| From | Greg Kroah-Hartman <> | Subject | [PATCH 5.9 249/252] mm: never attempt async page lock if weve transferred data already | Date | Mon, 23 Nov 2020 13:23:19 +0100 |
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From: Jens Axboe <axboe@kernel.dk>
commit 0abed7c69b956d135cb6d320c350b2adb213e7d8 upstream.
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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
--- mm/filemap.c | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-)
--- a/mm/filemap.c +++ b/mm/filemap.c @@ -2327,10 +2327,15 @@ page_ok: 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; @@ -2373,10 +2378,15 @@ readpage: } 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;
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