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@xxxxxx>
Index: xfs/fs/xfs/linux-2.6/xfs_buf.c
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_buf.c 2010-07-18 07:16:09.101494681 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_buf.c 2010-07-18 07:16:10.646494682 +0200
@@ -987,13 +987,12 @@ xfs_bwrite(
{
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 @@ xfs_bdwrite(
{
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_bioerror(
XFS_BUF_UNDONE(bp);
XFS_BUF_STALE(bp);
- XFS_BUF_CLR_BDSTRAT_FUNC(bp);
xfs_biodone(bp);
return EIO;
@@ -1074,7 +1071,6 @@ xfs_bioerror_relse(
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_.
@@ -1857,7 +1853,7 @@ xfsbufd(
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)
@@ -1904,7 +1900,7 @@ xfs_flush_buftarg(
bp->b_flags &= ~XBF_ASYNC;
list_add(&bp->b_list, &wait_list);
}
- xfs_buf_iostrategy(bp);
+ xfs_bdstrat_cb(bp);
}
if (wait) {
Index: xfs/fs/xfs/linux-2.6/xfs_buf.h
===================================================================
--- xfs.orig/fs/xfs/linux-2.6/xfs_buf.h 2010-07-18 07:16:09.108494681 +0200
+++ xfs/fs/xfs/linux-2.6/xfs_buf.h 2010-07-18 07:16:10.647494682 +0200
@@ -187,7 +187,6 @@ typedef struct xfs_buf {
atomic_t b_io_remaining; /* #outstanding I/O requests */
xfs_buf_iodone_t b_iodone; /* I/O completion function */
xfs_buf_relse_t b_relse; /* releasing function */
- xfs_buf_bdstrat_t b_strat; /* pre-write function */
struct completion b_iowait; /* queue for I/O waiters */
void *b_fspriv;
void *b_fspriv2;
@@ -245,11 +244,6 @@ extern int xfs_buf_iowait(xfs_buf_t *);
extern void xfs_buf_iomove(xfs_buf_t *, size_t, size_t, void *,
xfs_buf_rw_t);
-static inline int xfs_buf_iostrategy(xfs_buf_t *bp)
-{
- return bp->b_strat ? bp->b_strat(bp) : xfs_buf_iorequest(bp);
-}
-
static inline int xfs_buf_geterror(xfs_buf_t *bp)
{
return bp ? bp->b_error : ENOMEM;
@@ -321,8 +315,6 @@ extern void xfs_buf_terminate(void);
#define XFS_BUF_IODONE_FUNC(bp) ((bp)->b_iodone)
#define XFS_BUF_SET_IODONE_FUNC(bp, func) ((bp)->b_iodone = (func))
#define XFS_BUF_CLR_IODONE_FUNC(bp) ((bp)->b_iodone = NULL)
-#define XFS_BUF_SET_BDSTRAT_FUNC(bp, func) ((bp)->b_strat = (func))
-#define XFS_BUF_CLR_BDSTRAT_FUNC(bp) ((bp)->b_strat = NULL)
#define XFS_BUF_FSPRIVATE(bp, type) ((type)(bp)->b_fspriv)
#define XFS_BUF_SET_FSPRIVATE(bp, val) ((bp)->b_fspriv = (void*)(val))
Index: xfs/fs/xfs/xfs_buf_item.c
===================================================================
--- xfs.orig/fs/xfs/xfs_buf_item.c 2010-07-18 07:16:09.117494681 +0200
+++ xfs/fs/xfs/xfs_buf_item.c 2010-07-18 07:16:10.654494682 +0200
@@ -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) {
Index: xfs/fs/xfs/xfs_inode.c
===================================================================
--- xfs.orig/fs/xfs/xfs_inode.c 2010-07-18 07:16:09.127494681 +0200
+++ xfs/fs/xfs/xfs_inode.c 2010-07-18 07:16:10.662494682 +0200
@@ -2717,7 +2717,6 @@ cluster_corrupt_out:
* mark it as stale and brelse.
*/
if (XFS_BUF_IODONE_FUNC(bp)) {
- XFS_BUF_CLR_BDSTRAT_FUNC(bp);
XFS_BUF_UNDONE(bp);
XFS_BUF_STALE(bp);
XFS_BUF_ERROR(bp,EIO);
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