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| author | Filipe Manana <fdmanana@suse.com> | 2024-07-08 15:42:45 +0100 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2024-07-11 16:50:54 +0200 |
| commit | 4484940514295b75389f94787f8e179ba6255353 (patch) | |
| tree | 68de671f64cdfaa2309c83e3d76e358acaa481b9 /include | |
| parent | b3ebb9b7e92a928344a7a2c1f8514474bfa113cf (diff) | |
| download | lwn-4484940514295b75389f94787f8e179ba6255353.tar.gz lwn-4484940514295b75389f94787f8e179ba6255353.zip | |
btrfs: avoid races when tracking progress for extent map shrinking
We store the progress (root and inode numbers) of the extent map shrinker
in fs_info without any synchronization but we can have multiple tasks
calling into the shrinker during memory allocations when there's enough
memory pressure for example.
This can result in a task A reading fs_info->extent_map_shrinker_last_ino
after another task B updates it, and task A reading
fs_info->extent_map_shrinker_last_root before task B updates it, making
task A see an odd state that isn't necessarily harmful but may make it
skip certain inode ranges or do more work than necessary by going over
the same inodes again. These unprotected accesses would also trigger
warnings from tools like KCSAN.
So add a lock to protect access to these progress fields.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
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 'include')
| -rw-r--r-- | include/trace/events/btrfs.h | 18 |
1 files changed, 10 insertions, 8 deletions
diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h index d2d94d7c3fb5..0067e8443d38 100644 --- a/include/trace/events/btrfs.h +++ b/include/trace/events/btrfs.h @@ -2556,9 +2556,10 @@ TRACE_EVENT(btrfs_extent_map_shrinker_count, TRACE_EVENT(btrfs_extent_map_shrinker_scan_enter, - TP_PROTO(const struct btrfs_fs_info *fs_info, long nr_to_scan, long nr), + TP_PROTO(const struct btrfs_fs_info *fs_info, long nr_to_scan, long nr, + u64 last_root_id, u64 last_ino), - TP_ARGS(fs_info, nr_to_scan, nr), + TP_ARGS(fs_info, nr_to_scan, nr, last_root_id, last_ino), TP_STRUCT__entry_btrfs( __field( long, nr_to_scan ) @@ -2570,8 +2571,8 @@ TRACE_EVENT(btrfs_extent_map_shrinker_scan_enter, TP_fast_assign_btrfs(fs_info, __entry->nr_to_scan = nr_to_scan; __entry->nr = nr; - __entry->last_root_id = fs_info->extent_map_shrinker_last_root; - __entry->last_ino = fs_info->extent_map_shrinker_last_ino; + __entry->last_root_id = last_root_id; + __entry->last_ino = last_ino; ), TP_printk_btrfs("nr_to_scan=%ld nr=%ld last_root=%llu(%s) last_ino=%llu", @@ -2581,9 +2582,10 @@ TRACE_EVENT(btrfs_extent_map_shrinker_scan_enter, TRACE_EVENT(btrfs_extent_map_shrinker_scan_exit, - TP_PROTO(const struct btrfs_fs_info *fs_info, long nr_dropped, long nr), + TP_PROTO(const struct btrfs_fs_info *fs_info, long nr_dropped, long nr, + u64 last_root_id, u64 last_ino), - TP_ARGS(fs_info, nr_dropped, nr), + TP_ARGS(fs_info, nr_dropped, nr, last_root_id, last_ino), TP_STRUCT__entry_btrfs( __field( long, nr_dropped ) @@ -2595,8 +2597,8 @@ TRACE_EVENT(btrfs_extent_map_shrinker_scan_exit, TP_fast_assign_btrfs(fs_info, __entry->nr_dropped = nr_dropped; __entry->nr = nr; - __entry->last_root_id = fs_info->extent_map_shrinker_last_root; - __entry->last_ino = fs_info->extent_map_shrinker_last_ino; + __entry->last_root_id = last_root_id; + __entry->last_ino = last_ino; ), TP_printk_btrfs("nr_dropped=%ld nr=%ld last_root=%llu(%s) last_ino=%llu", |