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md/raid5: protect big_stripe_tree lookup with RCU

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big_stripe_tree is updated under tree_lock, and deleted radix-tree
nodes are freed after an RCU grace period.  r5c_big_stripe_cached()
used to run under an RCU read-side critical section, but that protection
was removed together with unrelated rdev lookup protection.

The lookup can now be preempted while walking the tree, allowing a
concurrent deletion and grace period to complete before the walk
resumes.  Protect the lookup locally with rcu_read_lock().  Only the
presence of the entry is used after unlocking.

Fixes: ad8606702f ("md/raid5: remove rcu protection to access rdev from conf")
Assisted-by: LLM
Signed-off-by: Sang-Hoon Choi <csh0052@gmail.com>
Link: https://patch.msgid.link/179070265341.12871.12495446593114993799.idr-bug-88@gmail.com
Signed-off-by: Yu Kuai <yukuai@fygo.io>
This commit is contained in:
Sang-Hoon Choi 2026-09-30 02:37:38 +09:00 committed by Yu Kuai
parent af560e357a
commit 73b0df9294
1 changed files with 2 additions and 0 deletions
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2
drivers/md/raid5-cache.c
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@ -2968,7 +2968,9 @@ bool r5c_big_stripe_cached(struct r5conf *conf, sector_t sect)
return false;
tree_index = r5c_tree_index(conf, sect);
rcu_read_lock();
slot = radix_tree_lookup(&log->big_stripe_tree, tree_index);
rcu_read_unlock();
return slot != NULL;
}