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List:       linux-stable-commits
Subject:    Patch "mm: mark async iocb read as NOWAIT once some data has been copied" has been added to the 5.9-
From:       <gregkh () linuxfoundation ! org>
Date:       2020-10-31 10:24:53
Message-ID: 160413989314432 () kroah ! com
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This is a note to let you know that I've just added the patch titled

    mm: mark async iocb read as NOWAIT once some data has been copied

to the 5.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     mm-mark-async-iocb-read-as-nowait-once-some-data-has-been-copied.patch
and it can be found in the queue-5.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From 13bd691421bc191a402d2e0d3da5f248d170a632 Mon Sep 17 00:00:00 2001
From: Jens Axboe <axboe@kernel.dk>
Date: Sat, 17 Oct 2020 08:31:29 -0600
Subject: mm: mark async iocb read as NOWAIT once some data has been copied

From: Jens Axboe <axboe@kernel.dk>

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>

---
 mm/filemap.c |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2179,6 +2179,14 @@ ssize_t generic_file_buffered_read(struc
 	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;


Patches currently in stable-queue which might be from axboe@kernel.dk are

queue-5.9/io_uring-convert-advanced-xarray-uses-to-the-normal-api.patch
queue-5.9/io_uring-reference-nsproxy-for-file-table-commands.patch
queue-5.9/io_uring-stash-ctx-task-reference-for-sqpoll.patch
queue-5.9/io_uring-return-cancelation-status-from-poll-timeout-files-handlers.patch
queue-5.9/io_uring-fix-xarray-usage-in-io_uring_add_task_file.patch
queue-5.9/io_uring-fix-use-of-xarray-in-__io_uring_files_cancel.patch
queue-5.9/io-wq-fix-use-after-free-in-io_wq_worker_running.patch
queue-5.9/io_uring-don-t-rely-on-weak-files-references.patch
queue-5.9/ata-ahci-mvebu-make-sata-phy-optional-for-armada-3720.patch
queue-5.9/io_uring-allow-timeout-poll-files-killing-to-take-task-into-account.patch
queue-5.9/mm-mark-async-iocb-read-as-nowait-once-some-data-has-been-copied.patch
queue-5.9/io_uring-move-dropping-of-files-into-separate-helper.patch
queue-5.9/io_uring-unconditionally-grab-req-task.patch
queue-5.9/io_uring-enable-task-files-specific-overflow-flushing.patch
queue-5.9/io_wq-make-io_wqe-lock-a-raw_spinlock_t.patch
queue-5.9/ata-sata_rcar-fix-dma-boundary-mask.patch
queue-5.9/io_uring-no-need-to-call-xa_destroy-on-empty-xarray.patch
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