mm: never attempt async page lock if we've transferred data already
We catch the case where we enter generic_file_buffered_read() with data
already transferred, but we also need to be careful not to allow an async
page lock if we're looping transferring data. If not, we could be
returning -EIOCBQUEUED instead of the transferred amount, and it could
result in double waitqueue additions as well.
Cc: stable@vger.kernel.org # v5.9
Fixes: 1a0a7853b901 ("mm: support async buffered reads in generic_file_buffered_read()")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/mm/filemap.c b/mm/filemap.c
index d5e7c20..3ebbe64 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2347,10 +2347,15 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
page_not_up_to_date:
/* Get exclusive access to the page ... */
- if (iocb->ki_flags & IOCB_WAITQ)
+ if (iocb->ki_flags & IOCB_WAITQ) {
+ if (written) {
+ put_page(page);
+ goto out;
+ }
error = lock_page_async(page, iocb->ki_waitq);
- else
+ } else {
error = lock_page_killable(page);
+ }
if (unlikely(error))
goto readpage_error;
@@ -2393,10 +2398,15 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb,
}
if (!PageUptodate(page)) {
- if (iocb->ki_flags & IOCB_WAITQ)
+ if (iocb->ki_flags & IOCB_WAITQ) {
+ if (written) {
+ put_page(page);
+ goto out;
+ }
error = lock_page_async(page, iocb->ki_waitq);
- else
+ } else {
error = lock_page_killable(page);
+ }
if (unlikely(error))
goto readpage_error;