Commit 921b81a8 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Trond Myklebust
Browse files

pnfs/blocklayout: correctly decrement extent length 



When we do non-page sized reads we can underflow the extent_length variable
and read incorrect data.  Fix the extent_length calculation and change to
defensive <= checks for the extent length in the read and write path.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent be98fd0a

fs/nfs/blocklayout/blocklayout.c

+4 −3
Original line number Diff line number Diff line
@@ -272,7 +272,7 @@ bl_read_pagelist(struct nfs_pgio_header *hdr) 
	isect = (sector_t) (f_offset >> SECTOR_SHIFT);

	/* Code assumes extents are page-aligned */

	for (i = pg_index; i < hdr->page_array.npages; i++) {

		if (!extent_length) {

		if (extent_length <= 0) {

			/* We've used up the previous extent */

			bl_put_extent(be);

			bl_put_extent(cow_read);
@@ -303,6 +303,7 @@ bl_read_pagelist(struct nfs_pgio_header *hdr) 
			f_offset += pg_len;

			bytes_left -= pg_len;

			isect += (pg_offset >> SECTOR_SHIFT);

			extent_length -= (pg_offset >> SECTOR_SHIFT);

		} else {

			pg_offset = 0;

			pg_len = PAGE_CACHE_SIZE;
@@ -333,7 +334,7 @@ bl_read_pagelist(struct nfs_pgio_header *hdr) 
			}

		}

		isect += (pg_len >> SECTOR_SHIFT);

		extent_length -= PAGE_CACHE_SECTORS;

		extent_length -= (pg_len >> SECTOR_SHIFT);

	}

	if ((isect << SECTOR_SHIFT) >= header->inode->i_size) {

		hdr->res.eof = 1;
@@ -797,7 +798,7 @@ next_page: 
	/* Middle pages */

	pg_index = header->args.pgbase >> PAGE_CACHE_SHIFT;

	for (i = pg_index; i < header->page_array.npages; i++) {

		if (!extent_length) {

		if (extent_length <= 0) {

			/* We've used up the previous extent */

			bl_put_extent(be);

			bl_put_extent(cow_read);

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