xfs: condense extended attributes after a mapping exchange operation

Add a new file mapping exchange flag that enables us to perform
post-exchange processing on file2 once we're done exchanging the extent
mappings.  If we were swapping mappings between extended attribute
forks, we want to be able to convert file2's attr fork from block to
inline format.

(This implies that all fork contents are exchanged.)

This isn't used anywhere right now, but we need to have the basic ondisk
flags in place so that a future online xattr repair feature can create
salvaged attrs in a temporary file and exchange the attr 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 file's attr fork
back down to inline format if possible.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

fs/xfs/libxfs/xfs_exchmaps.c

@@ -24,6 +24,10 @@
 #include "xfs_errortag.h"
 #include "xfs_health.h"
 #include "xfs_exchmaps_item.h"
+#include "xfs_da_format.h"
+#include "xfs_da_btree.h"
+#include "xfs_attr_leaf.h"
+#include "xfs_attr.h"
 
 struct kmem_cache	*xfs_exchmaps_intent_cache;
 
@@ -121,7 +125,8 @@ static inline bool
 xmi_has_postop_work(const struct xfs_exchmaps_intent *xmi)
 {
 	return xmi->xmi_flags & (XFS_EXCHMAPS_CLEAR_INO1_REFLINK |
-				 XFS_EXCHMAPS_CLEAR_INO2_REFLINK);
+				 XFS_EXCHMAPS_CLEAR_INO2_REFLINK |
+				 __XFS_EXCHMAPS_INO2_SHORTFORM);
 }
 
 /* Check all mappings to make sure we can actually exchange them. */
@@ -360,6 +365,36 @@ xfs_exchmaps_one_step(
 	xmi_advance(xmi, irec1);
 }
 
+/* Convert inode2's leaf attr fork back to shortform, if possible.. */
+STATIC int
+xfs_exchmaps_attr_to_sf(
+	struct xfs_trans		*tp,
+	struct xfs_exchmaps_intent	*xmi)
+{
+	struct xfs_da_args	args = {
+		.dp		= xmi->xmi_ip2,
+		.geo		= tp->t_mountp->m_attr_geo,
+		.whichfork	= XFS_ATTR_FORK,
+		.trans		= tp,
+	};
+	struct xfs_buf		*bp;
+	int			forkoff;
+	int			error;
+
+	if (!xfs_attr_is_leaf(xmi->xmi_ip2))
+		return 0;
+
+	error = xfs_attr3_leaf_read(tp, xmi->xmi_ip2, 0, &bp);
+	if (error)
+		return error;
+
+	forkoff = xfs_attr_shortform_allfit(bp, xmi->xmi_ip2);
+	if (forkoff == 0)
+		return 0;
+
+	return xfs_attr3_leaf_to_shortform(bp, &args, forkoff);
+}
+
 /* Clear the reflink flag after an exchange. */
 static inline void
 xfs_exchmaps_clear_reflink(
@@ -378,6 +413,16 @@ xfs_exchmaps_do_postop_work(
 	struct xfs_trans		*tp,
 	struct xfs_exchmaps_intent	*xmi)
 {
+	if (xmi->xmi_flags & __XFS_EXCHMAPS_INO2_SHORTFORM) {
+		int			error = 0;
+
+		if (xmi->xmi_flags & XFS_EXCHMAPS_ATTR_FORK)
+			error = xfs_exchmaps_attr_to_sf(tp, xmi);
+		xmi->xmi_flags &= ~__XFS_EXCHMAPS_INO2_SHORTFORM;
+		if (error)
+			return error;
+	}
+
 	if (xmi->xmi_flags & XFS_EXCHMAPS_CLEAR_INO1_REFLINK) {
 		xfs_exchmaps_clear_reflink(tp, xmi->xmi_ip1);
 		xmi->xmi_flags &= ~XFS_EXCHMAPS_CLEAR_INO1_REFLINK;
@@ -809,8 +854,10 @@ xfs_exchmaps_init_intent(
 	xmi->xmi_isize1 = xmi->xmi_isize2 = -1;
 	xmi->xmi_flags = req->flags & XFS_EXCHMAPS_PARAMS;
 
-	if (xfs_exchmaps_whichfork(xmi) == XFS_ATTR_FORK)
+	if (xfs_exchmaps_whichfork(xmi) == XFS_ATTR_FORK) {
+		xmi->xmi_flags |= __XFS_EXCHMAPS_INO2_SHORTFORM;
 		return xmi;
+	}
 
 	if (req->flags & XFS_EXCHMAPS_SET_SIZES) {
 		xmi->xmi_flags |= XFS_EXCHMAPS_SET_SIZES;
@@ -1031,6 +1078,8 @@ xfs_exchange_mappings(
 {
 	struct xfs_exchmaps_intent	*xmi;
 
+	BUILD_BUG_ON(XFS_EXCHMAPS_INTERNAL_FLAGS & XFS_EXCHMAPS_LOGGED_FLAGS);
+
 	xfs_assert_ilocked(req->ip1, XFS_ILOCK_EXCL);
 	xfs_assert_ilocked(req->ip2, XFS_ILOCK_EXCL);
 	ASSERT(!(req->flags & ~XFS_EXCHMAPS_LOGGED_FLAGS));

fs/xfs/libxfs/xfs_exchmaps.h

@@ -27,6 +27,11 @@ struct xfs_exchmaps_intent {
 	uint64_t		xmi_flags;	/* XFS_EXCHMAPS_* flags */
 };
 
+/* Try to convert inode2 from block to short format at the end, if possible. */
+#define __XFS_EXCHMAPS_INO2_SHORTFORM	(1ULL << 63)
+
+#define XFS_EXCHMAPS_INTERNAL_FLAGS	(__XFS_EXCHMAPS_INO2_SHORTFORM)
+
 /* flags that can be passed to xfs_exchmaps_{estimate,mappings} */
 #define XFS_EXCHMAPS_PARAMS		(XFS_EXCHMAPS_ATTR_FORK | \
 					 XFS_EXCHMAPS_SET_SIZES | \

fs/xfs/xfs_trace.h

@@ -4779,7 +4779,8 @@ DEFINE_XFBTREE_FREESP_EVENT(xfbtree_free_block);
 	{ XFS_EXCHMAPS_SET_SIZES,		"SETSIZES" }, \
 	{ XFS_EXCHMAPS_INO1_WRITTEN,		"INO1_WRITTEN" }, \
 	{ XFS_EXCHMAPS_CLEAR_INO1_REFLINK,	"CLEAR_INO1_REFLINK" }, \
-	{ XFS_EXCHMAPS_CLEAR_INO2_REFLINK,	"CLEAR_INO2_REFLINK" }
+	{ XFS_EXCHMAPS_CLEAR_INO2_REFLINK,	"CLEAR_INO2_REFLINK" }, \
+	{ __XFS_EXCHMAPS_INO2_SHORTFORM,	"INO2_SF" }
 
 DEFINE_INODE_IREC_EVENT(xfs_exchmaps_mapping1_skip);
 DEFINE_INODE_IREC_EVENT(xfs_exchmaps_mapping1);