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| author | Jens Axboe <axboe@kernel.dk> | 2020-10-17 08:31:29 -0600 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2020-11-01 12:47:09 +0100 |
| commit | 95528c8042a412a77e4769a2ff2abf31fee08b0d (patch) | |
| tree | b133aa9cac3209bf883453de572f59a5fdbb857c | |
| parent | 90adb2b40968fbf079917ee80058da3b57e23f72 (diff) | |
| download | linux-stable-95528c8042a412a77e4769a2ff2abf31fee08b0d.tar.gz linux-stable-95528c8042a412a77e4769a2ff2abf31fee08b0d.tar.bz2 linux-stable-95528c8042a412a77e4769a2ff2abf31fee08b0d.zip | |
mm: mark async iocb read as NOWAIT once some data has been copied
commit 13bd691421bc191a402d2e0d3da5f248d170a632 upstream.
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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -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 f6d36ccc2351..407b94d8ce00 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2179,6 +2179,14 @@ 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; |