2008-01-09 19:54:36

by Jan Kara

Subject: [PATCH resend] Fix reading of bitmaps from filesystem image

Hi Ted,

I've sent you the attached fix some time ago but it didn't seem to get
merged yet...
Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR
---

Subject: Fix reading of bitmaps from filesystem image

Reading of bitmaps from image file could never work with more than one
group in a filesystem... Fix the loops so that we read appropriate number
of blocks.

Signed-off-by: Jan Kara <[email protected]>

diff --git a/lib/ext2fs/rw_bitmaps.c b/lib/ext2fs/rw_bitmaps.c
index 1897ec3..abbe5e8 100644
--- a/lib/ext2fs/rw_bitmaps.c
+++ b/lib/ext2fs/rw_bitmaps.c
@@ -190,7 +190,7 @@ static errcode_t read_bitmaps(ext2_filsy
if (fs->flags & EXT2_FLAG_IMAGE_FILE) {
blk = (fs->image_header->offset_inodemap / fs->blocksize);
ino_cnt = fs->super->s_inodes_count;
- while (inode_nbytes > 0) {
+ while (do_inode && ino_cnt > 0) {
retval = io_channel_read_blk(fs->image_io, blk++,
1, inode_bitmap);
if (retval)
@@ -202,15 +202,14 @@ static errcode_t read_bitmaps(ext2_filsy
ino_itr, cnt, inode_bitmap);
if (retval)
goto cleanup;
- ino_itr += fs->blocksize << 3;
- ino_cnt -= fs->blocksize << 3;
- inode_nbytes -= fs->blocksize;
+ ino_itr += cnt;
+ ino_cnt -= cnt;
}
blk = (fs->image_header->offset_blockmap /
fs->blocksize);
blk_cnt = EXT2_BLOCKS_PER_GROUP(fs->super) *
fs->group_desc_count;
- while (block_nbytes > 0) {
+ while (do_block && blk_cnt > 0) {
retval = io_channel_read_blk(fs->image_io, blk++,
1, block_bitmap);
if (retval)
@@ -222,9 +221,8 @@ static errcode_t read_bitmaps(ext2_filsy
blk_itr, cnt, block_bitmap);
if (retval)
goto cleanup;
- blk_itr += fs->blocksize << 3;
- blk_cnt -= fs->blocksize << 3;
- block_nbytes -= fs->blocksize;
+ blk_itr += cnt;
+ blk_cnt -= cnt;
}
goto success_cleanup;
}

2008-01-14 16:00:09

by Theodore Ts'o

Subject: Re: [PATCH resend] Fix reading of bitmaps from filesystem image

On Wed, Jan 09, 2008 at 08:54:35PM +0100, Jan Kara wrote:
>
> Reading of bitmaps from image file could never work with more than one
> group in a filesystem... Fix the loops so that we read appropriate number
> of blocks.

OK, so I'm probably being dense, but.... what's the problem?

You changed the loop from counting in bytes to inodes, but either
method should work.

- Ted

2008-01-14 16:17:32

by Jan Kara

Subject: Re: [PATCH resend] Fix reading of bitmaps from filesystem image

On Mon 14-01-08 10:57:18, Theodore Tso wrote:
> On Wed, Jan 09, 2008 at 08:54:35PM +0100, Jan Kara wrote:
> >
> > Reading of bitmaps from image file could never work with more than one
> > group in a filesystem... Fix the loops so that we read appropriate number
> > of blocks.
>
> OK, so I'm probably being dense, but.... what's the problem?
>
> You changed the loop from counting in bytes to inodes, but either
> method should work.
At the beginning of read_bitmap() there is:
unsigned int block_nbytes = EXT2_BLOCKS_PER_GROUP(fs->super) / 8;
unsigned inode_nbytes = EXT2_INODES_PER_GROUP(fs->super) / 8;

Therefore in the loop:
while (inode_nbytes > 0)

we end up reading bitmap for just one group...

Honza
--
Jan Kara <[email protected]>
SUSE Labs, CR