xfs: format log items write directly into the linear CIL buffer

Instead of setting up pointers to memory locations in iop_format which then
get copied into the CIL linear buffer after return move the copy into
the individual inode items.  This avoids the need to always have a memory
block in the exact same layout that gets written into the log around, and
allow the log items to be much more flexible in their in-memory layouts.

The only caveat is that we need to properly align the data for each
iovec so that don't have structures misaligned in subsequent iovecs.

Note that all log item format routines now need to be careful to modify
the copy of the item that was placed into the CIL after calls to
xlog_copy_iovec instead of the in-memory copy.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

1 files changed, 14 insertions, 15 deletions

diff --git a/fs/xfs/xfs_buf_item.c b/fs/xfs/xfs_buf_item.c
index d49419d4bb4..76411730543 100644
--- a/fs/xfs/xfs_buf_item.c
+++ b/fs/xfs/xfs_buf_item.c
@@ -184,6 +184,7 @@ xfs_buf_item_size(
 
 static inline void
 xfs_buf_item_copy_iovec(
+	struct xfs_log_vec	*lv,
 	struct xfs_log_iovec	**vecp,
 	struct xfs_buf		*bp,
 	uint			offset,
@@ -191,7 +192,7 @@ xfs_buf_item_copy_iovec(
 	uint			nbits)
 {
 	offset += first_bit * XFS_BLF_CHUNK;
-	xlog_copy_iovec(vecp, XLOG_REG_TYPE_BCHUNK,
+	xlog_copy_iovec(lv, vecp, XLOG_REG_TYPE_BCHUNK,
 			xfs_buf_offset(bp, offset),
 			nbits * XFS_BLF_CHUNK);
 }
@@ -211,13 +212,13 @@ xfs_buf_item_straddle(
 static void
 xfs_buf_item_format_segment(
 	struct xfs_buf_log_item	*bip,
+	struct xfs_log_vec	*lv,
 	struct xfs_log_iovec	**vecp,
 	uint			offset,
 	struct xfs_buf_log_format *blfp)
 {
 	struct xfs_buf	*bp = bip->bli_buf;
 	uint		base_size;
-	uint		nvecs;
 	int		first_bit;
 	int		last_bit;
 	int		next_bit;
@@ -233,18 +234,17 @@ xfs_buf_item_format_segment(
 	 */
 	base_size = xfs_buf_log_format_size(blfp);
 
-	nvecs = 0;
 	first_bit = xfs_next_bit(blfp->blf_data_map, blfp->blf_map_size, 0);
 	if (!(bip->bli_flags & XFS_BLI_STALE) && first_bit == -1) {
 		/*
 		 * If the map is not be dirty in the transaction, mark
 		 * the size as zero and do not advance the vector pointer.
 		 */
-		goto out;
+		return;
 	}
 
-	xlog_copy_iovec(vecp, XLOG_REG_TYPE_BFORMAT, blfp, base_size);
-	nvecs = 1;
+	blfp = xlog_copy_iovec(lv, vecp, XLOG_REG_TYPE_BFORMAT, blfp, base_size);
+	blfp->blf_size = 1;
 
 	if (bip->bli_flags & XFS_BLI_STALE) {
 		/*
@@ -254,7 +254,7 @@ xfs_buf_item_format_segment(
 		 */
 		trace_xfs_buf_item_format_stale(bip);
 		ASSERT(blfp->blf_flags & XFS_BLF_CANCEL);
-		goto out;
+		return;
 	}
 
 
@@ -280,15 +280,15 @@ xfs_buf_item_format_segment(
 		 * same set of bits so just keep counting and scanning.
 		 */
 		if (next_bit == -1) {
-			xfs_buf_item_copy_iovec(vecp, bp, offset,
+			xfs_buf_item_copy_iovec(lv, vecp, bp, offset,
 						first_bit, nbits);
-			nvecs++;
+			blfp->blf_size++;
 			break;
 		} else if (next_bit != last_bit + 1 ||
 		           xfs_buf_item_straddle(bp, offset, next_bit, last_bit)) {
-			xfs_buf_item_copy_iovec(vecp, bp, offset,
+			xfs_buf_item_copy_iovec(lv, vecp, bp, offset,
 						first_bit, nbits);
-			nvecs++;
+			blfp->blf_size++;
 			first_bit = next_bit;
 			last_bit = next_bit;
 			nbits = 1;
@@ -297,8 +297,6 @@ xfs_buf_item_format_segment(
 			nbits++;
 		}
 	}
-out:
-	blfp->blf_size = nvecs;
 }
 
 /*
@@ -310,10 +308,11 @@ out:
 STATIC void
 xfs_buf_item_format(
 	struct xfs_log_item	*lip,
-	struct xfs_log_iovec	*vecp)
+	struct xfs_log_vec	*lv)
 {
 	struct xfs_buf_log_item	*bip = BUF_ITEM(lip);
 	struct xfs_buf		*bp = bip->bli_buf;
+	struct xfs_log_iovec	*vecp = NULL;
 	uint			offset = 0;
 	int			i;
 
@@ -354,7 +353,7 @@ xfs_buf_item_format(
 	}
 
 	for (i = 0; i < bip->bli_format_count; i++) {
-		xfs_buf_item_format_segment(bip, &vecp, offset,
+		xfs_buf_item_format_segment(bip, lv, &vecp, offset,
 					    &bip->bli_formats[i]);
 		offset += bp->b_maps[i].bm_len;
 	}