fs/ext4: get project quota from inode for mangling statfs results
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Message ID 157225912326.3929.8539227851002947260.stgit@buzz
State New
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  • fs/ext4: get project quota from inode for mangling statfs results
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Commit Message

Konstantin Khlebnikov Oct. 28, 2019, 10:38 a.m. UTC
Right now ext4_statfs_project() does quota lookup by id every time.
This is costly operation, especially if there is no inode who hold
reference to this quota and dqget() reads it from disk each time.

Function ext4_statfs_project() could be moved into generic quota code,
it is required for every filesystem which uses generic project quota.

Reported-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
 fs/ext4/super.c |   25 ++++++++++++++++---------
 1 file changed, 16 insertions(+), 9 deletions(-)

Comments

Jan Kara Oct. 30, 2019, 10:59 a.m. UTC | #1
On Mon 28-10-19 13:38:43, Konstantin Khlebnikov wrote:
> Right now ext4_statfs_project() does quota lookup by id every time.
> This is costly operation, especially if there is no inode who hold
> reference to this quota and dqget() reads it from disk each time.
> 
> Function ext4_statfs_project() could be moved into generic quota code,
> it is required for every filesystem which uses generic project quota.
> 
> Reported-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> ---
>  fs/ext4/super.c |   25 ++++++++++++++++---------
>  1 file changed, 16 insertions(+), 9 deletions(-)
> 
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index dd654e53ba3d..f841c66aa499 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -5532,18 +5532,23 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>  }
>  
>  #ifdef CONFIG_QUOTA
> -static int ext4_statfs_project(struct super_block *sb,
> -			       kprojid_t projid, struct kstatfs *buf)
> +static int ext4_statfs_project(struct inode *inode, struct kstatfs *buf)
>  {
> -	struct kqid qid;
> +	struct super_block *sb = inode->i_sb;
>  	struct dquot *dquot;
>  	u64 limit;
>  	u64 curblock;
> +	int err;
> +
> +	err = dquot_initialize(inode);

Hum, I'm kind of puzzled here: Your patch seems to be concerned with
performance but how is this any faster than what we do now?
dquot_initialize() will look up three dquots instead of one in the current
code? Oh, I guess you are concerned about *repeated* calls to statfs() and
thus repeated lookups of dquot structure? And this patch effectively caches
looked up dquots in the inode?

That starts to make some sense but still, even if dquot isn't cached in any
inode, we still hold on to it (it's in the free_list) until shrinker evicts
it. So lookup of such dquot should be just a hash table lookup which should
be very fast. Then there's the cost of dquot_acquire() / dquot_release()
that get always called on first / last get of a dquot. So are you concerned
about that cost? Or do you really see IO happening to fetch quota structure
on each statfs call again and again? The only situation where I could see
that happening is when the quota structure would be actually completely
empty (i.e., not originally present in the quota file). But then this
cannot be a case when there's actually an inode belonging to this
project...

So I'm really curious about the details of what you are seeing as the
changelog / patch doesn't quite make sense to me yet.

								Honza


> +	if (err)
> +		return err;
> +
> +	spin_lock(&inode->i_lock);
> +	dquot = ext4_get_dquots(inode)[PRJQUOTA];
> +	if (!dquot)
> +		goto out_unlock;
>  
> -	qid = make_kqid_projid(projid);
> -	dquot = dqget(sb, qid);
> -	if (IS_ERR(dquot))
> -		return PTR_ERR(dquot);
>  	spin_lock(&dquot->dq_dqb_lock);
>  
>  	limit = (dquot->dq_dqb.dqb_bsoftlimit ?
> @@ -5569,7 +5574,9 @@ static int ext4_statfs_project(struct super_block *sb,
>  	}
>  
>  	spin_unlock(&dquot->dq_dqb_lock);
> -	dqput(dquot);
> +out_unlock:
> +	spin_unlock(&inode->i_lock);
> +
>  	return 0;
>  }
>  #endif
> @@ -5609,7 +5616,7 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
>  #ifdef CONFIG_QUOTA
>  	if (ext4_test_inode_flag(dentry->d_inode, EXT4_INODE_PROJINHERIT) &&
>  	    sb_has_quota_limits_enabled(sb, PRJQUOTA))
> -		ext4_statfs_project(sb, EXT4_I(dentry->d_inode)->i_projid, buf);
> +		ext4_statfs_project(dentry->d_inode, buf);
>  #endif
>  	return 0;
>  }
>
Konstantin Khlebnikov Oct. 30, 2019, 11:43 a.m. UTC | #2
On 30/10/2019 13.59, Jan Kara wrote:
> On Mon 28-10-19 13:38:43, Konstantin Khlebnikov wrote:
>> Right now ext4_statfs_project() does quota lookup by id every time.
>> This is costly operation, especially if there is no inode who hold
>> reference to this quota and dqget() reads it from disk each time.
>>
>> Function ext4_statfs_project() could be moved into generic quota code,
>> it is required for every filesystem which uses generic project quota.
>>
>> Reported-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
>> ---
>>   fs/ext4/super.c |   25 ++++++++++++++++---------
>>   1 file changed, 16 insertions(+), 9 deletions(-)
>>
>> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>> index dd654e53ba3d..f841c66aa499 100644
>> --- a/fs/ext4/super.c
>> +++ b/fs/ext4/super.c
>> @@ -5532,18 +5532,23 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data)
>>   }
>>   
>>   #ifdef CONFIG_QUOTA
>> -static int ext4_statfs_project(struct super_block *sb,
>> -			       kprojid_t projid, struct kstatfs *buf)
>> +static int ext4_statfs_project(struct inode *inode, struct kstatfs *buf)
>>   {
>> -	struct kqid qid;
>> +	struct super_block *sb = inode->i_sb;
>>   	struct dquot *dquot;
>>   	u64 limit;
>>   	u64 curblock;
>> +	int err;
>> +
>> +	err = dquot_initialize(inode);
> 
> Hum, I'm kind of puzzled here: Your patch seems to be concerned with
> performance but how is this any faster than what we do now?
> dquot_initialize() will look up three dquots instead of one in the current
> code? Oh, I guess you are concerned about *repeated* calls to statfs() and
> thus repeated lookups of dquot structure? And this patch effectively caches
> looked up dquots in the inode?
> 
> That starts to make some sense but still, even if dquot isn't cached in any
> inode, we still hold on to it (it's in the free_list) until shrinker evicts
> it. So lookup of such dquot should be just a hash table lookup which should
> be very fast. Then there's the cost of dquot_acquire() / dquot_release()
> that get always called on first / last get of a dquot. So are you concerned
> about that cost? Or do you really see IO happening to fetch quota structure
> on each statfs call again and again? The only situation where I could see
> that happening is when the quota structure would be actually completely
> empty (i.e., not originally present in the quota file). But then this
> cannot be a case when there's actually an inode belonging to this
> project...
> 
> So I'm really curious about the details of what you are seeing as the
> changelog / patch doesn't quite make sense to me yet.

Yep, we have seen than disaster with non-present quota blocks.
For consistent quota performance loss should be much less significant,
but caching would not hurt.

Tools like "df" calls statfs for all mountpoints.
These inodes are never reclaimed because pinned by vfsmount.

> 
> 								Honza
> 
> 
>> +	if (err)
>> +		return err;
>> +
>> +	spin_lock(&inode->i_lock);
>> +	dquot = ext4_get_dquots(inode)[PRJQUOTA];
>> +	if (!dquot)
>> +		goto out_unlock;
>>   
>> -	qid = make_kqid_projid(projid);
>> -	dquot = dqget(sb, qid);
>> -	if (IS_ERR(dquot))
>> -		return PTR_ERR(dquot);
>>   	spin_lock(&dquot->dq_dqb_lock);
>>   
>>   	limit = (dquot->dq_dqb.dqb_bsoftlimit ?
>> @@ -5569,7 +5574,9 @@ static int ext4_statfs_project(struct super_block *sb,
>>   	}
>>   
>>   	spin_unlock(&dquot->dq_dqb_lock);
>> -	dqput(dquot);
>> +out_unlock:
>> +	spin_unlock(&inode->i_lock);
>> +
>>   	return 0;
>>   }
>>   #endif
>> @@ -5609,7 +5616,7 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
>>   #ifdef CONFIG_QUOTA
>>   	if (ext4_test_inode_flag(dentry->d_inode, EXT4_INODE_PROJINHERIT) &&
>>   	    sb_has_quota_limits_enabled(sb, PRJQUOTA))
>> -		ext4_statfs_project(sb, EXT4_I(dentry->d_inode)->i_projid, buf);
>> +		ext4_statfs_project(dentry->d_inode, buf);
>>   #endif
>>   	return 0;
>>   }
>>
Jan Kara Oct. 30, 2019, 12:57 p.m. UTC | #3
On Wed 30-10-19 15:06:13, Дмитрий Монахов wrote:
>  
>  
> 30.10.2019, 13:59, "Jan Kara" <jack@suse.cz>:
> 
> 
>     On Mon 28-10-19 13:38:43, Konstantin Khlebnikov wrote:
> 
>          Right now ext4_statfs_project() does quota lookup by id every time.
>          This is costly operation, especially if there is no inode who hold
>          reference to this quota and dqget() reads it from disk each time.
> 
>          Function ext4_statfs_project() could be moved into generic quota code,
>          it is required for every filesystem which uses generic project quota.
> 
>          Reported-by: Dmitry Monakhov <dmtrmonakhov@yandex-team.ru>
>          Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
>          ---
>           fs/ext4/super.c | 25 ++++++++++++++++---------
>           1 file changed, 16 insertions(+), 9 deletions(-)
> 
>          diff --git a/fs/ext4/super.c b/fs/ext4/super.c
>          index dd654e53ba3d..f841c66aa499 100644
>          --- a/fs/ext4/super.c
>          +++ b/fs/ext4/super.c
>          @@ -5532,18 +5532,23 @@ static int ext4_remount(struct super_block
>         *sb, int *flags, char *data)
>           }
> 
>           #ifdef CONFIG_QUOTA
>          -static int ext4_statfs_project(struct super_block *sb,
>          - kprojid_t projid, struct kstatfs *buf)
>          +static int ext4_statfs_project(struct inode *inode, struct kstatfs
>         *buf)
>           {
>          - struct kqid qid;
>          + struct super_block *sb = inode->i_sb;
>                   struct dquot *dquot;
>                   u64 limit;
>                   u64 curblock;
>          + int err;
>          +
>          + err = dquot_initialize(inode);
> 
> 
>     Hum, I'm kind of puzzled here: Your patch seems to be concerned with
>     performance but how is this any faster than what we do now?
>     dquot_initialize() will look up three dquots instead of one in the current
>     code? Oh, I guess you are concerned about *repeated* calls to statfs() and
>     thus repeated lookups of dquot structure? And this patch effectively caches
>     looked up dquots in the inode?
> 
>     That starts to make some sense but still, even if dquot isn't cached in any
>     inode, we still hold on to it (it's in the free_list) until shrinker evicts
>     it. So lookup of such dquot should be just a hash table lookup which should
>     be very fast. Then there's the cost of dquot_acquire() / dquot_release()
>     that get always called on first / last get of a dquot. So are you concerned
>     about that cost? Or do you really see IO happening to fetch quota structure
>     on each statfs call again and again?
> 
> Hi,
> No IO, only useless synchronization on journal
> Repeaded statfs result in dquot_acquire()/ dquot_release() which result in two
> ext4_journal_starts
> perf record -e 'ext4:*' -e 'jbd2:*'  stat -f  volume
> perf script
>            stat 520596 [002] 589927.123955:                      
> ext4:ext4_journal_start: dev 252,2 blocks, 73 rsv_blocks, 0 caller
> ext4_acquire_dquot
>             stat 520596 [002] 589927.123958:                      
>  jbd2:jbd2_handle_start: dev 252,2 tid 187859 type 6 line_no 5550
> requested_blocks 73
>             stat 520596 [002] 589927.123959:                      
>  jbd2:jbd2_handle_stats: dev 252,2 tid 187859 type 6 line_no 5550 interval 0
> sync 0 requested_blocks 73 dirtied_blocks 0
>             stat 520596 [002] 589927.123960:                      
> ext4:ext4_journal_start: dev 252,2 blocks, 9 rsv_blocks, 0 caller
> ext4_release_dquot
>             stat 520596 [002] 589927.123961:                      
>  jbd2:jbd2_handle_start: dev 252,2 tid 187859 type 6 line_no 5566
> requested_blocks 9
>             stat 520596 [002] 589927.123962:                      
>  jbd2:jbd2_handle_stats: dev 252,2 tid 187859 type 6 line_no 5566 interval 0
> sync 0 requested_blocks 9 dirtied_blocks 0
> On host under io load this will be blocked on __jbd2_log_wait_for_space() which
> is no what people expects from statfs()

OK, makes sense.

>     The only situation where I could seethat happening is when the quota
>     structure would be actually completely
>     empty (i.e., not originally present in the quota file). But then this
>     cannot be a case when there's actually an inode belonging to this
>     project...
> 
>     So I'm really curious about the details of what you are seeing as the
>     changelog / patch doesn't quite make sense to me yet.
> 
>  
> This indeed happens if project quota goes out of sync, which is quite simple
> for non journaled  quota case.
> And this provoke huge IO penalty on each statfs

Yes, but then I wonder how it can happen that project quota is out of sync
because ext4 does not support non-journalled project quotas (project quotas
must be stored in hidden system inodes). So it is a fs bug if project quota
goes out of sync.

Anyway, case 1 you mentioned above still makes sense so please just update
the changelog explaining more details about the problem and why your
patch helps that. Thanks!

								Honza

>  
> $perf record -e 'ext4:*' -e 'jbd2:*'  stat -f  volume-with-staled-quota
> $perf script
>             stat 528212 [002] 591269.007915:                      
> ext4:ext4_journal_start: dev 252,2 blocks, 73 rsv_blocks, 0 caller
> ext4_acquire_dquot
>             stat 528212 [002] 591269.007919:                      
>  jbd2:jbd2_handle_start: dev 252,2 tid 188107 type 6 line_no 5550
> requested_blocks 73
>             stat 528212 [002] 591269.007922:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 0
>             stat 528212 [002] 591269.007923:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [0/1) 190361090 W
>             stat 528212 [002] 591269.007926:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 3
>             stat 528212 [002] 591269.007926:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [3/1) 188785674 W
>             stat 528212 [002] 591269.007928:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 3
>             stat 528212 [002] 591269.007928:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [3/1) 188785674 W
>             stat 528212 [002] 591269.007929:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 3
>             stat 528212 [002] 591269.007930:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [3/1) 188785674 W
>             stat 528212 [002] 591269.007931:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 1
>             stat 528212 [002] 591269.007931:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [1/1) 138484739 W
>             stat 528212 [002] 591269.007933:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 1
>             stat 528212 [002] 591269.007933:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [1/1) 138484739 W
>             stat 528212 [002] 591269.007936:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 3
>             stat 528212 [002] 591269.007936:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [3/1) 188785674 W
>             stat 528212 [002] 591269.007938:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 1
>             stat 528212 [002] 591269.007938:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [1/1) 138484739 W
>             stat 528212 [002] 591269.007940:                      
>  jbd2:jbd2_handle_stats: dev 252,2 tid 188107 type 6 line_no 5550 interval 0
> sync 0 requested_blocks 73 dirtied_blocks 2
>             stat 528212 [002] 591269.007941:                      
> ext4:ext4_journal_start: dev 252,2 blocks, 9 rsv_blocks, 0 caller
> ext4_release_dquot
>             stat 528212 [002] 591269.007941:                      
>  jbd2:jbd2_handle_start: dev 252,2 tid 188107 type 6 line_no 5566
> requested_blocks 9
>             stat 528212 [002] 591269.007942:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 0
>             stat 528212 [002] 591269.007943:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [0/1) 190361090 W
>             stat 528212 [002] 591269.007944:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 3
>             stat 528212 [002] 591269.007944:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [3/1) 188785674 W
>             stat 528212 [002] 591269.007945:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 3
>             stat 528212 [002] 591269.007954:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [3/1) 188785674 W
>             stat 528212 [002] 591269.007954:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 3
>             stat 528212 [002] 591269.007955:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [3/1) 188785674 W
>             stat 528212 [002] 591269.007956:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 1
>             stat 528212 [002] 591269.007956:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [1/1) 138484739 W
>             stat 528212 [002] 591269.007957:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 1
>             stat 528212 [002] 591269.007957:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [1/1) 138484739 W
>             stat 528212 [002] 591269.007958:            
>  ext4:ext4_es_lookup_extent_enter: dev 252,2 ino 13 lblk 3
>             stat 528212 [002] 591269.007958:              
> ext4:ext4_es_lookup_extent_exit: dev 252,2 ino 13 found 1 [3/1) 188785674 W
>             stat 528212 [002] 591269.007959:                      
>  jbd2:jbd2_handle_stats: dev 252,2 tid 188107 type 6 line_no 5566 interval 0
> sync 0 requested_blocks 9 dirtied_blocks 0
> 
> 
> 
>      
> 
>          + if (err)
>          + return err;
>          +
>          + spin_lock(&inode->i_lock);
>          + dquot = ext4_get_dquots(inode)[PRJQUOTA];
>          + if (!dquot)
>          + goto out_unlock;
> 
>          - qid = make_kqid_projid(projid);
>          - dquot = dqget(sb, qid);
>          - if (IS_ERR(dquot))
>          - return PTR_ERR(dquot);
>                   spin_lock(&dquot->dq_dqb_lock);
> 
>                   limit = (dquot->dq_dqb.dqb_bsoftlimit ?
>          @@ -5569,7 +5574,9 @@ static int ext4_statfs_project(struct
>         super_block *sb,
>                   }
> 
>                   spin_unlock(&dquot->dq_dqb_lock);
>          - dqput(dquot);
>          +out_unlock:
>          + spin_unlock(&inode->i_lock);
>          +
>                   return 0;
>           }
>           #endif
>          @@ -5609,7 +5616,7 @@ static int ext4_statfs(struct dentry *dentry,
>         struct kstatfs *buf)
>           #ifdef CONFIG_QUOTA
>                   if (ext4_test_inode_flag(dentry->d_inode,
>         EXT4_INODE_PROJINHERIT) &&
>                       sb_has_quota_limits_enabled(sb, PRJQUOTA))
>          - ext4_statfs_project(sb, EXT4_I(dentry->d_inode)->i_projid, buf);
>          + ext4_statfs_project(dentry->d_inode, buf);
>           #endif
>                   return 0;
>           }
>          
> 
>     --
>     Jan Kara <jack@suse.com>
>     SUSE Labs, CR
>

Patch
diff mbox series

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index dd654e53ba3d..f841c66aa499 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5532,18 +5532,23 @@  static int ext4_remount(struct super_block *sb, int *flags, char *data)
 }
 
 #ifdef CONFIG_QUOTA
-static int ext4_statfs_project(struct super_block *sb,
-			       kprojid_t projid, struct kstatfs *buf)
+static int ext4_statfs_project(struct inode *inode, struct kstatfs *buf)
 {
-	struct kqid qid;
+	struct super_block *sb = inode->i_sb;
 	struct dquot *dquot;
 	u64 limit;
 	u64 curblock;
+	int err;
+
+	err = dquot_initialize(inode);
+	if (err)
+		return err;
+
+	spin_lock(&inode->i_lock);
+	dquot = ext4_get_dquots(inode)[PRJQUOTA];
+	if (!dquot)
+		goto out_unlock;
 
-	qid = make_kqid_projid(projid);
-	dquot = dqget(sb, qid);
-	if (IS_ERR(dquot))
-		return PTR_ERR(dquot);
 	spin_lock(&dquot->dq_dqb_lock);
 
 	limit = (dquot->dq_dqb.dqb_bsoftlimit ?
@@ -5569,7 +5574,9 @@  static int ext4_statfs_project(struct super_block *sb,
 	}
 
 	spin_unlock(&dquot->dq_dqb_lock);
-	dqput(dquot);
+out_unlock:
+	spin_unlock(&inode->i_lock);
+
 	return 0;
 }
 #endif
@@ -5609,7 +5616,7 @@  static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
 #ifdef CONFIG_QUOTA
 	if (ext4_test_inode_flag(dentry->d_inode, EXT4_INODE_PROJINHERIT) &&
 	    sb_has_quota_limits_enabled(sb, PRJQUOTA))
-		ext4_statfs_project(sb, EXT4_I(dentry->d_inode)->i_projid, buf);
+		ext4_statfs_project(dentry->d_inode, buf);
 #endif
 	return 0;
 }