can't use iget on XFS

["Tomaz Beltram" <tomazb@xxxxxxxxxxx>]

We have developed a stackable filesystem kernel module for a HSM 
application. The role of the filter module is to intercept operations 
between VFS and file system. It then sends events to userspace when these 
are invoked. We are using ext3 or reiserfs for bottom file system and are 
evaluating XFS, since it provides all required functionality (extended 
attributes, journals).

In some cases the filter module has to call iget instead of lookup, since it 
doesn't have the full pathname of the file but just its inode number (ino). 
On XFS this only works when the inode is found in the cache. If it has to be 
loaded from disk it oops-es. This is because iget calls read_inode which is 
not implemented in XFS and just jumps to nowhere.

We are considering to call xfs_iget instead of iget, but are not aware of 
all functional implications this might have. Could someone explain if this 
is the correct sequence to be called and why not:


struct super_block *sb;
struct inode *inode;

vfs_t       *vfsp = LINVFS_GET_VFS(sb);
xfs_mount_t *mp = XFS_BHVTOM(vfsp->vfs_fbhv);

xfs_inode_t *ip = NULL;

int error = xfs_iget(mp, NULL, ino, XFS_ILOCK_SHARED, &ip, 0);

vnode_t     *vpp = XFS_ITOV(ip);
inode = LINVFS_GET_IP(vpp);

/* access inode, e.g. read extended attributes */

xfs_iunlock(ip, XFS_ILOCK_SHARED);


Any other ideas/suggestion? Thanks in advance for your answer.
Tomaz

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