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Date: Tue, 08 Dec 2009 09:34:37 +0300
From: Dmitry Monakhov <dmonakhov@...nvz.org>
To: Mingming <cmm@...ibm.com>
Cc: linux-ext4@...r.kernel.org
Subject: Re: [PATCH 1/4] ext4: delalloc quota fixes
Mingming <cmm@...ibm.com> writes:
> On Tue, 2009-11-24 at 01:58 +0300, Dmitry Monakhov wrote:
>> This patch fix most visible problems with delalloc+quota issues
>> - ext4_get_reserved_space() must return bytes instead of blocks.
>> - Claim allocated meta blocks. Do it as we do for data blocks
>> but delay it untill proper moment.
>> - Move space claiming to ext4_da_update_reserve_space()
>> Only here we do know what we are dealing with data or metadata
>>
>
> Thanks for sending the first fix, I am actually surprisely to know the
> fix didn't get merged before, as Jan has pointed this out when he review
> the original patch and I have get this fixed...somehow the latest patch
> wasn't being picked at the end.
>
> here it is.
> http://marc.info/?l=linux-ext4&m=123185939602949&w=2
>
>
> About the second and third issue you are trying to fix here... I think
> the current code does what you want already.
>
> The current code does reserve quota for metadata blocks at
> ext4_da_update_reserve_space() already and delay the quota claim at the
> later time when metadata blocks are really allocated (via
> ext4_mb_mark_diskspace_used), extra reserved quota for metadata blocks
> will get freed at ext4_da_update_reserve_space().
> ext4_mb_mark_diskspace_used() is called for every block allocation
> including medatadata allocation, so we won't miss quota claim for
> metadata there.
>
> The reason that I keep all quota claim immediately at the block
> allocation time via ext4_mb_mark_diskspace_used() is to keep the block
> allocation space accounting/dirty/delayed block space accounting/quota
> accounting in the same place; Plus, when ext4_da_update_reserve_space()
> called, the number of blocks passed is the number of blocks mapped, may
> not necessarilly the the number of blocks just new allocated.
You have reviewed wrong patch version. Please read the latest one
http://article.gmane.org/gmane.comp.file-systems.ext4/16629 in order
to get my idea. But in fact as Aneesh have spotted, my I've missed
important issue aka #14739. Currently I'm working on new patch set
version. This patch series will fix "chown vs truncate issue" and
#14739 by one shot.
>
> cheers,
> Mingming
>
> put the space claiming under
>> The most useful test case for delalloc+quota is concurent tasks
>> with write+truncate vs chown for a same file.
>>
>> Signed-off-by: Dmitry Monakhov <dmonakhov@...nvz.org>
>> ---
>> fs/ext4/inode.c | 12 ++++++++----
>> fs/ext4/mballoc.c | 6 ------
>> 2 files changed, 8 insertions(+), 10 deletions(-)
>>
>> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
>> index ab22297..e642cdb 100644
>> --- a/fs/ext4/inode.c
>> +++ b/fs/ext4/inode.c
>> @@ -1057,7 +1057,7 @@ qsize_t ext4_get_reserved_space(struct inode *inode)
>> EXT4_I(inode)->i_reserved_meta_blocks;
>> spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
>>
>> - return total;
>> + return (total << inode->i_blkbits);
>> }
>
>
>
>> /*
>> * Calculate the number of metadata blocks need to reserve
>> @@ -1096,7 +1096,7 @@ static int ext4_calc_metadata_amount(struct inode *inode, int blocks)
>> static void ext4_da_update_reserve_space(struct inode *inode, int used)
>> {
>> struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
>> - int total, mdb, mdb_free;
>> + int total, mdb, mdb_free, mdb_claim = 0;
>>
>> spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
>> /* recalculate the number of metablocks still need to be reserved */
>> @@ -1109,7 +1109,9 @@ static void ext4_da_update_reserve_space(struct inode *inode, int used)
>>
>> if (mdb_free) {
>> /* Account for allocated meta_blocks */
>> - mdb_free -= EXT4_I(inode)->i_allocated_meta_blocks;
>> + mdb_claim = EXT4_I(inode)->i_allocated_meta_blocks;
>> + BUG_ON(mdb_free < mdb_claim);
>> + mdb_free -= mdb_claim;
>>
>> /* update fs dirty blocks counter */
>> percpu_counter_sub(&sbi->s_dirtyblocks_counter, mdb_free);
>> @@ -1119,7 +1121,9 @@ static void ext4_da_update_reserve_space(struct inode *inode, int used)
>>
>> /* update per-inode reservations */
>> BUG_ON(used > EXT4_I(inode)->i_reserved_data_blocks);
>> - EXT4_I(inode)->i_reserved_data_blocks -= used;
>> + EXT4_I(inode)->i_reserved_data_blocks -= used;
>> + percpu_counter_sub(&sbi->s_dirtyblocks_counter, used + mdb_claim);
>> + vfs_dq_claim_block(inode, used + mdb_claim);
>> spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);
>>
>> /*
>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index bba1282..d4c52db 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -2750,12 +2750,6 @@ ext4_mb_mark_diskspace_used(struct ext4_allocation_context *ac,
>> if (!(ac->ac_flags & EXT4_MB_DELALLOC_RESERVED))
>> /* release all the reserved blocks if non delalloc */
>> percpu_counter_sub(&sbi->s_dirtyblocks_counter, reserv_blks);
>> - else {
>> - percpu_counter_sub(&sbi->s_dirtyblocks_counter,
>> - ac->ac_b_ex.fe_len);
>> - /* convert reserved quota blocks to real quota blocks */
>> - vfs_dq_claim_block(ac->ac_inode, ac->ac_b_ex.fe_len);
>> - }
>>
>> if (sbi->s_log_groups_per_flex) {
>> ext4_group_t flex_group = ext4_flex_group(sbi,
>
>
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