Patch "quota: fix warning in dqgrab()" has been added to the 5.10-stable tree

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This is a note to let you know that I've just added the patch titled

    quota: fix warning in dqgrab()

to the 5.10-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     quota-fix-warning-in-dqgrab.patch
and it can be found in the queue-5.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 06f9687848f4012a3ed2777a7048eb159aed7924
Author: Ye Bin <yebin10@xxxxxxxxxx>
Date:   Mon Jun 5 22:07:31 2023 +0800

    quota: fix warning in dqgrab()
    
    [ Upstream commit d6a95db3c7ad160bc16b89e36449705309b52bcb ]
    
    There's issue as follows when do fault injection:
    WARNING: CPU: 1 PID: 14870 at include/linux/quotaops.h:51 dquot_disable+0x13b7/0x18c0
    Modules linked in:
    CPU: 1 PID: 14870 Comm: fsconfig Not tainted 6.3.0-next-20230505-00006-g5107a9c821af-dirty #541
    RIP: 0010:dquot_disable+0x13b7/0x18c0
    RSP: 0018:ffffc9000acc79e0 EFLAGS: 00010246
    RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff88825e41b980
    RDX: 0000000000000000 RSI: ffff88825e41b980 RDI: 0000000000000002
    RBP: ffff888179f68000 R08: ffffffff82087ca7 R09: 0000000000000000
    R10: 0000000000000001 R11: ffffed102f3ed026 R12: ffff888179f68130
    R13: ffff888179f68110 R14: dffffc0000000000 R15: ffff888179f68118
    FS:  00007f450a073740(0000) GS:ffff88882fc00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 00007ffe96f2efd8 CR3: 000000025c8ad000 CR4: 00000000000006e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     <TASK>
     dquot_load_quota_sb+0xd53/0x1060
     dquot_resume+0x172/0x230
     ext4_reconfigure+0x1dc6/0x27b0
     reconfigure_super+0x515/0xa90
     __x64_sys_fsconfig+0xb19/0xd20
     do_syscall_64+0x39/0xb0
     entry_SYSCALL_64_after_hwframe+0x63/0xcd
    
    Above issue may happens as follows:
    ProcessA              ProcessB                    ProcessC
    sys_fsconfig
      vfs_fsconfig_locked
       reconfigure_super
         ext4_remount
          dquot_suspend -> suspend all type quota
    
                     sys_fsconfig
                      vfs_fsconfig_locked
                        reconfigure_super
                         ext4_remount
                          dquot_resume
                           ret = dquot_load_quota_sb
                            add_dquot_ref
                                               do_open  -> open file O_RDWR
                                                vfs_open
                                                 do_dentry_open
                                                  get_write_access
                                                   atomic_inc_unless_negative(&inode->i_writecount)
                                                  ext4_file_open
                                                   dquot_file_open
                                                    dquot_initialize
                                                      __dquot_initialize
                                                       dqget
                                                        atomic_inc(&dquot->dq_count);
    
                              __dquot_initialize
                               __dquot_initialize
                                dqget
                                 if (!test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
                                   ext4_acquire_dquot
                                    -> Return error DQ_ACTIVE_B flag isn't set
                             dquot_disable
                              invalidate_dquots
                               if (atomic_read(&dquot->dq_count))
                                dqgrab
                                 WARN_ON_ONCE(!test_bit(DQ_ACTIVE_B, &dquot->dq_flags))
                                  -> Trigger warning
    
    In the above scenario, 'dquot->dq_flags' has no DQ_ACTIVE_B is normal when
    dqgrab().
    To solve above issue just replace the dqgrab() use in invalidate_dquots() with
    atomic_inc(&dquot->dq_count).
    
    Signed-off-by: Ye Bin <yebin10@xxxxxxxxxx>
    Signed-off-by: Jan Kara <jack@xxxxxxx>
    Message-Id: <20230605140731.2427629-3-yebin10@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 135984a1a52f4..8d0cd68fc90a4 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -557,7 +557,7 @@ static void invalidate_dquots(struct super_block *sb, int type)
 			continue;
 		/* Wait for dquot users */
 		if (atomic_read(&dquot->dq_count)) {
-			dqgrab(dquot);
+			atomic_inc(&dquot->dq_count);
 			spin_unlock(&dq_list_lock);
 			/*
 			 * Once dqput() wakes us up, we know it's time to free



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