pipe: wakeup wr_wait after setting max_usage

[ Upstream commit e95aada4cb93d42e25c30a0ef9eb2923d9711d4a ]

Commit c73be61cede5 ("pipe: Add general notification queue support") a
regression was introduced that would lock up resized pipes under certain
conditions. See the reproducer in [1].

The commit resizing the pipe ring size was moved to a different
function, doing that moved the wakeup for pipe->wr_wait before actually
raising pipe->max_usage. If a pipe was full before the resize occured it
would result in the wakeup never actually triggering pipe_write.

Set @max_usage and @nr_accounted before waking writers if this isn't a
watch queue.

Link: https://bugzilla.kernel.org/show_bug.cgi?id=212295
Link: https://lore.kernel.org/r/20231201-orchideen-modewelt-e009de4562c6@brauner
Fixes: c73be61cede5 ("pipe: Add general notification queue support")
Reviewed-by: David Howells <dhowells@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Lukas Schauer <lukas@schauer.dev>
[Christian Brauner <brauner@kernel.org>: rewrite to account for watch queues]
Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/pipe.c b/fs/pipe.c
index 603ab19..a234035 100644 (file)
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -1305,6 +1305,11 @@ int pipe_resize_ring(struct pipe_inode_info *pipe, unsigned int nr_slots)
        pipe->tail = tail;
        pipe->head = head;
 
+       if (!pipe_has_watch_queue(pipe)) {
+               pipe->max_usage = nr_slots;
+               pipe->nr_accounted = nr_slots;
+       }
+
        spin_unlock_irq(&pipe->rd_wait.lock);
 
        /* This might have made more room for writers */
@@ -1356,8 +1361,6 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned int arg)
        if (ret < 0)
                goto out_revert_acct;
 
-       pipe->max_usage = nr_slots;
-       pipe->nr_accounted = nr_slots;
        return pipe->max_usage * PAGE_SIZE;
 
 out_revert_acct: