2014-01-29 Jan Kara <jack@xxxxxxx>:
> On Tue 28-01-14 19:26:08, Linus Torvalds wrote:
>> On Mon, Jan 27, 2014 at 6:25 AM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote:
>> > Assorted stuff; the biggest pile here is Christoph's ACL series.
>> > Plus assorted cleanups and fixes all over the place... There will be
>> > another pile later this week.
>>
>> The posix_acl_chmod() code looks wrong.
>>
>> Not that it looked right before either, but whatever. The code
>> basically looks like some variation of this in most setattr()
>> implementations:
>>
>> if (ia_valid & ATTR_MODE)
>> rc = posix_acl_chmod(inode, inode->i_mode);
>>
>> but the mode we're changing to (and what ATTR_MODE guards) is actually
>> attr->ia_mode, not inode->i_mode.
> Yes, but posix_acl_chmod() is called after setattr_copy() was done so
> inode->i_mode should be the same as attr->ia_mode. Whether i_mode or
> ia_mode is mode logical depends on whether you view posix_acl_chmod() as
> "sync current i_mode into acls" or "reflect this i_mode change in acls".
> I agree the function name suggests more the latter semantics.
>
>> And quite frankly, passing in inode->i_mode looks stupid, since we're
>> already passing in the inode pointer, so that's just redundant and
>> pointless information.
> Yes, it looks stupid. We could almost drop that argument, except that f2fs
> tries to play some tricks with i_mode and stores i_mode in a different
> place when acls are enabled. Huh? Jaegeuk, can you explain why are you
> doing that?
As described to Christoph before, the reason is for acl consistency
between on-disk xattr->mode and on-disk inode->mode.
Previously, there are three i_modes managed by:
inode->mode on-disk xattr->mode on-disk->i_mode
f2fs_setattr [x] y y
[update_inode] x y [x]
[checkpoint] x [y] x
__f2fs_setxattr x [x] x
In this flow, f2fs is able to break the consistency between on-disk
xattr->mode and on-disk->i_mode after checkpoint followed by
sudden-power-off.
So, fi->i_mode was introduced to address the problem.
The new f2fs_setattr triggers:
inode->mode fi->i_mode on-disk xattr->mode on-disk->i_mode
f2fs_setattr y [x] y
y
[update_inode] y x y
y
[checkpoint] y x y
y
__f2fs_setxattr [x] x [x]
[x]
Finally, __f2fs_setxattr synchronizes inode->mode, on-disk xattr->mode,
and on-disk inode->i_mode all together.
Am I missing something?
Thanks,
>
> Honza
> --
> Jan Kara <jack@xxxxxxx>
> SUSE Labs, CR
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