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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: 1a0a7853b9 ("mm: support async buffered reads in generic_file_buffered_read()")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Jens Axboe 2020-11-16 13:36:24 -07:00
parent 944d1444d5
commit 0abed7c69b
1 changed files with 14 additions and 4 deletions
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18
mm/filemap.c
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@ -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;