On Sun, Sep 29, 2013 at 02:44:01PM +0800, Zheng Liu wrote:
> On Fri, Sep 27, 2013 at 05:14:04PM -0700, Darrick J. Wong wrote:
> > Perform a quick sanity check of bitmap and inode table block numbers when
> > loading them, and if there's something suspicious, mark the block group
> > corrupt.
> >
> > Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> One comment below. Otherwise the patch looks good to me.
> Reviewed-by: Zheng Liu <wenqing.lz@xxxxxxxxxx>
>
> > ---
> > fs/ext4/balloc.c | 7 +++++++
> > fs/ext4/ext4.h | 2 ++
> > fs/ext4/ialloc.c | 6 ++++++
> > fs/ext4/inode.c | 9 +++++++++
> > fs/ext4/super.c | 21 +++++++++++++++++++++
> > 5 files changed, 45 insertions(+)
> [...]
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index 2c2e6cb..d22248e 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -2049,6 +2049,27 @@ void ext4_group_desc_csum_set(struct super_block *sb, __u32 block_group,
> > gdp->bg_checksum = ext4_group_desc_csum(EXT4_SB(sb), block_group, gdp);
> > }
> >
> > +/* returns 1 if the location of a blockgroup data item seems sane */
> > +int ext4_is_sane_bgdata_location(struct super_block *sb, ext4_group_t grp,
> > + ext4_fsblk_t blk)
> > +{
> > + struct ext4_sb_info *sbi = EXT4_SB(sb);
> > + ext4_fsblk_t first_block = le32_to_cpu(sbi->s_es->s_first_data_block);
> > + ext4_fsblk_t last_block;
> > +
> > + if (EXT4_HAS_INCOMPAT_FEATURE(sb, EXT4_FEATURE_INCOMPAT_FLEX_BG))
> > + last_block = ext4_blocks_count(sbi->s_es) - 1;
> > + else {
> > + first_block += grp * sbi->s_blocks_per_group;
> > + last_block = first_block + (EXT4_BLOCKS_PER_GROUP(sb) - 1);
> > + }
> > +
> > + if (last_block >= ext4_blocks_count(sbi->s_es))
> > + last_block = ext4_blocks_count(sbi->s_es) - 1;
> > +
> > + return blk >= first_block && blk <= last_block;
> > +}
> > +
> > /* Called at mount-time, super-block is locked */
> > static int ext4_check_descriptors(struct super_block *sb,
> > ext4_group_t *first_not_zeroed)
>
> FWIW, I notice that in ext4_check_descriptors() we also check the
> location of bitmap. So maybe we could use ext4_is_sane_bgdata_location
> in that function.
That could be done, but all we'd be doing is trading this:
block_bitmap = ext4_block_bitmap(sb, gdp);
if (block_bitmap < first_block || block_bitmap > last_block) {
for this slightly slower code:
if (ext4_is_sane_bgdata_location(sb, gdp,
ext4_block_bitmap(sb, gdb))) {
I don't know if that's worth the code churn or not. It's an easy change, but I
don't think it adds much. Ted -- if you want me to make the change I'll do it,
but if you're content to leave the patch as it is, then so am I.
--D
>
> - Zheng
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