why does proc_fd_getattr() bother with S_ISDIR(inode->i_mode)?

why does proc_fd_getattr() bother with S_ISDIR(inode->i_mode)?

[Al Viro]

	... when the only way to get to it is via ->getattr() in
proc_fd_inode_operations?  Note that proc_fd_inode_operations
has ->lookup() in it; it _can't_ be ->i_op of a non-directory.

	Am I missing something here?

Re: why does proc_fd_getattr() bother with S_ISDIR(inode->i_mode)?

[Ivan Babrou]

On Mon, Jun 3, 2024 at 8:40 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
>         ... when the only way to get to it is via ->getattr() in
> proc_fd_inode_operations?  Note that proc_fd_inode_operations
> has ->lookup() in it; it _can't_ be ->i_op of a non-directory.
>
>         Am I missing something here?

It's been two years, but I think I was just extra cautious.

Re: why does proc_fd_getattr() bother with S_ISDIR(inode->i_mode)?

[Al Viro]

On Tue, Jun 04, 2024 at 10:35:43AM -0700, Ivan Babrou wrote:
> On Mon, Jun 3, 2024 at 8:40 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> >
> >         ... when the only way to get to it is via ->getattr() in
> > proc_fd_inode_operations?  Note that proc_fd_inode_operations
> > has ->lookup() in it; it _can't_ be ->i_op of a non-directory.
> >
> >         Am I missing something here?
> 
> It's been two years, but I think I was just extra cautious.

Does anyone have objections against the following?

[PATCH] proc_fd_getattr(): don't bother with S_ISDIR() check
    
that thing is callable only as ->i_op->getattr() instance and only
for directory inodes (/proc/*/fd and /proc/*/task/*/fd)

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
diff --git a/fs/proc/fd.c b/fs/proc/fd.c
index 586bbc84ca04..bda7abcf29fa 100644
--- a/fs/proc/fd.c
+++ b/fs/proc/fd.c
@@ -357,18 +357,9 @@ static int proc_fd_getattr(struct mnt_idmap *idmap,
 			u32 request_mask, unsigned int query_flags)
 {
 	struct inode *inode = d_inode(path->dentry);
-	int rv = 0;
 
 	generic_fillattr(&nop_mnt_idmap, request_mask, inode, stat);
-
-	/* If it's a directory, put the number of open fds there */
-	if (S_ISDIR(inode->i_mode)) {
-		rv = proc_readfd_count(inode, &stat->size);
-		if (rv < 0)
-			return rv;
-	}
-
-	return rv;
+	return proc_readfd_count(inode, &stat->size);
 }
 
 const struct inode_operations proc_fd_inode_operations = {

Re: why does proc_fd_getattr() bother with S_ISDIR(inode->i_mode)?

[Christian Brauner]

On Tue, Jun 04, 2024 at 06:40:59PM +0100, Al Viro wrote:
> On Tue, Jun 04, 2024 at 10:35:43AM -0700, Ivan Babrou wrote:
> > On Mon, Jun 3, 2024 at 8:40 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
> > >
> > >         ... when the only way to get to it is via ->getattr() in
> > > proc_fd_inode_operations?  Note that proc_fd_inode_operations
> > > has ->lookup() in it; it _can't_ be ->i_op of a non-directory.
> > >
> > >         Am I missing something here?
> > 
> > It's been two years, but I think I was just extra cautious.
> 
> Does anyone have objections against the following?
> 
> [PATCH] proc_fd_getattr(): don't bother with S_ISDIR() check
>     
> that thing is callable only as ->i_op->getattr() instance and only
> for directory inodes (/proc/*/fd and /proc/*/task/*/fd)
> 
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---

Kill it,
Reviewed-by: Christian Brauner <brauner@kernel.org>