[Devel] [PATCH VZ10] fs/fuse: remove the WARN_ON_ONCE() in fuse_revoke_readpages()

[Liu Kui]

A revoked page-cache read stays on ff->revoke_list until it completes.
It's possible and legitimate that a second invalidation of the same
inode is issued before a reply to the revoked read by userspace, so
so drop the bogus WARN_ON_ONCE() and just skip it.

https://virtuozzo.atlassian.net/browse/VSTOR-136315

Signed-off-by: Liu Kui <kui.liu at virtuozzo.com>
---
 fs/fuse/file.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index e804e3c0d6bd..17f1a21b0445 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1225,11 +1225,15 @@ void fuse_revoke_readpages(struct fuse_file *ff)
 	spin_lock(&ff->lock);
 	/* revoke all pending read issued from page cache */
 	list_for_each_entry(ia, &ff->revoke_list, revoke_entry) {
-		/* this should never happen unless userspace misbehaves */
-		if (unlikely(ia->ap.args.killed)) {
-			WARN_ON_ONCE(1);
+		/*
+		 * Already revoked by a previous invalidation and not yet completed,
+		 * its pages are already unlocked and its completion callback will
+		 * remove it from the list. This is a normal condition when the same
+		 * inode is invalidated more than once while a read is still outstanding,
+		 * so just skip it.
+		 */
+		if (ia->ap.args.killed)
 			continue;
-		}
 		ia->ap.args.killed = 1;
 		for (i = 0; i < ia->ap.num_pages; i++)
 			unlock_page(ia->ap.pages[i]);
-- 
2.50.1 (Apple Git-155)