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| author |  Filipe Manana <fdmanana@suse.com>
| 2023-10-04 11:38:48 +0100 |
|---|---|---|
| committer |  David Sterba <dsterba@suse.com>
| 2023-10-12 16:44:17 +0200 |
| commit | f9850787969953552266da579d0f1fbf2c2e1c10 (patch) | |
| tree | 1ba9afba0fd05be401ac6bcd4e9bd4b99dfd3c31 /fs/btrfs/ctree.h | |
| parent | btrfs: support cloned-device mount capability (diff) | |
| download | linux-f9850787969953552266da579d0f1fbf2c2e1c10.tar.gz linux-f9850787969953552266da579d0f1fbf2c2e1c10.tar.bz2 linux-f9850787969953552266da579d0f1fbf2c2e1c10.zip | |
btrfs: add and use helpers for reading and writing last_log_commit
Currently, the last_log_commit of a root can be accessed concurrently
without any lock protection. Readers can be calling btrfs_inode_in_log()
early in a fsync call, which reads a root's last_log_commit, while a
writer can change the last_log_commit while a log tree if being synced,
at btrfs_sync_log(). Any races here should be harmless, and in the worst
case they may cause a fsync to log an inode when it's not really needed,
so nothing bad from a functional perspective.
To avoid data race warnings from tools like KCSAN and other issues such
as load and store tearing (amongst others, see [1]), create helpers to
access the last_log_commit field of a root using READ_ONCE() and
WRITE_ONCE(), and use these helpers everywhere.
[1] https://lwn.net/Articles/793253/
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/ctree.h')
| -rw-r--r-- | fs/btrfs/ctree.h | 16 |
1 files changed, 15 insertions, 1 deletions
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 208a1888ca07..3ebb5229660a 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -194,7 +194,11 @@ struct btrfs_root { int log_transid; /* No matter the commit succeeds or not*/ int log_transid_committed; - /* Just be updated when the commit succeeds. */ + /* + * Just be updated when the commit succeeds. Use + * btrfs_get_root_last_log_commit() and btrfs_set_root_last_log_commit() + * to access this field. + */ int last_log_commit; pid_t log_start_pid; @@ -328,6 +332,16 @@ static inline u64 btrfs_root_id(const struct btrfs_root *root) return root->root_key.objectid; } +static inline int btrfs_get_root_last_log_commit(const struct btrfs_root *root) +{ + return READ_ONCE(root->last_log_commit); +} + +static inline void btrfs_set_root_last_log_commit(struct btrfs_root *root, int commit_id) +{ + WRITE_ONCE(root->last_log_commit, commit_id); +} + /* * Structure that conveys information about an extent that is going to replace * all the extents in a file range. |