[PATCH 2/4] netfs: handle single writeback rolling buffer allocation failure

[David Howells]

From: Yichong Chen <chenyichong@xxxxxxxxxxxxx>

netfs_write_folio_single() takes an extra folio reference before
appending the folio to the rolling buffer.

rolling_buffer_append() can fail if it cannot allocate another
folio_queue. Check the return value and drop the extra folio reference
before returning the error.

Fixes: 49866ce7ea8d ("netfs: Add support for caching single monolithic objects such as AFS dirs")
Signed-off-by: Yichong Chen <chenyichong@xxxxxxxxxxxxx>
Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: Paulo Alcantara <pc@xxxxxxxxxxxxx>
cc: netfs@xxxxxxxxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
---
 fs/netfs/write_issue.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/fs/netfs/write_issue.c b/fs/netfs/write_issue.c
index f2761c99795a..14efe4cb9393 100644
--- a/fs/netfs/write_issue.c
+++ b/fs/netfs/write_issue.c
@@ -720,6 +720,7 @@ static int netfs_write_folio_single(struct netfs_io_request *wreq,
 	size_t iter_off = 0;
 	size_t fsize = folio_size(folio), flen;
 	loff_t fpos = folio_pos(folio);
+	ssize_t ret;
 	bool to_eof = false;
 	bool no_debug = false;
 
@@ -748,7 +749,11 @@ static int netfs_write_folio_single(struct netfs_io_request *wreq,
 
 	/* Attach the folio to the rolling buffer. */
 	folio_get(folio);
-	rolling_buffer_append(&wreq->buffer, folio, NETFS_ROLLBUF_PUT_MARK);
+	ret = rolling_buffer_append(&wreq->buffer, folio, NETFS_ROLLBUF_PUT_MARK);
+	if (ret < 0) {
+		folio_put(folio);
+		return ret;
+	}
 
 	/* Move the submission point forward to allow for write-streaming data
 	 * not starting at the front of the page.  We don't do write-streaming