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Date: Wed, 21 Jun 2017 21:26:09 -0400
From: "Theodore Ts'o" <tytso@mit.edu>
To: Tahsin Erdogan <tahsin@google.com>
Cc: Andreas Dilger <adilger@dilger.ca>,
        "Darrick J . Wong" <darrick.wong@oracle.com>, Jan Kara <jack@suse.cz>,
        linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 05/32] ext4: attach jinode after creation of xattr inode
Message-ID: <20170622012608.gzvj37gfsjupukph@thunk.org>
Mail-Followup-To: Theodore Ts'o <tytso@mit.edu>,
        Tahsin Erdogan <tahsin@google.com>,
        Andreas Dilger <adilger@dilger.ca>,
        "Darrick J . Wong" <darrick.wong@oracle.com>,
        Jan Kara <jack@suse.cz>, linux-ext4@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20170621212142.16581-1-tahsin@google.com>
 <20170621212142.16581-5-tahsin@google.com>
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On Wed, Jun 21, 2017 at 02:21:15PM -0700, Tahsin Erdogan wrote:
> In data=ordered mode jinode needs to be attached to the xattr inode when
> writing data to it. Attachment normally occurs during file open for regular
> files. Since we are not using file interface to write to the xattr inode,
> the jinode attach needs to be done manually.
> 
> Otherwise the following crash occurs in data=ordered mode.
> 
>  BUG: unable to handle kernel NULL pointer dereference at           (null)
>  IP: jbd2_journal_file_inode+0x37/0x110
>  PGD 13b3c0067
>  P4D 13b3c0067
>  PUD 137660067
>  PMD 0
> 
>  Oops: 0000 [#1] SMP
>  CPU: 3 PID: 1877 Comm: python Not tainted 4.12.0-rc1+ #749
>  Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>  task: ffff88010e368980 task.stack: ffffc90000374000
>  RIP: 0010:jbd2_journal_file_inode+0x37/0x110
>  RSP: 0018:ffffc90000377980 EFLAGS: 00010246
>  RAX: 0000000000000000 RBX: ffff880123b06230 RCX: 0000000000280000
>  RDX: 0000000000000006 RSI: 0000000000000000 RDI: ffff88012c8585d0
>  RBP: ffffc900003779b0 R08: 0000000000000202 R09: 0000000000000001
>  R10: 0000000000000000 R11: 0000000000000400 R12: ffff8801111f81c0
>  R13: ffff88013b2b6800 R14: ffffc90000377ab0 R15: 0000000000000001
>  FS:  00007f0c99b77740(0000) GS:ffff88013fd80000(0000) knlGS:0000000000000000
>  CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
>  CR2: 0000000000000000 CR3: 0000000136d91000 CR4: 00000000000006e0
>  Call Trace:
>   jbd2_journal_inode_add_write+0xe/0x10
>   ext4_map_blocks+0x59e/0x620
>   ext4_xattr_set_entry+0x501/0x7d0
>   ext4_xattr_block_set+0x1b2/0x9b0
>   ext4_xattr_set_handle+0x322/0x4f0
>   ext4_xattr_set+0x144/0x1a0
>   ext4_xattr_user_set+0x34/0x40
>   __vfs_setxattr+0x66/0x80
>   __vfs_setxattr_noperm+0x69/0x1c0
>   vfs_setxattr+0xa2/0xb0
>   setxattr+0x12e/0x150
>   path_setxattr+0x87/0xb0
>   SyS_setxattr+0xf/0x20
>   entry_SYSCALL_64_fastpath+0x18/0xad
> 
> Signed-off-by: Tahsin Erdogan <tahsin@google.com>

Thanks, applied.

					- Ted