[PATCH 082/102] xfs: check for buffer errors before waiting

[Dave Chinner <david@xxxxxxxxxxxxx>]

From: Dave Chinner <dchinner@xxxxxxxxxx>

Upstream commit: 0e95f19ad983e72a9cb93a67b3290b58f0467b36

If we call xfs_buf_iowait() on a buffer that failed dispatch due to
an IO error, it will wait forever for an Io that does not exist.
This is hndled in xfs_buf_read, but there is other code that calls
xfs_buf_iowait directly that doesn't.

Rather than make the call sites have to handle checking for dispatch
errors and then checking for completion errors, make
xfs_buf_iowait() check for dispatch errors on the buffer before
waiting. This means we handle both dispatch and completion errors
with one set of error handling at the caller sites.

Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Mark Tinguely <tinguely@xxxxxxx>
Signed-off-by: Ben Myers <bpm@xxxxxxx>
---
 fs/xfs/linux-2.6/xfs_buf.c |   24 +++++++++++-------------
 fs/xfs/linux-2.6/xfs_buf.h |    2 +-
 fs/xfs/xfs_log_recover.c   |    2 ++
 3 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/fs/xfs/linux-2.6/xfs_buf.c b/fs/xfs/linux-2.6/xfs_buf.c
index 0858fe1..5487eaa 100644
--- a/fs/xfs/linux-2.6/xfs_buf.c
+++ b/fs/xfs/linux-2.6/xfs_buf.c
@@ -597,8 +597,6 @@ _xfs_buf_read(
        xfs_buf_t               *bp,
        xfs_buf_flags_t         flags)
 {
-       int                     status;
-
        ASSERT(!(flags & (XBF_DELWRI|XBF_WRITE)));
        ASSERT(bp->b_bn != XFS_BUF_DADDR_NULL);
 
@@ -607,9 +605,9 @@ _xfs_buf_read(
        bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | \
                        XBF_READ_AHEAD | _XBF_RUN_QUEUES);
 
-       status = xfs_buf_iorequest(bp);
-       if (status || XFS_BUF_ISERROR(bp) || (flags & XBF_ASYNC))
-               return status;
+       xfs_buf_iorequest(bp);
+       if (flags & XBF_ASYNC)
+               return 0;
        return xfs_buf_iowait(bp);
 }
 
@@ -696,7 +694,7 @@ xfs_buf_read_uncached(
 
        xfsbdstrat(mp, bp);
        error = xfs_buf_iowait(bp);
-       if (error || bp->b_error) {
+       if (error) {
                xfs_buf_relse(bp);
                return NULL;
        }
@@ -1288,7 +1286,7 @@ next_chunk:
        }
 }
 
-int
+void
 xfs_buf_iorequest(
        xfs_buf_t               *bp)
 {
@@ -1296,7 +1294,7 @@ xfs_buf_iorequest(
 
        if (bp->b_flags & XBF_DELWRI) {
                xfs_buf_delwri_queue(bp, 1);
-               return 0;
+               return;
        }
 
        if (bp->b_flags & XBF_WRITE) {
@@ -1314,13 +1312,12 @@ xfs_buf_iorequest(
        _xfs_buf_ioend(bp, 0);
 
        xfs_buf_rele(bp);
-       return 0;
 }
 
 /*
- *     Waits for I/O to complete on the buffer supplied.
- *     It returns immediately if no I/O is pending.
- *     It returns the I/O error code, if any, or 0 if there was no error.
+ * Waits for I/O to complete on the buffer supplied.  It returns immediately if
+ * no I/O is pending or there is already a pending error on the buffer.  It
+ * returns the I/O error code, if any, or 0 if there was no error.
  */
 int
 xfs_buf_iowait(
@@ -1328,7 +1325,8 @@ xfs_buf_iowait(
 {
        trace_xfs_buf_iowait(bp, _RET_IP_);
 
-       wait_for_completion(&bp->b_iowait);
+       if (!bp->b_error)
+               wait_for_completion(&bp->b_iowait);
 
        trace_xfs_buf_iowait_done(bp, _RET_IP_);
        return bp->b_error;
diff --git a/fs/xfs/linux-2.6/xfs_buf.h b/fs/xfs/linux-2.6/xfs_buf.h
index 71d6698..edb8d7c 100644
--- a/fs/xfs/linux-2.6/xfs_buf.h
+++ b/fs/xfs/linux-2.6/xfs_buf.h
@@ -208,7 +208,7 @@ extern int xfs_bdstrat_cb(struct xfs_buf *);
 extern void xfs_buf_ioend(xfs_buf_t *, int);
 extern void xfs_buf_ioerror(xfs_buf_t *, int);
 extern void xfs_buf_ioerror_alert(struct xfs_buf *, const char *func);
-extern int xfs_buf_iorequest(xfs_buf_t *);
+extern void xfs_buf_iorequest(xfs_buf_t *);
 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);
diff --git a/fs/xfs/xfs_log_recover.c b/fs/xfs/xfs_log_recover.c
index 82f7d18..13c057b 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -177,6 +177,7 @@ xlog_bread_noalign(
        XFS_BUF_BUSY(bp);
        XFS_BUF_SET_COUNT(bp, BBTOB(nbblks));
        XFS_BUF_SET_TARGET(bp, log->l_mp->m_logdev_targp);
+       bp->b_error = 0;
 
        xfsbdstrat(log->l_mp, bp);
        error = xfs_buf_iowait(bp);
@@ -266,6 +267,7 @@ xlog_bwrite(
        XFS_BUF_PSEMA(bp, PRIBIO);
        XFS_BUF_SET_COUNT(bp, BBTOB(nbblks));
        XFS_BUF_SET_TARGET(bp, log->l_mp->m_logdev_targp);
+       bp->b_error = 0;
 
        error = xfs_bwrite(log->l_mp, bp);
        if (error)
-- 
1.7.10