Re: [PATCH 1/3] quota: Check next/prev free block number after reading from quota file

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在 2022/9/22 19:39, Jan Kara 写道:
On Thu 22-09-22 16:13:59, Zhihao Cheng wrote:
[...]

The free block should actually be > QT_TREEOFF so I'd add the check to
do_check_range().

'dh->dqdh_next_free' may be updated when quota entry removed,
'dh->dqdh_next_free' can be used for next new quota entris.
Before sending v2, I found 'dh->dqdh_next_free' and 'dh->dqdh_prev_free' can
easily be zero in newly allocated blocks when continually creating files
onwed by different users:
find_free_dqentry
   get_free_dqblk
     write_blk(info, info->dqi_blocks, buf)  // zero'd qt_disk_dqdbheader
     blk = info->dqi_blocks++   // allocate new one block
   info->dqi_free_entry = blk   // will be used for new quota entries

find_free_dqentry
   if (info->dqi_free_entry)
     blk = info->dqi_free_entry
     read_blk(info, blk, buf)   // dh->dqdh_next_free = dh->dqdh_prev_free =
0

I think it's normal when 'dh->dqdh_next_free' or 'dh->dqdh_prev_free' equals
to 0.

Good point! 0 means "not present". So any block number (either in free list
or pointed from the quota tree) should be either 0 or > QT_TREEOFF.

								Honza


In case my emails being filtered agagin, this is notification of v2:
https://lore.kernel.org/linux-ext4/20220922130401.1792256-1-chengzhihao1@xxxxxxxxxx/T/#m9676d64e8f7cdd7b7decdd0d6b725ec658110b3e



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