diff options
| author | Filipe Manana <fdmanana@suse.com> | 2024-07-01 11:51:28 +0200 |
|---|---|---|
| committer | David Sterba <dsterba@suse.com> | 2024-07-11 15:52:25 +0200 |
| commit | ca84529a842f3a15a5f17beac6252aa11955923f (patch) | |
| tree | 6eb1e32366165c310442dfeb25b39ac0067210cd /fs/btrfs/ctree.h | |
| parent | btrfs: rename the extra_gfp parameter of btrfs_alloc_page_array() (diff) | |
| download | linux-ca84529a842f3a15a5f17beac6252aa11955923f.tar.xz linux-ca84529a842f3a15a5f17beac6252aa11955923f.zip | |
btrfs: fix data race when accessing the last_trans field of a root
KCSAN complains about a data race when accessing the last_trans field of a
root:
[ 199.553628] BUG: KCSAN: data-race in btrfs_record_root_in_trans [btrfs] / record_root_in_trans [btrfs]
[ 199.555186] read to 0x000000008801e308 of 8 bytes by task 2812 on cpu 1:
[ 199.555210] btrfs_record_root_in_trans+0x9a/0x128 [btrfs]
[ 199.555999] start_transaction+0x154/0xcd8 [btrfs]
[ 199.556780] btrfs_join_transaction+0x44/0x60 [btrfs]
[ 199.557559] btrfs_dirty_inode+0x9c/0x140 [btrfs]
[ 199.558339] btrfs_update_time+0x8c/0xb0 [btrfs]
[ 199.559123] touch_atime+0x16c/0x1e0
[ 199.559151] pipe_read+0x6a8/0x7d0
[ 199.559179] vfs_read+0x466/0x498
[ 199.559204] ksys_read+0x108/0x150
[ 199.559230] __s390x_sys_read+0x68/0x88
[ 199.559257] do_syscall+0x1c6/0x210
[ 199.559286] __do_syscall+0xc8/0xf0
[ 199.559318] system_call+0x70/0x98
[ 199.559431] write to 0x000000008801e308 of 8 bytes by task 2808 on cpu 0:
[ 199.559464] record_root_in_trans+0x196/0x228 [btrfs]
[ 199.560236] btrfs_record_root_in_trans+0xfe/0x128 [btrfs]
[ 199.561097] start_transaction+0x154/0xcd8 [btrfs]
[ 199.561927] btrfs_join_transaction+0x44/0x60 [btrfs]
[ 199.562700] btrfs_dirty_inode+0x9c/0x140 [btrfs]
[ 199.563493] btrfs_update_time+0x8c/0xb0 [btrfs]
[ 199.564277] file_update_time+0xb8/0xf0
[ 199.564301] pipe_write+0x8ac/0xab8
[ 199.564326] vfs_write+0x33c/0x588
[ 199.564349] ksys_write+0x108/0x150
[ 199.564372] __s390x_sys_write+0x68/0x88
[ 199.564397] do_syscall+0x1c6/0x210
[ 199.564424] __do_syscall+0xc8/0xf0
[ 199.564452] system_call+0x70/0x98
This is because we update and read last_trans concurrently without any
type of synchronization. This should be generally harmless and in the
worst case it can make us do extra locking (btrfs_record_root_in_trans())
trigger some warnings at ctree.c or do extra work during relocation - this
would probably only happen in case of load or store tearing.
So fix this by always reading and updating the field using READ_ONCE()
and WRITE_ONCE(), this silences KCSAN and prevents load and store tearing.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs/btrfs/ctree.h')
| -rw-r--r-- | fs/btrfs/ctree.h | 10 |
1 files changed, 10 insertions, 0 deletions
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 1004cb934b4a..c8568b1a61c4 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -356,6 +356,16 @@ static inline void btrfs_set_root_last_log_commit(struct btrfs_root *root, int c WRITE_ONCE(root->last_log_commit, commit_id); } +static inline u64 btrfs_get_root_last_trans(const struct btrfs_root *root) +{ + return READ_ONCE(root->last_trans); +} + +static inline void btrfs_set_root_last_trans(struct btrfs_root *root, u64 transid) +{ + WRITE_ONCE(root->last_trans, transid); +} + /* * Structure that conveys information about an extent that is going to replace * all the extents in a file range. |