xfs: condense symbolic links after a mapping exchange operation

The previous commit added a new file mapping exchange flag that enables
us to perform post-exchange processing on file2 once we're done
exchanging the extent mappings.  Now add this ability for symlinks.

This isn't used anywhere right now, but we need to have the basic ondisk
flags in place so that a future online symlink repair feature can
salvage the remote target in a temporary link and exchange the data fork
mappings when ready.  If one file is in extents format and the other is
inline, we will have to promote both to extents format to perform the
exchange.  After the exchange, we can try to condense the fixed symlink
down to inline format if possible.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

1 files changed, 48 insertions, 1 deletions

diff --git a/fs/xfs/libxfs/xfs_exchmaps.c b/fs/xfs/libxfs/xfs_exchmaps.c
index f199629adbf0..f58240466b1c 100644
--- a/fs/xfs/libxfs/xfs_exchmaps.c
+++ b/fs/xfs/libxfs/xfs_exchmaps.c
@@ -30,6 +30,7 @@
 #include "xfs_attr.h"
 #include "xfs_dir2_priv.h"
 #include "xfs_dir2.h"
+#include "xfs_symlink_remote.h"
 
 struct kmem_cache	*xfs_exchmaps_intent_cache;
 
@@ -433,6 +434,49 @@ xfs_exchmaps_dir_to_sf(
 	return xfs_dir2_block_to_sf(&args, bp, size, &sfh);
 }
 
+/* Convert inode2's remote symlink target back to shortform, if possible. */
+STATIC int
+xfs_exchmaps_link_to_sf(
+	struct xfs_trans		*tp,
+	struct xfs_exchmaps_intent	*xmi)
+{
+	struct xfs_inode		*ip = xmi->xmi_ip2;
+	struct xfs_ifork		*ifp = xfs_ifork_ptr(ip, XFS_DATA_FORK);
+	char				*buf;
+	int				error;
+
+	if (ifp->if_format == XFS_DINODE_FMT_LOCAL ||
+	    ip->i_disk_size > xfs_inode_data_fork_size(ip))
+		return 0;
+
+	/* Read the current symlink target into a buffer. */
+	buf = kmalloc(ip->i_disk_size + 1,
+			GFP_KERNEL | __GFP_NOLOCKDEP | __GFP_NOFAIL);
+	if (!buf) {
+		ASSERT(0);
+		return -ENOMEM;
+	}
+
+	error = xfs_symlink_remote_read(ip, buf);
+	if (error)
+		goto free;
+
+	/* Remove the blocks. */
+	error = xfs_symlink_remote_truncate(tp, ip);
+	if (error)
+		goto free;
+
+	/* Convert fork to local format and log our changes. */
+	xfs_idestroy_fork(ifp);
+	ifp->if_bytes = 0;
+	ifp->if_format = XFS_DINODE_FMT_LOCAL;
+	xfs_init_local_fork(ip, XFS_DATA_FORK, buf, ip->i_disk_size);
+	xfs_trans_log_inode(tp, ip, XFS_ILOG_DDATA | XFS_ILOG_CORE);
+free:
+	kfree(buf);
+	return error;
+}
+
 /* Clear the reflink flag after an exchange. */
 static inline void
 xfs_exchmaps_clear_reflink(
@@ -458,6 +502,8 @@ xfs_exchmaps_do_postop_work(
 			error = xfs_exchmaps_attr_to_sf(tp, xmi);
 		else if (S_ISDIR(VFS_I(xmi->xmi_ip2)->i_mode))
 			error = xfs_exchmaps_dir_to_sf(tp, xmi);
+		else if (S_ISLNK(VFS_I(xmi->xmi_ip2)->i_mode))
+			error = xfs_exchmaps_link_to_sf(tp, xmi);
 		xmi->xmi_flags &= ~__XFS_EXCHMAPS_INO2_SHORTFORM;
 		if (error)
 			return error;
@@ -922,7 +968,8 @@ xfs_exchmaps_init_intent(
 			xmi->xmi_flags |= XFS_EXCHMAPS_CLEAR_INO2_REFLINK;
 	}
 
-	if (S_ISDIR(VFS_I(xmi->xmi_ip2)->i_mode))
+	if (S_ISDIR(VFS_I(xmi->xmi_ip2)->i_mode) ||
+	    S_ISLNK(VFS_I(xmi->xmi_ip2)->i_mode))
 		xmi->xmi_flags |= __XFS_EXCHMAPS_INO2_SHORTFORM;
 
 	return xmi;