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* [PATCH v2] ext4: fix a possible ABBA deadlock dued to busy PA
@ 2021-09-29  1:12 brookxu
  2021-11-22 17:50 ` Jan Kara
  0 siblings, 1 reply; 4+ messages in thread
From: brookxu @ 2021-09-29  1:12 UTC (permalink / raw)
  To: tytso, adilger.kernel; +Cc: linux-ext4, linux-kernel

From: Chunguang Xu <brookxu@tencent.com>

We found on older kernel (3.10) that in the scenario of insufficient
disk space, system may trigger an ABBA deadlock problem, it seems that
this problem still exists in latest kernel, try to fix it here. The
main process triggered by this problem is that task A occupies the PA
and waits for the jbd2 transaction finish, the jbd2 transaction waits
for the completion of task B's IO (plug_list), but task B waits for
the release of PA by task A to finish discard, which indirectly forms
an ABBA deadlock. The related calltrace is as follows:

    Task A
    vfs_write
    ext4_mb_new_blocks()
    ext4_mb_mark_diskspace_used()       JBD2
    jbd2_journal_get_write_access()  -> jbd2_journal_commit_transaction()
  ->schedule()                          filemap_fdatawait()
 |                                              |
 | Task B                                       |
 | do_unlinkat()                                |
 | ext4_evict_inode()                           |
 | jbd2_journal_begin_ordered_truncate()        |
 | filemap_fdatawrite_range()                   |
 | ext4_mb_new_blocks()                         |
  -ext4_mb_discard_group_preallocations() <-----

Here, try to cancel ext4_mb_discard_group_preallocations() internal
retry due to PA busy, and do a limited number of retries inside
ext4_mb_discard_preallocations(), which can circumvent the above
problems, but also has some advantages:

1. Since the PA is in a busy state, if other groups have free PAs,
   keeping the current PA may help to reduce fragmentation.
2. Continue to traverse forward instead of waiting for the current
   group PA to be released. In most scenarios, the PA discard time
   can be reduced.

However, in the case of smaller free space, if only a few groups have
space, then due to multiple traversals of the group, it may increase
CPU overhead. But in contrast, I feel that the overall benefit is
better than the cost.

Signed-off-by: Chunguang Xu <brookxu@tencent.com>
---
v2: reset busy to zero before goto repeat.

 fs/ext4/mballoc.c | 35 ++++++++++++++++-------------------
 1 file changed, 16 insertions(+), 19 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 72bfac2..72de6c1 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4814,7 +4814,7 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
  */
 static noinline_for_stack int
 ext4_mb_discard_group_preallocations(struct super_block *sb,
-					ext4_group_t group, int needed)
+				     ext4_group_t group, int needed, int *busy)
 {
 	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
 	struct buffer_head *bitmap_bh = NULL;
@@ -4822,8 +4822,7 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
 	struct list_head list;
 	struct ext4_buddy e4b;
 	int err;
-	int busy = 0;
-	int free, free_total = 0;
+	int free = 0;
 
 	mb_debug(sb, "discard preallocation for group %u\n", group);
 	if (list_empty(&grp->bb_prealloc_list))
@@ -4850,15 +4849,13 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
 		needed = EXT4_CLUSTERS_PER_GROUP(sb) + 1;
 
 	INIT_LIST_HEAD(&list);
-repeat:
-	free = 0;
 	ext4_lock_group(sb, group);
 	list_for_each_entry_safe(pa, tmp,
 				&grp->bb_prealloc_list, pa_group_list) {
 		spin_lock(&pa->pa_lock);
 		if (atomic_read(&pa->pa_count)) {
 			spin_unlock(&pa->pa_lock);
-			busy = 1;
+			*busy = 1;
 			continue;
 		}
 		if (pa->pa_deleted) {
@@ -4898,22 +4895,13 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
 		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
 	}
 
-	free_total += free;
-
-	/* if we still need more blocks and some PAs were used, try again */
-	if (free_total < needed && busy) {
-		ext4_unlock_group(sb, group);
-		cond_resched();
-		busy = 0;
-		goto repeat;
-	}
 	ext4_unlock_group(sb, group);
 	ext4_mb_unload_buddy(&e4b);
 	put_bh(bitmap_bh);
 out_dbg:
 	mb_debug(sb, "discarded (%d) blocks preallocated for group %u bb_free (%d)\n",
-		 free_total, group, grp->bb_free);
-	return free_total;
+		 free, group, grp->bb_free);
+	return free;
 }
 
 /*
@@ -5455,13 +5443,22 @@ static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
 {
 	ext4_group_t i, ngroups = ext4_get_groups_count(sb);
 	int ret;
-	int freed = 0;
+	int freed = 0, busy = 0;
+	int retry = 0;
 
 	trace_ext4_mb_discard_preallocations(sb, needed);
+ repeat:
+	retry++;
 	for (i = 0; i < ngroups && needed > 0; i++) {
-		ret = ext4_mb_discard_group_preallocations(sb, i, needed);
+		ret = ext4_mb_discard_group_preallocations(sb, i, needed, &busy);
 		freed += ret;
 		needed -= ret;
+		cond_resched();
+	}
+
+	if (needed > 0 && busy && retry < 3) {
+		busy = 0;
+		goto repeat;
 	}
 
 	return freed;
-- 
1.8.3.1


^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH v2] ext4: fix a possible ABBA deadlock dued to busy PA
  2021-09-29  1:12 [PATCH v2] ext4: fix a possible ABBA deadlock dued to busy PA brookxu
@ 2021-11-22 17:50 ` Jan Kara
  2021-11-23  1:26   ` brookxu
  0 siblings, 1 reply; 4+ messages in thread
From: Jan Kara @ 2021-11-22 17:50 UTC (permalink / raw)
  To: brookxu; +Cc: tytso, adilger.kernel, linux-ext4, linux-kernel, Ritesh Harjani

Hello,

it seems this patch has fallen through the cracks.

On Wed 29-09-21 09:12:25, brookxu wrote:
> From: Chunguang Xu <brookxu@tencent.com>
> 
> We found on older kernel (3.10) that in the scenario of insufficient
> disk space, system may trigger an ABBA deadlock problem, it seems that
> this problem still exists in latest kernel, try to fix it here. The
> main process triggered by this problem is that task A occupies the PA
> and waits for the jbd2 transaction finish, the jbd2 transaction waits
> for the completion of task B's IO (plug_list), but task B waits for
> the release of PA by task A to finish discard, which indirectly forms
> an ABBA deadlock. The related calltrace is as follows:
> 
>     Task A
>     vfs_write
>     ext4_mb_new_blocks()
>     ext4_mb_mark_diskspace_used()       JBD2
>     jbd2_journal_get_write_access()  -> jbd2_journal_commit_transaction()
>   ->schedule()                          filemap_fdatawait()
>  |                                              |
>  | Task B                                       |
>  | do_unlinkat()                                |
>  | ext4_evict_inode()                           |
>  | jbd2_journal_begin_ordered_truncate()        |
>  | filemap_fdatawrite_range()                   |
>  | ext4_mb_new_blocks()                         |
>   -ext4_mb_discard_group_preallocations() <-----
> 
> Here, try to cancel ext4_mb_discard_group_preallocations() internal
> retry due to PA busy, and do a limited number of retries inside
> ext4_mb_discard_preallocations(), which can circumvent the above
> problems, but also has some advantages:
> 
> 1. Since the PA is in a busy state, if other groups have free PAs,
>    keeping the current PA may help to reduce fragmentation.
> 2. Continue to traverse forward instead of waiting for the current
>    group PA to be released. In most scenarios, the PA discard time
>    can be reduced.
> 
> However, in the case of smaller free space, if only a few groups have
> space, then due to multiple traversals of the group, it may increase
> CPU overhead. But in contrast, I feel that the overall benefit is
> better than the cost.
> 
> Signed-off-by: Chunguang Xu <brookxu@tencent.com>

Thanks for the patch! I guess this is a reasonable middle-ground so feel
free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

I think Ritesh was last touching this logic so let's check he doesn't see
anything wrong with this change. Ritesh?

								Honza


> ---
> v2: reset busy to zero before goto repeat.
> 
>  fs/ext4/mballoc.c | 35 ++++++++++++++++-------------------
>  1 file changed, 16 insertions(+), 19 deletions(-)
> 
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 72bfac2..72de6c1 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4814,7 +4814,7 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
>   */
>  static noinline_for_stack int
>  ext4_mb_discard_group_preallocations(struct super_block *sb,
> -					ext4_group_t group, int needed)
> +				     ext4_group_t group, int needed, int *busy)
>  {
>  	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
>  	struct buffer_head *bitmap_bh = NULL;
> @@ -4822,8 +4822,7 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
>  	struct list_head list;
>  	struct ext4_buddy e4b;
>  	int err;
> -	int busy = 0;
> -	int free, free_total = 0;
> +	int free = 0;
>  
>  	mb_debug(sb, "discard preallocation for group %u\n", group);
>  	if (list_empty(&grp->bb_prealloc_list))
> @@ -4850,15 +4849,13 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
>  		needed = EXT4_CLUSTERS_PER_GROUP(sb) + 1;
>  
>  	INIT_LIST_HEAD(&list);
> -repeat:
> -	free = 0;
>  	ext4_lock_group(sb, group);
>  	list_for_each_entry_safe(pa, tmp,
>  				&grp->bb_prealloc_list, pa_group_list) {
>  		spin_lock(&pa->pa_lock);
>  		if (atomic_read(&pa->pa_count)) {
>  			spin_unlock(&pa->pa_lock);
> -			busy = 1;
> +			*busy = 1;
>  			continue;
>  		}
>  		if (pa->pa_deleted) {
> @@ -4898,22 +4895,13 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
>  		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
>  	}
>  
> -	free_total += free;
> -
> -	/* if we still need more blocks and some PAs were used, try again */
> -	if (free_total < needed && busy) {
> -		ext4_unlock_group(sb, group);
> -		cond_resched();
> -		busy = 0;
> -		goto repeat;
> -	}
>  	ext4_unlock_group(sb, group);
>  	ext4_mb_unload_buddy(&e4b);
>  	put_bh(bitmap_bh);
>  out_dbg:
>  	mb_debug(sb, "discarded (%d) blocks preallocated for group %u bb_free (%d)\n",
> -		 free_total, group, grp->bb_free);
> -	return free_total;
> +		 free, group, grp->bb_free);
> +	return free;
>  }
>  
>  /*
> @@ -5455,13 +5443,22 @@ static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
>  {
>  	ext4_group_t i, ngroups = ext4_get_groups_count(sb);
>  	int ret;
> -	int freed = 0;
> +	int freed = 0, busy = 0;
> +	int retry = 0;
>  
>  	trace_ext4_mb_discard_preallocations(sb, needed);
> + repeat:
> +	retry++;
>  	for (i = 0; i < ngroups && needed > 0; i++) {
> -		ret = ext4_mb_discard_group_preallocations(sb, i, needed);
> +		ret = ext4_mb_discard_group_preallocations(sb, i, needed, &busy);
>  		freed += ret;
>  		needed -= ret;
> +		cond_resched();
> +	}
> +
> +	if (needed > 0 && busy && retry < 3) {
> +		busy = 0;
> +		goto repeat;
>  	}
>  
>  	return freed;
> -- 
> 1.8.3.1
> 
-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH v2] ext4: fix a possible ABBA deadlock dued to busy PA
  2021-11-22 17:50 ` Jan Kara
@ 2021-11-23  1:26   ` brookxu
  0 siblings, 0 replies; 4+ messages in thread
From: brookxu @ 2021-11-23  1:26 UTC (permalink / raw)
  To: Jan Kara; +Cc: tytso, adilger.kernel, linux-ext4, linux-kernel, Ritesh Harjani

Hi Jan & riteshh:

Thanks for your time to review this patch. But kernel test robot has
reported an warning for the v2 version. I have fixed it and submitted
the v3 version, maybe we should goto v3 version, thanks all.

Jan Kara wrote on 2021/11/23 1:50:
> Hello,
> 
> it seems this patch has fallen through the cracks.
> 
> On Wed 29-09-21 09:12:25, brookxu wrote:
>> From: Chunguang Xu <brookxu@tencent.com>
>>
>> We found on older kernel (3.10) that in the scenario of insufficient
>> disk space, system may trigger an ABBA deadlock problem, it seems that
>> this problem still exists in latest kernel, try to fix it here. The
>> main process triggered by this problem is that task A occupies the PA
>> and waits for the jbd2 transaction finish, the jbd2 transaction waits
>> for the completion of task B's IO (plug_list), but task B waits for
>> the release of PA by task A to finish discard, which indirectly forms
>> an ABBA deadlock. The related calltrace is as follows:
>>
>>     Task A
>>     vfs_write
>>     ext4_mb_new_blocks()
>>     ext4_mb_mark_diskspace_used()       JBD2
>>     jbd2_journal_get_write_access()  -> jbd2_journal_commit_transaction()
>>   ->schedule()                          filemap_fdatawait()
>>  |                                              |
>>  | Task B                                       |
>>  | do_unlinkat()                                |
>>  | ext4_evict_inode()                           |
>>  | jbd2_journal_begin_ordered_truncate()        |
>>  | filemap_fdatawrite_range()                   |
>>  | ext4_mb_new_blocks()                         |
>>   -ext4_mb_discard_group_preallocations() <-----
>>
>> Here, try to cancel ext4_mb_discard_group_preallocations() internal
>> retry due to PA busy, and do a limited number of retries inside
>> ext4_mb_discard_preallocations(), which can circumvent the above
>> problems, but also has some advantages:
>>
>> 1. Since the PA is in a busy state, if other groups have free PAs,
>>    keeping the current PA may help to reduce fragmentation.
>> 2. Continue to traverse forward instead of waiting for the current
>>    group PA to be released. In most scenarios, the PA discard time
>>    can be reduced.
>>
>> However, in the case of smaller free space, if only a few groups have
>> space, then due to multiple traversals of the group, it may increase
>> CPU overhead. But in contrast, I feel that the overall benefit is
>> better than the cost.
>>
>> Signed-off-by: Chunguang Xu <brookxu@tencent.com>
> 
> Thanks for the patch! I guess this is a reasonable middle-ground so feel
> free to add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 
> I think Ritesh was last touching this logic so let's check he doesn't see
> anything wrong with this change. Ritesh?
> 
> 								Honza
> 
> 
>> ---
>> v2: reset busy to zero before goto repeat.
>>
>>  fs/ext4/mballoc.c | 35 ++++++++++++++++-------------------
>>  1 file changed, 16 insertions(+), 19 deletions(-)
>>
>> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
>> index 72bfac2..72de6c1 100644
>> --- a/fs/ext4/mballoc.c
>> +++ b/fs/ext4/mballoc.c
>> @@ -4814,7 +4814,7 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
>>   */
>>  static noinline_for_stack int
>>  ext4_mb_discard_group_preallocations(struct super_block *sb,
>> -					ext4_group_t group, int needed)
>> +				     ext4_group_t group, int needed, int *busy)
>>  {
>>  	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
>>  	struct buffer_head *bitmap_bh = NULL;
>> @@ -4822,8 +4822,7 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
>>  	struct list_head list;
>>  	struct ext4_buddy e4b;
>>  	int err;
>> -	int busy = 0;
>> -	int free, free_total = 0;
>> +	int free = 0;
>>  
>>  	mb_debug(sb, "discard preallocation for group %u\n", group);
>>  	if (list_empty(&grp->bb_prealloc_list))
>> @@ -4850,15 +4849,13 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
>>  		needed = EXT4_CLUSTERS_PER_GROUP(sb) + 1;
>>  
>>  	INIT_LIST_HEAD(&list);
>> -repeat:
>> -	free = 0;
>>  	ext4_lock_group(sb, group);
>>  	list_for_each_entry_safe(pa, tmp,
>>  				&grp->bb_prealloc_list, pa_group_list) {
>>  		spin_lock(&pa->pa_lock);
>>  		if (atomic_read(&pa->pa_count)) {
>>  			spin_unlock(&pa->pa_lock);
>> -			busy = 1;
>> +			*busy = 1;
>>  			continue;
>>  		}
>>  		if (pa->pa_deleted) {
>> @@ -4898,22 +4895,13 @@ static void ext4_mb_new_preallocation(struct ext4_allocation_context *ac)
>>  		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
>>  	}
>>  
>> -	free_total += free;
>> -
>> -	/* if we still need more blocks and some PAs were used, try again */
>> -	if (free_total < needed && busy) {
>> -		ext4_unlock_group(sb, group);
>> -		cond_resched();
>> -		busy = 0;
>> -		goto repeat;
>> -	}
>>  	ext4_unlock_group(sb, group);
>>  	ext4_mb_unload_buddy(&e4b);
>>  	put_bh(bitmap_bh);
>>  out_dbg:
>>  	mb_debug(sb, "discarded (%d) blocks preallocated for group %u bb_free (%d)\n",
>> -		 free_total, group, grp->bb_free);
>> -	return free_total;
>> +		 free, group, grp->bb_free);
>> +	return free;
>>  }
>>  
>>  /*
>> @@ -5455,13 +5443,22 @@ static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
>>  {
>>  	ext4_group_t i, ngroups = ext4_get_groups_count(sb);
>>  	int ret;
>> -	int freed = 0;
>> +	int freed = 0, busy = 0;
>> +	int retry = 0;
>>  
>>  	trace_ext4_mb_discard_preallocations(sb, needed);
>> + repeat:
>> +	retry++;
>>  	for (i = 0; i < ngroups && needed > 0; i++) {
>> -		ret = ext4_mb_discard_group_preallocations(sb, i, needed);
>> +		ret = ext4_mb_discard_group_preallocations(sb, i, needed, &busy);
>>  		freed += ret;
>>  		needed -= ret;
>> +		cond_resched();
>> +	}
>> +
>> +	if (needed > 0 && busy && retry < 3) {
>> +		busy = 0;
>> +		goto repeat;
>>  	}
>>  
>>  	return freed;
>> -- 
>> 1.8.3.1
>>

^ permalink raw reply	[flat|nested] 4+ messages in thread

* Re: [PATCH v2] ext4: fix a possible ABBA deadlock dued to busy PA
       [not found] <202111100102.2XcQrTDQ-lkp@intel.com>
@ 2021-11-11 10:03 ` kernel test robot
  0 siblings, 0 replies; 4+ messages in thread
From: kernel test robot @ 2021-11-11 10:03 UTC (permalink / raw)
  To: brookxu; +Cc: llvm, kbuild-all, linux-ext4, Linux Kernel Mailing List

[-- Attachment #1: Type: text/plain, Size: 10053 bytes --]

Hi Chunguang,

Thank you for the patch! Perhaps something to improve:

[auto build test WARNING on tytso-ext4/dev]
[also build test WARNING on v5.15 next-20211109]
[cannot apply to tytso-fscrypt/master]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]

url:    https://github.com/0day-ci/linux/commits/brookxu/ext4-fix-a-possible-ABBA-deadlock-dued-to-busy-PA/20210929-091410
base:   https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git dev
config: i386-randconfig-c001-20210929 (attached as .config)
compiler: clang version 14.0.0 (https://github.com/llvm/llvm-project dc6e8dfdfe7efecfda318d43a06fae18b40eb498)
reproduce (this is a W=1 build):
         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
         chmod +x ~/bin/make.cross
         # https://github.com/0day-ci/linux/commit/5e956ecab47126f1d065a1ac6e6d5077e02e6f87
         git remote add linux-review https://github.com/0day-ci/linux
         git fetch --no-tags linux-review brookxu/ext4-fix-a-possible-ABBA-deadlock-dued-to-busy-PA/20210929-091410
         git checkout 5e956ecab47126f1d065a1ac6e6d5077e02e6f87
         # save the attached .config to linux build tree
         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang make.cross ARCH=i386 clang-analyzer

If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>


clang-analyzer warnings: (new ones prefixed by >>)

 >> fs/ext4/mballoc.c:4849:3: warning: Value stored to 'needed' is never read [clang-analyzer-deadcode.DeadStores]
                    needed = EXT4_CLUSTERS_PER_GROUP(sb) + 1;
                    ^

vim +/needed +4849 fs/ext4/mballoc.c

c9de560ded61faa Alex Tomas            2008-01-29  4805
c9de560ded61faa Alex Tomas            2008-01-29  4806  /*
c9de560ded61faa Alex Tomas            2008-01-29  4807   * releases all preallocations in given group
c9de560ded61faa Alex Tomas            2008-01-29  4808   *
c9de560ded61faa Alex Tomas            2008-01-29  4809   * first, we need to decide discard policy:
c9de560ded61faa Alex Tomas            2008-01-29  4810   * - when do we discard
c9de560ded61faa Alex Tomas            2008-01-29  4811   *   1) ENOSPC
c9de560ded61faa Alex Tomas            2008-01-29  4812   * - how many do we discard
c9de560ded61faa Alex Tomas            2008-01-29  4813   *   1) how many requested
c9de560ded61faa Alex Tomas            2008-01-29  4814   */
4ddfef7b41aebbb Eric Sandeen          2008-04-29  4815  static noinline_for_stack int
4ddfef7b41aebbb Eric Sandeen          2008-04-29  4816  ext4_mb_discard_group_preallocations(struct super_block *sb,
5e956ecab47126f Chunguang Xu          2021-09-29  4817  				     ext4_group_t group, int needed, int *busy)
c9de560ded61faa Alex Tomas            2008-01-29  4818  {
c9de560ded61faa Alex Tomas            2008-01-29  4819  	struct ext4_group_info *grp = ext4_get_group_info(sb, group);
c9de560ded61faa Alex Tomas            2008-01-29  4820  	struct buffer_head *bitmap_bh = NULL;
c9de560ded61faa Alex Tomas            2008-01-29  4821  	struct ext4_prealloc_space *pa, *tmp;
c9de560ded61faa Alex Tomas            2008-01-29  4822  	struct list_head list;
c9de560ded61faa Alex Tomas            2008-01-29  4823  	struct ext4_buddy e4b;
c9de560ded61faa Alex Tomas            2008-01-29  4824  	int err;
5e956ecab47126f Chunguang Xu          2021-09-29  4825  	int free = 0;
c9de560ded61faa Alex Tomas            2008-01-29  4826
d3df14535f4a5b5 Ritesh Harjani        2020-05-10  4827  	mb_debug(sb, "discard preallocation for group %u\n", group);
c9de560ded61faa Alex Tomas            2008-01-29  4828  	if (list_empty(&grp->bb_prealloc_list))
bbc4ec77e9f9c7a Ritesh Harjani        2020-05-10  4829  		goto out_dbg;
c9de560ded61faa Alex Tomas            2008-01-29  4830
574ca174c97f790 Theodore Ts'o         2008-07-11  4831  	bitmap_bh = ext4_read_block_bitmap(sb, group);
9008a58e5dcee01 Darrick J. Wong       2015-10-17  4832  	if (IS_ERR(bitmap_bh)) {
9008a58e5dcee01 Darrick J. Wong       2015-10-17  4833  		err = PTR_ERR(bitmap_bh);
54d3adbc29f0c7c Theodore Ts'o         2020-03-28  4834  		ext4_error_err(sb, -err,
54d3adbc29f0c7c Theodore Ts'o         2020-03-28  4835  			       "Error %d reading block bitmap for %u",
9008a58e5dcee01 Darrick J. Wong       2015-10-17  4836  			       err, group);
bbc4ec77e9f9c7a Ritesh Harjani        2020-05-10  4837  		goto out_dbg;
c9de560ded61faa Alex Tomas            2008-01-29  4838  	}
c9de560ded61faa Alex Tomas            2008-01-29  4839
c9de560ded61faa Alex Tomas            2008-01-29  4840  	err = ext4_mb_load_buddy(sb, group, &e4b);
ce89f46cb833f89 Aneesh Kumar K.V      2008-07-23  4841  	if (err) {
9651e6b2e20648d Konstantin Khlebnikov 2017-05-21  4842  		ext4_warning(sb, "Error %d loading buddy information for %u",
9651e6b2e20648d Konstantin Khlebnikov 2017-05-21  4843  			     err, group);
ce89f46cb833f89 Aneesh Kumar K.V      2008-07-23  4844  		put_bh(bitmap_bh);
bbc4ec77e9f9c7a Ritesh Harjani        2020-05-10  4845  		goto out_dbg;
ce89f46cb833f89 Aneesh Kumar K.V      2008-07-23  4846  	}
c9de560ded61faa Alex Tomas            2008-01-29  4847
c9de560ded61faa Alex Tomas            2008-01-29  4848  	if (needed == 0)
7137d7a48e2213e Theodore Ts'o         2011-09-09 @4849  		needed = EXT4_CLUSTERS_PER_GROUP(sb) + 1;
c9de560ded61faa Alex Tomas            2008-01-29  4850
c9de560ded61faa Alex Tomas            2008-01-29  4851  	INIT_LIST_HEAD(&list);
c9de560ded61faa Alex Tomas            2008-01-29  4852  	ext4_lock_group(sb, group);
c9de560ded61faa Alex Tomas            2008-01-29  4853  	list_for_each_entry_safe(pa, tmp,
c9de560ded61faa Alex Tomas            2008-01-29  4854  				&grp->bb_prealloc_list, pa_group_list) {
c9de560ded61faa Alex Tomas            2008-01-29  4855  		spin_lock(&pa->pa_lock);
c9de560ded61faa Alex Tomas            2008-01-29  4856  		if (atomic_read(&pa->pa_count)) {
c9de560ded61faa Alex Tomas            2008-01-29  4857  			spin_unlock(&pa->pa_lock);
5e956ecab47126f Chunguang Xu          2021-09-29  4858  			*busy = 1;
c9de560ded61faa Alex Tomas            2008-01-29  4859  			continue;
c9de560ded61faa Alex Tomas            2008-01-29  4860  		}
c9de560ded61faa Alex Tomas            2008-01-29  4861  		if (pa->pa_deleted) {
c9de560ded61faa Alex Tomas            2008-01-29  4862  			spin_unlock(&pa->pa_lock);
c9de560ded61faa Alex Tomas            2008-01-29  4863  			continue;
c9de560ded61faa Alex Tomas            2008-01-29  4864  		}
c9de560ded61faa Alex Tomas            2008-01-29  4865
c9de560ded61faa Alex Tomas            2008-01-29  4866  		/* seems this one can be freed ... */
27bc446e2def38d brookxu               2020-08-17  4867  		ext4_mb_mark_pa_deleted(sb, pa);
c9de560ded61faa Alex Tomas            2008-01-29  4868
70022da804f0f3f Ye Bin                2020-09-16  4869  		if (!free)
70022da804f0f3f Ye Bin                2020-09-16  4870  			this_cpu_inc(discard_pa_seq);
70022da804f0f3f Ye Bin                2020-09-16  4871
c9de560ded61faa Alex Tomas            2008-01-29  4872  		/* we can trust pa_free ... */
c9de560ded61faa Alex Tomas            2008-01-29  4873  		free += pa->pa_free;
c9de560ded61faa Alex Tomas            2008-01-29  4874
c9de560ded61faa Alex Tomas            2008-01-29  4875  		spin_unlock(&pa->pa_lock);
c9de560ded61faa Alex Tomas            2008-01-29  4876
c9de560ded61faa Alex Tomas            2008-01-29  4877  		list_del(&pa->pa_group_list);
c9de560ded61faa Alex Tomas            2008-01-29  4878  		list_add(&pa->u.pa_tmp_list, &list);
c9de560ded61faa Alex Tomas            2008-01-29  4879  	}
c9de560ded61faa Alex Tomas            2008-01-29  4880
c9de560ded61faa Alex Tomas            2008-01-29  4881  	/* now free all selected PAs */
c9de560ded61faa Alex Tomas            2008-01-29  4882  	list_for_each_entry_safe(pa, tmp, &list, u.pa_tmp_list) {
c9de560ded61faa Alex Tomas            2008-01-29  4883
c9de560ded61faa Alex Tomas            2008-01-29  4884  		/* remove from object (inode or locality group) */
c9de560ded61faa Alex Tomas            2008-01-29  4885  		spin_lock(pa->pa_obj_lock);
c9de560ded61faa Alex Tomas            2008-01-29  4886  		list_del_rcu(&pa->pa_inode_list);
c9de560ded61faa Alex Tomas            2008-01-29  4887  		spin_unlock(pa->pa_obj_lock);
c9de560ded61faa Alex Tomas            2008-01-29  4888
cc0fb9ad7dbc5a1 Aneesh Kumar K.V      2009-03-27  4889  		if (pa->pa_type == MB_GROUP_PA)
3e1e5f501632460 Eric Sandeen          2010-10-27  4890  			ext4_mb_release_group_pa(&e4b, pa);
c9de560ded61faa Alex Tomas            2008-01-29  4891  		else
3e1e5f501632460 Eric Sandeen          2010-10-27  4892  			ext4_mb_release_inode_pa(&e4b, bitmap_bh, pa);
c9de560ded61faa Alex Tomas            2008-01-29  4893
c9de560ded61faa Alex Tomas            2008-01-29  4894  		list_del(&pa->u.pa_tmp_list);
c9de560ded61faa Alex Tomas            2008-01-29  4895  		call_rcu(&(pa)->u.pa_rcu, ext4_mb_pa_callback);
c9de560ded61faa Alex Tomas            2008-01-29  4896  	}
c9de560ded61faa Alex Tomas            2008-01-29  4897
c9de560ded61faa Alex Tomas            2008-01-29  4898  	ext4_unlock_group(sb, group);
e39e07fdfd98be8 Jing Zhang            2010-05-14  4899  	ext4_mb_unload_buddy(&e4b);
c9de560ded61faa Alex Tomas            2008-01-29  4900  	put_bh(bitmap_bh);
bbc4ec77e9f9c7a Ritesh Harjani        2020-05-10  4901  out_dbg:
d3df14535f4a5b5 Ritesh Harjani        2020-05-10  4902  	mb_debug(sb, "discarded (%d) blocks preallocated for group %u bb_free (%d)\n",
5e956ecab47126f Chunguang Xu          2021-09-29  4903  		 free, group, grp->bb_free);
5e956ecab47126f Chunguang Xu          2021-09-29  4904  	return free;
c9de560ded61faa Alex Tomas            2008-01-29  4905  }
c9de560ded61faa Alex Tomas            2008-01-29  4906

---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org

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^ permalink raw reply	[flat|nested] 4+ messages in thread

end of thread, other threads:[~2021-11-23  1:26 UTC | newest]

Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-09-29  1:12 [PATCH v2] ext4: fix a possible ABBA deadlock dued to busy PA brookxu
2021-11-22 17:50 ` Jan Kara
2021-11-23  1:26   ` brookxu
     [not found] <202111100102.2XcQrTDQ-lkp@intel.com>
2021-11-11 10:03 ` kernel test robot

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