diff options
| author | Jens Axboe <axboe@kernel.dk> | 2020-10-17 08:31:29 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2020-10-17 13:49:05 -0600 |
| commit | 13bd691421bc191a402d2e0d3da5f248d170a632 (patch) | |
| tree | 464cd1511166ea7adb526f7f1911755d7833bb7f | |
| parent | 58852d4d673760cf7c88b9360b3c24a041bec298 (diff) | |
| download | ext4-13bd691421bc191a402d2e0d3da5f248d170a632.tar.gz | |
mm: mark async iocb read as NOWAIT once some data has been copied
Once we've copied some data for an iocb that is marked with IOCB_WAITQ,
we should no longer attempt to async lock a new page. Instead make sure
we return the copied amount, and let the caller retry, instead of
returning -EIOCBQUEUED for a new page.
This should only be possible with read-ahead disabled on the below
device, and multiple threads racing on the same file. Haven't been able
to reproduce on anything else.
Cc: stable@vger.kernel.org # v5.9
Fixes: 1a0a7853b901 ("mm: support async buffered reads in generic_file_buffered_read()")
Reported-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | mm/filemap.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/mm/filemap.c b/mm/filemap.c index 1a6beaf69f49f3..e4101b5bfa82c8 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2199,6 +2199,14 @@ ssize_t generic_file_buffered_read(struct kiocb *iocb, last_index = (*ppos + iter->count + PAGE_SIZE-1) >> PAGE_SHIFT; offset = *ppos & ~PAGE_MASK; + /* + * If we've already successfully copied some data, then we + * can no longer safely return -EIOCBQUEUED. Hence mark + * an async read NOWAIT at that point. + */ + if (written && (iocb->ki_flags & IOCB_WAITQ)) + iocb->ki_flags |= IOCB_NOWAIT; + for (;;) { struct page *page; pgoff_t end_index; |