xfs: combine [a]sync buffer submission apis

The buffer I/O submission path consists of separate function calls
per type. The buffer I/O type is already controlled via buffer
state (XBF_ASYNC), however, so there is no real need for separate
submission functions.

Combine the buffer submission functions into a single function that
processes the buffer appropriately based on XBF_ASYNC. Retain an
internal helper with a conditional wait parameter to continue to
support batched !XBF_ASYNC submission/completion required by delwri
queues.

Suggested-by: Christoph Hellwig <hch@infradead.org>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index ef23484..be79dd2 100644 (file)
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -757,11 +757,7 @@ _xfs_buf_read(
        bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
        bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
 
-       if (flags & XBF_ASYNC) {
-               xfs_buf_submit(bp);
-               return 0;
-       }
-       return xfs_buf_submit_wait(bp);
+       return xfs_buf_submit(bp);
 }
 
 xfs_buf_t *
@@ -846,7 +842,7 @@ xfs_buf_read_uncached(
        bp->b_flags |= XBF_READ;
        bp->b_ops = ops;
 
-       xfs_buf_submit_wait(bp);
+       xfs_buf_submit(bp);
        if (bp->b_error) {
                int     error = bp->b_error;
                xfs_buf_relse(bp);
@@ -1249,7 +1245,7 @@ xfs_bwrite(
        bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q |
                         XBF_WRITE_FAIL | XBF_DONE);
 
-       error = xfs_buf_submit_wait(bp);
+       error = xfs_buf_submit(bp);
        if (error) {
                xfs_force_shutdown(bp->b_target->bt_mount,
                                   SHUTDOWN_META_IO_ERROR);
@@ -1459,7 +1455,7 @@ _xfs_buf_ioapply(
  * itself.
  */
 static int
-__xfs_buf_submit(
+__xfs_buf_submit_common(
        struct xfs_buf  *bp)
 {
        trace_xfs_buf_submit(bp, _RET_IP_);
@@ -1505,32 +1501,6 @@ __xfs_buf_submit(
        return 0;
 }
 
-void
-xfs_buf_submit(
-       struct xfs_buf  *bp)
-{
-       int             error;
-
-       ASSERT(bp->b_flags & XBF_ASYNC);
-
-       /*
-        * The caller's reference is released during I/O completion.
-        * This occurs some time after the last b_io_remaining reference is
-        * released, so after we drop our Io reference we have to have some
-        * other reference to ensure the buffer doesn't go away from underneath
-        * us. Take a direct reference to ensure we have safe access to the
-        * buffer until we are finished with it.
-        */
-       xfs_buf_hold(bp);
-
-       error = __xfs_buf_submit(bp);
-       if (error)
-               xfs_buf_ioend(bp);
-
-       /* Note: it is not safe to reference bp now we've dropped our ref */
-       xfs_buf_rele(bp);
-}
-
 /*
  * Wait for I/O completion of a sync buffer and return the I/O error code.
  */
@@ -1538,6 +1508,8 @@ static int
 xfs_buf_iowait(
        struct xfs_buf  *bp)
 {
+       ASSERT(!(bp->b_flags & XBF_ASYNC));
+
        trace_xfs_buf_iowait(bp, _RET_IP_);
        wait_for_completion(&bp->b_iowait);
        trace_xfs_buf_iowait_done(bp, _RET_IP_);
@@ -1549,30 +1521,33 @@ xfs_buf_iowait(
  * Synchronous buffer IO submission path, read or write.
  */
 int
-xfs_buf_submit_wait(
-       struct xfs_buf  *bp)
+__xfs_buf_submit(
+       struct xfs_buf  *bp,
+       bool            wait)
 {
        int             error;
 
-       ASSERT(!(bp->b_flags & XBF_ASYNC));
-
        /*
-        * For synchronous IO, the IO does not inherit the submitters reference
-        * count, nor the buffer lock. Hence we cannot release the reference we
-        * are about to take until we've waited for all IO completion to occur,
-        * including any xfs_buf_ioend_async() work that may be pending.
+        * Grab a reference so the buffer does not go away underneath us. For
+        * async buffers, I/O completion drops the callers reference, which
+        * could occur before submission returns.
         */
        xfs_buf_hold(bp);
 
-       error = __xfs_buf_submit(bp);
-       if (error)
+       error = __xfs_buf_submit_common(bp);
+       if (error) {
+               if (bp->b_flags & XBF_ASYNC)
+                       xfs_buf_ioend(bp);
                goto out;
-       error = xfs_buf_iowait(bp);
+       }
 
+       if (wait)
+               error = xfs_buf_iowait(bp);
 out:
        /*
-        * all done now, we can release the hold that keeps the buffer
-        * referenced for the entire IO.
+        * Release the hold that keeps the buffer referenced for the entire
+        * I/O. Note that if the buffer is async, it is not safe to reference
+        * after this release.
         */
        xfs_buf_rele(bp);
        return error;
@@ -2026,12 +2001,11 @@ xfs_buf_delwri_submit_buffers(
                if (wait_list) {
                        bp->b_flags &= ~XBF_ASYNC;
                        list_move_tail(&bp->b_list, wait_list);
-                       __xfs_buf_submit(bp);
                } else {
                        bp->b_flags |= XBF_ASYNC;
                        list_del_init(&bp->b_list);
-                       xfs_buf_submit(bp);
                }
+               __xfs_buf_submit(bp, false);
        }
        blk_finish_plug(&plug);
 

diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h
index 6ddf190..f046131 100644 (file)
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -297,8 +297,14 @@ extern void __xfs_buf_ioerror(struct xfs_buf *bp, int error,
                xfs_failaddr_t failaddr);
 #define xfs_buf_ioerror(bp, err) __xfs_buf_ioerror((bp), (err), __this_address)
 extern void xfs_buf_ioerror_alert(struct xfs_buf *, const char *func);
-extern void xfs_buf_submit(struct xfs_buf *bp);
-extern int xfs_buf_submit_wait(struct xfs_buf *bp);
+
+extern int __xfs_buf_submit(struct xfs_buf *bp, bool);
+static inline int xfs_buf_submit(struct xfs_buf *bp)
+{
+       bool wait = bp->b_flags & XBF_ASYNC ? false : true;
+       return __xfs_buf_submit(bp, wait);
+}
+
 extern void xfs_buf_iomove(xfs_buf_t *, size_t, size_t, void *,
                                xfs_buf_rw_t);
 #define xfs_buf_zero(bp, off, len) \

diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 8317023..cbac943 100644 (file)
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -196,7 +196,7 @@ xlog_bread_noalign(
        bp->b_io_length = nbblks;
        bp->b_error = 0;
 
-       error = xfs_buf_submit_wait(bp);
+       error = xfs_buf_submit(bp);
        if (error && !XFS_FORCED_SHUTDOWN(log->l_mp))
                xfs_buf_ioerror_alert(bp, __func__);
        return error;
@@ -5706,7 +5706,7 @@ xlog_do_recover(
        bp->b_flags |= XBF_READ;
        bp->b_ops = &xfs_sb_buf_ops;
 
-       error = xfs_buf_submit_wait(bp);
+       error = xfs_buf_submit(bp);
        if (error) {
                if (!XFS_FORCED_SHUTDOWN(mp)) {
                        xfs_buf_ioerror_alert(bp, __func__);