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resize2fs: Fix data corruption bug when growing an ext4 filesystem off-line 

When allocating a new set of block group metadata as part of growing
the filesystem, the resize2fs code assumes that the bitmap and inode
table blocks are in their own block group; an assumption which is
changed by the flex_bg feature.  This commit works around the problem
by temporarily turning off flex_bg while allocating the new block
group metadata, to avoid potentially overwriting previously allocated
data blocks.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
bitmap-optimize
Theodore Ts'o 2009-04-18 13:31:54 -04:00
parent c927bec16f
commit 1ac84a948d
1 changed files with 21 additions and 0 deletions
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21
resize/resize2fs.c
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@ -746,6 +746,7 @@ static errcode_t blocks_to_move(ext2_resize_t rfs)
errcode_t retval;
ext2_filsys fs, old_fs;
ext2fs_block_bitmap meta_bmap;
__u32 save_incompat_flag;
fs = rfs->new_fs;
old_fs = rfs->old_fs;
@ -890,9 +891,29 @@ static errcode_t blocks_to_move(ext2_resize_t rfs)
/*
* Allocate the missing data structures
*
* XXX We have a problem with FLEX_BG and off-line
* resizing where we are growing the size of the
* filesystem. ext2fs_allocate_group_table() will try
* to reserve the inode table in the desired flex_bg
* location. However, passing rfs->reserve_blocks
* doesn't work since it only has reserved the blocks
* that will be used in the new block group -- and
* with flex_bg, we can and will allocate the tables
* outside of the block group. And we can't pass in
* the fs->block_map because it doesn't handle
* overlapping inode table movements right. So for
* now, we temporarily disable flex_bg to force
* ext2fs_allocate_group_tables() to allocate the bg
* metadata in side the block group, and the restore
* it afterwards. Ugly, until we can fix this up
* right later.
*/
save_incompat_flag = fs->super->s_feature_incompat;
fs->super->s_feature_incompat &= ~EXT4_FEATURE_INCOMPAT_FLEX_BG;
retval = ext2fs_allocate_group_table(fs, i,
rfs->reserve_blocks);
fs->super->s_feature_incompat = save_incompat_flag;
if (retval)
goto errout;