[Devel] [PATCH] vz6 ext4: Discard preallocated block before swap_extents

[Dmitry Monakhov]

Vasily Averin <vvs at virtuozzo.com> writes:

> Dima,
> please take look at comment below.
>
> On 2017-02-25 18:16, Dmitry Monakhov wrote:
>> Inode preallocation consists of two parts (used and unused) fully controlled
>> by inode, so it must be discarded before swap extents.
>> Currently we may skip drop_preallocation if file is sparse.
>> 
>> This patch does:
>> - Moves ext4_discard_preallocations to ext4_swap_extents.
>>   This makes more readable and reliable for future changes.
>> - Cleanup main move_extent loop
>> 
>> https://jira.sw.ru/browse/PSBM-57003
>> xfstests:ext4/024 (pended: https://github.com/dmonakhov/xfstests/commit/7a4763963f73ea5d5bba45eefa484494aa3df7cf)
>> Signed-off-by: Dmitry Monakhov <dmonakhov at openvz.org>
>> ---
>>  fs/ext4/extents.c     |  3 +++
>>  fs/ext4/move_extent.c | 17 +++++++----------
>>  2 files changed, 10 insertions(+), 10 deletions(-)
>> 
>> diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
>> index 85c4d4e..fd49ab0 100644
>> --- a/fs/ext4/extents.c
>> +++ b/fs/ext4/extents.c
>> @@ -4371,6 +4371,9 @@ ext4_swap_extents(handle_t *handle, struct inode *inode1,
>>  	BUG_ON(!mutex_is_locked(&inode1->i_mutex));
>>  	BUG_ON(!mutex_is_locked(&inode1->i_mutex));
>>  
>> +	ext4_discard_preallocations(inode1);
>> +	ext4_discard_preallocations(inode2);
>> +
>>  	while (count) {
>>  		struct ext4_extent *ex1, *ex2, tmp_ex;
>>  		ext4_lblk_t e1_blk, e2_blk;
>> diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
>> index 39eaa8f..97a7db5 100644
>> --- a/fs/ext4/move_extent.c
>> +++ b/fs/ext4/move_extent.c
>> @@ -628,6 +628,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
>>  	ext4_lblk_t o_end, o_start = orig_blk;
>>  	ext4_lblk_t d_start = donor_blk;
>>  	int ret;
>> +	__u64 m_len = *moved_len;
>>  
>>  	if (orig_inode->i_sb != donor_inode->i_sb) {
>>  		ext4_debug("ext4 move extent: The argument files "
>> @@ -696,7 +697,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
>>  			if (next_blk == EXT_MAX_BLOCKS) {
>>  				o_start = o_end;
>>  				ret = -ENODATA;
>> -				goto out;
>> +				break;
>>  			}
>>  			d_start += next_blk - o_start;
>>  			o_start = next_blk;
>> @@ -708,7 +709,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
>>  			o_start = cur_blk;
>>  			/* Extent inside requested range ?*/
>>  			if (cur_blk >= o_end)
>> -				goto out;
>> +				break;
>>  		} else { /* in_range(o_start, o_blk, o_len) */
>>  			cur_len += cur_blk - o_start;
>>  		}
>> @@ -743,6 +744,7 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
>>  			break;
>>  		o_start += cur_len;
>>  		d_start += cur_len;
>> +		m_len += cur_len;
>>  	repeat:
>>  		if (path) {
>>  			ext4_ext_drop_refs(path);
>> @@ -755,15 +757,10 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
>>  		*moved_len = len;
>>  
>>  out:
>> -	if (*moved_len) {
>> -		ext4_discard_preallocations(orig_inode);
>> -		ext4_discard_preallocations(donor_inode);
>> -	}
>> +	WARN_ON(m_len > len);
>> +	if (ret == 0)
>> +		*moved_len = m_len;
>>  
>> -	if (path) {
>> -		ext4_ext_drop_refs(path);
>> -		kfree(path);
>> -	}
>
> I do not understand why kfree for path is dropped here. 
> Rest places looks reasonable for me,
> but this one looks like some mistake.
Yes, this is copy-paste mistake. Please see updated verstion

From: Dmitry Monakhov <dmonakhov at openvz.org>
To: devel at openvz.org
Cc: dmonakhov at openvz.org,
	vvs at virtuozzo.com
Subject: [PATCH] vz6 ext4: Discard preallocated block before swap_extents v2
Date: Mon, 27 Feb 2017 15:33:07 +0400
Message-Id: <1488195187-26606-1-git-send-email-dmonakhov at openvz.org>

>
> Take a look -- path is still was freed inside cycle,
> why it should not be freed at finish too?
>
>>  	up_write(&EXT4_I(orig_inode)->i_data_sem);
>>  	up_write(&EXT4_I(donor_inode)->i_data_sem);
>>  	up_write(&orig_inode->i_alloc_sem);
>>