[PATCH v4 04/11] md/raid5: Ensure array is suspended for calls to log_exit()
From: Logan Gunthorpe <logang@deltatee.com>
Date: 2022-06-08 16:29:16
Also in:
lkml
Subsystem:
software raid (multiple disks) support, the rest · Maintainers:
Song Liu, Yu Kuai, Linus Torvalds
The raid5-cache code relies on there being no IO in flight when log_exit() is called. There are two places where this is not guaranteed so add mddev_suspend() and mddev_resume() calls to these sites. The site in raid5_remove_disk() has a comment saying that it is called in raid5d and thus cannot wait for pending writes; however that does not appear to be correct anymore (if it ever was) as raid5_remove_disk() is called from hot_remove_disk() which only appears to be called in the md_ioctl(). Thus, the comment is removed, as well as the racy check and replaced with calls to suspend/resume. The site in raid5_change_consistency_policy() is in the error path, and another similar call site already has suspend/resume calls just below it; so it should be equally safe to make that change here. Signed-off-by: Logan Gunthorpe <logang@deltatee.com> Reviewed-by: Christoph Hellwig <hch@lst.de> --- drivers/md/raid5.c | 18 ++++++------------ 1 file changed, 6 insertions(+), 12 deletions(-)
diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index 5d09256d7f81..3ad37dd4c5cd 100644
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c@@ -7938,18 +7938,9 @@ static int raid5_remove_disk(struct mddev *mddev, struct md_rdev *rdev) print_raid5_conf(conf); if (test_bit(Journal, &rdev->flags) && conf->log) { - /* - * we can't wait pending write here, as this is called in - * raid5d, wait will deadlock. - * neilb: there is no locking about new writes here, - * so this cannot be safe. - */ - if (atomic_read(&conf->active_stripes) || - atomic_read(&conf->r5c_cached_full_stripes) || - atomic_read(&conf->r5c_cached_partial_stripes)) { - return -EBUSY; - } + mddev_suspend(mddev); log_exit(conf); + mddev_resume(mddev); return 0; } if (rdev == rcu_access_pointer(p->rdev))
@@ -8697,8 +8688,11 @@ static int raid5_change_consistency_policy(struct mddev *mddev, const char *buf) err = log_init(conf, NULL, true); if (!err) { err = resize_stripes(conf, conf->pool_size); - if (err) + if (err) { + mddev_suspend(mddev); log_exit(conf); + mddev_resume(mddev); + } } } else err = -EINVAL;
--
2.30.2