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    SubjectRe: [PATCH 07/11] vfs: add cross-rename
    On Wed 08-01-14 23:10:11, Miklos Szeredi wrote:
    > From: Miklos Szeredi <mszeredi@suse.cz>
    >
    > 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.
    >
    > Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
    > ---
    > 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/namei.c b/fs/namei.c
    > index 3fbc95c72e31..97c6dbb47eca 100644
    > --- a/fs/namei.c
    > +++ b/fs/namei.c
    > @@ -4020,6 +4020,8 @@ 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;
    > @@ -4028,10 +4030,16 @@ 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;
    >
    > @@ -4042,10 +4050,17 @@ 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,
    > @@ -4055,25 +4070,24 @@ 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)
    This should be >=, shouldn't it?

    > goto out;
    > -
    > - if (target)
    > - shrink_dcache_parent(new_dentry);
    > } else {
    > error = try_break_deleg(source, delegated_inode);
    > if (error)
    > @@ -4084,27 +4098,40 @@ 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;
    > @@ -4124,9 +4151,12 @@ 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)) {
    > @@ -4161,7 +4191,8 @@ 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);
    > @@ -4181,12 +4212,23 @@ 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;
    Should this be d_is_positive()?

    Honza
    --
    Jan Kara <jack@suse.cz>
    SUSE Labs, CR


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