In the following scenario xfs_bulkstat() returns incorrect
stale inode state:

1. File_A is created and its inode synced to disk.
2. File_A is unlinked and doesn't exist anymore.
3. Filesystem sync is invoked.
4. File_B is created. File_B happens to reclaim File_A's inode.
5. xfs_bulkstat() is called and detects File_B but reports the
  incorrect File_A inode state.

Explanation for the incorrect inode state is that inodes are not immediately
synced on file create for performance reasons. This leaves the on-disk inode
buffer uninitialized (or with old state from a previous generation inode)
and this is what xfs_bulkstat() would report.

Solutions:

One solution provided by the attached patch is to mark the on-disk
inode buffer "dirty" on unlink. When the inode is reclaimed
(by a new file create), xfs_bulkstat() would filter this inode by the
"dirty" mark. Once the inode is flushed to disk, the on-disk buffer "dirty"
mark is automatically removed and a following xfs_bulkstat() would return
the correct inode state.

A better solution would be if the inode is immediately synced at create.
This would make the on-disk inode buffer up to date and xfs_bulkstat() 
should
return the correct inode state.

Disadvantages of the above solutions:

The first solution marks the inode "dirty" on unlink by setting the on-disk
di_nlink field to 0. Note that the in-core di_nlink has already been set to
0 and a corresponding transaction logged by xfs_droplink().
This is an exception from the rule that any on-disk inode buffer changes
has to be followed by a disk write (inode flush).
Synchronizing the in-core to on-disk di_nlink values in advance (before the
actual inode flush to disk) should be fine in this case because the inode
is already unlinked and it would never change its di_nlink again for this
inode generation.

The second solution would be a performance hit as it would require disk
write for each new file create to flush the inode to disk. Dave suggested
modifying the inode sync code to allow on-disk buffer updates without
disk writes. This doesn't seem to be very simple and would require some
time for a proper implementation and testing. I have been assigned to
do it in the near future.

In the mean time we have XFS users that urgently need a solution
and the patch bellow seems to fix the problem for them.

Regards,
Vlad