xfs: Add support to RENAME_EXCHANGE flag

Adds a new function named xfs_cross_rename(), responsible for
handling requests from sys_renameat2() using RENAME_EXCHANGE flag.

Signed-off-by: Carlos Maiolino <cmaiolino@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>

3 files changed, 142 insertions, 6 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 41f804e740d7..9916aef60997 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2656,6 +2656,124 @@ xfs_sort_for_rename(
 }
 
 /*
+ * xfs_cross_rename()
+ *
+ * responsible for handling RENAME_EXCHANGE flag in renameat2() sytemcall
+ */
+STATIC int
+xfs_cross_rename(
+        struct xfs_trans        *tp,
+        struct xfs_inode        *dp1,
+        struct xfs_name         *name1,
+        struct xfs_inode        *ip1,
+        struct xfs_inode        *dp2,
+        struct xfs_name         *name2,
+        struct xfs_inode        *ip2,
+        struct xfs_bmap_free    *free_list,
+        xfs_fsblock_t           *first_block,
+        int                     spaceres)
+{
+        int             error = 0;
+        int             ip1_flags = 0;
+        int             ip2_flags = 0;
+        int             dp2_flags = 0;
+
+        /* Swap inode number for dirent in first parent */
+        error = xfs_dir_replace(tp, dp1, name1,
+                                ip2->i_ino,
+                                first_block, free_list, spaceres);
+        if (error)
+                goto out;
+
+        /* Swap inode number for dirent in second parent */
+        error = xfs_dir_replace(tp, dp2, name2,
+                                ip1->i_ino,
+                                first_block, free_list, spaceres);
+        if (error)
+                goto out;
+
+        /*
+         * If we're renaming one or more directories across different parents,
+         * update the respective ".." entries (and link counts) to match the new
+         * parents.
+         */
+        if (dp1 != dp2) {
+                dp2_flags = XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG;
+
+                if (S_ISDIR(ip2->i_d.di_mode)) {
+                        error = xfs_dir_replace(tp, ip2, &xfs_name_dotdot,
+                                                dp1->i_ino, first_block,
+                                                free_list, spaceres);
+                        if (error)
+                                goto out;
+
+                        /* transfer ip2 ".." reference to dp1 */
+                        if (!S_ISDIR(ip1->i_d.di_mode)) {
+                                error = xfs_droplink(tp, dp2);
+                                if (error)
+                                        goto out;
+                                error = xfs_bumplink(tp, dp1);
+                                if (error)
+                                        goto out;
+                        }
+
+                        /*
+                         * Although ip1 isn't changed here, userspace needs
+                         * to be warned about the change, so that applications
+                         * relying on it (like backup ones), will properly
+                         * notify the change
+                         */
+                        ip1_flags |= XFS_ICHGTIME_CHG;
+                        ip2_flags |= XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG;
+                }
+
+                if (S_ISDIR(ip1->i_d.di_mode)) {
+                        error = xfs_dir_replace(tp, ip1, &xfs_name_dotdot,
+                                                dp2->i_ino, first_block,
+                                                free_list, spaceres);
+                        if (error)
+                                goto out;
+
+                        /* transfer ip1 ".." reference to dp2 */
+                        if (!S_ISDIR(ip2->i_d.di_mode)) {
+                                error = xfs_droplink(tp, dp1);
+                                if (error)
+                                        goto out;
+                                error = xfs_bumplink(tp, dp2);
+                                if (error)
+                                        goto out;
+                        }
+
+                        /*
+                         * Although ip2 isn't changed here, userspace needs
+                         * to be warned about the change, so that applications
+                         * relying on it (like backup ones), will properly
+                         * notify the change
+                         */
+                        ip1_flags |= XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG;
+                        ip2_flags |= XFS_ICHGTIME_CHG;
+                }
+        }
+
+        if (ip1_flags) {
+                xfs_trans_ichgtime(tp, ip1, ip1_flags);
+                xfs_trans_log_inode(tp, ip1, XFS_ILOG_CORE);
+        }
+        if (ip2_flags) {
+                xfs_trans_ichgtime(tp, ip2, ip2_flags);
+                xfs_trans_log_inode(tp, ip2, XFS_ILOG_CORE);
+        }
+        if (dp2_flags) {
+                xfs_trans_ichgtime(tp, dp2, dp2_flags);
+                xfs_trans_log_inode(tp, dp2, XFS_ILOG_CORE);
+        }
+        xfs_trans_ichgtime(tp, dp1, XFS_ICHGTIME_MOD | XFS_ICHGTIME_CHG);
+        xfs_trans_log_inode(tp, dp1, XFS_ILOG_CORE);
+out:
+        return error;
+}
+
+/*
  * xfs_rename
  */
 int
@@ -2665,7 +2783,8 @@ xfs_rename(
         xfs_inode_t     *src_ip,
         xfs_inode_t     *target_dp,
         struct xfs_name *target_name,
-        xfs_inode_t     *target_ip)
+        xfs_inode_t     *target_ip,
+        unsigned int    flags)
 {
         xfs_trans_t     *tp = NULL;
         xfs_mount_t     *mp = src_dp->i_mount;
@@ -2743,6 +2862,18 @@ xfs_rename(
         }
 
         /*
+         * Handle RENAME_EXCHANGE flags
+         */
+        if (flags & RENAME_EXCHANGE) {
+                error = xfs_cross_rename(tp, src_dp, src_name, src_ip,
+                                         target_dp, target_name, target_ip,
+                                         &free_list, &first_block, spaceres);
+                if (error)
+                        goto abort_return;
+                goto finish_rename;
+        }
+
+        /*
          * Set up the target.
          */
         if (target_ip == NULL) {
@@ -2881,6 +3012,7 @@ xfs_rename(
         if (new_parent)
                 xfs_trans_log_inode(tp, target_dp, XFS_ILOG_CORE);
 
+finish_rename:
         /*
          * If this is a synchronous mount, make sure that the
          * rename transaction goes to disk before returning to
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 4ed2ba9342dc..f7722960b69c 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -338,7 +338,7 @@ int		xfs_link(struct xfs_inode *tdp, struct xfs_inode *sip,
 int             xfs_rename(struct xfs_inode *src_dp, struct xfs_name *src_name,
                            struct xfs_inode *src_ip, struct xfs_inode *target_dp,
                            struct xfs_name *target_name,
-                           struct xfs_inode *target_ip);
+                           struct xfs_inode *target_ip, unsigned int flags);
 
 void            xfs_ilock(xfs_inode_t *, uint);
 int             xfs_ilock_nowait(xfs_inode_t *, uint);
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index abb838a565ee..ce80eeb8faa4 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -384,19 +384,23 @@ xfs_vn_rename(
         unsigned int    flags)
 {
         struct inode    *new_inode = ndentry->d_inode;
+        int             omode = 0;
         struct xfs_name oname;
         struct xfs_name nname;
 
-        /* XFS does not support RENAME_EXCHANGE yet */
-        if (flags & ~RENAME_NOREPLACE)
+        if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
                 return -EINVAL;
 
-        xfs_dentry_to_name(&oname, odentry, 0);
+        /* if we are exchanging files, we need to set i_mode of both files */
+        if (flags & RENAME_EXCHANGE)
+                omode = ndentry->d_inode->i_mode;
+
+        xfs_dentry_to_name(&oname, odentry, omode);
         xfs_dentry_to_name(&nname, ndentry, odentry->d_inode->i_mode);
 
         return xfs_rename(XFS_I(odir), &oname, XFS_I(odentry->d_inode),
                           XFS_I(ndir), &nname,
-                          new_inode ? XFS_I(new_inode) : NULL);
+                          new_inode ? XFS_I(new_inode) : NULL, flags);
 }
 
 /*