On 09/21/2015 05:13 PM, Jan Kara wrote:
On Mon 21-09-15 12:35:01, Dongsheng Yang wrote:
On 09/18/2015 07:20 PM, Jan Kara wrote:
.... TBH, there is a little different with other filesystems. I did not
use the "disk" space, but the file space in ubifs quota, although dquot
means disk quota. Same with btrfs quota. If we use disk space for quota,
the most common problem from user is that: why I did not reach the limit
but I can not write any byte. COW in btrfs or out-place-updating in
ubifs makes this problem much worse.
So I choose file space here for ubifs.
OK, so these are really two separate questions. I understand your choice of
using file space as the amount of space to account for quota purposes and
I'm fine with that choice. Another thing is that regardless of how you
decide to do quota accounting, you must maintain i_blocks / i_bytes to
contain proper value because dquot_transfer() uses that information to update
quota usage when inode owner is changed.
But if we don't use i_blocks to get qsize, what we care only in
dquot_transter() is dquot->dq_dqb. That means, even if the i_blocks
is not correct in dquot_transfer() in ubifs, that's okey, because we
will never use this value, right?
dquot_transfer() will use the value - when file F changes owner from user A
to user B, then you need to decrement amount of space used by F from A's
quota usage and add that amount to B's quota usage. And the amount of space
is obtained via inode_get_bytes() which uses i_blocks and i_bytes. See
__dquot_transfer() in fs/quota/dquot.c for details.
Yes, I see it. But if ubifs doesn't use i_blocks and i_bytes to stand
for quota size, as I mentioned I want to use i_size. Then we will never
use i_blocks. So we only need a to transfer dquot->dq_dqb values. That
means, even the i_blocks in dquot_transfer() is not correct, we don't
care it. we only need to make sure values in dquot_dq_dqb are
transfered, such as dquot->dq_dqb->curspace for user B is equal with
i_size.
Yang
Honza
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