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>
diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index f4d4e70..ea79072 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -987,13 +987,12 @@
{
int error;
- bp->b_strat = xfs_bdstrat_cb;
bp->b_mount = mp;
bp->b_flags |= XBF_WRITE;
bp->b_flags &= ~(XBF_ASYNC | XBF_READ);
xfs_buf_delwri_dequeue(bp);
- xfs_buf_iostrategy(bp);
+ xfs_bdstrat_cb(bp);
error = xfs_buf_iowait(bp);
if (error)
@@ -1009,7 +1008,6 @@
{
trace_xfs_buf_bdwrite(bp, _RET_IP_);
- bp->b_strat = xfs_bdstrat_cb;
bp->b_mount = mp;
bp->b_flags &= ~XBF_READ;
@@ -1044,7 +1042,6 @@
XFS_BUF_UNDONE(bp);
XFS_BUF_STALE(bp);
- XFS_BUF_CLR_BDSTRAT_FUNC(bp);
xfs_biodone(bp);
return EIO;
@@ -1074,7 +1071,6 @@
XFS_BUF_DONE(bp);
XFS_BUF_STALE(bp);
XFS_BUF_CLR_IODONE_FUNC(bp);
- XFS_BUF_CLR_BDSTRAT_FUNC(bp);
if (!(fl & XBF_ASYNC)) {
/*
* Mark b_error and B_ERROR _both_.
@@ -1869,7 +1865,7 @@
struct xfs_buf *bp;
bp = list_first_entry(&tmp, struct xfs_buf, b_list);
list_del_init(&bp->b_list);
- xfs_buf_iostrategy(bp);
+ xfs_bdstrat_cb(bp);
count++;
}
if (count)
@@ -1916,7 +1912,7 @@
bp->b_flags &= ~XBF_ASYNC;
list_add(&bp->b_list, &wait_list);
}
- xfs_buf_iostrategy(bp);
+ xfs_bdstrat_cb(bp);
}
if (wait) {