Re: [PATCH v1 6/9] fs/fuse: support idmapped ->setattr op

[Christian Brauner]

On Mon, Jan 29, 2024 at 04:48:49PM +0100, Alexander Mikhalitsyn wrote:
> On Sat, 20 Jan 2024 16:23:38 +0100
> Christian Brauner <brauner@xxxxxxxxxx> wrote:
> 
> > On Mon, Jan 08, 2024 at 01:08:21PM +0100, Alexander Mikhalitsyn wrote:
> > > Cc: Christian Brauner <brauner@xxxxxxxxxx>
> > > Cc: Seth Forshee <sforshee@xxxxxxxxxx>
> > > Cc: Miklos Szeredi <miklos@xxxxxxxxxx>
> > > Cc: Amir Goldstein <amir73il@xxxxxxxxx>
> > > Cc: Bernd Schubert <bschubert@xxxxxxx>
> > > Cc: <linux-fsdevel@xxxxxxxxxxxxxxx>
> > > Signed-off-by: Alexander Mikhalitsyn <aleksandr.mikhalitsyn@xxxxxxxxxxxxx>
> > > ---
> > >  fs/fuse/dir.c    | 32 +++++++++++++++++++++-----------
> > >  fs/fuse/file.c   |  2 +-
> > >  fs/fuse/fuse_i.h |  4 ++--
> > >  3 files changed, 24 insertions(+), 14 deletions(-)
> > > 
> > > diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c
> > > index f7c2c54f7122..5fbb7100ad1c 100644
> > > --- a/fs/fuse/dir.c
> > > +++ b/fs/fuse/dir.c
> > > @@ -1739,17 +1739,27 @@ static bool update_mtime(unsigned ivalid, bool trust_local_mtime)
> > >  	return true;
> > >  }
> > >  
> > > -static void iattr_to_fattr(struct fuse_conn *fc, struct iattr *iattr,
> > > -			   struct fuse_setattr_in *arg, bool trust_local_cmtime)
> > > +static void iattr_to_fattr(struct mnt_idmap *idmap, struct fuse_conn *fc,
> > > +			   struct iattr *iattr, struct fuse_setattr_in *arg,
> > > +			   bool trust_local_cmtime)
> > >  {
> > >  	unsigned ivalid = iattr->ia_valid;
> > >  
> > >  	if (ivalid & ATTR_MODE)
> > >  		arg->valid |= FATTR_MODE,   arg->mode = iattr->ia_mode;
> > > -	if (ivalid & ATTR_UID)
> > > -		arg->valid |= FATTR_UID,    arg->uid = from_kuid(fc->user_ns, iattr->ia_uid);
> > > -	if (ivalid & ATTR_GID)
> > > -		arg->valid |= FATTR_GID,    arg->gid = from_kgid(fc->user_ns, iattr->ia_gid);
> > > +
> > > +	if (ivalid & ATTR_UID) {
> > > +		kuid_t fsuid = from_vfsuid(idmap, fc->user_ns, iattr->ia_vfsuid);
> > > +		arg->valid |= FATTR_UID;
> > > +		arg->uid = from_kuid(fc->user_ns, fsuid);
> > > +	}
> > > +
> > > +	if (ivalid & ATTR_GID) {
> > > +		kgid_t fsgid = from_vfsgid(idmap, fc->user_ns, iattr->ia_vfsgid);
> > > +		arg->valid |= FATTR_GID;
> > > +		arg->gid = from_kgid(fc->user_ns, fsgid);
> > > +	}
> > > +
> > >  	if (ivalid & ATTR_SIZE)
> > >  		arg->valid |= FATTR_SIZE,   arg->size = iattr->ia_size;
> > >  	if (ivalid & ATTR_ATIME) {
> > > @@ -1869,8 +1879,8 @@ int fuse_flush_times(struct inode *inode, struct fuse_file *ff)
> > >   * vmtruncate() doesn't allow for this case, so do the rlimit checking
> > >   * and the actual truncation by hand.
> > >   */
> > > -int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
> > > -		    struct file *file)
> > > +int fuse_do_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> > > +		    struct iattr *attr, struct file *file)
> > >  {
> > >  	struct inode *inode = d_inode(dentry);
> > >  	struct fuse_mount *fm = get_fuse_mount(inode);
> > > @@ -1890,7 +1900,7 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
> > >  	if (!fc->default_permissions)
> > >  		attr->ia_valid |= ATTR_FORCE;
> > >  
> > > -	err = setattr_prepare(&nop_mnt_idmap, dentry, attr);
> > > +	err = setattr_prepare(idmap, dentry, attr);
> > >  	if (err)
> > >  		return err;
> > >  
> > > @@ -1949,7 +1959,7 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr,
> > >  
> > >  	memset(&inarg, 0, sizeof(inarg));
> > >  	memset(&outarg, 0, sizeof(outarg));
> > > -	iattr_to_fattr(fc, attr, &inarg, trust_local_cmtime);
> > > +	iattr_to_fattr(idmap, fc, attr, &inarg, trust_local_cmtime);
> > >  	if (file) {
> > >  		struct fuse_file *ff = file->private_data;
> > >  		inarg.valid |= FATTR_FH;
> > > @@ -2084,7 +2094,7 @@ static int fuse_setattr(struct mnt_idmap *idmap, struct dentry *entry,
> > >  	if (!attr->ia_valid)
> > >  		return 0;
> > >  
> > > -	ret = fuse_do_setattr(entry, attr, file);
> > > +	ret = fuse_do_setattr(idmap, entry, attr, file);
> > >  	if (!ret) {
> > >  		/*
> > >  		 * If filesystem supports acls it may have updated acl xattrs in
> > > diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> > > index a660f1f21540..e0fe5497a548 100644
> > > --- a/fs/fuse/file.c
> > > +++ b/fs/fuse/file.c
> > > @@ -2870,7 +2870,7 @@ static void fuse_do_truncate(struct file *file)
> > >  	attr.ia_file = file;
> > >  	attr.ia_valid |= ATTR_FILE;
> > >  
> > > -	fuse_do_setattr(file_dentry(file), &attr, file);
> > > +	fuse_do_setattr(&nop_mnt_idmap, file_dentry(file), &attr, file);
> > 
> > Same as for the other patch. Please leave a comment in the commit
> > message that briefly explains why it's ok to pass &nop_mnt_idmap here.
> > It'll help us later. :)
> 
> Sure, will be fixed in -v2 ;-)
> 
> Explanation here is that in this specific case attr.ia_valid = ATTR_SIZE | ATTR_FILE,
> which but we only need an idmapping for ATTR_UID | ATTR_GID.
> 
> From the other side, having struct file pointer means that getting an idmapping as easy as file_mnt_idmap(file),
> and probably it's easier to pass an idmapping in this specific case rather than skipping it for a valid reasons.
> What do you think about this?

Yeah, I'd just pass it through because then we don't have to think about
why we're not passing it through here.