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pnfs/blocklayout: correctly decrement extent length

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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: Christoph Hellwig <hch@lst.de>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
This commit is contained in:
Christoph Hellwig 2014-08-21 11:09:29 -05:00 committed by Trond Myklebust
parent be98fd0ac3
commit 921b81a8cd
1 changed files with 4 additions and 3 deletions
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7
fs/nfs/blocklayout/blocklayout.c
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@ -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 @@ bl_write_pagelist(struct nfs_pgio_header *header, int sync)
/* 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);