[PATCH V2] xfs_repair: test for bad level in dir2 node

[Eric Sandeen]

On 9/10/13 1:03 PM, Mark Tinguely wrote:
>> 1) The block magic is LEAFN.  If so, we stop.  We warn if it's not root level (but don't fix?  Maybe that's a bug for another patch?)
> 
> Yes. We do not loop if "i == 1", so another LEAF should not be found.



>> 2) The block magic is NODE.  If not, we error out.
> 
> Yes.
> 
>> and as I showed above:
>> 3) The level matches each level we're at in the loop.
>>
>> So:
>>
>> Any block which isn't LEAFN or NODE is caught prior to the (i == -1) block.
> 
> Yes must be a NODE.
> 
>> Any block which has a level that doesn't match is caught on the else of the (i == -1) block.
> 
> Yes, and "i" has to be larger than 1 because of the loop. Which I did not catch before.
>>
>> And those are the only 2 valid types here.
>>
>> What case is missing?
>>
>> -eric
>>
> 
> With loop condition of "i > 1" then it cannot miss what I first thought was being missed, but the level of 1 being a leaf is not checked.

But I don't think that's right, is it?  level[0] is leaf; level[1] is a node, right?

Argh.  Now I'm more confused; xfs_check has:

        case XFS_DA_NODE_MAGIC:
                node = iocur_top->data;
                xfs_da3_node_hdr_from_disk(&nodehdr, node);
                if (nodehdr.level < 1 || nodehdr.level > XFS_DA_NODE_MAXDEPTH) {
                        if (!sflag || v)
                                dbprintf(_("bad node block level %d for dir ino "
                                         "%lld block %d\n"),
                                        nodehdr.level, id->ino,
                                        dabno);
                        error++;

so nodehdr.level == XFS_DA_NODE_MAXDEPTH is valid there (and level == 1 is a valid
node), but repair says:

                        if (i >= XFS_DA_NODE_MAXDEPTH) {
                                do_warn(
_("bad header depth for directory inode %" PRIu64 "\n"),
                                        da_cursor->ino);

so nodehdr.level == XFS_DA_NODE_MAXDEPTH is *not* valid here.

indices and counters and depths, oh my.  I need to back up and remember what's what.  :(

... Still not sure any of this invalidates my targeted fix - although I should just 
make it a one-liner and do:

                if (i == -1) {
                        i = da_cursor->active = nodehdr.level;
-                       if (i >= XFS_DA_NODE_MAXDEPTH) {
+                       if (i < 1 || i >= XFS_DA_NODE_MAXDEPTH) {
                                do_warn(
 _("bad header depth for directory inode %" PRIu64 "\n"),

-Eric

> --Mark.