linux-kernel - Re: [External Mail]Re: [PATCH v2] f2fs: fix inconsistent dirty state of atomic file

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Message-ID: <1f2255ed-64db-4989-918a-0a38362e8eb1@xiaomi.com>
Date: Fri, 24 Jan 2025 05:50:22 +0000
From: Huang Jianan <huangjianan@...omi.com>
To: Chao Yu <chao@...nel.org>, "linux-f2fs-devel@...ts.sourceforge.net"
	<linux-f2fs-devel@...ts.sourceforge.net>, "jaegeuk@...nel.org"
	<jaegeuk@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"daehojeong@...gle.com" <daehojeong@...gle.com>, 何云蕾
	<heyunlei@...omi.com>, 王辉 <wanghui33@...omi.com>,
	俞东斌 <yudongbin@...omi.com>, "jnhuang95@...il.com"
	<jnhuang95@...il.com>
Subject: Re: [External Mail]Re: [PATCH v2] f2fs: fix inconsistent dirty state
 of atomic file

On 2025/1/24 13:14, Chao Yu wrote:
> 
> On 1/24/25 09:50, Jianan Huang wrote:
>> When testing the atomic write fix patches, the f2fs_bug_on was
>> triggered as below:
>>
>> ------------[ cut here ]------------
>> kernel BUG at fs/f2fs/inode.c:935!
>> Oops: invalid opcode: 0000 [#1] PREEMPT SMP PTI
>> CPU: 3 UID: 0 PID: 257 Comm: bash Not tainted 6.13.0-rc1-00033-gc283a70d3497 #5
>> RIP: 0010:f2fs_evict_inode+0x50f/0x520
>> Call Trace:
>>   <TASK>
>>   ? __die_body+0x65/0xb0
>>   ? die+0x9f/0xc0
>>   ? do_trap+0xa1/0x170
>>   ? f2fs_evict_inode+0x50f/0x520
>>   ? f2fs_evict_inode+0x50f/0x520
>>   ? handle_invalid_op+0x65/0x80
>>   ? f2fs_evict_inode+0x50f/0x520
>>   ? exc_invalid_op+0x39/0x50
>>   ? asm_exc_invalid_op+0x1a/0x20
>>   ? __pfx_f2fs_get_dquots+0x10/0x10
>>   ? f2fs_evict_inode+0x50f/0x520
>>   ? f2fs_evict_inode+0x2e5/0x520
>>   evict+0x186/0x2f0
>>   prune_icache_sb+0x75/0xb0
>>   super_cache_scan+0x1a8/0x200
>>   do_shrink_slab+0x163/0x320
>>   shrink_slab+0x2fc/0x470
>>   drop_slab+0x82/0xf0
>>   drop_caches_sysctl_handler+0x4e/0xb0
>>   proc_sys_call_handler+0x183/0x280
>>   vfs_write+0x36d/0x450
>>   ksys_write+0x68/0xd0
>>   do_syscall_64+0xc8/0x1a0
>>   ? arch_exit_to_user_mode_prepare+0x11/0x60
>>   ? irqentry_exit_to_user_mode+0x7e/0xa0
>>
>> The root cause is: f2fs uses FI_ATOMIC_DIRTIED to indicate dirty
>> atomic files during commit. If the inode is dirtied during commit,
>> such as by f2fs_i_pino_write, the vfs inode keeps clean and the
>> f2fs inode is set to FI_DIRTY_INODE. The FI_DIRTY_INODE flag cann't
>> be cleared by write_inode later due to the clean vfs inode. Finally,
>> f2fs_bug_on is triggered due to this inconsistent state when evict.
>>
>> To reproduce this situation:
>> - fd = open("/mnt/test.db", O_WRONLY)
>> - ioctl(fd, F2FS_IOC_START_ATOMIC_WRITE)
>> - mv /mnt/test.db /mnt/test1.db
>> - ioctl(fd, F2FS_IOC_COMMIT_ATOMIC_WRITE)
>> - echo 3 > /proc/sys/vm/drop_caches
>>
>> To fix this problem, clear FI_DIRTY_INODE after commit, then
>> f2fs_mark_inode_dirty_sync will ensure a consistent dirty state.
>>
>> Fixes: fccaa81de87e ("f2fs: prevent atomic file from being dirtied before commit")
>> Signed-off-by: Yunlei He <heyunlei@...omi.com>
>> Signed-off-by: Jianan Huang <huangjianan@...omi.com>
>> ---
>> Changes since v1:
>> - Add comments suggested by Chao.
>> - Add missing stat reduction.
>>
>>   fs/f2fs/segment.c | 9 +++++++++
>>   1 file changed, 9 insertions(+)
>>
>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>> index dc1b47f9269a..de1597110f76 100644
>> --- a/fs/f2fs/segment.c
>> +++ b/fs/f2fs/segment.c
>> @@ -201,6 +201,15 @@ void f2fs_abort_atomic_write(struct inode *inode, bool clean)
>>        clear_inode_flag(inode, FI_ATOMIC_FILE);
>>        if (is_inode_flag_set(inode, FI_ATOMIC_DIRTIED)) {
>>                clear_inode_flag(inode, FI_ATOMIC_DIRTIED);
>> +             /*
>> +              * The vfs inode keeps clean during commit, but the f2fs inode
>> +              * doesn't. So clear the dirty state after commit and let
>> +              * f2fs_mark_inode_dirty_sync ensure a consistent dirty state.
>> +              */
>> +             if (is_inode_flag_set(inode, FI_DIRTY_INODE)) {
>> +                     clear_inode_flag(inode, FI_DIRTY_INODE);
>> +                     stat_dec_dirty_inode(F2FS_I_SB(inode), DIRTY_META);
>> +             }
> 
> How about calling f2fs_inode_synced() directly?

It looks more clear, I will update it in v3.

Thanks,

> 
>>                f2fs_mark_inode_dirty_sync(inode, true);
>>        }
>>        stat_dec_atomic_inode(inode);
>