[PATCH v3 36/39] ubifs: implement ubifs_get_qsize to get quota size in ubifs
Jan Kara
jack at suse.cz
Wed Sep 23 00:42:36 PDT 2015
On Mon 21-09-15 19:02:30, Dongsheng Yang wrote:
> On 09/21/2015 05:44 PM, Jan Kara wrote:
> >On Mon 21-09-15 17:16:49, Dongsheng Yang wrote:
> >>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.
> >
> >I think you are missing one thing:
> >
> >Assume user A has files F1 (1MB) F2 (2MB) F3 (3MB).
> >User B has one file G1 (4MB).
> >
> >So user A uses 6 MB in total (stored in dquot for user A in dqb_curspace
> >field). User B uses 4MB.
> >
> >Now you do "chown B F1"
> >
> >You need to change dq_dqb of F1 to point to user B quota structure as you
> >explain, that is correct. However you also need to subtract 1MB from user
> >A's total usage (which is stored in struct dquot for user A) since file F1
> >no longer belongs to him. And you need to add 1 MB to user B's total usage.
> >
> >After this user A will have total usage of 5 MB and user B has usage of 5
> >MB as well. You need to properly update the total usage of each user so
> >that you can check the usage against quota limits.
>
> But that's all done in dquot_transfer(). It dquot_decr_space(from) and
> dquot_incr_space(to). Let me show the test result in my implementation.
Yes, dquot_decr_space(transfer_from[cnt], cur_space) and
dquot_incr_space(transfer_to[cnt], cur_space) are the functions changing
usage. However have a look at what cur_space is. It is set as:
cur_space = inode_get_bytes(inode);
and inode_get_bytes() is:
ret = (((loff_t)inode->i_blocks) << 9) + inode->i_bytes;
So for dquot_transfer() to work correctly, filesystem has to properly
maintain i_blocks and i_bytes.
> (1). root -> 1M/2M/3M yds ->4M
>
> [root at atest-guest linux_compile]# ll -h /mnt/ubifs/
> total 11M
> -rw-r--r--. 1 root root 1.0M Sep 21 15:54 1M
> -rw-r--r--. 1 root root 2.0M Sep 21 15:54 2M
> -rw-r--r--. 1 root root 3.0M Sep 21 15:54 3M
> -rw-r--r--. 1 yds root 4.0M Sep 21 15:55 4M
> -rw-------. 1 root root 6.0K Sep 21 15:53 aquota.group
> -rw-------. 1 root root 7.0K Sep 21 15:53 aquota.user
> [root at atest-guest linux_compile]# repquota -u /mnt/ubifs/
> *** Report for user quotas on device /dev/ubi0_0
> Block grace time: 7days; Inode grace time: 7days
> Block limits File limits
> User used soft hard grace used soft hard grace
> ----------------------------------------------------------------------
> root -- 6144 0 0 4 0 0
> yds -- 4096 0 0 1 0 0
>
>
> (2). chown yds /mnt/ubifs/1M
> [root at atest-guest linux_compile]# chown yds /mnt/ubifs/1M
> [root at atest-guest linux_compile]# ll -h /mnt/ubifs/
> total 11M
> -rw-r--r--. 1 yds root 1.0M Sep 21 15:54 1M
> -rw-r--r--. 1 root root 2.0M Sep 21 15:54 2M
> -rw-r--r--. 1 root root 3.0M Sep 21 15:54 3M
> -rw-r--r--. 1 yds root 4.0M Sep 21 15:55 4M
> -rw-------. 1 root root 6.0K Sep 21 15:53 aquota.group
> -rw-------. 1 root root 7.0K Sep 21 15:53 aquota.user
> [root at atest-guest linux_compile]# repquota -u /mnt/ubifs/
> *** Report for user quotas on device /dev/ubi0_0
> Block grace time: 7days; Inode grace time: 7days
> Block limits File limits
> User used soft hard grace used soft hard grace
> ----------------------------------------------------------------------
> root -- 5120 0 0 3 0 0
> yds -- 5120 0 0 2 0 0
>
>
> (3). quotacheck and check again.
> [root at atest-guest linux_compile]# quotaoff /mnt/ubifs && quotacheck
> -u /mnt/ubifs/
> [root at atest-guest linux_compile]# ll -h /mnt/ubifs
> total 11M
> -rw-r--r--. 1 yds root 1.0M Sep 21 15:54 1M
> -rw-r--r--. 1 root root 2.0M Sep 21 15:54 2M
> -rw-r--r--. 1 root root 3.0M Sep 21 15:54 3M
> -rw-r--r--. 1 yds root 4.0M Sep 21 15:55 4M
> -rw-------. 1 root root 6.0K Sep 21 15:53 aquota.group
> -rw-------. 1 root root 7.0K Sep 21 16:00 aquota.user
> [root at atest-guest linux_compile]# repquota -u /mnt/ubifs/
> *** Report for user quotas on device /dev/ubi0_0
> Block grace time: 7days; Inode grace time: 7days
> Block limits File limits
> User used soft hard grace used soft hard grace
> ----------------------------------------------------------------------
> root -- 5120 0 0 3 0 0
> yds -- 5120 0 0 2 0 0
Yes, this case is working because quota code updated i_blocks properly when
creating files. But if you do not set i_blocks when reading inodes
(which seems to be the case) I expect the following would not work:
mount -t ubifs -o usrjquota=aquota.user,jqfmt=vfsv0 <dev> /mnt
quotacheck -vu /mnt
quotaon -vu /mnt
dd if=/dev/zero of=file1 bs=1M count=1
# Umount fs to prune cached information
umount /mnt
mount -t ubifs -o usrjquota=aquota.user,jqfmt=vfsv0 <dev> /mnt
quotaon -vu /mnt
chown yds /mnt/file1
repquota -u /mnt/
Now unless you set i_blocks when reading inode, yds would not be accounted
for 1 MB /mnt/file1 is using...
Honza
--
Jan Kara <jack at suse.com>
SUSE Labs, CR
More information about the linux-mtd
mailing list