[RFC] ntfs3: remove atomic_open

Commit Message

Jeffrey Layton March 18, 2024, 6:28 p.m. UTC

atomic_open is an optional VFS operation, and is primarily for network
filesystems. NFS (for instance) can just send an open call for the last
path component rather than doing a lookup and then having to follow that
up with an open when it doesn't have a dentry in cache.

ntfs3 is a local filesystem however, and its atomic_open just does a
typical lookup + open, but in a convoluted way. atomic_open will also
make directory leases more difficult to implement on the filesystem.

Remove ntfs_atomic_open.

Signed-off-by: Jeff Layton <[e-mail]>
---
Am I missing something about why ntfs3 requires an atomic_open op? In
any case, this is only lightly tested, but it seems to work.
---
 fs/ntfs3/namei.c | 90 --------------------------------------------------------
 1 file changed, 90 deletions(-)


---
base-commit: 0a7b0acecea273c8816f4f5b0e189989470404cf
change-id: 20240318-ntfs3-atomic-open-0cc979d7c024

Best regards,

Comments

Christian Brauner March 19, 2024, 3:29 p.m. UTC | #1

On Mon, Mar 18, 2024 at 02:28:50PM -0400, Jeff Layton wrote:
> atomic_open is an optional VFS operation, and is primarily for network
> filesystems. NFS (for instance) can just send an open call for the last
> path component rather than doing a lookup and then having to follow that
> up with an open when it doesn't have a dentry in cache.
> 
> ntfs3 is a local filesystem however, and its atomic_open just does a
> typical lookup + open, but in a convoluted way. atomic_open will also
> make directory leases more difficult to implement on the filesystem.
> 
> Remove ntfs_atomic_open.
> 
> Signed-off-by: Jeff Layton <[e-mail]>
> ---
> Am I missing something about why ntfs3 requires an atomic_open op? In
> any case, this is only lightly tested, but it seems to work.

Seems we should just remove it.

Al Viro March 22, 2024, 2:35 a.m. UTC | #2

On Mon, Mar 18, 2024 at 02:28:50PM -0400, Jeff Layton wrote:
> atomic_open is an optional VFS operation, and is primarily for network
> filesystems. NFS (for instance) can just send an open call for the last
> path component rather than doing a lookup and then having to follow that
> up with an open when it doesn't have a dentry in cache.
> 
> ntfs3 is a local filesystem however, and its atomic_open just does a
> typical lookup + open, but in a convoluted way. atomic_open will also
> make directory leases more difficult to implement on the filesystem.

FWIW, I'm not sure they are actually doing it correctly, but in any
case - there's no reason whatsoever for implementing that sucker on
a local filesystem.  Kill it.

> -	inode = ntfs_create_inode(file_mnt_idmap(file), dir, dentry, uni,
> -				  mode, 0, NULL, 0, fnd);
> -	err = IS_ERR(inode) ? PTR_ERR(inode) :
> -			      finish_open(file, dentry, ntfs_file_open);

... incidentally, this ntfs_create_inode() thing should not have the
calling conventions it has.

It does create inode, all right - and attaches it to dentry.  Then it
proceeds to return the pointer to that new inode, with dentry->d_inode
being the only thing that keeps it alive.  That would be defendable
(we are holding a reference to dentry and nobody else could turn
it negative under us), but... look at the callers.

4 out of 5 are of the same form:
	inode = ntfs_create_inode(....);
	return IS_ERR(inode) ? PTR_ERR(inode) : 0;

The fifth one is the crap above and there we *also* never look at the
return value downstream of that IS_ERR(inode) ? PTR_ERR(inode) : ...;

Which is to say, all callers of that thing don't give a damn about
the pointer per se - they only want to know if it's ERR_PTR(-E...)
or not and if it is, what error had been wrapped into that ERR_PTR().

Simply make it return 0 or -E... - if some future caller really
wants a reference to struct inode that had been created, they can
bloody well pick it from dentry->d_inode.

In any case, this caller should simply die - ->atomic_open() instance
does not buy *anything* here.

Acked-by: Al Viro <[e-mail]>

Patch

diff --git a/fs/ntfs3/namei.c b/fs/ntfs3/namei.c
index 084d19d78397..edb6a7141246 100644
--- a/fs/ntfs3/namei.c
+++ b/fs/ntfs3/namei.c
@@ -358,95 +358,6 @@  static int ntfs_rename(struct mnt_idmap *idmap, struct inode *dir,
 	return err;
 }
 
-/*
- * ntfs_atomic_open
- *
- * inode_operations::atomic_open
- */
-static int ntfs_atomic_open(struct inode *dir, struct dentry *dentry,
-			    struct file *file, u32 flags, umode_t mode)
-{
-	int err;
-	struct inode *inode;
-	struct ntfs_fnd *fnd = NULL;
-	struct ntfs_inode *ni = ntfs_i(dir);
-	struct dentry *d = NULL;
-	struct cpu_str *uni = __getname();
-	bool locked = false;
-
-	if (!uni)
-		return -ENOMEM;
-
-	err = ntfs_nls_to_utf16(ni->mi.sbi, dentry->d_name.name,
-				dentry->d_name.len, uni, NTFS_NAME_LEN,
-				UTF16_HOST_ENDIAN);
-	if (err < 0)
-		goto out;
-
-#ifdef CONFIG_NTFS3_FS_POSIX_ACL
-	if (IS_POSIXACL(dir)) {
-		/*
-		 * Load in cache current acl to avoid ni_lock(dir):
-		 * ntfs_create_inode -> ntfs_init_acl -> posix_acl_create ->
-		 * ntfs_get_acl -> ntfs_get_acl_ex -> ni_lock
-		 */
-		struct posix_acl *p = get_inode_acl(dir, ACL_TYPE_DEFAULT);
-
-		if (IS_ERR(p)) {
-			err = PTR_ERR(p);
-			goto out;
-		}
-		posix_acl_release(p);
-	}
-#endif
-
-	if (d_in_lookup(dentry)) {
-		ni_lock_dir(ni);
-		locked = true;
-		fnd = fnd_get();
-		if (!fnd) {
-			err = -ENOMEM;
-			goto out1;
-		}
-
-		d = d_splice_alias(dir_search_u(dir, uni, fnd), dentry);
-		if (IS_ERR(d)) {
-			err = PTR_ERR(d);
-			d = NULL;
-			goto out2;
-		}
-
-		if (d)
-			dentry = d;
-	}
-
-	if (!(flags & O_CREAT) || d_really_is_positive(dentry)) {
-		err = finish_no_open(file, d);
-		goto out2;
-	}
-
-	file->f_mode |= FMODE_CREATED;
-
-	/*
-	 * fnd contains tree's path to insert to.
-	 * If fnd is not NULL then dir is locked.
-	 */
-	inode = ntfs_create_inode(file_mnt_idmap(file), dir, dentry, uni,
-				  mode, 0, NULL, 0, fnd);
-	err = IS_ERR(inode) ? PTR_ERR(inode) :
-			      finish_open(file, dentry, ntfs_file_open);
-	dput(d);
-
-out2:
-	fnd_put(fnd);
-out1:
-	if (locked)
-		ni_unlock(ni);
-out:
-	__putname(uni);
-	return err;
-}
-
 struct dentry *ntfs3_get_parent(struct dentry *child)
 {
 	struct inode *inode = d_inode(child);
@@ -612,7 +523,6 @@  const struct inode_operations ntfs_dir_inode_operations = {
 	.setattr	= ntfs3_setattr,
 	.getattr	= ntfs_getattr,
 	.listxattr	= ntfs_listxattr,
-	.atomic_open	= ntfs_atomic_open,
 	.fiemap		= ntfs_fiemap,
 };