[PATCH v4 0/8] New rescue mount options

[PATCH v4 0/8] New rescue mount options

[Josef Bacik]

v3->v4:
- Add more reviewed-bys.
- Addressed Johannes's comment about the helper for spitting out the rescue
  options in showmount.

v2->v3:
- Re-worked the showmount format for rescue= options, so it's in the format of
  rescue=option1:option2:option3.
- Added aliases for ignore* with just a i<opt>.
- Added a sysfs file to spit out supported rescue options.
- Fixed where we weren't spitting out rescue=usebackuproot in showmount.
- The only thing I didn't do was the no/^ options, since that's trickier and
  puts us in a murky place for some things (nonologreplay).

v1->v2:
- Add Qu's reviewed-bys.
- Addressed the comment about dev extent verification for ignorebadroots.

--- Original email ---
Hello,

This is the next version of my rescue=all patches, this time broken up in to a
few discrete patches, with some cleanups as well.  I have a PR for the xfstest
that exercises these options, it can be found here

  https://github.com/btrfs/fstests/pull/35

This is the same idea as the previous versions, except I've made a mechanical
change.  Instead we have rescue=ignorebadroots, which ignores any global roots
that we may not be able to read.  We will still fail to mount if thinks like the
chunk root or the tree root are corrupt, but this will allow us to mount read
only if the extent root or csum root are completely hosed.

I've added a new patch this go around, rescue=ignoredatacsums.  Somebody had
indicated that they would prefer that the original rescue=all allowed us to
continue to read csums if the root was still intact.  In order to handle that
usecase that's what you get with rescue=ignorebadroots, however if your csum
tree is corrupt in the middle of the tree you could still end up with problems.
Thus we have rescue=ignoredatacsums which will completely disable the csum tree
as well.

And finally we have rescue=all, which simply enables ignoredatacsums,
ignorebadroots, and notreelogreplay.  We need an easy catch-all option for
distros to fallback on to get users the highest probability of being able to
recover their data, so we will use rescue=all to turn on all the fanciest rescue
options that we have, and then use the discrete options for more fine grained
recovery.  Thanks,

Josef

Josef Bacik (8):
  btrfs: unify the ro checking for mount options
  btrfs: push the NODATASUM check into btrfs_lookup_bio_sums
  btrfs: add a supported_rescue_options file to sysfs
  btrfs: add a helper to print out rescue= options
  btrfs: show rescue=usebackuproot in /proc/mounts
  btrfs: introduce rescue=ignorebadroots
  btrfs: introduce rescue=ignoredatacsums
  btrfs: introduce rescue=all

 fs/btrfs/block-group.c | 48 +++++++++++++++++++++++++++
 fs/btrfs/block-rsv.c   |  8 +++++
 fs/btrfs/compression.c | 17 ++++------
 fs/btrfs/ctree.h       |  2 ++
 fs/btrfs/disk-io.c     | 74 +++++++++++++++++++++++++++---------------
 fs/btrfs/file-item.c   |  4 +++
 fs/btrfs/inode.c       | 18 +++++++---
 fs/btrfs/super.c       | 68 +++++++++++++++++++++++++++++++++-----
 fs/btrfs/sysfs.c       | 25 ++++++++++++++
 fs/btrfs/volumes.c     | 13 ++++++++
 10 files changed, 228 insertions(+), 49 deletions(-)

-- 
2.26.2

[PATCH v4 1/8] btrfs: unify the ro checking for mount options

[Josef Bacik]

We're going to be adding more options that require RDONLY, so add a
helper to do the check and error out if we don't have RDONLY set.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/super.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 8840a4fa81eb..f99e89ec46b2 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -458,6 +458,17 @@ static const match_table_t rescue_tokens = {
 	{Opt_err, NULL},
 };
 
+static bool check_ro_option(struct btrfs_fs_info *fs_info, unsigned long opt,
+			    const char *opt_name)
+{
+	if (fs_info->mount_opt & opt) {
+		btrfs_err(fs_info, "%s must be used with ro mount option",
+			  opt_name);
+		return true;
+	}
+	return false;
+}
+
 static int parse_rescue_options(struct btrfs_fs_info *info, const char *options)
 {
 	char *opts;
@@ -968,14 +979,12 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 		}
 	}
 check:
-	/*
-	 * Extra check for current option against current flag
-	 */
-	if (btrfs_test_opt(info, NOLOGREPLAY) && !(new_flags & SB_RDONLY)) {
-		btrfs_err(info,
-			  "nologreplay must be used with ro mount option");
+	/* We're read-only, don't have to check. */
+	if (new_flags & SB_RDONLY)
+		goto out;
+
+	if (check_ro_option(info, BTRFS_MOUNT_NOLOGREPLAY, "nologreplay"))
 		ret = -EINVAL;
-	}
 out:
 	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE) &&
 	    !btrfs_test_opt(info, FREE_SPACE_TREE) &&
-- 
2.26.2

[PATCH v4 2/8] btrfs: push the NODATASUM check into btrfs_lookup_bio_sums

[Josef Bacik]

When we move to being able to handle NULL csum_roots it'll be cleaner to
just check in btrfs_lookup_bio_sums instead of at all of the caller
locations, so push the NODATASUM check into it as well so it's unified.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/compression.c | 14 +++++---------
 fs/btrfs/file-item.c   |  3 +++
 fs/btrfs/inode.c       | 12 +++++++++---
 3 files changed, 17 insertions(+), 12 deletions(-)

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index eeface30facd..7e1eb57b923c 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -722,11 +722,9 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 			 */
 			refcount_inc(&cb->pending_bios);
 
-			if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
-				ret = btrfs_lookup_bio_sums(inode, comp_bio,
-							    (u64)-1, sums);
-				BUG_ON(ret); /* -ENOMEM */
-			}
+			ret = btrfs_lookup_bio_sums(inode, comp_bio, (u64)-1,
+						    sums);
+			BUG_ON(ret); /* -ENOMEM */
 
 			nr_sectors = DIV_ROUND_UP(comp_bio->bi_iter.bi_size,
 						  fs_info->sectorsize);
@@ -751,10 +749,8 @@ blk_status_t btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,
 	ret = btrfs_bio_wq_end_io(fs_info, comp_bio, BTRFS_WQ_ENDIO_DATA);
 	BUG_ON(ret); /* -ENOMEM */
 
-	if (!(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)) {
-		ret = btrfs_lookup_bio_sums(inode, comp_bio, (u64)-1, sums);
-		BUG_ON(ret); /* -ENOMEM */
-	}
+	ret = btrfs_lookup_bio_sums(inode, comp_bio, (u64)-1, sums);
+	BUG_ON(ret); /* -ENOMEM */
 
 	ret = btrfs_map_bio(fs_info, comp_bio, mirror_num);
 	if (ret) {
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 8f4f2bd6d9b9..8083d71d6af6 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -272,6 +272,9 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
 	int count = 0;
 	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 
+	if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
+		return BLK_STS_OK;
+
 	path = btrfs_alloc_path();
 	if (!path)
 		return BLK_STS_RESOURCE;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index da58c58ef9aa..de69bef92c9a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2202,7 +2202,12 @@ blk_status_t btrfs_submit_data_bio(struct inode *inode, struct bio *bio,
 							   mirror_num,
 							   bio_flags);
 			goto out;
-		} else if (!skip_sum) {
+		} else {
+			/*
+			 * Lookup bio sums does extra checks around whether we
+			 * need to csum or not, which is why we ignore skip_sum
+			 * here.
+			 */
 			ret = btrfs_lookup_bio_sums(inode, bio, (u64)-1, NULL);
 			if (ret)
 				goto out;
@@ -7778,7 +7783,6 @@ static blk_qc_t btrfs_submit_direct(struct inode *inode, struct iomap *iomap,
 		struct bio *dio_bio, loff_t file_offset)
 {
 	const bool write = (bio_op(dio_bio) == REQ_OP_WRITE);
-	const bool csum = !(BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM);
 	struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
 	const bool raid56 = (btrfs_data_alloc_profile(fs_info) &
 			     BTRFS_BLOCK_GROUP_RAID56_MASK);
@@ -7805,10 +7809,12 @@ static blk_qc_t btrfs_submit_direct(struct inode *inode, struct iomap *iomap,
 		return BLK_QC_T_NONE;
 	}
 
-	if (!write && csum) {
+	if (!write) {
 		/*
 		 * Load the csums up front to reduce csum tree searches and
 		 * contention when submitting bios.
+		 *
+		 * If we have csums disabled this will do nothing.
 		 */
 		status = btrfs_lookup_bio_sums(inode, dio_bio, file_offset,
 					       dip->csums);
-- 
2.26.2

[PATCH v4 3/8] btrfs: add a supported_rescue_options file to sysfs

[Josef Bacik]

We're going to be adding a variety of different rescue options, we
should advertise which ones we support to make user spaces life easier
in the future.

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/sysfs.c | 22 ++++++++++++++++++++++
 1 file changed, 22 insertions(+)

diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 8424f5d0e5ed..8f0462d6855d 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -329,10 +329,32 @@ static ssize_t send_stream_version_show(struct kobject *kobj,
 }
 BTRFS_ATTR(static_feature, send_stream_version, send_stream_version_show);
 
+static const char *rescue_opts[] = {
+	"usebackuproot",
+	"nologreplay",
+};
+
+static ssize_t supported_rescue_options_show(struct kobject *kobj,
+					     struct kobj_attribute *a,
+					     char *buf)
+{
+	ssize_t ret = 0;
+	int i;
+
+	for (i = 0; i < ARRAY_SIZE(rescue_opts); i++)
+		ret += scnprintf(buf + ret, PAGE_SIZE - ret, "%s%s",
+				 (i ? " " : ""), rescue_opts[i]);
+	ret += scnprintf(buf + ret, PAGE_SIZE - ret, "\n");
+	return ret;
+}
+BTRFS_ATTR(static_feature, supported_rescue_options,
+	   supported_rescue_options_show);
+
 static struct attribute *btrfs_supported_static_feature_attrs[] = {
 	BTRFS_ATTR_PTR(static_feature, rmdir_subvol),
 	BTRFS_ATTR_PTR(static_feature, supported_checksums),
 	BTRFS_ATTR_PTR(static_feature, send_stream_version),
+	BTRFS_ATTR_PTR(static_feature, supported_rescue_options),
 	NULL
 };
 
-- 
2.26.2

[PATCH v4 4/8] btrfs: add a helper to print out rescue= options

[Josef Bacik]

We're going to have a lot of rescue options, add a helper to collapse
the /proc/mounts output to rescue=option1:option2:option3 format.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/super.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index f99e89ec46b2..f41f7af27ff7 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1392,11 +1392,19 @@ int btrfs_sync_fs(struct super_block *sb, int wait)
 	return btrfs_commit_transaction(trans);
 }
 
+static void print_rescue_option(struct seq_file *seq, const char *s,
+				bool *printed)
+{
+	seq_printf(seq, "%s%s", (*printed) ? ":" : ",rescue=", s);
+	*printed = true;
+}
+
 static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 {
 	struct btrfs_fs_info *info = btrfs_sb(dentry->d_sb);
 	const char *compress_type;
 	const char *subvol_name;
+	bool printed = false;
 
 	if (btrfs_test_opt(info, DEGRADED))
 		seq_puts(seq, ",degraded");
@@ -1429,7 +1437,7 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 	if (btrfs_test_opt(info, NOTREELOG))
 		seq_puts(seq, ",notreelog");
 	if (btrfs_test_opt(info, NOLOGREPLAY))
-		seq_puts(seq, ",rescue=nologreplay");
+		print_rescue_option(seq, "nologreplay", &printed);
 	if (btrfs_test_opt(info, FLUSHONCOMMIT))
 		seq_puts(seq, ",flushoncommit");
 	if (btrfs_test_opt(info, DISCARD_SYNC))
-- 
2.26.2

Re: [PATCH v4 4/8] btrfs: add a helper to print out rescue= options

[Johannes Thumshirn]

Looks good to me,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

[PATCH v4 5/8] btrfs: show rescue=usebackuproot in /proc/mounts

[Josef Bacik]

This got missed somehow, so add it in.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/super.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index f41f7af27ff7..ca270649fe10 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -1438,6 +1438,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		seq_puts(seq, ",notreelog");
 	if (btrfs_test_opt(info, NOLOGREPLAY))
 		print_rescue_option(seq, "nologreplay", &printed);
+	if (btrfs_test_opt(info, USEBACKUPROOT))
+		print_rescue_option(seq, "usebackuproot", &printed);
 	if (btrfs_test_opt(info, FLUSHONCOMMIT))
 		seq_puts(seq, ",flushoncommit");
 	if (btrfs_test_opt(info, DISCARD_SYNC))
-- 
2.26.2

Re: [PATCH v4 5/8] btrfs: show rescue=usebackuproot in /proc/mounts

[Johannes Thumshirn]

Looks good,
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>

Re: [PATCH v4 5/8] btrfs: show rescue=usebackuproot in /proc/mounts

[David Sterba]

On Fri, Oct 16, 2020 at 11:29:17AM -0400, Josef Bacik wrote:
> This got missed somehow, so add it in.

No, that it's not in the list is intentional, see disk-io.c:

3348         /*
3349          * backuproot only affect mount behavior, and if open_ctree succeeded,
3350          * no need to keep the flag
3351          */
3352         btrfs_clear_opt(fs_info->mount_opt, USEBACKUPROOT);

so it would never reach show_options, but the question is if it should
be in the list. I'd vote for yes, it maybe made some sense for a
standalone option but now that it's a one of rescue, it should not
randomy disappear.

Re: [PATCH v4 5/8] btrfs: show rescue=usebackuproot in /proc/mounts

[Josef Bacik]

On 10/20/20 12:03 PM, David Sterba wrote:
> On Fri, Oct 16, 2020 at 11:29:17AM -0400, Josef Bacik wrote:
>> This got missed somehow, so add it in.
> 
> No, that it's not in the list is intentional, see disk-io.c:
> 
> 3348         /*
> 3349          * backuproot only affect mount behavior, and if open_ctree succeeded,
> 3350          * no need to keep the flag
> 3351          */
> 3352         btrfs_clear_opt(fs_info->mount_opt, USEBACKUPROOT);
> 
> so it would never reach show_options, but the question is if it should
> be in the list. I'd vote for yes, it maybe made some sense for a
> standalone option but now that it's a one of rescue, it should not
> randomy disappear.
> 

I think yes, especially since it's one of the rescue=<> options.  I'm not a big 
fan of mount options that don't get shown afterwards, we still probably want to 
know that the fs was mounted with the special option after the fact, rather than 
just clearing it after we're done with it.  I'll follow up to remove this part. 
  Thanks,

Josef

[PATCH v4 6/8] btrfs: introduce rescue=ignorebadroots

[Josef Bacik]

In the face of extent root corruption, or any other core fs wide root
corruption we will fail to mount the file system.  This makes recovery
kind of a pain, because you need to fall back to userspace tools to
scrape off data.  Instead provide a mechanism to gracefully handle bad
roots, so we can at least mount read-only and possibly recover data from
the file system.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/block-group.c | 48 +++++++++++++++++++++++++++++++
 fs/btrfs/block-rsv.c   |  8 ++++++
 fs/btrfs/compression.c |  3 +-
 fs/btrfs/ctree.h       |  1 +
 fs/btrfs/disk-io.c     | 65 ++++++++++++++++++++++++++----------------
 fs/btrfs/file-item.c   |  3 +-
 fs/btrfs/inode.c       |  6 +++-
 fs/btrfs/super.c       | 12 +++++++-
 fs/btrfs/sysfs.c       |  1 +
 fs/btrfs/volumes.c     | 13 +++++++++
 10 files changed, 132 insertions(+), 28 deletions(-)

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 3ba6f3839d39..faf98571d746 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1985,6 +1985,51 @@ static int read_one_block_group(struct btrfs_fs_info *info,
 	return ret;
 }
 
+static int fill_dummy_bgs(struct btrfs_fs_info *fs_info)
+{
+	struct extent_map_tree *em_tree = &fs_info->mapping_tree;
+	struct extent_map *em;
+	struct map_lookup *map;
+	struct btrfs_block_group *bg;
+	struct btrfs_space_info *space_info;
+	struct rb_node *node;
+	int ret = 0;
+
+	for (node = rb_first_cached(&em_tree->map); node;
+	     node = rb_next(node)) {
+		em = rb_entry(node, struct extent_map, rb_node);
+		map = em->map_lookup;
+		bg = btrfs_create_block_group_cache(fs_info, em->start);
+		if (!bg) {
+			ret = -ENOMEM;
+			break;
+		}
+
+		/* Fill dummy cache as FULL */
+		bg->length = em->len;
+		bg->flags = map->type;
+		bg->last_byte_to_unpin = (u64)-1;
+		bg->cached = BTRFS_CACHE_FINISHED;
+		bg->used = em->len;
+		bg->flags = map->type;
+		ret = btrfs_add_block_group_cache(fs_info, bg);
+		if (ret) {
+			btrfs_remove_free_space_cache(bg);
+			btrfs_put_block_group(bg);
+			break;
+		}
+		btrfs_update_space_info(fs_info, bg->flags, em->len, em->len,
+					0, &space_info);
+		bg->space_info = space_info;
+		link_block_group(bg);
+
+		set_avail_alloc_bits(fs_info, bg->flags);
+	}
+	if (!ret)
+		btrfs_init_global_block_rsv(fs_info);
+	return ret;
+}
+
 int btrfs_read_block_groups(struct btrfs_fs_info *info)
 {
 	struct btrfs_path *path;
@@ -1995,6 +2040,9 @@ int btrfs_read_block_groups(struct btrfs_fs_info *info)
 	int need_clear = 0;
 	u64 cache_gen;
 
+	if (!info->extent_root)
+		return fill_dummy_bgs(info);
+
 	key.objectid = 0;
 	key.offset = 0;
 	key.type = BTRFS_BLOCK_GROUP_ITEM_KEY;
diff --git a/fs/btrfs/block-rsv.c b/fs/btrfs/block-rsv.c
index 7e1549a84fcc..58b38912498d 100644
--- a/fs/btrfs/block-rsv.c
+++ b/fs/btrfs/block-rsv.c
@@ -426,6 +426,14 @@ void btrfs_init_global_block_rsv(struct btrfs_fs_info *fs_info)
 	fs_info->delayed_block_rsv.space_info = space_info;
 	fs_info->delayed_refs_rsv.space_info = space_info;
 
+	/*
+	 * Our various recovery options can leave us with NULL roots, so check
+	 * here and just bail before we go deref'ing NULLS everywhere.
+	 */
+	if (!fs_info->extent_root || !fs_info->csum_root ||
+	    !fs_info->dev_root || !fs_info->chunk_root || !fs_info->tree_root)
+		return;
+
 	fs_info->extent_root->block_rsv = &fs_info->delayed_refs_rsv;
 	fs_info->csum_root->block_rsv = &fs_info->delayed_refs_rsv;
 	fs_info->dev_root->block_rsv = &fs_info->global_block_rsv;
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index 7e1eb57b923c..46dc621f599d 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -150,7 +150,8 @@ static int check_compressed_csum(struct btrfs_inode *inode, struct bio *bio,
 	struct compressed_bio *cb = bio->bi_private;
 	u8 *cb_sum = cb->sums;
 
-	if (inode->flags & BTRFS_INODE_NODATASUM)
+	if (!fs_info->csum_root ||
+	    inode->flags & BTRFS_INODE_NODATASUM)
 		return 0;
 
 	shash->tfm = fs_info->csum_shash;
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index aac3d6f4e35b..fb3cfd0aaf1e 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1295,6 +1295,7 @@ static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
 #define BTRFS_MOUNT_NOLOGREPLAY		(1 << 27)
 #define BTRFS_MOUNT_REF_VERIFY		(1 << 28)
 #define BTRFS_MOUNT_DISCARD_ASYNC	(1 << 29)
+#define BTRFS_MOUNT_IGNOREBADROOTS	(1 << 30)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
 #define BTRFS_DEFAULT_MAX_INLINE	(2048)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index c5d3e7f75066..82f125a77911 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2246,30 +2246,39 @@ static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
 
 	root = btrfs_read_tree_root(tree_root, &location);
 	if (IS_ERR(root)) {
-		ret = PTR_ERR(root);
-		goto out;
+		if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
+			ret = PTR_ERR(root);
+			goto out;
+		}
+	} else {
+		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+		fs_info->extent_root = root;
 	}
-	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
-	fs_info->extent_root = root;
 
 	location.objectid = BTRFS_DEV_TREE_OBJECTID;
 	root = btrfs_read_tree_root(tree_root, &location);
 	if (IS_ERR(root)) {
-		ret = PTR_ERR(root);
-		goto out;
+		if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
+			ret = PTR_ERR(root);
+			goto out;
+		}
+	} else {
+		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+		fs_info->dev_root = root;
+		btrfs_init_devices_late(fs_info);
 	}
-	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
-	fs_info->dev_root = root;
-	btrfs_init_devices_late(fs_info);
 
 	location.objectid = BTRFS_CSUM_TREE_OBJECTID;
 	root = btrfs_read_tree_root(tree_root, &location);
 	if (IS_ERR(root)) {
-		ret = PTR_ERR(root);
-		goto out;
+		if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
+			ret = PTR_ERR(root);
+			goto out;
+		}
+	} else {
+		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+		fs_info->csum_root = root;
 	}
-	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
-	fs_info->csum_root = root;
 
 	/*
 	 * This tree can share blocks with some other fs tree during relocation
@@ -2278,11 +2287,14 @@ static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
 	root = btrfs_get_fs_root(tree_root->fs_info,
 				 BTRFS_DATA_RELOC_TREE_OBJECTID, true);
 	if (IS_ERR(root)) {
-		ret = PTR_ERR(root);
-		goto out;
+		if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
+			ret = PTR_ERR(root);
+			goto out;
+		}
+	} else {
+		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+		fs_info->data_reloc_root = root;
 	}
-	set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
-	fs_info->data_reloc_root = root;
 
 	location.objectid = BTRFS_QUOTA_TREE_OBJECTID;
 	root = btrfs_read_tree_root(tree_root, &location);
@@ -2295,9 +2307,11 @@ static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
 	location.objectid = BTRFS_UUID_TREE_OBJECTID;
 	root = btrfs_read_tree_root(tree_root, &location);
 	if (IS_ERR(root)) {
-		ret = PTR_ERR(root);
-		if (ret != -ENOENT)
-			goto out;
+		if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
+			ret = PTR_ERR(root);
+			if (ret != -ENOENT)
+				goto out;
+		}
 	} else {
 		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
 		fs_info->uuid_root = root;
@@ -2307,11 +2321,14 @@ static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
 		location.objectid = BTRFS_FREE_SPACE_TREE_OBJECTID;
 		root = btrfs_read_tree_root(tree_root, &location);
 		if (IS_ERR(root)) {
-			ret = PTR_ERR(root);
-			goto out;
+			if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
+				ret = PTR_ERR(root);
+				goto out;
+			}
+		}  else {
+			set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+			fs_info->free_space_root = root;
 		}
-		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
-		fs_info->free_space_root = root;
 	}
 
 	return 0;
diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 8083d71d6af6..90c728652033 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -272,7 +272,8 @@ blk_status_t btrfs_lookup_bio_sums(struct inode *inode, struct bio *bio,
 	int count = 0;
 	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 
-	if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
+	if (!fs_info->csum_root ||
+	    BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
 		return BLK_STS_OK;
 
 	path = btrfs_alloc_path();
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index de69bef92c9a..b50a5f468b67 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2187,7 +2187,8 @@ blk_status_t btrfs_submit_data_bio(struct inode *inode, struct bio *bio,
 	int skip_sum;
 	int async = !atomic_read(&BTRFS_I(inode)->sync_writers);
 
-	skip_sum = BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM;
+	skip_sum = (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM) ||
+		!fs_info->csum_root;
 
 	if (btrfs_is_free_space_inode(BTRFS_I(inode)))
 		metadata = BTRFS_WQ_ENDIO_FREE_SPACE;
@@ -2844,6 +2845,9 @@ int btrfs_verify_data_csum(struct btrfs_io_bio *io_bio, u64 phy_offset,
 	if (BTRFS_I(inode)->flags & BTRFS_INODE_NODATASUM)
 		return 0;
 
+	if (!root->fs_info->csum_root)
+		return 0;
+
 	if (root->root_key.objectid == BTRFS_DATA_RELOC_TREE_OBJECTID &&
 	    test_range_bit(io_tree, start, end, EXTENT_NODATASUM, 1, NULL)) {
 		clear_extent_bits(io_tree, start, end, EXTENT_NODATASUM);
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index ca270649fe10..230caa4252b3 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -360,6 +360,7 @@ enum {
 	Opt_rescue,
 	Opt_usebackuproot,
 	Opt_nologreplay,
+	Opt_ignorebadroots,
 
 	/* Deprecated options */
 	Opt_recovery,
@@ -455,6 +456,8 @@ static const match_table_t tokens = {
 static const match_table_t rescue_tokens = {
 	{Opt_usebackuproot, "usebackuproot"},
 	{Opt_nologreplay, "nologreplay"},
+	{Opt_ignorebadroots, "ignorebadroots"},
+	{Opt_ignorebadroots, "ibadroots"},
 	{Opt_err, NULL},
 };
 
@@ -498,6 +501,10 @@ static int parse_rescue_options(struct btrfs_fs_info *info, const char *options)
 			btrfs_set_and_info(info, NOLOGREPLAY,
 					   "disabling log replay at mount time");
 			break;
+		case Opt_ignorebadroots:
+			btrfs_set_and_info(info, IGNOREBADROOTS,
+					   "ignoring bad roots");
+			break;
 		case Opt_err:
 			btrfs_info(info, "unrecognized rescue option '%s'", p);
 			ret = -EINVAL;
@@ -983,7 +990,8 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 	if (new_flags & SB_RDONLY)
 		goto out;
 
-	if (check_ro_option(info, BTRFS_MOUNT_NOLOGREPLAY, "nologreplay"))
+	if (check_ro_option(info, BTRFS_MOUNT_NOLOGREPLAY, "nologreplay") ||
+	    check_ro_option(info, BTRFS_MOUNT_IGNOREBADROOTS, "ignorebadroots"))
 		ret = -EINVAL;
 out:
 	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE) &&
@@ -1440,6 +1448,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		print_rescue_option(seq, "nologreplay", &printed);
 	if (btrfs_test_opt(info, USEBACKUPROOT))
 		print_rescue_option(seq, "usebackuproot", &printed);
+	if (btrfs_test_opt(info, IGNOREBADROOTS))
+		print_rescue_option(seq, "ignorebadroots", &printed);
 	if (btrfs_test_opt(info, FLUSHONCOMMIT))
 		seq_puts(seq, ",flushoncommit");
 	if (btrfs_test_opt(info, DISCARD_SYNC))
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 8f0462d6855d..e9f482989415 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -332,6 +332,7 @@ BTRFS_ATTR(static_feature, send_stream_version, send_stream_version_show);
 static const char *rescue_opts[] = {
 	"usebackuproot",
 	"nologreplay",
+	"ignorebadroots",
 };
 
 static ssize_t supported_rescue_options_show(struct kobject *kobj,
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index 58b9c419a2b6..1dc0b9425a28 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -7662,6 +7662,19 @@ int btrfs_verify_dev_extents(struct btrfs_fs_info *fs_info)
 	u64 prev_dev_ext_end = 0;
 	int ret = 0;
 
+	/*
+	 * We don't have a dev_root because we mounted with ignorebadroots and
+	 * failed to load the root, so we want to skip the verification in this
+	 * case for sure.
+	 *
+	 * However if the dev root is fine, but the tree itself is corrupt we'd
+	 * still fail to mount.  This verification is only to make sure writes
+	 * can happen safely, so instead just bypass this check completely in
+	 * the case of IGNOREBADROOTS.
+	 */
+	if (btrfs_test_opt(fs_info, IGNOREBADROOTS))
+		return 0;
+
 	key.objectid = 1;
 	key.type = BTRFS_DEV_EXTENT_KEY;
 	key.offset = 0;
-- 
2.26.2

[PATCH v4 7/8] btrfs: introduce rescue=ignoredatacsums

[Josef Bacik]

There are cases where you can end up with bad data csums because of
misbehaving applications.  This happens when an application modifies a
buffer in-flight when doing an O_DIRECT write.  In order to recover the
file we need a way to turn off data checksums so you can copy the file
off, and then you can delete the file and restore it properly later.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/ctree.h   |  1 +
 fs/btrfs/disk-io.c | 21 ++++++++++++---------
 fs/btrfs/super.c   | 14 +++++++++++++-
 fs/btrfs/sysfs.c   |  1 +
 4 files changed, 27 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index fb3cfd0aaf1e..397f5f6b88a4 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1296,6 +1296,7 @@ static inline u32 BTRFS_MAX_XATTR_SIZE(const struct btrfs_fs_info *info)
 #define BTRFS_MOUNT_REF_VERIFY		(1 << 28)
 #define BTRFS_MOUNT_DISCARD_ASYNC	(1 << 29)
 #define BTRFS_MOUNT_IGNOREBADROOTS	(1 << 30)
+#define BTRFS_MOUNT_IGNOREDATACSUMS	(1 << 31)
 
 #define BTRFS_DEFAULT_COMMIT_INTERVAL	(30)
 #define BTRFS_DEFAULT_MAX_INLINE	(2048)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 82f125a77911..504262e7c7d5 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2268,16 +2268,19 @@ static int btrfs_read_roots(struct btrfs_fs_info *fs_info)
 		btrfs_init_devices_late(fs_info);
 	}
 
-	location.objectid = BTRFS_CSUM_TREE_OBJECTID;
-	root = btrfs_read_tree_root(tree_root, &location);
-	if (IS_ERR(root)) {
-		if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
-			ret = PTR_ERR(root);
-			goto out;
+	/* If IGNOREDATASCUMS is set don't bother reading the csum root. */
+	if (!btrfs_test_opt(fs_info, IGNOREDATACSUMS)) {
+		location.objectid = BTRFS_CSUM_TREE_OBJECTID;
+		root = btrfs_read_tree_root(tree_root, &location);
+		if (IS_ERR(root)) {
+			if (!btrfs_test_opt(fs_info, IGNOREBADROOTS)) {
+				ret = PTR_ERR(root);
+				goto out;
+			}
+		} else {
+			set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
+			fs_info->csum_root = root;
 		}
-	} else {
-		set_bit(BTRFS_ROOT_TRACK_DIRTY, &root->state);
-		fs_info->csum_root = root;
 	}
 
 	/*
diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 230caa4252b3..83689e6659fc 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -361,6 +361,7 @@ enum {
 	Opt_usebackuproot,
 	Opt_nologreplay,
 	Opt_ignorebadroots,
+	Opt_ignoredatacsums,
 
 	/* Deprecated options */
 	Opt_recovery,
@@ -458,6 +459,8 @@ static const match_table_t rescue_tokens = {
 	{Opt_nologreplay, "nologreplay"},
 	{Opt_ignorebadroots, "ignorebadroots"},
 	{Opt_ignorebadroots, "ibadroots"},
+	{Opt_ignoredatacsums, "ignoredatacsums"},
+	{Opt_ignoredatacsums, "idatacsums"},
 	{Opt_err, NULL},
 };
 
@@ -505,6 +508,10 @@ static int parse_rescue_options(struct btrfs_fs_info *info, const char *options)
 			btrfs_set_and_info(info, IGNOREBADROOTS,
 					   "ignoring bad roots");
 			break;
+		case Opt_ignoredatacsums:
+			btrfs_set_and_info(info, IGNOREDATACSUMS,
+					   "ignoring data csums");
+			break;
 		case Opt_err:
 			btrfs_info(info, "unrecognized rescue option '%s'", p);
 			ret = -EINVAL;
@@ -991,7 +998,10 @@ int btrfs_parse_options(struct btrfs_fs_info *info, char *options,
 		goto out;
 
 	if (check_ro_option(info, BTRFS_MOUNT_NOLOGREPLAY, "nologreplay") ||
-	    check_ro_option(info, BTRFS_MOUNT_IGNOREBADROOTS, "ignorebadroots"))
+	    check_ro_option(info, BTRFS_MOUNT_IGNOREBADROOTS,
+			    "ignorebadroots") ||
+	    check_ro_option(info, BTRFS_MOUNT_IGNOREDATACSUMS,
+			    "ignoredatacsums"))
 		ret = -EINVAL;
 out:
 	if (btrfs_fs_compat_ro(info, FREE_SPACE_TREE) &&
@@ -1450,6 +1460,8 @@ static int btrfs_show_options(struct seq_file *seq, struct dentry *dentry)
 		print_rescue_option(seq, "usebackuproot", &printed);
 	if (btrfs_test_opt(info, IGNOREBADROOTS))
 		print_rescue_option(seq, "ignorebadroots", &printed);
+	if (btrfs_test_opt(info, IGNOREDATACSUMS))
+		print_rescue_option(seq, "ignoredatacsums", &printed);
 	if (btrfs_test_opt(info, FLUSHONCOMMIT))
 		seq_puts(seq, ",flushoncommit");
 	if (btrfs_test_opt(info, DISCARD_SYNC))
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index e9f482989415..86f70a60447b 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -333,6 +333,7 @@ static const char *rescue_opts[] = {
 	"usebackuproot",
 	"nologreplay",
 	"ignorebadroots",
+	"ignoredatacsums",
 };
 
 static ssize_t supported_rescue_options_show(struct kobject *kobj,
-- 
2.26.2

[PATCH v4 8/8] btrfs: introduce rescue=all

[Josef Bacik]

Now that we have the building blocks for some better recovery options
with corrupted file systems, add a rescue=all option to enable all of
the relevant rescue options.  This will allow distro's to simply default
to rescue=all for the "oh dear lord the world's on fire" recovery
without needing to know all the different options that we have and may
add in the future.

Reviewed-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/super.c | 11 +++++++++++
 fs/btrfs/sysfs.c |  1 +
 2 files changed, 12 insertions(+)

diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
index 83689e6659fc..bc28747cf7b3 100644
--- a/fs/btrfs/super.c
+++ b/fs/btrfs/super.c
@@ -362,6 +362,7 @@ enum {
 	Opt_nologreplay,
 	Opt_ignorebadroots,
 	Opt_ignoredatacsums,
+	Opt_all,
 
 	/* Deprecated options */
 	Opt_recovery,
@@ -461,6 +462,7 @@ static const match_table_t rescue_tokens = {
 	{Opt_ignorebadroots, "ibadroots"},
 	{Opt_ignoredatacsums, "ignoredatacsums"},
 	{Opt_ignoredatacsums, "idatacsums"},
+	{Opt_all, "all"},
 	{Opt_err, NULL},
 };
 
@@ -512,6 +514,15 @@ static int parse_rescue_options(struct btrfs_fs_info *info, const char *options)
 			btrfs_set_and_info(info, IGNOREDATACSUMS,
 					   "ignoring data csums");
 			break;
+		case Opt_all:
+			btrfs_info(info, "enabling all of the rescue options");
+			btrfs_set_and_info(info, IGNOREDATACSUMS,
+					   "ignoring data csums");
+			btrfs_set_and_info(info, IGNOREBADROOTS,
+					   "ignoring bad roots");
+			btrfs_set_and_info(info, NOLOGREPLAY,
+					   "disabling log replay at mount time");
+			break;
 		case Opt_err:
 			btrfs_info(info, "unrecognized rescue option '%s'", p);
 			ret = -EINVAL;
diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
index 86f70a60447b..fcd6c7a9bbd1 100644
--- a/fs/btrfs/sysfs.c
+++ b/fs/btrfs/sysfs.c
@@ -334,6 +334,7 @@ static const char *rescue_opts[] = {
 	"nologreplay",
 	"ignorebadroots",
 	"ignoredatacsums",
+	"all",
 };
 
 static ssize_t supported_rescue_options_show(struct kobject *kobj,
-- 
2.26.2

Re: [PATCH v4 8/8] btrfs: introduce rescue=all

[David Sterba]

On Fri, Oct 16, 2020 at 11:29:20AM -0400, Josef Bacik wrote:
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -362,6 +362,7 @@ enum {
>  	Opt_nologreplay,
>  	Opt_ignorebadroots,
>  	Opt_ignoredatacsums,
> +	Opt_all,
>  
>  	/* Deprecated options */
>  	Opt_recovery,
> @@ -461,6 +462,7 @@ static const match_table_t rescue_tokens = {
>  	{Opt_ignorebadroots, "ibadroots"},
>  	{Opt_ignoredatacsums, "ignoredatacsums"},
>  	{Opt_ignoredatacsums, "idatacsums"},
> +	{Opt_all, "all"},

The way the sysfs supported_rescue_options works right now it also
prints 'all':

  # cat supported_rescue_options
  usebackuproot nologreplay ignorebadroots ignoredatacsums all

It's not wrong just that I did not expect to see it there, let's keep it.