On Mon, 2025-02-17 at 11:27 +1100, NeilBrown wrote: > Callers of lookup_one_qstr_excl() often check if the result is negative or > positive. > These changes can easily be moved into lookup_one_qstr_excl() by checking the > lookup flags: > LOOKUP_CREATE means it is NOT an error if the name doesn't exist. > LOOKUP_EXCL means it IS an error if the name DOES exist. > > This patch adds these checks, then removes error checks from callers, > and ensures that appropriate flags are passed. > > This subtly changes the meaning of LOOKUP_EXCL. Previously it could > only accompany LOOKUP_CREATE. Now it can accompany LOOKUP_RENAME_TARGET > as well. A couple of small changes are needed to accommodate this. The > NFS change is functionally a no-op but ensures nfs_is_exclusive_create() does > exactly what the name says. > > Signed-off-by: NeilBrown <neilb@xxxxxxx> > Link: https://lore.kernel.org/r/20250207034040.3402438-3-neilb@xxxxxxx > Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx> > --- > Documentation/filesystems/porting.rst | 12 ++++++ > fs/namei.c | 61 +++++++++------------------ > fs/nfs/dir.c | 3 +- > fs/smb/server/vfs.c | 26 +++++------- > 4 files changed, 45 insertions(+), 57 deletions(-) > > diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst > index 2ead47e20677..3b6622fbd66b 100644 > --- a/Documentation/filesystems/porting.rst > +++ b/Documentation/filesystems/porting.rst > @@ -1165,3 +1165,15 @@ magic. > kern_path_locked() and user_path_locked() no longer return a negative > dentry so this doesn't need to be checked. If the name cannot be found, > ERR_PTR(-ENOENT) is returned. > + > +** recommend** > + > +lookup_one_qstr_excl() is changed to return errors in more cases, so > +these conditions don't require explicit checks. > + - if LOOKUP_CREATE is NOT given, then the dentry won't be negative, > + ERR_PTR(-ENOENT) is returned instead > + - if LOOKUP_EXCL IS given, then the dentry won't be positive, > + ERR_PTR(-EEXIST) is rreturned instread > + > +LOOKUP_EXCL now means "target must not exist". It can be combined with > +LOOK_CREATE or LOOKUP_RENAME_TARGET. > diff --git a/fs/namei.c b/fs/namei.c > index fb6da3ca0ca5..b7cdca902803 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -1670,6 +1670,8 @@ static struct dentry *lookup_dcache(const struct qstr *name, > * dentries - as the matter of fact, this only gets called > * when directory is guaranteed to have no in-lookup children > * at all. > + * Will return -ENOENT if name isn't found and LOOKUP_CREATE wasn't passed. > + * Will return -EEXIST if name is found and LOOKUP_EXCL was passed. > */ > struct dentry *lookup_one_qstr_excl(const struct qstr *name, > struct dentry *base, > @@ -1680,7 +1682,7 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name, > struct inode *dir = base->d_inode; > > if (dentry) > - return dentry; > + goto found; > > /* Don't create child dentry for a dead directory. */ > if (unlikely(IS_DEADDIR(dir))) > @@ -1695,6 +1697,17 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name, > dput(dentry); > dentry = old; > } > +found: > + if (IS_ERR(dentry)) > + return dentry; > + if (d_is_negative(dentry) && !(flags & LOOKUP_CREATE)) { > + dput(dentry); > + return ERR_PTR(-ENOENT); > + } > + if (d_is_positive(dentry) && (flags & LOOKUP_EXCL)) { > + dput(dentry); > + return ERR_PTR(-EEXIST); > + } > return dentry; > } > EXPORT_SYMBOL(lookup_one_qstr_excl); > @@ -2741,10 +2754,6 @@ static struct dentry *__kern_path_locked(int dfd, struct filename *name, struct > } > inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); > d = lookup_one_qstr_excl(&last, path->dentry, 0); > - if (!IS_ERR(d) && d_is_negative(d)) { > - dput(d); > - d = ERR_PTR(-ENOENT); > - } > if (IS_ERR(d)) { > inode_unlock(path->dentry->d_inode); > path_put(path); > @@ -4082,27 +4091,13 @@ static struct dentry *filename_create(int dfd, struct filename *name, > * '/', and a directory wasn't requested. > */ > if (last.name[last.len] && !want_dir) > - create_flags = 0; > + create_flags &= ~LOOKUP_CREATE; > inode_lock_nested(path->dentry->d_inode, I_MUTEX_PARENT); > dentry = lookup_one_qstr_excl(&last, path->dentry, > reval_flag | create_flags); > if (IS_ERR(dentry)) > goto unlock; > > - error = -EEXIST; > - if (d_is_positive(dentry)) > - goto fail; > - > - /* > - * Special case - lookup gave negative, but... we had foo/bar/ > - * From the vfs_mknod() POV we just have a negative dentry - > - * all is fine. Let's be bastards - you had / on the end, you've > - * been asking for (non-existent) directory. -ENOENT for you. > - */ > - if (unlikely(!create_flags)) { > - error = -ENOENT; > - goto fail; > - } > if (unlikely(err2)) { > error = err2; > goto fail; > @@ -4449,10 +4444,6 @@ int do_rmdir(int dfd, struct filename *name) > error = PTR_ERR(dentry); > if (IS_ERR(dentry)) > goto exit3; > - if (!dentry->d_inode) { > - error = -ENOENT; > - goto exit4; > - } > error = security_path_rmdir(&path, dentry); > if (error) > goto exit4; > @@ -4583,7 +4574,7 @@ int do_unlinkat(int dfd, struct filename *name) > if (!IS_ERR(dentry)) { > > /* Why not before? Because we want correct error value */ > - if (last.name[last.len] || d_is_negative(dentry)) > + if (last.name[last.len]) > goto slashes; > inode = dentry->d_inode; > ihold(inode); > @@ -4617,9 +4608,7 @@ int do_unlinkat(int dfd, struct filename *name) > return error; > > slashes: > - if (d_is_negative(dentry)) > - error = -ENOENT; > - else if (d_is_dir(dentry)) > + if (d_is_dir(dentry)) > error = -EISDIR; > else > error = -ENOTDIR; > @@ -5119,7 +5108,8 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd, > struct qstr old_last, new_last; > int old_type, new_type; > struct inode *delegated_inode = NULL; > - unsigned int lookup_flags = 0, target_flags = LOOKUP_RENAME_TARGET; > + unsigned int lookup_flags = 0, target_flags = > + LOOKUP_RENAME_TARGET | LOOKUP_CREATE; > bool should_retry = false; > int error = -EINVAL; > > @@ -5132,6 +5122,8 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd, > > if (flags & RENAME_EXCHANGE) > target_flags = 0; > + if (flags & RENAME_NOREPLACE) > + target_flags |= LOOKUP_EXCL; > > retry: > error = filename_parentat(olddfd, from, lookup_flags, &old_path, > @@ -5173,23 +5165,12 @@ int do_renameat2(int olddfd, struct filename *from, int newdfd, > error = PTR_ERR(old_dentry); > if (IS_ERR(old_dentry)) > goto exit3; > - /* source must exist */ > - error = -ENOENT; > - if (d_is_negative(old_dentry)) > - goto exit4; > new_dentry = lookup_one_qstr_excl(&new_last, new_path.dentry, > lookup_flags | target_flags); > error = PTR_ERR(new_dentry); > if (IS_ERR(new_dentry)) > goto exit4; > - error = -EEXIST; > - if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry)) > - goto exit5; > if (flags & RENAME_EXCHANGE) { > - error = -ENOENT; > - if (d_is_negative(new_dentry)) > - goto exit5; > - > if (!d_is_dir(new_dentry)) { > error = -ENOTDIR; > if (new_last.name[new_last.len]) > diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c > index 2b04038b0e40..56cf16a72334 100644 > --- a/fs/nfs/dir.c > +++ b/fs/nfs/dir.c > @@ -1532,7 +1532,8 @@ static int nfs_is_exclusive_create(struct inode *dir, unsigned int flags) > { > if (NFS_PROTO(dir)->version == 2) > return 0; > - return flags & LOOKUP_EXCL; > + return (flags & (LOOKUP_CREATE | LOOKUP_EXCL)) == > + (LOOKUP_CREATE | LOOKUP_EXCL); > } > > /* > diff --git a/fs/smb/server/vfs.c b/fs/smb/server/vfs.c > index 6890016e1923..fe29acef5872 100644 > --- a/fs/smb/server/vfs.c > +++ b/fs/smb/server/vfs.c > @@ -113,11 +113,6 @@ static int ksmbd_vfs_path_lookup_locked(struct ksmbd_share_config *share_conf, > if (IS_ERR(d)) > goto err_out; > > - if (d_is_negative(d)) { > - dput(d); > - goto err_out; > - } > - > path->dentry = d; > path->mnt = mntget(parent_path->mnt); > > @@ -693,6 +688,7 @@ int ksmbd_vfs_rename(struct ksmbd_work *work, const struct path *old_path, > struct ksmbd_file *parent_fp; > int new_type; > int err, lookup_flags = LOOKUP_NO_SYMLINKS; > + int target_lookup_flags = LOOKUP_RENAME_TARGET; > > if (ksmbd_override_fsids(work)) > return -ENOMEM; > @@ -703,6 +699,14 @@ int ksmbd_vfs_rename(struct ksmbd_work *work, const struct path *old_path, > goto revert_fsids; > } > > + /* > + * explicitly handle file overwrite case, for compatibility with > + * filesystems that may not support rename flags (e.g: fuse) > + */ > + if (flags & RENAME_NOREPLACE) > + target_lookup_flags |= LOOKUP_EXCL; > + flags &= ~(RENAME_NOREPLACE); > + > retry: > err = vfs_path_parent_lookup(to, lookup_flags | LOOKUP_BENEATH, > &new_path, &new_last, &new_type, > @@ -743,7 +747,7 @@ int ksmbd_vfs_rename(struct ksmbd_work *work, const struct path *old_path, > } > > new_dentry = lookup_one_qstr_excl(&new_last, new_path.dentry, > - lookup_flags | LOOKUP_RENAME_TARGET); > + lookup_flags | target_lookup_flags); > if (IS_ERR(new_dentry)) { > err = PTR_ERR(new_dentry); > goto out3; > @@ -754,16 +758,6 @@ int ksmbd_vfs_rename(struct ksmbd_work *work, const struct path *old_path, > goto out4; > } > > - /* > - * explicitly handle file overwrite case, for compatibility with > - * filesystems that may not support rename flags (e.g: fuse) > - */ > - if ((flags & RENAME_NOREPLACE) && d_is_positive(new_dentry)) { > - err = -EEXIST; > - goto out4; > - } > - flags &= ~(RENAME_NOREPLACE); > - > if (old_child == trap) { > err = -EINVAL; > goto out4; Nice simplification. Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
