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>
This commit is contained in:
Chris Mason 2014-11-30 08:56:33 -05:00 committed by Linus Torvalds
parent 7a5a4f9787
commit 2f19cad94c
4 changed files with 67 additions and 5 deletions

View file

@ -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;
}
}

View file

@ -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);

View file

@ -373,6 +373,8 @@ static int lzo_decompress_biovec(struct list_head *ws,
}
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;

View file

@ -299,6 +299,8 @@ static int zlib_decompress_biovec(struct list_head *ws, struct page **pages_in,
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 @@ static int zlib_decompress(struct list_head *ws, unsigned char *data_in,
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;
}