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, 9 insertions, 32 deletions

diff --git a/fs/xfs/xfs_log_cil.c b/fs/xfs/xfs_log_cil.c
index 0a7a8cef6019..cdebd832c3db 100644
--- a/fs/xfs/xfs_log_cil.c
+++ b/fs/xfs/xfs_log_cil.c
@@ -82,36 +82,6 @@ xlog_cil_init_post_recovery(
 								log->l_curr_block);
 }
 
-STATIC int
-xlog_cil_lv_item_format(
-	struct xfs_log_item	*lip,
-	struct xfs_log_vec	*lv)
-{
-	int	index;
-	char	*ptr;
-
-	/* format new vectors into array */
-	lip->li_ops->iop_format(lip, lv->lv_iovecp);
-
-	/* copy data into existing array */
-	ptr = lv->lv_buf;
-	for (index = 0; index < lv->lv_niovecs; index++) {
-		struct xfs_log_iovec *vec = &lv->lv_iovecp[index];
-
-		memcpy(ptr, vec->i_addr, vec->i_len);
-		vec->i_addr = ptr;
-		ptr += vec->i_len;
-	}
-
-	/*
-	 * some size calculations for log vectors over-estimate, so the caller
-	 * doesn't know the amount of space actually used by the item. Return
-	 * the byte count to the caller so they can check and store it
-	 * appropriately.
-	 */
-	return ptr - lv->lv_buf;
-}
-
 /*
  * Prepare the log item for insertion into the CIL. Calculate the difference in
  * log space and vectors it will consume, and if it is a new item pin it as
@@ -232,6 +202,13 @@ xlog_cil_insert_format_items(
 			nbytes = 0;
 		}
 
+		/*
+		 * We 64-bit align the length of each iovec so that the start
+		 * of the next one is naturally aligned.  We'll need to
+		 * account for that slack space here.
+		 */
+		nbytes += niovecs * sizeof(uint64_t);
+
 		/* grab the old item if it exists for reservation accounting */
 		old_lv = lip->li_lv;
 
@@ -272,9 +249,9 @@ xlog_cil_insert_format_items(
 		lv->lv_niovecs = niovecs;
 
 		/* The allocated data region lies beyond the iovec region */
+		lv->lv_buf_len = 0;
 		lv->lv_buf = (char *)lv + buf_size - nbytes;
-
-		lv->lv_buf_len = xlog_cil_lv_item_format(lip, lv);
+		lip->li_ops->iop_format(lip, lv);
 insert:
 		ASSERT(lv->lv_buf_len <= nbytes);
 		xfs_cil_prepare_item(log, lv, old_lv, diff_len, diff_iovecs);