xfs: kill the b_strat callback in xfs_buf

The b_strat callback is used by xfs_buf_iostrategy to perform additional
checks before submitting a buffer.  It is used in xfs_bwrite and when
writing out delayed buffers.  In xfs_bwrite it we can de-virtualize the
call easily as b_strat is set a few lines above the call to
xfs_buf_iostrategy.  For the delayed buffers the rationale is a bit
more complicated:

 - there are three callers of xfs_buf_delwri_queue, which places buffers
   on the delwri list:
    (1) xfs_bdwrite - this sets up b_strat, so it's fine
    (2) xfs_buf_iorequest.  None of the callers can have XBF_DELWRI set:
	- xlog_bdstrat is only used for log buffers, which are never delwri
	- _xfs_buf_read explicitly clears the delwri flag
	- xfs_buf_iodone_work retries log buffers only
	- xfsbdstrat - only used for reads, superblock writes without the
	  delwri flag, log I/O and file zeroing with explicitly allocated
	  buffers.
	- xfs_buf_iostrategy - only calls xfs_buf_iorequest if b_strat is
	  not set
    (3) xfs_buf_unlock
	- only puts the buffer on the delwri list if the DELWRI flag is
	  already set.  The DELWRI flag is only ever set in xfs_bwrite,
	  xfs_buf_iodone_callbacks, or xfs_trans_log_buf.  For
	  xfs_buf_iodone_callbacks and xfs_trans_log_buf we require
	  an initialized buf item, which means b_strat was set to
	  xfs_bdstrat_cb in xfs_buf_item_init.

Conclusion: we can just get rid of the callback and replace it with
explicit calls to xfs_bdstrat_cb.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 0 insertions, 1 deletions

diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index 2a9e4ef12110..1b09d7a280df 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -694,7 +694,6 @@ xfs_buf_item_init(
 	 */
 	if (bp->b_mount != mp)
 		bp->b_mount = mp;
-	XFS_BUF_SET_BDSTRAT_FUNC(bp, xfs_bdstrat_cb);
 	if (XFS_BUF_FSPRIVATE(bp, void *) != NULL) {
 		lip = XFS_BUF_FSPRIVATE(bp, xfs_log_item_t *);
 		if (lip->li_type == XFS_LI_BUF) {