Re: [PATCH v18 21/22] ext4: Add richacl support

Andreas Gruenbacher
2016-03-13T23:50:01Z

On Fri, Mar 11, 2016 at 3:27 PM, Christoph Hellwig <hch@infradead.org> wrote:
>> +static int
>> +__ext4_set_richacl(handle_t *handle, struct inode *inode, struct richacl *acl)
>> +{
>> + const int name_index = EXT4_XATTR_INDEX_RICHACL;
>> + umode_t mode = inode->i_mode;
>> + int retval, size;
>> + void *value;
>> +
>> + if (richacl_equiv_mode(acl, &mode) == 0) {
>> + inode->i_ctime = ext4_current_time(inode);
>> + inode->i_mode = mode;
>> + ext4_mark_inode_dirty(handle, inode);
>> + return __ext4_remove_richacl(handle, inode);
>> + }
>
> Should this check for a NULL acl instead of special casing that
> in ext4_set_richacl?

I'm not sure I understand what you mean. When iop->set_richacl is
called with a richacl that is mode-equivalent, the file permission
bits need to be updated and any existing acl needs to be removed.
Doing this at the vfs level would result in two calls, iop->setattr
and iop->set_richacl, which can cause problems. To remove an existing
acl without setting the mode, set_richacl is called with a NULL
richacl.

__ext4_set_richacl() was split into __ext4_set_richacl() and
__ext4_remove_richacl() to align with the xfs code due to the
following comment from Dave Chinner:
http://oss.sgi.com/archives/xfs/2015-10/msg00354.html

Diff here:
https://git.kernel.org/cgit/linux/kernel/git/agruen/linux-richacl.git/diff/fs/ext4/richacl.c?id=richacl-2015-10-16&id2=richacl-2015-10-12

>> +int
>> +ext4_init_richacl(handle_t *handle, struct inode *inode, struct inode *dir)
>> +{
>> + struct richacl *acl = richacl_create(&inode->i_mode, dir);
>> + int error;
>> +
>> + error = PTR_ERR(acl);
>> + if (IS_ERR(acl))
>> + return error;
>
> if (IS_ERR(acl))
> return PTR_ERR(acl);
>
>> + if (acl) {
>> + error = __ext4_set_richacl(handle, inode, acl);
>> + richacl_put(acl);
>> + }
>
> Shouldn't richacl_create return NULL if the ACL is equivalent to the
> mode bits instead of letting every filesystem figure that out on it's
> own?

Hm, that's what it does?

Thanks,
Andreas