Hello, Darrick,
On Sat, Jan 05, 2013 at 11:50:54AM -0800, Darrick J. Wong wrote:
> On Sat, Jan 05, 2013 at 03:42:59PM +0800, Guo Chao wrote:
> > In ext4_dx_csum_verify(), if we detect corrupted data,
> > we do not compare checksum because checksum itself may
> > be wrong, but we should report error in this case.
> >
> > Cc: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> > Signed-off-by: Guo Chao <yan@xxxxxxxxxxxxxxxxxx>
> > ---
> > fs/ext4/namei.c | 4 ++--
> > 1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
> > index cac4482..843e29f 100644
> > --- a/fs/ext4/namei.c
> > +++ b/fs/ext4/namei.c
> > @@ -370,14 +370,14 @@ static int ext4_dx_csum_verify(struct inode *inode,
> > c = get_dx_countlimit(inode, dirent, &count_offset);
> > if (!c) {
> > EXT4_ERROR_INODE(inode, "dir seems corrupt? Run e2fsck -D.");
> > - return 1;
> > + return 0;
> > }
> > limit = le16_to_cpu(c->limit);
> > count = le16_to_cpu(c->count);
> > if (count_offset + (limit * sizeof(struct dx_entry)) >
> > EXT4_BLOCK_SIZE(inode->i_sb) - sizeof(struct dx_tail)) {
> > warn_no_space_for_csum(inode);
> > - return 1;
> > + return 0;
>
> In both of these cases we cannot figure out where the dx block checksum lives,
> and therefore we have no stored checksum to compare against. This can result
> from enabling checksums on a existing filesystem and ignoring tune2fs' request
> to run fsck -D to rebuild dx blocks that are completely full. However, since
> we haven't a checksum that we could use to decide if there's real corruption,
> there's no cause to return -EIO to the user. Therefore, we print a warning and
> trust the sanity checks to catch totally bogus blocks, which is the best we can
> hope for.
>
> Sorry, but this doesn't seem necessary.
Thanks for the explaination.
I think ext4_dirent_csum_verify() can encounter similar problem but return
error. But I'm not sure it's the same case.
Thanks,
Guo Chao
> --D
> > }
> > t = (struct dx_tail *)(((struct dx_entry *)c) + limit);
> >
> > --
> > 1.7.9.5
> >
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