Re: [PATCH] futex: Remove unnecessary warning from get_futex_key

[Davidlohr Bueso]

On Wed, 09 Aug 2017, Mel Gorman wrote:

> @@ -676,7 +676,7 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
> 		 * cases, therefore a successful atomic_inc return below will
> 		 * guarantee that get_futex_key() will still imply smp_mb(); (B).

You missed the comment above.

diff --git a/kernel/futex.c b/kernel/futex.c
index 16dbe4c93895..6b4a6a7cad3d 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -670,13 +670,14 @@ get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key, int rw)
		 * this reference was taken by ihold under the page lock
		 * pinning the inode in place so i_lock was unnecessary. The
		 * only way for this check to fail is if the inode was
-		 * truncated in parallel so warn for now if this happens.
+		 * truncated in parallel -- which is a bizarre scenario, in
+		 * any case, just retry.
		 *
		 * We are not calling into get_futex_key_refs() in file-backed
		 * cases, therefore a successful atomic_inc return below will
		 * guarantee that get_futex_key() will still imply smp_mb(); (B).
		 */
-		if (WARN_ON_ONCE(!atomic_inc_not_zero(&inode->i_count))) {
+		if (!atomic_inc_not_zero(&inode->i_count)) {
			rcu_read_unlock();
			put_page(page);


Thanks,
Davidlohr