[PATCH 5/7] shmem: support RENAME_EXCHANGE

[Miklos Szeredi]

From: Miklos Szeredi <mszeredi@xxxxxxx>

This is really simple in tmpfs since the VFS already takes care of
shuffling the dentries.  Just adjust nlink on parent directories and touch
c & mtimes.

Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
---
 mm/shmem.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 791b05514f9a..75d5ac806f1e 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2016,6 +2016,28 @@ static int shmem_rmdir(struct inode *dir, struct dentry *dentry)
 	return shmem_unlink(dir, dentry);
 }
 
+static int shmem_exchange(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry)
+{
+	bool old_is_dir = S_ISDIR(old_dentry->d_inode->i_mode);
+	bool new_is_dir = S_ISDIR(new_dentry->d_inode->i_mode);
+
+	if (old_dir != new_dir && old_is_dir != new_is_dir) {
+		if (old_is_dir) {
+			drop_nlink(old_dir);
+			inc_nlink(new_dir);
+		} else {
+			drop_nlink(new_dir);
+			inc_nlink(old_dir);
+		}
+	}
+	old_dir->i_ctime = old_dir->i_mtime =
+	new_dir->i_ctime = new_dir->i_mtime =
+	old_dentry->d_inode->i_ctime =
+	new_dentry->d_inode->i_ctime = CURRENT_TIME;
+
+	return 0;
+}
+
 /*
  * The VFS layer already does all the dentry stuff for rename,
  * we just have to decrement the usage count for the target if
@@ -2027,9 +2049,12 @@ static int shmem_rename2(struct inode *old_dir, struct dentry *old_dentry, struc
 	struct inode *inode = old_dentry->d_inode;
 	int they_are_dirs = S_ISDIR(inode->i_mode);
 
-	if (flags & ~(RENAME_NOREPLACE))
+	if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
 		return -EINVAL;
 
+	if (flags & RENAME_EXCHANGE)
+		return shmem_exchange(old_dir, old_dentry, new_dir, new_dentry);
+
 	if (!simple_empty(new_dentry))
 		return -ENOTEMPTY;
 
-- 
1.8.1.4

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