[PATCH 3/4] libxfs: make xfs_buf_delwri_submit actually do something

["Darrick J. Wong" <darrick.wong@oracle.com>]

From: Darrick J. Wong <darrick.wong@oracle.com>

xfs_buf_delwri_queue doesn't report errors, which means that if the
buffer write fails we have no way of knowing that something bad
happened.  In the kernel we queue and then submit buffers, and the
submit call communicates errors to callers.  Do the same here since
we're going to start using the AG header initialization functions, which
use delwri_{queue,submit} heavily.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
 libxfs/libxfs_io.h   |    6 +++++-
 libxfs/libxfs_priv.h |    1 -
 libxfs/rdwr.c        |   25 +++++++++++++++++++++++++
 3 files changed, 30 insertions(+), 2 deletions(-)


diff --git a/libxfs/libxfs_io.h b/libxfs/libxfs_io.h
index 09ed043b..579df52b 100644
--- a/libxfs/libxfs_io.h
+++ b/libxfs/libxfs_io.h
@@ -71,6 +71,7 @@ typedef struct xfs_buf {
 	struct xfs_buf_map	*b_maps;
 	struct xfs_buf_map	__b_map;
 	int			b_nmaps;
+	struct list_head	b_list;
 #ifdef XFS_BUF_TRACING
 	struct list_head	b_lock_list;
 	const char		*b_func;
@@ -245,11 +246,14 @@ xfs_buf_get_uncached(struct xfs_buftarg *targ, size_t bblen, int flags)
 	return bp;
 }
 
+/* Push a single buffer on a delwri queue. */
 static inline void
 xfs_buf_delwri_queue(struct xfs_buf *bp, struct list_head *buffer_list)
 {
 	bp->b_node.cn_count++;
-	libxfs_writebuf(bp, 0);
+	list_add_tail(&bp->b_list, buffer_list);
 }
 
+int xfs_buf_delwri_submit(struct list_head *buffer_list);
+
 #endif	/* __LIBXFS_IO_H__ */
diff --git a/libxfs/libxfs_priv.h b/libxfs/libxfs_priv.h
index 13dab58a..ff35c51e 100644
--- a/libxfs/libxfs_priv.h
+++ b/libxfs/libxfs_priv.h
@@ -382,7 +382,6 @@ roundup_64(uint64_t x, uint32_t y)
 #define xfs_buf_relse(bp)		libxfs_putbuf(bp)
 #define xfs_buf_get(devp,blkno,len)	(libxfs_getbuf((devp), (blkno), (len)))
 #define xfs_bwrite(bp)			libxfs_writebuf((bp), 0)
-#define xfs_buf_delwri_submit(bl)	(0)
 #define xfs_buf_oneshot(bp)		((void) 0)
 
 #define XBRW_READ			LIBXFS_BREAD
diff --git a/libxfs/rdwr.c b/libxfs/rdwr.c
index 3282f6de..0d3e6089 100644
--- a/libxfs/rdwr.c
+++ b/libxfs/rdwr.c
@@ -1473,3 +1473,28 @@ libxfs_irele(
 	libxfs_idestroy(ip);
 	kmem_zone_free(xfs_inode_zone, ip);
 }
+
+/*
+ * Write out a buffer list synchronously.
+ *
+ * This will take the @buffer_list, write all buffers out and wait for I/O
+ * completion on all of the buffers. @buffer_list is consumed by the function,
+ * so callers must have some other way of tracking buffers if they require such
+ * functionality.
+ */
+int
+xfs_buf_delwri_submit(
+	struct list_head	*buffer_list)
+{
+	struct xfs_buf		*bp, *n;
+	int			error = 0, error2;
+
+	list_for_each_entry_safe(bp, n, buffer_list, b_list) {
+		list_del_init(&bp->b_list);
+		error2 = libxfs_writebuf(bp, 0);
+		if (!error)
+			error = error2;
+	}
+
+	return error;
+}