ++++++
 3 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
index 5c1fccc32b43..1d44fbdd5891 100644
--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -10,6 +10,7 @@
 #include "ctree.h"
 #include "xattr.h"
 #include "compression.h"
+#include "volumes.h"
 
 #define BTRFS_PROP_HANDLERS_HT_BITS 8
 static DEFINE_HASHTABLE(prop_handlers_ht, BTRFS_PROP_HANDLERS_HT_BITS);
@@ -316,6 +317,39 @@ static const char *prop_compression_extract(struct inode *inode)
 	return NULL;
 }
 
+static int prop_readmirror_validate(struct inode *inode, const char *value,
+				    size_t len)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+
+	if (root->root_key.objectid != BTRFS_FS_TREE_OBJECTID)
+		return -EINVAL;
+
+	if (!len)
+		return 0;
+
+	return -EINVAL;
+}
+
+static int prop_readmirror_apply(struct inode *inode, const char *value,
+				 size_t len)
+{
+	struct btrfs_fs_devices *fs_devices = btrfs_sb(inode->i_sb)->fs_devices;
+
+	fs_devices->readmirror_policy = BTRFS_READMIRROR_DEFAULT;
+
+	return 0;
+}
+
+static const char *prop_readmirror_extract(struct inode *inode)
+{
+	/*
+	 * readmirror policy is applied for the whole FS, inheritance is not
+	 * applicable.
+	 */
+	return NULL;
+}
+
 static struct prop_handler prop_handlers[] = {
 	{
 		.xattr_name = XATTR_BTRFS_PREFIX "compression",
@@ -324,6 +358,13 @@ static struct prop_handler prop_handlers[] = {
 		.extract = prop_compression_extract,
 		.inheritable = 1
 	},
+	{
+		.xattr_name = XATTR_BTRFS_PREFIX "readmirror",
+		.validate = prop_readmirror_validate,
+		.apply = prop_readmirror_apply,
+		.extract = prop_readmirror_extract,
+		.inheritable = 0
+	},
 };
 
 static int inherit_props(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 78bab7803bda..64c3a2d8b264 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5504,7 +5504,14 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
 	else
 		num_stripes = map->num_stripes;
 
-	preferred_mirror = first + current->pid % num_stripes;
+	switch(fs_info->fs_devices->readmirror_policy) {
+	case BTRFS_READMIRROR_DEFAULT:
+		/* fall through */
+	default:
+		/* readmirror as per thread pid */
+		preferred_mirror = first + current->pid % num_stripes;
+		break;
+	}
 
 	if (dev_replace_is_ongoing &&
 	    fs_info->dev_replace.cont_reading_from_srcdev_mode ==
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index b3a89d767512..5dffaa6f9d18 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -204,6 +204,10 @@ BTRFS_DEVICE_GETSET_FUNCS(total_bytes);
 BTRFS_DEVICE_GETSET_FUNCS(disk_total_bytes);
 BTRFS_DEVICE_GETSET_FUNCS(bytes_used);
 
+enum btrfs_readmirror_policy {
+	BTRFS_READMIRROR_DEFAULT,
+};
+
 struct btrfs_fs_devices {
 	u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */
 	u8 metadata_uuid[BTRFS_FSID_SIZE];
@@ -249,6 +253,8 @@ struct btrfs_fs_devices {
 	struct kobject fsid_kobj;
 	struct kobject *device_dir_kobj;
 	struct completion kobj_unregister;
+
+	int readmirror_policy;
 };
 
 #define BTRFS_BIO_INLINE_CSUM_SIZE	64
-- 
2.20.1 (Apple Git-117)

[PATCH 3/3] btrfs: add readmirror devid property

[Anand Jain]

From: Anand Jain <asj@dhcp-10-186-51-152.sg.oracle.com>

Introduces devid readmirror property, to direct read IO to the specified
device(s).

The readmirror property is stored as extended attribute on the root
inode. The readmirror input format is devid1,2,3.. etc. And for the
each devid provided, a new flag BTRFS_DEV_STATE_READ_OPTIMISED is set.

As of now readmirror by devid supports only raid1s. Raid10 support has
to leverage device grouping feature, which is yet to be implemented.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/props.c   | 69 +++++++++++++++++++++++++++++++++++++++++++++-
 fs/btrfs/volumes.c | 16 +++++++++++
 fs/btrfs/volumes.h |  2 ++
 3 files changed, 86 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
index 1d44fbdd5891..c5d17e29ab4e 100644
--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -320,7 +320,10 @@ static const char *prop_compression_extract(struct inode *inode)
 static int prop_readmirror_validate(struct inode *inode, const char *value,
 				    size_t len)
 {
+	char *value_dup;
+	char *devid_str;
 	struct btrfs_root *root = BTRFS_I(inode)->root;
+	struct btrfs_fs_devices *fs_devices = root->fs_info->fs_devices;
 
 	if (root->root_key.objectid != BTRFS_FS_TREE_OBJECTID)
 		return -EINVAL;
@@ -328,16 +331,80 @@ static int prop_readmirror_validate(struct inode *inode, const char *value,
 	if (!len)
 		return 0;
 
-	return -EINVAL;
+	if (len <= 5 || strncmp("devid", value, 5))
+		return -EINVAL;
+
+	value_dup = kstrndup(value + 5, len - 5, GFP_KERNEL);
+	if (!value_dup)
+		return -ENOMEM;
+
+	while ((devid_str = strsep(&value_dup, ",")) != NULL) {
+		u64 devid;
+		struct btrfs_device *device;
+
+		if (kstrtoull(devid_str, 10, &devid)) {
+			kfree(value_dup);
+			return -EINVAL;
+		}
+
+		device = btrfs_find_device(fs_devices, devid, NULL, NULL, false);
+		if (!device) {
+			kfree(value_dup);
+			return -EINVAL;
+		}
+	}
+
+	return 0;
 }
 
 static int prop_readmirror_apply(struct inode *inode, const char *value,
 				 size_t len)
 {
+	char *value_dup;
+	char *devid_str;
+	struct btrfs_device *device;
 	struct btrfs_fs_devices *fs_devices = btrfs_sb(inode->i_sb)->fs_devices;
 
+	if (value) {
+		value_dup = kstrndup(value + 5, len - 5, GFP_KERNEL);
+		if (!value_dup)
+			return -ENOMEM;
+	}
+
+	/* Both set and reset has to clear the exisiting values */
+	list_for_each_entry(device, &fs_devices->devices, dev_list) {
+		if (test_bit(BTRFS_DEV_STATE_READ_OPTIMISED,
+			     &device->dev_state)) {
+			clear_bit(BTRFS_DEV_STATE_READ_OPTIMISED,
+				  &device->dev_state);
+		}
+	}
 	fs_devices->readmirror_policy = BTRFS_READMIRROR_DEFAULT;
 
+	/* Its only reset so just return */
+	if (!value)
+		return 0;
+
+	while ((devid_str = strsep(&value_dup, ",")) != NULL) {
+		u64 devid;
+
+		/* Has been verified in validate() this will not fail */
+		if (kstrtoull(devid_str, 10, &devid)) {
+			kfree(value_dup);
+			return -EINVAL;
+		}
+
+		device = btrfs_find_device(fs_devices, devid, NULL, NULL, false);
+		if (!device) {
+			kfree(value_dup);
+			return -EINVAL;
+		}
+
+		set_bit(BTRFS_DEV_STATE_READ_OPTIMISED, &device->dev_state);
+		fs_devices->readmirror_policy = BTRFS_READMIRROR_DEVID;
+	}
+
+	kfree(value_dup);
 	return 0;
 }
 
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 64c3a2d8b264..90cbc03a20f6 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5495,6 +5495,7 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
 	int preferred_mirror;
 	int tolerance;
 	struct btrfs_device *srcdev;
+	bool found = false;
 
 	ASSERT((map->type &
 		 (BTRFS_BLOCK_GROUP_RAID1 | BTRFS_BLOCK_GROUP_RAID10)));
@@ -5505,6 +5506,21 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
 		num_stripes = map->num_stripes;
 
 	switch(fs_info->fs_devices->readmirror_policy) {
+	case BTRFS_READMIRROR_DEVID:
+		/* skip raid10 for now */
+		if (map->type & BTRFS_BLOCK_GROUP_RAID1) {
+			for (i = first; i < first + num_stripes; i++) {
+				if (test_bit(BTRFS_DEV_STATE_READ_OPTIMISED,
+					     &map->stripes[i].dev->dev_state)) {
+					preferred_mirror = i;
+					found = true;
+					break;
+				}
+			}
+			if (found)
+				break;
+		}
+		/* fall through */
 	case BTRFS_READMIRROR_DEFAULT:
 		/* fall through */
 	default:
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 5dffaa6f9d18..6c223790dc4c 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -41,6 +41,7 @@ struct btrfs_pending_bios {
 #define BTRFS_DEV_STATE_MISSING		(2)
 #define BTRFS_DEV_STATE_REPLACE_TGT	(3)
 #define BTRFS_DEV_STATE_FLUSH_SENT	(4)
+#define BTRFS_DEV_STATE_READ_OPTIMISED	(5)
 
 struct btrfs_device {
 	struct list_head dev_list;
@@ -206,6 +207,7 @@ BTRFS_DEVICE_GETSET_FUNCS(bytes_used);
 
 enum btrfs_readmirror_policy {
 	BTRFS_READMIRROR_DEFAULT,
+	BTRFS_READMIRROR_DEVID,
 };
 
 struct btrfs_fs_devices {
-- 
2.20.1 (Apple Git-117)

[PATCH 2/3] btrfs: add readmirror property framework

[Anand Jain]

Function call chain  __btrfs_map_block()->find_live_mirror() uses
thread %pid to determine the %mirror_num for the read when mirror_num=0
in the argument.

This patch introduces a framework so that readmirror is a configurable
parameter, with default set to pid.

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 fs/btrfs/props.c   | 41 +++++++++++++++++++++++++++++++++++++++++
 fs/btrfs/volumes.c |  9 ++++++++-
 fs/btrfs/volumes.h |  6 ++++++
 3 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
index 5c1fccc32b43..1d44fbdd5891 100644
--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -10,6 +10,7 @@
 #include "ctree.h"
 #include "xattr.h"
 #include "compression.h"
+#include "volumes.h"
 
 #define BTRFS_PROP_HANDLERS_HT_BITS 8
 static DEFINE_HASHTABLE(prop_handlers_ht, BTRFS_PROP_HANDLERS_HT_BITS);
@@ -316,6 +317,39 @@ static const char *prop_compression_extract(struct inode *inode)
 	return NULL;
 }
 
+static int prop_readmirror_validate(struct inode *inode, const char *value,
+				    size_t len)
+{
+	struct btrfs_root *root = BTRFS_I(inode)->root;
+
+	if (root->root_key.objectid != BTRFS_FS_TREE_OBJECTID)
+		return -EINVAL;
+
+	if (!len)
+		return 0;
+
+	return -EINVAL;
+}
+
+static int prop_readmirror_apply(struct inode *inode, const char *value,
+				 size_t len)
+{
+	struct btrfs_fs_devices *fs_devices = btrfs_sb(inode->i_sb)->fs_devices;
+
+	fs_devices->readmirror_policy = BTRFS_READMIRROR_DEFAULT;
+
+	return 0;
+}
+
+static const char *prop_readmirror_extract(struct inode *inode)
+{
+	/*
+	 * readmirror policy is applied for the whole FS, inheritance is not
+	 * applicable.
+	 */
+	return NULL;
+}
+
 static struct prop_handler prop_handlers[] = {
 	{
 		.xattr_name = XATTR_BTRFS_PREFIX "compression",
@@ -324,6 +358,13 @@ static struct prop_handler prop_handlers[] = {
 		.extract = prop_compression_extract,
 		.inheritable = 1
 	},
+	{
+		.xattr_name = XATTR_BTRFS_PREFIX "readmirror",
+		.validate = prop_readmirror_validate,
+		.apply = prop_readmirror_apply,
+		.extract = prop_readmirror_extract,
+		.inheritable = 0
+	},
 };
 
 static int inherit_props(struct btrfs_trans_handle *trans,
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 78bab7803bda..64c3a2d8b264 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5504,7 +5504,14 @@ static int find_live_mirror(struct btrfs_fs_info *fs_info,
 	else
 		num_stripes = map->num_stripes;
 
-	preferred_mirror = first + current->pid % num_stripes;
+	switch(fs_info->fs_devices->readmirror_policy) {
+	case BTRFS_READMIRROR_DEFAULT:
+		/* fall through */
+	default:
+		/* readmirror as per thread pid */
+		preferred_mirror = first + current->pid % num_stripes;
+		break;
+	}
 
 	if (dev_replace_is_ongoing &&
 	    fs_info->dev_replace.cont_reading_from_srcdev_mode ==
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index b3a89d767512..5dffaa6f9d18 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -204,6 +204,10 @@ BTRFS_DEVICE_GETSET_FUNCS(total_bytes);
 BTRFS_DEVICE_GETSET_FUNCS(disk_total_bytes);
 BTRFS_DEVICE_GETSET_FUNCS(bytes_used);
 
+enum btrfs_readmirror_policy {
+	BTRFS_READMIRROR_DEFAULT,
+};
+
 struct btrfs_fs_devices {
 	u8 fsid[BTRFS_FSID_SIZE]; /* FS specific uuid */
 	u8 metadata_uuid[BTRFS_FSID_SIZE];
@@ -249,6 +253,8 @@ struct btrfs_fs_devices {
 	struct kobject fsid_kobj;
 	struct kobject *device_dir_kobj;
 	struct completion kobj_unregister;
+
+	int readmirror_policy;
 };
 
 #define BTRFS_BIO_INLINE_CSUM_SIZE	64
-- 
2.20.1 (Apple Git-117)