linux-kernel - Re: [f2fs-dev] [PATCH 1/2] f2fs: evict inode cache for frozen fs

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Date:   Fri, 11 Mar 2022 11:10:50 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>, linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 1/2] f2fs: evict inode cache for frozen fs

Jaegeuk,

Could you please send v2 patch to mailing list? as I saw the revised
one has been merged in dev branch.

Otherwise, I've no idea where I should reply "Reviewed-by" tag to...

Thanks,

On 2022/3/10 9:53, Chao Yu wrote:
> On 2022/3/10 5:48, Jaegeuk Kim wrote:
>> Let's purge inode cache in order to avoid the below deadlock.
>>
>> [freeze test]                         shrinkder
>> freeze_super
>>   - pwercpu_down_write(SB_FREEZE_FS)
>>                                         - super_cache_scan
>>                                           - down_read(&sb->s_umount)
>>                                             - prune_icache_sb
>>                                              - dispose_list
>>                                               - evict
>>                                                - f2fs_evict_inode
>> thaw_super
>>   - down_write(&sb->s_umount);
>>                                                - __percpu_down_read(SB_FREEZE_FS)
> 
> Ah, finally we catch this. :)
> 
>>
>> Signed-off-by: Jaegeuk Kim <jaegeuk@...nel.org>
>> ---
>>   fs/f2fs/debug.c | 1 +
>>   fs/f2fs/f2fs.h  | 1 +
>>   fs/f2fs/inode.c | 6 ++++--
>>   fs/f2fs/super.c | 4 ++++
>>   4 files changed, 10 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
>> index 9a13902c7702..cba5eab24595 100644
>> --- a/fs/f2fs/debug.c
>> +++ b/fs/f2fs/debug.c
>> @@ -338,6 +338,7 @@ static char *s_flag[] = {
>>       [SBI_QUOTA_SKIP_FLUSH]    = " quota_skip_flush",
>>       [SBI_QUOTA_NEED_REPAIR]    = " quota_need_repair",
>>       [SBI_IS_RESIZEFS]    = " resizefs",
>> +    [SBI_IS_FREEZING]    = " freezefs",
> 
> Could you please update description of "sb_status" entry in
> Documentation/ABI/testing/sysfs-fs-f2fs as well?
> 
> Thanks,
> 
>>   };
>>   static int stat_show(struct seq_file *s, void *v)
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 68d791ec8b27..da729f53daa8 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -1293,6 +1293,7 @@ enum {
>>       SBI_QUOTA_SKIP_FLUSH,            /* skip flushing quota in current CP */
>>       SBI_QUOTA_NEED_REPAIR,            /* quota file may be corrupted */
>>       SBI_IS_RESIZEFS,            /* resizefs is in process */
>> +    SBI_IS_FREEZING,            /* freezefs is in process */
>>   };
>>   enum {
>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>> index ab8e0c06c78c..71f232dcf3c2 100644
>> --- a/fs/f2fs/inode.c
>> +++ b/fs/f2fs/inode.c
>> @@ -778,7 +778,8 @@ void f2fs_evict_inode(struct inode *inode)
>>       f2fs_remove_ino_entry(sbi, inode->i_ino, UPDATE_INO);
>>       f2fs_remove_ino_entry(sbi, inode->i_ino, FLUSH_INO);
>> -    sb_start_intwrite(inode->i_sb);
>> +    if (!is_sbi_flag_set(sbi, SBI_IS_FREEZING))
>> +        sb_start_intwrite(inode->i_sb);
>>       set_inode_flag(inode, FI_NO_ALLOC);
>>       i_size_write(inode, 0);
>>   retry:
>> @@ -809,7 +810,8 @@ void f2fs_evict_inode(struct inode *inode)
>>           if (dquot_initialize_needed(inode))
>>               set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
>>       }
>> -    sb_end_intwrite(inode->i_sb);
>> +    if (!is_sbi_flag_set(sbi, SBI_IS_FREEZING))
>> +        sb_end_intwrite(inode->i_sb);
>>   no_delete:
>>       dquot_drop(inode);
>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>> index 8e3840973077..4b570b5c2674 100644
>> --- a/fs/f2fs/super.c
>> +++ b/fs/f2fs/super.c
>> @@ -1663,11 +1663,15 @@ static int f2fs_freeze(struct super_block *sb)
>>       /* ensure no checkpoint required */
>>       if (!llist_empty(&F2FS_SB(sb)->cprc_info.issue_list))
>>           return -EINVAL;
>> +
>> +    /* to avoid deadlock on f2fs_evict_inode->SB_FREEZE_FS */
>> +    set_sbi_flag(F2FS_SB(sb), SBI_IS_FREEZING);
>>       return 0;
>>   }
>>   static int f2fs_unfreeze(struct super_block *sb)
>>   {
>> +    clear_sbi_flag(F2FS_SB(sb), SBI_IS_FREEZING);
>>       return 0;
>>   }
> 
> 
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