linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: remove circular locking between sb_internal and fs

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Message-ID: <c93106ef-b567-b973-7241-ea2fcef84855@kernel.org>
Date:   Tue, 26 Oct 2021 09:09:33 +0800
From:   Chao Yu <chao@...nel.org>
To:     Daeho Jeong <daeho43@...il.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: remove circular locking between
 sb_internal and fs_reclaim

On 2021/10/26 0:22, Daeho Jeong wrote:
> On Fri, Oct 22, 2021 at 8:32 AM Chao Yu <chao@...nel.org> wrote:
>>
>> On 2021/10/22 0:44, Daeho Jeong wrote:
>>> There is a deadlock between sb_internal lock (sb_start_intwrite()) and
>>> dquot related lock.
>>> It's because we call f2fs_truncate(), which eventually calls
>>> dquot_initialize(), while holding sb_internal lock.
>>> So, I called dquot_initialize() in advance to make the 2nd calling of
>>> it in f2fs_truncate() ineffective.
>>> This is similar with the thing in f2fs_evict_inode() in inode.c
>>
>> Well, if dquot_initialize() fails in f2fs_drop_inode(), will we still run
>> into deadlock?
>>
> 
> Do you think the same issue is in f2fs_evict_inode() in inode.c?

Yes, I doubt the problem may also happen in f2fs_evict_inode() with below
callpath:

- evict_inode
  - dquot_initialize failed
  - sb_start_intwrite
  - f2fs_truncate
   - dquot_initialize lock dqio_sem

How about this?

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
old mode 100644
new mode 100755
index b24b9bc..0e49593
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -728,6 +728,7 @@ enum {
      FI_ENABLE_COMPRESS,    /* enable compression in "user" compression mode */
      FI_COMPRESS_RELEASED,    /* compressed blocks were released */
      FI_ALIGNED_WRITE,    /* enable aligned write */
+    FI_QUOTA_INIT_FAIL,    /* inidicate failed to initialize quota in drop_inode()/evict_inode() */
      FI_MAX,            /* max flag, never be used */
  };

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
old mode 100644
new mode 100755
index 13deae0..2fb53f54
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -789,9 +789,11 @@ int f2fs_truncate(struct inode *inode)
          return -EIO;
      }

-    err = dquot_initialize(inode);
-    if (err)
-        return err;
+    if (!is_inode_flag_set(inode, FI_QUOTA_INIT_FAIL)) {
+        err = dquot_initialize(inode);
+        if (err)
+            return err;
+    }

      /* we should check inline_data size */
      if (!f2fs_may_inline_data(inode)) {
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
old mode 100644
new mode 100755
index 1213f15..16cf50c
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -758,6 +758,7 @@ void f2fs_evict_inode(struct inode *inode)
      if (err) {
          err = 0;
          set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
+        set_inode_flag(inode, FI_QUOTA_INIT_FAIL);
      }

      f2fs_remove_ino_entry(sbi, inode->i_ino, APPEND_INO);
@@ -770,6 +771,8 @@ void f2fs_evict_inode(struct inode *inode)
  retry:
      if (F2FS_HAS_BLOCKS(inode))
          err = f2fs_truncate(inode);
+    if (is_inode_flag_set(inode, FI_QUOTA_INIT_FAIL))
+        clear_inode_flag(inode, FI_QUOTA_INIT_FAIL);

      if (time_to_inject(sbi, FAULT_EVICT_INODE)) {
          f2fs_show_injection_info(sbi, FAULT_EVICT_INODE);

Thanks,


> In fact, I picked up the idea from here.
> 
>          err = dquot_initialize(inode);
>          if (err) {
>                  err = 0;
>                  set_sbi_flag(sbi, SBI_QUOTA_NEED_REPAIR);
>          }
> 
>          f2fs_remove_ino_entry(sbi, inode->i_ino, APPEND_INO);
>          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);
>          set_inode_flag(inode, FI_NO_ALLOC);
>          i_size_write(inode, 0);
> retry:
>          if (F2FS_HAS_BLOCKS(inode))
>                  err = f2fs_truncate(inode);
>