[PATCH 01/16] xfs: allow non-empty forks in xfs_bmap_local_to_extents_empty

[Christoph Hellwig <hch@lst.de>]

Currently xfs_bmap_local_to_extents_empty expects the caller to set the
for size to 0, which implies freeing if_data.  That is highly suboptimal
because the callers need the data in the local fork so that they can
copy it to the newly allocated extent.

Change xfs_bmap_local_to_extents_empty to return the old fork data and
clear if_bytes to zero instead and let the callers free the memory for
the local fork, which allows them to access the data directly while
formatting the extent format data.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/xfs/libxfs/xfs_bmap.c | 13 +++++++------
 fs/xfs/libxfs/xfs_bmap.h |  2 +-
 2 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 6053f5e5c71eec..eb826fae8fd878 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -754,31 +754,32 @@ xfs_bmap_extents_to_btree(
 
 /*
  * Convert a local file to an extents file.
- * This code is out of bounds for data forks of regular files,
- * since the file data needs to get logged so things will stay consistent.
- * (The bmap-level manipulations are ok, though).
+ *
+ * Returns the content of the old data fork, which needs to be freed by the
+ * caller.
  */
-void
+void *
 xfs_bmap_local_to_extents_empty(
 	struct xfs_trans	*tp,
 	struct xfs_inode	*ip,
 	int			whichfork)
 {
 	struct xfs_ifork	*ifp = xfs_ifork_ptr(ip, whichfork);
+	void			*old_data = ifp->if_data;
 
 	ASSERT(whichfork != XFS_COW_FORK);
 	ASSERT(ifp->if_format == XFS_DINODE_FMT_LOCAL);
-	ASSERT(ifp->if_bytes == 0);
 	ASSERT(ifp->if_nextents == 0);
 
 	xfs_bmap_forkoff_reset(ip, whichfork);
 	ifp->if_data = NULL;
+	ifp->if_bytes = 0;
 	ifp->if_height = 0;
 	ifp->if_format = XFS_DINODE_FMT_EXTENTS;
 	xfs_trans_log_inode(tp, ip, XFS_ILOG_CORE);
+	return old_data;
 }
 
-
 int					/* error */
 xfs_bmap_local_to_extents(
 	xfs_trans_t	*tp,		/* transaction pointer */
diff --git a/fs/xfs/libxfs/xfs_bmap.h b/fs/xfs/libxfs/xfs_bmap.h
index e98849eb9bbae3..6e0b6081bf3aa5 100644
--- a/fs/xfs/libxfs/xfs_bmap.h
+++ b/fs/xfs/libxfs/xfs_bmap.h
@@ -178,7 +178,7 @@ void	xfs_trim_extent(struct xfs_bmbt_irec *irec, xfs_fileoff_t bno,
 unsigned int xfs_bmap_compute_attr_offset(struct xfs_mount *mp);
 int	xfs_bmap_add_attrfork(struct xfs_trans *tp, struct xfs_inode *ip,
 		int size, int rsvd);
-void	xfs_bmap_local_to_extents_empty(struct xfs_trans *tp,
+void	*xfs_bmap_local_to_extents_empty(struct xfs_trans *tp,
 		struct xfs_inode *ip, int whichfork);
 int xfs_bmap_local_to_extents(struct xfs_trans *tp, struct xfs_inode *ip,
 		xfs_extlen_t total, int *logflagsp, int whichfork,
-- 
2.39.2