Commit ab2125df authored by Pavel Begunkov's avatar Pavel Begunkov Committed by Linus Torvalds
Browse files

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: default avatarPavel Begunkov <asml.silence@gmail.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 1f7ef657

mm/filemap.c

+4 −2
Original line number Diff line number Diff line
@@ -2615,6 +2615,7 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter) 
			iocb->ki_pos += retval;

			count -= retval;

		}

		if (retval != -EIOCBQUEUED)

			iov_iter_revert(iter, count - iov_iter_count(iter));



		/*
@@ -3426,6 +3427,7 @@ generic_file_direct_write(struct kiocb *iocb, struct iov_iter *from) 
		}

		iocb->ki_pos = pos;

	}

	if (written != -EIOCBQUEUED)

		iov_iter_revert(from, write_len - iov_iter_count(from));

out:

	return written;