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Commit 3239d834 authored by Milosz Tanski's avatar Milosz Tanski Committed by Al Viro
Browse files

fs: support IOCB_NOWAIT in generic_file_buffered_read 



Allow generic_file_buffered_read to bail out early instead of waiting for
the page lock or reading a page if IOCB_NOWAIT is specified.

Signed-off-by: default avatarMilosz Tanski <milosz@adfin.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Acked-by: default avatarSage Weil <sage@redhat.com>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 47c27bc4

mm/filemap.c

+9 −0
Original line number Diff line number Diff line
@@ -1939,6 +1939,8 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb, 


		page = find_get_page(mapping, index);

		if (!page) {

			if (iocb->ki_flags & IOCB_NOWAIT)

				goto would_block;

			page_cache_sync_readahead(mapping,

					ra, filp,

					index, last_index - index);
@@ -1952,6 +1954,11 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb, 
					index, last_index - index);

		}

		if (!PageUptodate(page)) {

			if (iocb->ki_flags & IOCB_NOWAIT) {

				put_page(page);

				goto would_block;

			}



			/*

			 * See comment in do_read_cache_page on why

			 * wait_on_page_locked is used to avoid unnecessarily
@@ -2133,6 +2140,8 @@ static ssize_t generic_file_buffered_read(struct kiocb *iocb, 
		goto readpage;

	}



would_block:

	error = -EAGAIN;

out:

	ra->prev_pos = prev_index;

	ra->prev_pos <<= PAGE_SHIFT;