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authorAl Viro <viro@zeniv.linux.org.uk>2023-03-16 01:34:34 +0300
committerAl Viro <viro@zeniv.linux.org.uk>2023-04-21 05:37:05 +0300
commit9bc37e04823b5280dd0f22b6680fc23fe81ca325 (patch)
tree1245ba4968615c26a692b4d294acac30dd66db81 /fs/namei.c
parent211db0ac9e3dc6c46f2dd53395b34d76af929faf (diff)
downloadlinux-9bc37e04823b5280dd0f22b6680fc23fe81ca325.tar.xz
fs: introduce lock_rename_child() helper
Pass the dentry of a source file and the dentry of a destination directory to lock parent inodes for rename. As soon as this function returns, ->d_parent of the source file dentry is stable and inodes are properly locked for calling vfs-rename. This helper is needed for ksmbd server. rename request of SMB protocol has to rename an opened file, no matter which directory it's in. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Namjae Jeon <linkinjeon@kernel.org> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/namei.c')
-rw-r--r--fs/namei.c68
1 files changed, 57 insertions, 11 deletions
diff --git a/fs/namei.c b/fs/namei.c
index edfedfbccaef..6bc1964e2214 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2980,20 +2980,10 @@ static inline int may_create(struct mnt_idmap *idmap,
return inode_permission(idmap, dir, MAY_WRITE | MAY_EXEC);
}
-/*
- * p1 and p2 should be directories on the same fs.
- */
-struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
+static struct dentry *lock_two_directories(struct dentry *p1, struct dentry *p2)
{
struct dentry *p;
- if (p1 == p2) {
- inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
- return NULL;
- }
-
- mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
-
p = d_ancestor(p2, p1);
if (p) {
inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
@@ -3012,8 +3002,64 @@ struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
inode_lock_nested(p2->d_inode, I_MUTEX_PARENT2);
return NULL;
}
+
+/*
+ * p1 and p2 should be directories on the same fs.
+ */
+struct dentry *lock_rename(struct dentry *p1, struct dentry *p2)
+{
+ if (p1 == p2) {
+ inode_lock_nested(p1->d_inode, I_MUTEX_PARENT);
+ return NULL;
+ }
+
+ mutex_lock(&p1->d_sb->s_vfs_rename_mutex);
+ return lock_two_directories(p1, p2);
+}
EXPORT_SYMBOL(lock_rename);
+/*
+ * c1 and p2 should be on the same fs.
+ */
+struct dentry *lock_rename_child(struct dentry *c1, struct dentry *p2)
+{
+ if (READ_ONCE(c1->d_parent) == p2) {
+ /*
+ * hopefully won't need to touch ->s_vfs_rename_mutex at all.
+ */
+ inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
+ /*
+ * now that p2 is locked, nobody can move in or out of it,
+ * so the test below is safe.
+ */
+ if (likely(c1->d_parent == p2))
+ return NULL;
+
+ /*
+ * c1 got moved out of p2 while we'd been taking locks;
+ * unlock and fall back to slow case.
+ */
+ inode_unlock(p2->d_inode);
+ }
+
+ mutex_lock(&c1->d_sb->s_vfs_rename_mutex);
+ /*
+ * nobody can move out of any directories on this fs.
+ */
+ if (likely(c1->d_parent != p2))
+ return lock_two_directories(c1->d_parent, p2);
+
+ /*
+ * c1 got moved into p2 while we were taking locks;
+ * we need p2 locked and ->s_vfs_rename_mutex unlocked,
+ * for consistency with lock_rename().
+ */
+ inode_lock_nested(p2->d_inode, I_MUTEX_PARENT);
+ mutex_unlock(&c1->d_sb->s_vfs_rename_mutex);
+ return NULL;
+}
+EXPORT_SYMBOL(lock_rename_child);
+
void unlock_rename(struct dentry *p1, struct dentry *p2)
{
inode_unlock(p1->d_inode);