Re: [GIT PULL] bcachefs

Darrick J. Wong
2023-08-11T22:56:39Z

On Fri, Aug 11, 2023 at 09:21:41AM -0400, Kent Overstreet wrote:
> On Fri, Aug 11, 2023 at 12:54:42PM +0200, Christian Brauner wrote:
> > > I don't want to do that to Christian either, I think highly of the work
> > > he's been doing and I don't want to be adding to his frustration. So I
> > > apologize for loosing my cool earlier; a lot of that was frustration
> > > from other threads spilling over.
> > >
> > > But: if he's going to be raising objections, I need to know what his
> > > concerns are if we're going to get anywhere. Raising objections without
> > > saying what the concerns are shuts down discussion; I don't think it's
> > > unreasonable to ask people not to do that, and to try and stay focused
> > > on the code.
> >
> > The technical aspects were made clear off-list and I believe multiple
> > times on-list by now. Any VFS and block related patches are to be
> > reviewed and accepted before bcachefs gets merged.
>
> Here's the one VFS patch in the series - could we at least get an ack
> for this? It's a new helper, just breaks the existing d_tmpfile() up
> into two functions - I hope we can at least agree that this patch
> shouldn't be controversial?
>
> -->--
> Subject: [PATCH] fs: factor out d_mark_tmpfile()
>
> New helper for bcachefs - bcachefs doesn't want the
> inode_dec_link_count() call that d_tmpfile does, it handles i_nlink on
> its own atomically with other btree updates
>
> Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
> Cc: Alexander Viro <viro@zeniv.linux.org.uk>
> Cc: Christian Brauner <brauner@kernel.org>
> Cc: linux-fsdevel@vger.kernel.org

Yes, we can finally clean up this braindamage in xfs_generic_create:

if (tmpfile) {
/*
* The VFS requires that any inode fed to d_tmpfile must
* have nlink == 1 so that it can decrement the nlink in
* d_tmpfile. However, we created the temp file with
* nlink == 0 because we're not allowed to put an inode
* with nlink > 0 on the unlinked list. Therefore we
* have to set nlink to 1 so that d_tmpfile can
* immediately set it back to zero.
*/
set_nlink(inode, 1);
d_tmpfile(tmpfile, inode);
}

Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

>
> diff --git a/fs/dcache.c b/fs/dcache.c
> index 52e6d5fdab..dbdafa2617 100644
> --- a/fs/dcache.c
> +++ b/fs/dcache.c
> @@ -3249,11 +3249,10 @@ void d_genocide(struct dentry *parent)
>
> EXPORT_SYMBOL(d_genocide);
>
> -void d_tmpfile(struct file *file, struct inode *inode)
> +void d_mark_tmpfile(struct file *file, struct inode *inode)
> {
> struct dentry *dentry = file->f_path.dentry;
>
> - inode_dec_link_count(inode);
> BUG_ON(dentry->d_name.name != dentry->d_iname ||
> !hlist_unhashed(&dentry->d_u.d_alias) ||
> !d_unlinked(dentry));
> @@ -3263,6 +3262,15 @@ void d_tmpfile(struct file *file, struct inode *inode)
> (unsigned long long)inode->i_ino);
> spin_unlock(&dentry->d_lock);
> spin_unlock(&dentry->d_parent->d_lock);
> +}
> +EXPORT_SYMBOL(d_mark_tmpfile);
> +
> +void d_tmpfile(struct file *file, struct inode *inode)
> +{
> + struct dentry *dentry = file->f_path.dentry;
> +
> + inode_dec_link_count(inode);
> + d_mark_tmpfile(file, inode);
> d_instantiate(dentry, inode);
> }
> EXPORT_SYMBOL(d_tmpfile);
> diff --git a/include/linux/dcache.h b/include/linux/dcache.h
> index 6b351e009f..3da2f0545d 100644
> --- a/include/linux/dcache.h
> +++ b/include/linux/dcache.h
> @@ -251,6 +251,7 @@ extern struct dentry * d_make_root(struct inode *);
> /* <clickety>-<click> the ramfs-type tree */
> extern void d_genocide(struct dentry *);
>
> +extern void d_mark_tmpfile(struct file *, struct inode *);
> extern void d_tmpfile(struct file *, struct inode *);
>
> extern struct dentry *d_find_alias(struct inode *);