btrfs: zero out left over bytes after processing compression streams

Don Bailey noticed that our page zeroing for compression at end-io time
isn't complete.  This reworks a patch from Linus to push the zeroing
into the zlib and lzo specific functions instead of trying to handle the
corners inside btrfs_decompress_buf2page

Signed-off-by: Chris Mason <clm@fb.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Reported-by: Don A. Bailey <donb@securitymouse.com>
cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 31 insertions, 2 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index d3220d31d3cb..dcd9be32ac57 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1011,8 +1011,6 @@ int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
 		bytes = min(bytes, working_bytes);
 		kaddr = kmap_atomic(page_out);
 		memcpy(kaddr + *pg_offset, buf + buf_offset, bytes);
-		if (*pg_index == (vcnt - 1) && *pg_offset == 0)
-			memset(kaddr + bytes, 0, PAGE_CACHE_SIZE - bytes);
 		kunmap_atomic(kaddr);
 		flush_dcache_page(page_out);
 
@@ -1054,3 +1052,34 @@ int btrfs_decompress_buf2page(char *buf, unsigned long buf_start,
 
 	return 1;
 }
+
+/*
+ * When uncompressing data, we need to make sure and zero any parts of
+ * the biovec that were not filled in by the decompression code.  pg_index
+ * and pg_offset indicate the last page and the last offset of that page
+ * that have been filled in.  This will zero everything remaining in the
+ * biovec.
+ */
+void btrfs_clear_biovec_end(struct bio_vec *bvec, int vcnt,
+				   unsigned long pg_index,
+				   unsigned long pg_offset)
+{
+	while (pg_index < vcnt) {
+		struct page *page = bvec[pg_index].bv_page;
+		unsigned long off = bvec[pg_index].bv_offset;
+		unsigned long len = bvec[pg_index].bv_len;
+
+		if (pg_offset < off)
+			pg_offset = off;
+		if (pg_offset < off + len) {
+			unsigned long bytes = off + len - pg_offset;
+			char *kaddr;
+
+			kaddr = kmap_atomic(page);
+			memset(kaddr + pg_offset, 0, bytes);
+			kunmap_atomic(kaddr);
+		}
+		pg_index++;
+		pg_offset = 0;
+	}
+}