A soft lockup in ilookup was reported when stress-testing a 512-way system [1] (see [2] for full context) and it was verified that not taking the lock shifts issues back to mm. [1] https://lore.kernel.org/linux-mm/56865e57-c250-44da-9713-cf1404595bcc@xxxxxxx/ [2] https://lore.kernel.org/linux-mm/d2841226-e27b-4d3d-a578-63587a3aa4f3@xxxxxxx/ Signed-off-by: Mateusz Guzik <mjguzik@xxxxxxxxx> --- fwiw the originally sent patch to the reporter performs a lockless lookup first and falls back to the locked variant, but that was me playing overfly safe. I would add tested-by but patches are not the same in the end. This is the only spot which can get this fixup, everything else taking the lock is also using custom callbacks, so filesystems invoking such code will need to get patched up on case-by-case basis (but realistically they probably already can do RCU-only operation). fs/inode.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/fs/inode.c b/fs/inode.c index f356fe2ec2b6..52ca063c552c 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -1525,9 +1525,7 @@ struct inode *ilookup(struct super_block *sb, unsigned long ino) struct hlist_head *head = inode_hashtable + hash(sb, ino); struct inode *inode; again: - spin_lock(&inode_hash_lock); - inode = find_inode_fast(sb, head, ino, true); - spin_unlock(&inode_hash_lock); + inode = find_inode_fast(sb, head, ino, false); if (inode) { if (IS_ERR(inode)) -- 2.43.0
