+ mm-filemap-dont-revert-iter-on-eiocbqueued.patch added to -mm tree

+ mm-filemap-dont-revert-iter-on-eiocbqueued.patch added to -mm tree

[akpm]

The patch titled
     Subject: mm/filemap: don't revert iter on -EIOCBQUEUED
has been added to the -mm tree.  Its filename is
     mm-filemap-dont-revert-iter-on-eiocbqueued.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-filemap-dont-revert-iter-on-eiocbqueued.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-filemap-dont-revert-iter-on-eiocbqueued.patch

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------------------------------------------------------
From: Pavel Begunkov <asml.silence@gmail.com>
Subject: mm/filemap: don't revert iter on -EIOCBQUEUED

Currently, if I/O is enqueued for async execution direct paths of
generic_file_{read,write}_iter() will always revert the iter.  There are
no users expecting that, and that is also costly.  Leave iterators as is
on -EIOCBQUEUED.

Link: https://lkml.kernel.org/r/f5247b60e7abbd2ff850cd108491f53a2e0c501a.1610207781.git.asml.silence@gmail.com
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/filemap.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/mm/filemap.c~mm-filemap-dont-revert-iter-on-eiocbqueued
+++ a/mm/filemap.c
@@ -2609,7 +2609,8 @@ generic_file_read_iter(struct kiocb *ioc
 			iocb->ki_pos += retval;
 			count -= retval;
 		}
-		iov_iter_revert(iter, count - iov_iter_count(iter));
+		if (retval != -EIOCBQUEUED)
+			iov_iter_revert(iter, count - iov_iter_count(iter));
 
 		/*
 		 * Btrfs can have a short DIO read if we encounter
@@ -3331,7 +3332,8 @@ generic_file_direct_write(struct kiocb *
 		}
 		iocb->ki_pos = pos;
 	}
-	iov_iter_revert(from, write_len - iov_iter_count(from));
+	if (written != -EIOCBQUEUED)
+		iov_iter_revert(from, write_len - iov_iter_count(from));
 out:
 	return written;
 }
_

Patches currently in -mm which might be from asml.silence@gmail.com are

mm-filemap-dont-revert-iter-on-eiocbqueued.patch