[PATCH 16/37] xfs: check for buffer errors before waiting

From: Dave Chinner <dchinner@...>

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@...>
Reviewed-by: Christoph Hellwig <hch@...>
Reviewed-by: Mark Tinguely <tinguely@...>
---
 fs/xfs/xfs_buf.c         |   22 ++++++++++------------
 fs/xfs/xfs_buf.h         |    2 +-
 fs/xfs/xfs_log_recover.c |    2 ++
 3 files changed, 13 insertions(+), 13 deletions(-)

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index da2541e..86d9af7 100644
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -600,17 +600,15 @@ _xfs_buf_read(
  xfs_buf_t *bp,
  xfs_buf_flags_t flags)
 {
- int status;
-
  ASSERT(!(flags & XBF_WRITE));
  ASSERT(bp->b_bn != XFS_BUF_DADDR_NULL);
 
  bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
  bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
 
- status = xfs_buf_iorequest(bp);
- if (status || bp->b_error || (flags & XBF_ASYNC))
- return status;
+ xfs_buf_iorequest(bp);
+ if (flags & XBF_ASYNC)
+ return 0;
  return xfs_buf_iowait(bp);
 }
 
@@ -695,7 +693,7 @@ 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;
  }
@@ -1252,7 +1250,7 @@ next_chunk:
  }
 }
 
-int
+void
 xfs_buf_iorequest(
  xfs_buf_t *bp)
 {
@@ -1273,13 +1271,12 @@ 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(
@@ -1287,7 +1284,8 @@ 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/xfs_buf.h b/fs/xfs/xfs_buf.h
index 7083cf4..87a4748 100644
--- a/fs/xfs/xfs_buf.h
+++ b/fs/xfs/xfs_buf.h
@@ -191,7 +191,7 @@ 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 396e3bf..64ed6ff 100644
--- a/fs/xfs/xfs_log_recover.c
+++ b/fs/xfs/xfs_log_recover.c
@@ -179,6 +179,7 @@ xlog_bread_noalign(
  XFS_BUF_SET_ADDR(bp, log->l_logBBstart + blk_no);
  XFS_BUF_READ(bp);
  XFS_BUF_SET_COUNT(bp, BBTOB(nbblks));
+ bp->b_error = 0;
 
  xfsbdstrat(log->l_mp, bp);
  error = xfs_buf_iowait(bp);
@@ -266,6 +267,7 @@ xlog_bwrite(
  xfs_buf_hold(bp);
  xfs_buf_lock(bp);
  XFS_BUF_SET_COUNT(bp, BBTOB(nbblks));
+ bp->b_error = 0;
 
  error = xfs_bwrite(bp);
  if (error)
--
1.7.9.5

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