Fix zvol+btrfs hang #1083
Closed
Fix zvol+btrfs hang #1083
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
When using a zvol to back a btrfs filesystem the btrfs mount would hang. This was due to the bio completion callback used in btrfs assuming that lower level drivers would never modify the bio->bi_io_vecs after they were submitted via bio_submit(). If they are modified btrfs will miscalculate which pages need to be unlocked resulting in a hang. It's worth mentioning that other file systems such as ext[234] and xfs work fine because they do not make the same assumption in the bio completion callback. The most straight forward way to fix the issue is to present the semantics expected by btrfs. This is done by cloning the bios attached to each request and then using the clones bvecs to perform the required accounting. The clones are freed after each read/write and the original unmodified bios are linked back in to the request. Signed-off-by: Brian Behlendorf <[email protected]> Issue openzfs#469
|
Merged as commit e26ade5 |
pcd1193182
pushed a commit
to pcd1193182/zfs
that referenced
this pull request
Sep 26, 2023
merge with 'zdb: include cloned blocks in block statistics'
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
When using a zvol to back a btrfs filesystem the btrfs mount
would hang. This was due to the bio completion callback used
in btrfs assuming that lower level drivers would never modify
the bio->bi_io_vecs after they were submitted via bio_submit().
If they are modified btrfs will miscalculate which pages need
to be unlocked resulting in a hang.
It's worth mentioning that other file systems such as ext[234]
and xfs work fine because they do not make the same assumption
in the bio completion callback.
The most straight forward way to fix the issue is to present
the semantics expected by btrfs. This is done by cloning the
bios attached to each request and then using the clones bvecs
to perform the required accounting. The clones are freed after
each read/write and the original unmodified bios are linked back
in to the request.
Signed-off-by: Brian Behlendorf [email protected]
Issue #469