xfs: simplify xfs_trans_iget

xfs_trans_iget is a wrapper for xfs_iget that adds the inode to the
transaction after it is read.  Except when the inode already is in the
inode cache, in which case it returns the existing locked inode with
increment lock recursion counts.

Now, no one in the tree every decrements these lock recursion counts,
so any user of this gets a potential double unlock when both the original
owner of the inode and the xfs_trans_iget caller unlock it.  When looking
back in a git bisect in the historic XFS tree there was only one place
that decremented these counts, xfs_trans_iput.  Introduced in commit
ca25df7a840f426eb566d52667b6950b92bb84b5 by Adam Sweeney in 1993,
and removed in commit 19f899a3ab155ff6a49c0c79b06f2f61059afaf3 by
Steve Lord in 2003.  And as long as it didn't slip through git bisects
cracks never actually used in that time frame.

A quick audit of the callers of xfs_trans_iget shows that no caller
really relies on this behaviour fortunately - xfs_ialloc allows this
inode from disk so it must not be there before, and all the RT allocator
routines only every add each RT bitmap inode once.

In addition to removing lots of code and reducing the size of the inode
item this patch also avoids the double inode cache lookup in each
create/mkdir/mknod transaction.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Alex Elder <aelder@sgi.com>
Signed-off-by: Felix Blyakher <felixb@sgi.com>

1 files changed, 0 insertions, 2 deletions

diff --git a/fs/xfs/xfs_inode_item.h b/fs/xfs/xfs_inode_item.h
index a52ac125f055..65bae4c9b8bf 100644
--- a/fs/xfs/xfs_inode_item.h
+++ b/fs/xfs/xfs_inode_item.h
@@ -137,8 +137,6 @@ typedef struct xfs_inode_log_item {
         struct xfs_inode        *ili_inode;        /* inode ptr */
         xfs_lsn_t               ili_flush_lsn;     /* lsn at last flush */
         xfs_lsn_t               ili_last_lsn;      /* lsn at last transaction */
-        unsigned short          ili_ilock_recur;   /* lock recursion count */
-        unsigned short          ili_iolock_recur;  /* lock recursion count */
         unsigned short          ili_flags;         /* misc flags */
         unsigned short          ili_logged;        /* flushed logged data */
         unsigned int            ili_last_fields;   /* fields when flushed */