Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 6b7a03f0 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Ben Myers
Browse files

xfs: handle EOF correctly in xfs_vm_writepage 



We need to zero out part of a page which beyond EOF before setting uptodate,
otherwise, mapread or write will see non-zero data beyond EOF.

Based on the code in fs/buffer.c and the following ext4 commit:

  ext4: handle EOF correctly in ext4_bio_write_page()

And yes, I wish we had a good test case for it.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarMark Tinguely <tinguely@sgi.com>
Signed-off-by: default avatarBen Myers <bpm@sgi.com>
parent 69ff2826

fs/xfs/xfs_aops.c

+17 −2
Original line number Original line Diff line number Diff line
@@ -927,11 +927,26 @@ xfs_vm_writepage( 
	end_index = offset >> PAGE_CACHE_SHIFT;

	end_index = offset >> PAGE_CACHE_SHIFT;

	last_index = (offset - 1) >> PAGE_CACHE_SHIFT;

	last_index = (offset - 1) >> PAGE_CACHE_SHIFT;

	if (page->index >= end_index) {

	if (page->index >= end_index) {

		if ((page->index >= end_index + 1) ||

		unsigned offset_into_page = offset & (PAGE_CACHE_SIZE - 1);

		    !(i_size_read(inode) & (PAGE_CACHE_SIZE - 1))) {



		/*

		 * Just skip the page if it is fully outside i_size, e.g. due

		 * to a truncate operation that is in progress.

		 */

		if (page->index >= end_index + 1 || offset_into_page == 0) {

			unlock_page(page);

			unlock_page(page);

			return 0;

			return 0;

		}

		}



		/*

		 * The page straddles i_size.  It must be zeroed out on each

		 * and every writepage invocation because it may be mmapped.

		 * "A file is mapped in multiples of the page size.  For a file

		 * that is not a multiple of the  page size, the remaining

		 * memory is zeroed when mapped, and writes to that region are

		 * not written out to the file."

		 */

		zero_user_segment(page, offset_into_page, PAGE_CACHE_SIZE);

	}

	}





	end_offset = min_t(unsigned long long,

	end_offset = min_t(unsigned long long,