diff options
| author | Chen Cheng <chencheng@fnnas.com> | 2026-06-19 12:41:14 +0800 |
|---|---|---|
| committer | Yu Kuai <yukuai@fygo.io> | 2026-06-21 04:44:42 +0800 |
| commit | 601d3c21b2e26b676cc67ae8804e991bbbcd4507 (patch) | |
| tree | 90f8161d850557aa1f2d097711ccb0241b281b03 /drivers | |
| parent | 69ad6ce47f9bf2b9fe0ed69b042db993d33bbf12 (diff) | |
md/raid1: protect head_position for read balance
KCSAN reports a data race between raid1_end_read_request() and
raid1_read_request().
The completion path updates conf->mirrors[disk].head_position in
update_head_pos() without a lock, while the read-balance heuristic reads
the same field locklessly in is_sequential() and choose_best_rdev().
KCSAN report:
=========================
BUG: KCSAN: data-race in raid1_end_read_request / raid1_read_request
write to 0xffff8f0306ba7868 of 8 bytes by interrupt on cpu 9:
raid1_end_read_request+0xb5/0x440
bio_endio+0x3c9/0x3e0
blk_update_request+0x257/0x770
scsi_end_request+0x4d/0x520
scsi_io_completion+0x6f/0x990
scsi_finish_command+0x188/0x280
scsi_complete+0xac/0x160
blk_complete_reqs+0x8e/0xb0
blk_done_softirq+0x1d/0x30
[...]
read to 0xffff8f0306ba7868 of 8 bytes by task 667002 on cpu 11:
raid1_read_request+0x497/0x1a10
raid1_make_request+0xdf/0x1950
md_handle_request+0x2c5/0x700
md_submit_bio+0x126/0x320
__submit_bio+0x2ec/0x3a0
submit_bio_noacct_nocheck+0x572/0x890
[...]
value changed: 0x0000000000000078 -> 0x00000000005fe448
Signed-off-by: Chen Cheng <chencheng@fnnas.com>
Link: https://patch.msgid.link/20260619044114.1208456-1-chencheng@fnnas.com
Signed-off-by: Yu Kuai <yukuai@fygo.io>
Diffstat (limited to 'drivers')
| -rw-r--r-- | drivers/md/raid1.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index 41d9094fa50a..afe2ca96ad8c 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -359,8 +359,8 @@ static inline void update_head_pos(int disk, struct r1bio *r1_bio) { struct r1conf *conf = r1_bio->mddev->private; - conf->mirrors[disk].head_position = - r1_bio->sector + (r1_bio->sectors); + WRITE_ONCE(conf->mirrors[disk].head_position, + r1_bio->sector + r1_bio->sectors); } /* @@ -737,7 +737,7 @@ static bool is_sequential(struct r1conf *conf, int disk, struct r1bio *r1_bio) { /* TODO: address issues with this check and concurrency. */ return conf->mirrors[disk].next_seq_sect == r1_bio->sector || - conf->mirrors[disk].head_position == r1_bio->sector; + READ_ONCE(conf->mirrors[disk].head_position) == r1_bio->sector; } /* @@ -814,7 +814,8 @@ static int choose_best_rdev(struct r1conf *conf, struct r1bio *r1_bio) set_bit(R1BIO_FailFast, &r1_bio->state); pending = atomic_read(&rdev->nr_pending); - dist = abs(r1_bio->sector - conf->mirrors[disk].head_position); + dist = abs(r1_bio->sector - + READ_ONCE(conf->mirrors[disk].head_position)); /* Don't change to another disk for sequential reads */ if (is_sequential(conf, disk, r1_bio)) { |