[PATCH 5/5] xfs: allow linkat() on O_TMPFILE files

[Zhi Yong Wu <zwu.kernel@gmail.com>]

From: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>

Enable O_TMPFILE support in linkat().
For more info, please refer to:
  http://oss.sgi.com/archives/xfs/2013-08/msg00341.html

Signed-off-by: Zhi Yong Wu <wuzhy@linux.vnet.ibm.com>
---
 fs/xfs/xfs_inode.c      |   21 ++++++++++++++++++---
 fs/xfs/xfs_trans_resv.c |   20 ++++++++++++++++++++
 fs/xfs/xfs_trans_resv.h |    2 ++
 3 files changed, 40 insertions(+), 3 deletions(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 48e09c5..2e1fd96 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -62,6 +62,8 @@ kmem_zone_t *xfs_inode_zone;
 
 STATIC int xfs_iflush_int(xfs_inode_t *, xfs_buf_t *);
 
+STATIC int xfs_iunlink_remove(xfs_trans_t *, xfs_inode_t *);
+
 /*
  * helper function to extract extent size hint from inode
  */
@@ -1119,7 +1121,7 @@ xfs_bumplink(
 {
 	xfs_trans_ichgtime(tp, ip, XFS_ICHGTIME_CHG);
 
-	ASSERT(ip->i_d.di_nlink > 0);
+	ASSERT(ip->i_d.di_nlink > 0 || (VFS_I(ip)->i_state & I_LINKABLE));
 	ip->i_d.di_nlink++;
 	inc_nlink(VFS_I(ip));
 	if ((ip->i_d.di_version == 1) &&
@@ -1455,6 +1457,7 @@ xfs_link(
 {
 	xfs_mount_t		*mp = tdp->i_mount;
 	xfs_trans_t		*tp;
+	struct xfs_trans_res	*tres;
 	int			error;
 	xfs_bmap_free_t         free_list;
 	xfs_fsblock_t           first_block;
@@ -1480,10 +1483,16 @@ xfs_link(
 	tp = xfs_trans_alloc(mp, XFS_TRANS_LINK);
 	cancel_flags = XFS_TRANS_RELEASE_LOG_RES;
 	resblks = XFS_LINK_SPACE_RES(mp, target_name->len);
-	error = xfs_trans_reserve(tp, &M_RES(mp)->tr_link, resblks, 0);
+
+	if (sip->i_d.di_nlink == 0)
+		tres = &M_RES(mp)->tr_link_tmpfile;
+	else
+		tres = &M_RES(mp)->tr_link;
+
+	error = xfs_trans_reserve(tp, tres, resblks, 0);
 	if (error == ENOSPC) {
 		resblks = 0;
-		error = xfs_trans_reserve(tp, &M_RES(mp)->tr_link, 0, 0);
+		error = xfs_trans_reserve(tp, tres, 0, 0);
 	}
 	if (error) {
 		cancel_flags = 0;
@@ -1512,6 +1521,12 @@ xfs_link(
 
 	xfs_bmap_init(&free_list, &first_block);
 
+	if (sip->i_d.di_nlink == 0) {
+		error = xfs_iunlink_remove(tp, sip);
+		if (error)
+			goto abort_return;
+	}
+
 	error = xfs_dir_createname(tp, tdp, target_name, sip->i_ino,
 					&first_block, &free_list, resblks);
 	if (error)
diff --git a/fs/xfs/xfs_trans_resv.c b/fs/xfs/xfs_trans_resv.c
index 04519a9..f2da7f4 100644
--- a/fs/xfs/xfs_trans_resv.c
+++ b/fs/xfs/xfs_trans_resv.c
@@ -228,6 +228,22 @@ xfs_calc_link_reservation(
 				      XFS_FSB_TO_B(mp, 1))));
 }
 
+/* For creating a link to an O_TMPFILE inode, except modifying
+ * those metadata for regular inode, we still need to remove an inode
+ * from unlinked list at first. That is,  we can modify:
+ *    the agi hash list and counters: sector size
+ *    the on disk inode before ours in the agi hash list: inode cluster size
+ */
+STATIC uint
+xfs_calc_link_tmpfile_reservation(
+	struct xfs_mount        *mp)
+{
+	return xfs_calc_link_reservation(mp) +
+		xfs_calc_buf_res(1, mp->m_sb.sb_sectsize) +
+		MAX((__uint16_t)XFS_FSB_TO_B(mp, 1),
+		    (__uint16_t)XFS_INODE_CLUSTER_SIZE(mp));
+}
+
 /*
  * For removing a directory entry we can modify:
  *    the parent directory inode: inode size
@@ -743,6 +759,10 @@ xfs_trans_resv_calc(
 	resp->tr_link.tr_logcount = XFS_LINK_LOG_COUNT;
 	resp->tr_link.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
 
+	resp->tr_link_tmpfile.tr_logres = xfs_calc_link_tmpfile_reservation(mp);
+	resp->tr_link_tmpfile.tr_logcount = XFS_LINK_TMPFILE_LOG_COUNT;
+	resp->tr_link_tmpfile.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
+
 	resp->tr_remove.tr_logres = xfs_calc_remove_reservation(mp);
 	resp->tr_remove.tr_logcount = XFS_REMOVE_LOG_COUNT;
 	resp->tr_remove.tr_logflags |= XFS_TRANS_PERM_LOG_RES;
diff --git a/fs/xfs/xfs_trans_resv.h b/fs/xfs/xfs_trans_resv.h
index 285621d..86a0daf 100644
--- a/fs/xfs/xfs_trans_resv.h
+++ b/fs/xfs/xfs_trans_resv.h
@@ -35,6 +35,7 @@ struct xfs_trans_resv {
 	struct xfs_trans_res	tr_itruncate;	/* truncate trans */
 	struct xfs_trans_res	tr_rename;	/* rename trans */
 	struct xfs_trans_res	tr_link;	/* link trans */
+	struct xfs_trans_res	tr_link_tmpfile; /* link O_TMPFILE trans */
 	struct xfs_trans_res	tr_remove;	/* unlink trans */
 	struct xfs_trans_res	tr_symlink;	/* symlink trans */
 	struct xfs_trans_res	tr_create;	/* create trans */
@@ -106,6 +107,7 @@ struct xfs_trans_resv {
 #define	XFS_SYMLINK_LOG_COUNT		3
 #define	XFS_REMOVE_LOG_COUNT		2
 #define	XFS_LINK_LOG_COUNT		2
+#define	XFS_LINK_TMPFILE_LOG_COUNT	2
 #define	XFS_RENAME_LOG_COUNT		2
 #define	XFS_WRITE_LOG_COUNT		2
 #define	XFS_ADDAFORK_LOG_COUNT		2
-- 
1.7.6.5