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

Dave Chinner
2012-04-23T05:59:29Z

From: Dave Chinner <dchinner@redhat.com>

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@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Mark Tinguely <tinguely@sgi.com>
---
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