3.16.57-rc1 review patch. If anyone has any objections, please let me know.
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From: Yufen Yu yuyufen@huawei.com
commit 01a69cab01c184d3786af09e9339311123d63d22 upstream.
In the case of 'recover', an r10bio with R10BIO_WriteError & R10BIO_IsRecover will be progressed by handle_write_completed(). This function traverses all r10bio->devs[copies]. If devs[m].repl_bio != NULL, it thinks conf->mirrors[dev].replacement is also not NULL. However, this is not always true.
When there is an rdev of raid10 has replacement, then each r10bio ->devs[m].repl_bio != NULL in conf->r10buf_pool. However, in 'recover', even if corresponded replacement is NULL, it doesn't clear r10bio ->devs[m].repl_bio, resulting in replacement NULL deference.
This bug was introduced when replacement support for raid10 was added in Linux 3.3.
As NeilBrown suggested: Elsewhere the determination of "is this device part of the resync/recovery" is made by resting bio->bi_end_io. If this is end_sync_write, then we tried to write here. If it is NULL, then we didn't try to write.
Fixes: 9ad1aefc8ae8 ("md/raid10: Handle replacement devices during resync.") Cc: stable (V3.3+) Suggested-by: NeilBrown neilb@suse.com Signed-off-by: Yufen Yu yuyufen@huawei.com Signed-off-by: Shaohua Li sh.li@alibaba-inc.com Signed-off-by: Ben Hutchings ben@decadent.org.uk --- drivers/md/raid10.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -2746,7 +2746,8 @@ static void handle_write_completed(struc for (m = 0; m < conf->copies; m++) { int dev = r10_bio->devs[m].devnum; rdev = conf->mirrors[dev].rdev; - if (r10_bio->devs[m].bio == NULL) + if (r10_bio->devs[m].bio == NULL || + r10_bio->devs[m].bio->bi_end_io == NULL) continue; if (test_bit(BIO_UPTODATE, &r10_bio->devs[m].bio->bi_flags)) { @@ -2762,7 +2763,8 @@ static void handle_write_completed(struc md_error(conf->mddev, rdev); } rdev = conf->mirrors[dev].replacement; - if (r10_bio->devs[m].repl_bio == NULL) + if (r10_bio->devs[m].repl_bio == NULL || + r10_bio->devs[m].repl_bio->bi_end_io == NULL) continue; if (test_bit(BIO_UPTODATE, &r10_bio->devs[m].repl_bio->bi_flags)) {