Commit 32502b84 authored Jul 04, 2008 by Miklos Szeredi Committed by Jens Axboe Jul 04, 2008

splice: fix generic_file_splice_read() race with page invalidation



If a page was invalidated during splicing from file to a pipe, then
generic_file_splice_read() could return a short or zero count.

This manifested itself in rare I/O errors seen on nfs exported fuse
filesystems.  This is because nfsd uses splice_direct_to_actor() to read
files, and fuse uses invalidate_inode_pages2() to invalidate stale data on
open.

Fix by redoing the page find/create if it was found to be truncated
(invalidated).

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

parent 8b3d3567

fs/splice.c

+13 −4

Original line number	Diff line number	Diff line
		@@ -379,14 +379,23 @@ __generic_file_splice_read(struct file in, loff_t ppos,
		lock_page(page);

		/*
		* page was truncated, stop here. if this isn't the
		* first page, we'll just complete what we already
		* added
		* Page was truncated, or invalidated by the
		* filesystem. Redo the find/create, but this time the
		* page is kept locked, so there's no chance of another
		* race with truncate/invalidate.
		*/
		if (!page->mapping) {
		unlock_page(page);
		page = find_or_create_page(mapping, index,
		mapping_gfp_mask(mapping));

		if (!page) {
		error = -ENOMEM;
		break;
		}
		page_cache_release(pages[page_nr]);
		pages[page_nr] = page;
		}
		/*
		* page was already under io and is now done, great
		*/