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lock_rename_child() (for ksmbd folks)

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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Merge tag 'pull-lock_rename_child' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs into ksmbd-for-next

lock_rename_child() (for ksmbd folks)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Steve French 2023-04-24 00:07:14 -05:00
commit 42bc6793e4
4 changed files with 60 additions and 15 deletions
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2
fs/internal.h
View File

@ -59,8 +59,6 @@ extern int finish_clean_context(struct fs_context *fc);
*/
extern int filename_lookup(int dfd, struct filename *name, unsigned flags,
struct path *path, struct path *root);
extern int vfs_path_lookup(struct dentry *, struct vfsmount *,
const char *, unsigned int, struct path *);
int do_rmdir(int dfd, struct filename *name);
int do_unlinkat(int dfd, struct filename *name);
int may_linkat(struct mnt_idmap *idmap, const struct path *link);

2
fs/ksmbd/vfs.c
View File

@ -19,8 +19,6 @@
#include <linux/sched/xacct.h>
#include <linux/crc32c.h>
#include "../internal.h" /* for vfs_path_lookup */
#include "glob.h"
#include "oplock.h"
#include "connection.h"

68
fs/namei.c
View File

@ -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);

3
include/linux/namei.h
View File

@ -63,6 +63,8 @@ extern struct dentry *kern_path_create(int, const char *, struct path *, unsigne
extern struct dentry *user_path_create(int, const char __user *, struct path *, unsigned int);
extern void done_path_create(struct path *, struct dentry *);
extern struct dentry *kern_path_locked(const char *, struct path *);
int vfs_path_lookup(struct dentry *, struct vfsmount *, const char *,
unsigned int, struct path *);
extern struct dentry *try_lookup_one_len(const char *, struct dentry *, int);
extern struct dentry *lookup_one_len(const char *, struct dentry *, int);
@ -81,6 +83,7 @@ extern int follow_down(struct path *path, unsigned int flags);
extern int follow_up(struct path *);
extern struct dentry *lock_rename(struct dentry *, struct dentry *);
extern struct dentry *lock_rename_child(struct dentry *, struct dentry *);
extern void unlock_rename(struct dentry *, struct dentry *);
extern int __must_check nd_jump_link(const struct path *path);