Commit 2f19cad9 authored by Chris Mason's avatar Chris Mason Committed by Linus Torvalds
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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: default avatarChris Mason <clm@fb.com>
Reviewed-by: default avatarJosef Bacik <jbacik@fb.com>
Reported-by: default avatarDon A. Bailey <donb@securitymouse.com>
cc: stable@vger.kernel.org
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 7a5a4f97

fs/btrfs/compression.c

+31 −2
Original line number Diff line number Diff line
@@ -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;

	}

}

fs/btrfs/compression.h

+3 −1
Original line number Diff line number Diff line
@@ -45,7 +45,9 @@ int btrfs_submit_compressed_write(struct inode *inode, u64 start, 
				  unsigned long nr_pages);

int btrfs_submit_compressed_read(struct inode *inode, struct bio *bio,

				 int mirror_num, unsigned long bio_flags);



void btrfs_clear_biovec_end(struct bio_vec *bvec, int vcnt,

				   unsigned long pg_index,

				   unsigned long pg_offset);

struct btrfs_compress_op {

	struct list_head *(*alloc_workspace)(void);

fs/btrfs/lzo.c

+15 −0
Original line number Diff line number Diff line
@@ -373,6 +373,8 @@ cont: 
	}

done:

	kunmap(pages_in[page_in_index]);

	if (!ret)

		btrfs_clear_biovec_end(bvec, vcnt, page_out_index, pg_offset);

	return ret;

}
@@ -410,10 +412,23 @@ static int lzo_decompress(struct list_head *ws, unsigned char *data_in, 
		goto out;

	}



	/*

	 * the caller is already checking against PAGE_SIZE, but lets

	 * move this check closer to the memcpy/memset

	 */

	destlen = min_t(unsigned long, destlen, PAGE_SIZE);

	bytes = min_t(unsigned long, destlen, out_len - start_byte);



	kaddr = kmap_atomic(dest_page);

	memcpy(kaddr, workspace->buf + start_byte, bytes);



	/*

	 * btrfs_getblock is doing a zero on the tail of the page too,

	 * but this will cover anything missing from the decompressed

	 * data.

	 */

	if (bytes < destlen)

		memset(kaddr+bytes, 0, destlen-bytes);

	kunmap_atomic(kaddr);

out:

	return ret;

fs/btrfs/zlib.c

+18 −2
Original line number Diff line number Diff line
@@ -299,6 +299,8 @@ done: 
	zlib_inflateEnd(&workspace->strm);

	if (data_in)

		kunmap(pages_in[page_in_index]);

	if (!ret)

		btrfs_clear_biovec_end(bvec, vcnt, page_out_index, pg_offset);

	return ret;

}
@@ -310,10 +312,14 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in, 
	struct workspace *workspace = list_entry(ws, struct workspace, list);

	int ret = 0;

	int wbits = MAX_WBITS;

	unsigned long bytes_left = destlen;

	unsigned long bytes_left;

	unsigned long total_out = 0;

	unsigned long pg_offset = 0;

	char *kaddr;



	destlen = min_t(unsigned long, destlen, PAGE_SIZE);

	bytes_left = destlen;



	workspace->strm.next_in = data_in;

	workspace->strm.avail_in = srclen;

	workspace->strm.total_in = 0;
@@ -341,7 +347,6 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in, 
		unsigned long buf_start;

		unsigned long buf_offset;

		unsigned long bytes;

		unsigned long pg_offset = 0;



		ret = zlib_inflate(&workspace->strm, Z_NO_FLUSH);

		if (ret != Z_OK && ret != Z_STREAM_END)
@@ -384,6 +389,17 @@ next: 
		ret = 0;



	zlib_inflateEnd(&workspace->strm);



	/*

	 * this should only happen if zlib returned fewer bytes than we

	 * expected.  btrfs_get_block is responsible for zeroing from the

	 * end of the inline extent (destlen) to the end of the page

	 */

	if (pg_offset < destlen) {

		kaddr = kmap_atomic(dest_page);

		memset(kaddr + pg_offset, 0, destlen - pg_offset);

		kunmap_atomic(kaddr);

	}

	return ret;

}

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