Re: [PATCH 07/11] vfs: add cross-rename

From: Andy Lutomirski
Date: Wed Nov 20 2013 - 11:51:53 EST

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On Wed, Nov 20, 2013 at 8:44 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
> On Wed, Nov 20, 2013 at 5:39 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
>> On Wed, Nov 20, 2013 at 5:01 AM, Miklos Szeredi <miklos@xxxxxxxxxx> wrote:
>>> From: Miklos Szeredi <mszeredi@xxxxxxx>
>>>
>>> If flags contain RENAME_EXCHANGE then exchange source and destination files.
>>> There's no restriction on the type of the files; e.g. a directory can be
>>> exchanged with a symlink.
>>
>> What happens if both RENAME_EXCHANGE and RENAME_NOREPLACE are set?
>
> It fails with EINVAL, since it's a nonsensical combination.
> RENAME_EXCHANGE requires the target to exist, RENAME_NOREPLACE
> requires the target to _not_ exist.

*facepalm*

I looked for that and didn't find it. I'm not sure how I missed the
explicit check.

--Andy

>
> Thanks,
> Miklos
>
>>
>> --Andy
>>
>>>
>>> Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
>>> ---
>>> fs/dcache.c | 46 +++++++++++++++++----
>>> fs/namei.c | 107 +++++++++++++++++++++++++++++++++---------------
>>> include/linux/dcache.h | 1 +
>>> include/uapi/linux/fs.h | 1 +
>>> security/security.c | 16 ++++++++
>>> 5 files changed, 131 insertions(+), 40 deletions(-)
>>>
>>> diff --git a/fs/dcache.c b/fs/dcache.c
>>> index 0a38ef8d7f00..ea2fca1a2ec9 100644
>>> --- a/fs/dcache.c
>>> +++ b/fs/dcache.c
>>> @@ -2527,12 +2527,14 @@ static void switch_names(struct dentry *dentry, struct dentry *target)
>>> dentry->d_name.name = dentry->d_iname;
>>> } else {
>>> /*
>>> - * Both are internal. Just copy target to dentry
>>> + * Both are internal.
>>> */
>>> - memcpy(dentry->d_iname, target->d_name.name,
>>> - target->d_name.len + 1);
>>> - dentry->d_name.len = target->d_name.len;
>>> - return;
>>> + unsigned int i;
>>> + BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
>>> + for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
>>> + swap(((long *) &dentry->d_iname)[i],
>>> + ((long *) &target->d_iname)[i]);
>>> + }
>>> }
>>> }
>>> swap(dentry->d_name.len, target->d_name.len);
>>> @@ -2589,13 +2591,15 @@ static void dentry_unlock_parents_for_move(struct dentry *dentry,
>>> * __d_move - move a dentry
>>> * @dentry: entry to move
>>> * @target: new dentry
>>> + * @exchange: exchange the two dentries
>>> *
>>> * Update the dcache to reflect the move of a file name. Negative
>>> * dcache entries should not be moved in this way. Caller must hold
>>> * rename_lock, the i_mutex of the source and target directories,
>>> * and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
>>> */
>>> -static void __d_move(struct dentry * dentry, struct dentry * target)
>>> +static void __d_move(struct dentry *dentry, struct dentry *target,
>>> + bool exchange)
>>> {
>>> if (!dentry->d_inode)
>>> printk(KERN_WARNING "VFS: moving negative dcache entry\n");
>>> @@ -2619,6 +2623,10 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
>>>
>>> /* Unhash the target: dput() will then get rid of it */
>>> __d_drop(target);
>>> + if (exchange) {
>>> + __d_rehash(target,
>>> + d_hash(dentry->d_parent, dentry->d_name.hash));
>>> + }
>>>
>>> list_del(&dentry->d_u.d_child);
>>> list_del(&target->d_u.d_child);
>>> @@ -2645,6 +2653,8 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
>>> write_seqcount_end(&dentry->d_seq);
>>>
>>> dentry_unlock_parents_for_move(dentry, target);
>>> + if (exchange)
>>> + fsnotify_d_move(target);
>>> spin_unlock(&target->d_lock);
>>> fsnotify_d_move(dentry);
>>> spin_unlock(&dentry->d_lock);
>>> @@ -2662,11 +2672,31 @@ static void __d_move(struct dentry * dentry, struct dentry * target)
>>> void d_move(struct dentry *dentry, struct dentry *target)
>>> {
>>> write_seqlock(&rename_lock);
>>> - __d_move(dentry, target);
>>> + __d_move(dentry, target, false);
>>> write_sequnlock(&rename_lock);
>>> }
>>> EXPORT_SYMBOL(d_move);
>>>
>>> +/*
>>> + * d_exchange - exchange two dentries
>>> + * @dentry1: first dentry
>>> + * @dentry2: second dentry
>>> + */
>>> +void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
>>> +{
>>> + write_seqlock(&rename_lock);
>>> +
>>> + WARN_ON(!dentry1->d_inode);
>>> + WARN_ON(!dentry2->d_inode);
>>> + WARN_ON(IS_ROOT(dentry1));
>>> + WARN_ON(IS_ROOT(dentry2));
>>> +
>>> + __d_move(dentry1, dentry2, true);
>>> +
>>> + write_sequnlock(&rename_lock);
>>> +}
>>> +
>>> +
>>> /**
>>> * d_ancestor - search for an ancestor
>>> * @p1: ancestor dentry
>>> @@ -2714,7 +2744,7 @@ static struct dentry *__d_unalias(struct inode *inode,
>>> m2 = &alias->d_parent->d_inode->i_mutex;
>>> out_unalias:
>>> if (likely(!d_mountpoint(alias))) {
>>> - __d_move(alias, dentry);
>>> + __d_move(alias, dentry, false);
>>> ret = alias;
>>> }
>>> out_err:
>>> diff --git a/fs/namei.c b/fs/namei.c
>>> index 5b41d4bfecd1..c23621255df0 100644
>>> --- a/fs/namei.c
>>> +++ b/fs/namei.c
>>> @@ -4025,6 +4025,8 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>>> const unsigned char *old_name;
>>> struct inode *source = old_dentry->d_inode;
>>> struct inode *target = new_dentry->d_inode;
>>> + bool new_is_dir = false;
>>> + unsigned max_links = new_dir->i_sb->s_max_links;
>>>
>>> if (source == target)
>>> return 0;
>>> @@ -4033,10 +4035,16 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>>> if (error)
>>> return error;
>>>
>>> - if (!target)
>>> + if (!target) {
>>> error = may_create(new_dir, new_dentry);
>>> - else
>>> - error = may_delete(new_dir, new_dentry, is_dir);
>>> + } else {
>>> + new_is_dir = d_is_dir(new_dentry);
>>> +
>>> + if (!(flags & RENAME_EXCHANGE))
>>> + error = may_delete(new_dir, new_dentry, is_dir);
>>> + else
>>> + error = may_delete(new_dir, new_dentry, new_is_dir);
>>> + }
>>> if (error)
>>> return error;
>>>
>>> @@ -4047,10 +4055,17 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>>> * If we are going to change the parent - check write permissions,
>>> * we'll need to flip '..'.
>>> */
>>> - if (is_dir && new_dir != old_dir) {
>>> - error = inode_permission(source, MAY_WRITE);
>>> - if (error)
>>> - return error;
>>> + if (new_dir != old_dir) {
>>> + if (is_dir) {
>>> + error = inode_permission(source, MAY_WRITE);
>>> + if (error)
>>> + return error;
>>> + }
>>> + if ((flags & RENAME_EXCHANGE) && new_is_dir) {
>>> + error = inode_permission(target, MAY_WRITE);
>>> + if (error)
>>> + return error;
>>> + }
>>> }
>>>
>>> error = security_inode_rename(old_dir, old_dentry, new_dir, new_dentry,
>>> @@ -4060,25 +4075,24 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>>>
>>> old_name = fsnotify_oldname_init(old_dentry->d_name.name);
>>> dget(new_dentry);
>>> - if (!is_dir)
>>> - lock_two_nondirectories(source, target);
>>> - else if (target)
>>> - mutex_lock(&target->i_mutex);
>>> + if (!(flags & RENAME_EXCHANGE)) {
>>> + if (!is_dir)
>>> + lock_two_nondirectories(source, target);
>>> + else if (target)
>>> + mutex_lock(&target->i_mutex);
>>> + }
>>>
>>> error = -EBUSY;
>>> if (d_mountpoint(old_dentry) || d_mountpoint(new_dentry))
>>> goto out;
>>>
>>> - if (is_dir) {
>>> - unsigned max_links = new_dir->i_sb->s_max_links;
>>> -
>>> + if (max_links && new_dir != old_dir) {
>>> error = -EMLINK;
>>> - if (max_links && !target && new_dir != old_dir &&
>>> - new_dir->i_nlink >= max_links)
>>> + if (is_dir && !new_is_dir && new_dir->i_nlink >= max_links)
>>> + goto out;
>>> + if ((flags & RENAME_EXCHANGE) && !is_dir && new_is_dir &&
>>> + old_dir->i_nlink > max_links)
>>> goto out;
>>> -
>>> - if (target)
>>> - shrink_dcache_parent(new_dentry);
>>> } else {
>>> error = try_break_deleg(source, delegated_inode);
>>> if (error)
>>> @@ -4089,27 +4103,40 @@ int vfs_rename(struct inode *old_dir, struct dentry *old_dentry,
>>> goto out;
>>> }
>>> }
>>> + if (is_dir && !(flags & RENAME_EXCHANGE) && target)
>>> + shrink_dcache_parent(new_dentry);
>>> error = old_dir->i_op->rename(old_dir, old_dentry, new_dir, new_dentry,
>>> flags);
>>> if (error)
>>> goto out;
>>>
>>> - if (target) {
>>> + if (!(flags & RENAME_EXCHANGE) && target) {
>>> if (is_dir)
>>> target->i_flags |= S_DEAD;
>>> dont_mount(new_dentry);
>>> }
>>> - if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE))
>>> - d_move(old_dentry, new_dentry);
>>> + if (!(old_dir->i_sb->s_type->fs_flags & FS_RENAME_DOES_D_MOVE)) {
>>> + if (!(flags & RENAME_EXCHANGE))
>>> + d_move(old_dentry, new_dentry);
>>> + else
>>> + d_exchange(old_dentry, new_dentry);
>>> + }
>>> out:
>>> - if (!is_dir)
>>> - unlock_two_nondirectories(source, target);
>>> - else if (target)
>>> - mutex_unlock(&target->i_mutex);
>>> + if (!(flags & RENAME_EXCHANGE)) {
>>> + if (!is_dir)
>>> + unlock_two_nondirectories(source, target);
>>> + else if (target)
>>> + mutex_unlock(&target->i_mutex);
>>> + }
>>> dput(new_dentry);
>>> - if (!error)
>>> + if (!error) {
>>> fsnotify_move(old_dir, new_dir, old_name, is_dir,
>>> - target, old_dentry);
>>> + !(flags & RENAME_EXCHANGE) ? target : NULL, old_dentry);
>>> + if (flags & RENAME_EXCHANGE) {
>>> + fsnotify_move(new_dir, old_dir, old_dentry->d_name.name,
>>> + new_is_dir, NULL, new_dentry);
>>> + }
>>> + }
>>> fsnotify_oldname_free(old_name);
>>>
>>> return error;
>>> @@ -4129,9 +4156,12 @@ SYSCALL_DEFINE5(renameat2, int, olddfd, const char __user *, oldname,
>>> bool should_retry = false;
>>> int error;
>>>
>>> - if (flags & ~RENAME_NOREPLACE)
>>> + if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
>>> return -EOPNOTSUPP;
>>>
>>> + if ((flags & RENAME_NOREPLACE) && (flags & RENAME_EXCHANGE))
>>> + return -EINVAL;
>>> +
>>> retry:
>>> from = user_path_parent(olddfd, oldname, &oldnd, lookup_flags);
>>> if (IS_ERR(from)) {
>>> @@ -4166,7 +4196,8 @@ retry:
>>>
>>> oldnd.flags &= ~LOOKUP_PARENT;
>>> newnd.flags &= ~LOOKUP_PARENT;
>>> - newnd.flags |= LOOKUP_RENAME_TARGET;
>>> + if (!(flags & RENAME_EXCHANGE))
>>> + newnd.flags |= LOOKUP_RENAME_TARGET;
>>>
>>> retry_deleg:
>>> trap = lock_rename(new_dir, old_dir);
>>> @@ -4186,12 +4217,23 @@ retry_deleg:
>>> error = -EEXIST;
>>> if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry))
>>> goto exit5;
>>> + if (flags & RENAME_EXCHANGE) {
>>> + error = -ENOENT;
>>> + if (!new_dentry->d_inode)
>>> + goto exit5;
>>> +
>>> + if (!d_is_dir(new_dentry)) {
>>> + error = -ENOTDIR;
>>> + if (newnd.last.name[newnd.last.len])
>>> + goto exit5;
>>> + }
>>> + }
>>> /* unless the source is a directory trailing slashes give -ENOTDIR */
>>> if (!d_is_dir(old_dentry)) {
>>> error = -ENOTDIR;
>>> if (oldnd.last.name[oldnd.last.len])
>>> goto exit5;
>>> - if (newnd.last.name[newnd.last.len])
>>> + if (!(flags & RENAME_EXCHANGE) && newnd.last.name[newnd.last.len])
>>> goto exit5;
>>> }
>>> /* source should not be ancestor of target */
>>> @@ -4199,7 +4241,8 @@ retry_deleg:
>>> if (old_dentry == trap)
>>> goto exit5;
>>> /* target should not be an ancestor of source */
>>> - error = -ENOTEMPTY;
>>> + if (!(flags & RENAME_EXCHANGE))
>>> + error = -ENOTEMPTY;
>>> if (new_dentry == trap)
>>> goto exit5;
>>>
>>> diff --git a/include/linux/dcache.h b/include/linux/dcache.h
>>> index 901616910e0a..87e14e698f89 100644
>>> --- a/include/linux/dcache.h
>>> +++ b/include/linux/dcache.h
>>> @@ -306,6 +306,7 @@ extern void dentry_update_name_case(struct dentry *, struct qstr *);
>>>
>>> /* used for rename() and baskets */
>>> extern void d_move(struct dentry *, struct dentry *);
>>> +extern void d_exchange(struct dentry *, struct dentry *);
>>> extern struct dentry *d_ancestor(struct dentry *, struct dentry *);
>>>
>>> /* appendix may either be NULL or be used for transname suffixes */
>>> diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
>>> index 9250f4dd7d96..ca1a11bb4443 100644
>>> --- a/include/uapi/linux/fs.h
>>> +++ b/include/uapi/linux/fs.h
>>> @@ -36,6 +36,7 @@
>>> #define SEEK_MAX SEEK_HOLE
>>>
>>> #define RENAME_NOREPLACE (1 << 0) /* Don't overwrite target */
>>> +#define RENAME_EXCHANGE (1 << 1) /* Exchange source and dest */
>>>
>>> struct fstrim_range {
>>> __u64 start;
>>> diff --git a/security/security.c b/security/security.c
>>> index d00ae28dea76..0ef72cd2255f 100644
>>> --- a/security/security.c
>>> +++ b/security/security.c
>>> @@ -439,6 +439,14 @@ int security_path_rename(struct path *old_dir, struct dentry *old_dentry,
>>> if (unlikely(IS_PRIVATE(old_dentry->d_inode) ||
>>> (new_dentry->d_inode && IS_PRIVATE(new_dentry->d_inode))))
>>> return 0;
>>> +
>>> + if (flags & RENAME_EXCHANGE) {
>>> + int err = security_ops->path_rename(new_dir, new_dentry,
>>> + old_dir, old_dentry);
>>> + if (err)
>>> + return err;
>>> + }
>>> +
>>> return security_ops->path_rename(old_dir, old_dentry, new_dir,
>>> new_dentry);
>>> }
>>> @@ -531,6 +539,14 @@ int security_inode_rename(struct inode *old_dir, struct dentry *old_dentry,
>>> if (unlikely(IS_PRIVATE(old_dentry->d_inode) ||
>>> (new_dentry->d_inode && IS_PRIVATE(new_dentry->d_inode))))
>>> return 0;
>>> +
>>> + if (flags & RENAME_EXCHANGE) {
>>> + int err = security_ops->inode_rename(new_dir, new_dentry,
>>> + old_dir, old_dentry);
>>> + if (err)
>>> + return err;
>>> + }
>>> +
>>> return security_ops->inode_rename(old_dir, old_dentry,
>>> new_dir, new_dentry);
>>> }
>>> --
>>> 1.8.1.4
>>>
>>
>>
>>
>> --
>> Andy Lutomirski
>> AMA Capital Management, LLC

--
Andy Lutomirski
AMA Capital Management, LLC
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Next message: Scott Wood: "Re: BUG: Patch "Convert some mftb/mftbu into mfspr" breaks MPC885"
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In reply to: Miklos Szeredi: "Re: [PATCH 07/11] vfs: add cross-rename"
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