ext4: add cross rename support

Implement RENAME_EXCHANGE flag in renameat2 syscall.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 75f1bde..1cb84f7 100644 (file)
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -3004,6 +3004,8 @@ struct ext4_renament {
        struct inode *dir;
        struct dentry *dentry;
        struct inode *inode;
+       bool is_dir;
+       int dir_nlink_delta;
 
        /* entry for "dentry" */
        struct buffer_head *bh;
@@ -3135,6 +3137,17 @@ static void ext4_rename_delete(handle_t *handle, struct ext4_renament *ent)
        }
 }
 
+static void ext4_update_dir_count(handle_t *handle, struct ext4_renament *ent)
+{
+       if (ent->dir_nlink_delta) {
+               if (ent->dir_nlink_delta == -1)
+                       ext4_dec_count(handle, ent->dir);
+               else
+                       ext4_inc_count(handle, ent->dir);
+               ext4_mark_inode_dirty(handle, ent->dir);
+       }
+}
+
 /*
  * Anybody can rename anything with this: the permission checks are left to the
  * higher-level routines.
@@ -3274,13 +3287,137 @@ end_rename:
        return retval;
 }
 
+static int ext4_cross_rename(struct inode *old_dir, struct dentry *old_dentry,
+                            struct inode *new_dir, struct dentry *new_dentry)
+{
+       handle_t *handle = NULL;
+       struct ext4_renament old = {
+               .dir = old_dir,
+               .dentry = old_dentry,
+               .inode = old_dentry->d_inode,
+       };
+       struct ext4_renament new = {
+               .dir = new_dir,
+               .dentry = new_dentry,
+               .inode = new_dentry->d_inode,
+       };
+       u8 new_file_type;
+       int retval;
+
+       dquot_initialize(old.dir);
+       dquot_initialize(new.dir);
+
+       old.bh = ext4_find_entry(old.dir, &old.dentry->d_name,
+                                &old.de, &old.inlined);
+       /*
+        *  Check for inode number is _not_ due to possible IO errors.
+        *  We might rmdir the source, keep it as pwd of some process
+        *  and merrily kill the link to whatever was created under the
+        *  same name. Goodbye sticky bit ;-<
+        */
+       retval = -ENOENT;
+       if (!old.bh || le32_to_cpu(old.de->inode) != old.inode->i_ino)
+               goto end_rename;
+
+       new.bh = ext4_find_entry(new.dir, &new.dentry->d_name,
+                                &new.de, &new.inlined);
+
+       /* RENAME_EXCHANGE case: old *and* new must both exist */
+       if (!new.bh || le32_to_cpu(new.de->inode) != new.inode->i_ino)
+               goto end_rename;
+
+       handle = ext4_journal_start(old.dir, EXT4_HT_DIR,
+               (2 * EXT4_DATA_TRANS_BLOCKS(old.dir->i_sb) +
+                2 * EXT4_INDEX_EXTRA_TRANS_BLOCKS + 2));
+       if (IS_ERR(handle))
+               return PTR_ERR(handle);
+
+       if (IS_DIRSYNC(old.dir) || IS_DIRSYNC(new.dir))
+               ext4_handle_sync(handle);
+
+       if (S_ISDIR(old.inode->i_mode)) {
+               old.is_dir = true;
+               retval = ext4_rename_dir_prepare(handle, &old);
+               if (retval)
+                       goto end_rename;
+       }
+       if (S_ISDIR(new.inode->i_mode)) {
+               new.is_dir = true;
+               retval = ext4_rename_dir_prepare(handle, &new);
+               if (retval)
+                       goto end_rename;
+       }
+
+       /*
+        * Other than the special case of overwriting a directory, parents'
+        * nlink only needs to be modified if this is a cross directory rename.
+        */
+       if (old.dir != new.dir && old.is_dir != new.is_dir) {
+               old.dir_nlink_delta = old.is_dir ? -1 : 1;
+               new.dir_nlink_delta = -old.dir_nlink_delta;
+               retval = -EMLINK;
+               if ((old.dir_nlink_delta > 0 && EXT4_DIR_LINK_MAX(old.dir)) ||
+                   (new.dir_nlink_delta > 0 && EXT4_DIR_LINK_MAX(new.dir)))
+                       goto end_rename;
+       }
+
+       new_file_type = new.de->file_type;
+       retval = ext4_setent(handle, &new, old.inode->i_ino, old.de->file_type);
+       if (retval)
+               goto end_rename;
+
+       retval = ext4_setent(handle, &old, new.inode->i_ino, new_file_type);
+       if (retval)
+               goto end_rename;
+
+       /*
+        * Like most other Unix systems, set the ctime for inodes on a
+        * rename.
+        */
+       old.inode->i_ctime = ext4_current_time(old.inode);
+       new.inode->i_ctime = ext4_current_time(new.inode);
+       ext4_mark_inode_dirty(handle, old.inode);
+       ext4_mark_inode_dirty(handle, new.inode);
+
+       if (old.dir_bh) {
+               retval = ext4_rename_dir_finish(handle, &old, new.dir->i_ino);
+               if (retval)
+                       goto end_rename;
+       }
+       if (new.dir_bh) {
+               retval = ext4_rename_dir_finish(handle, &new, old.dir->i_ino);
+               if (retval)
+                       goto end_rename;
+       }
+       ext4_update_dir_count(handle, &old);
+       ext4_update_dir_count(handle, &new);
+       retval = 0;
+
+end_rename:
+       brelse(old.dir_bh);
+       brelse(new.dir_bh);
+       brelse(old.bh);
+       brelse(new.bh);
+       if (handle)
+               ext4_journal_stop(handle);
+       return retval;
+}
+
 static int ext4_rename2(struct inode *old_dir, struct dentry *old_dentry,
                        struct inode *new_dir, struct dentry *new_dentry,
                        unsigned int flags)
 {
-       if (flags & ~RENAME_NOREPLACE)
+       if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
                return -EINVAL;
 
+       if (flags & RENAME_EXCHANGE) {
+               return ext4_cross_rename(old_dir, old_dentry,
+                                        new_dir, new_dentry);
+       }
+       /*
+        * Existence checking was done by the VFS, otherwise "RENAME_NOREPLACE"
+        * is equivalent to regular rename.
+        */
        return ext4_rename(old_dir, old_dentry, new_dir, new_dentry);
 }