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Message-ID: <5c7b34d8-6efa-4716-ab89-a0b7b7583cb2@kernel.org>
Date: Wed, 4 Sep 2024 11:35:16 +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: prevent atomic file from being dirtied
before commit
On 2024/9/4 10:52, Daeho Jeong wrote:
> On Tue, Sep 3, 2024 at 7:26 PM Chao Yu <chao@...nel.org> wrote:
>>
>> On 2024/9/4 1:07, Daeho Jeong wrote:
>>> On Mon, Sep 2, 2024 at 3:08 AM Chao Yu <chao@...nel.org> wrote:
>>>>
>>>> On 2024/8/27 4:23, Daeho Jeong wrote:
>>>>> From: Daeho Jeong <daehojeong@...gle.com>
>>>>>
>>>>> Keep atomic file clean while updating and make it dirtied during commit
>>>>> in order to avoid unnecessary and excessive inode updates in the previous
>>>>> fix.
>>>>>
>>>>> Fixes: 4bf78322346f ("f2fs: mark inode dirty for FI_ATOMIC_COMMITTED flag")
>>>>> Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
>>>>> ---
>>>>> fs/f2fs/f2fs.h | 3 +--
>>>>> fs/f2fs/inode.c | 10 ++++++----
>>>>> fs/f2fs/segment.c | 10 ++++++++--
>>>>> 3 files changed, 15 insertions(+), 8 deletions(-)
>>>>>
>>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>>> index 465b2fd50c70..5a7f6fa8b585 100644
>>>>> --- a/fs/f2fs/f2fs.h
>>>>> +++ b/fs/f2fs/f2fs.h
>>>>> @@ -801,7 +801,7 @@ enum {
>>>>> FI_COMPRESS_RELEASED, /* compressed blocks were released */
>>>>> FI_ALIGNED_WRITE, /* enable aligned write */
>>>>> FI_COW_FILE, /* indicate COW file */
>>>>> - FI_ATOMIC_COMMITTED, /* indicate atomic commit completed except disk sync */
>>>>> + FI_ATOMIC_DIRTIED, /* indicate atomic file is dirtied */
>>>>> FI_ATOMIC_REPLACE, /* indicate atomic replace */
>>>>> FI_OPENED_FILE, /* indicate file has been opened */
>>>>> FI_MAX, /* max flag, never be used */
>>>>> @@ -3042,7 +3042,6 @@ static inline void __mark_inode_dirty_flag(struct inode *inode,
>>>>> case FI_INLINE_DOTS:
>>>>> case FI_PIN_FILE:
>>>>> case FI_COMPRESS_RELEASED:
>>>>> - case FI_ATOMIC_COMMITTED:
>>>>> f2fs_mark_inode_dirty_sync(inode, true);
>>>>> }
>>>>> }
>>>>> diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
>>>>> index 1eb250c6b392..5dd3e55d2be2 100644
>>>>> --- a/fs/f2fs/inode.c
>>>>> +++ b/fs/f2fs/inode.c
>>>>> @@ -35,6 +35,11 @@ void f2fs_mark_inode_dirty_sync(struct inode *inode, bool sync)
>>>>> if (f2fs_inode_dirtied(inode, sync))
>>>>
>>>> It will return directly here if inode was dirtied, so it may missed to set
>>>> FI_ATOMIC_DIRTIED flag?
>>>
>>> Is it possible for it to be already dirty, since we already made it
>>> clean with f2fs_write_inode() when we started the atomic write?
>>
>> Some ioctl interfaces may race w/ atomic write? e.g. set_pin_file won't
>> check atomic_file status, and may dirty inode after we started atomic
>> write, so we'd better detect such race condition and break ioctl to
>> avoid ruin atomic write? and maybe we can add f2fs_bug_on() in
>> f2fs_mark_inode_dirty_sync() to detect any other missing cases?
>>
>
> How about exchanging the positions of f2fs_write_inode() and
> set_inode_flag() in f2fs_ioc_start_atomic_write()?
>
> ...
> f2fs_write_inode(inode, NULL);
>
> stat_inc_atomic_inode(inode);
>
> set_inode_flag(inode, FI_ATOMIC_FILE);
> ...
Oh, I'm not sure I've got your point, after exchanging we still may suffer
below race condition, right?
- f2fs_ioc_start_atomic_write
- set_inode_flag(inode, FI_ATOMIC_FILE)
- f2fs_write_inode(inode, NULL)
- f2fs_ioc_set_pin_file
- set_inode_flag(inode, FI_PIN_FILE)
- __mark_inode_dirty_flag()
- f2fs_ioc_commit_atomic_write
So that I proposed a fix for this:
https://lore.kernel.org/linux-f2fs-devel/20240904032047.1264706-1-chao@kernel.org
Thanks,
>
>> Thanks,
>>
>>>
>>>>
>>>> Thanks,
>>>>
>>>>> return;
>>>>>
>>>>> + if (f2fs_is_atomic_file(inode)) {
>>>>> + set_inode_flag(inode, FI_ATOMIC_DIRTIED);
>>>>> + return;
>>>>> + }
>>>>> +
>>>>> mark_inode_dirty_sync(inode);
>>>>> }
>>>>>
>>>>> @@ -653,10 +658,7 @@ void f2fs_update_inode(struct inode *inode, struct page *node_page)
>>>>> ri->i_gid = cpu_to_le32(i_gid_read(inode));
>>>>> ri->i_links = cpu_to_le32(inode->i_nlink);
>>>>> ri->i_blocks = cpu_to_le64(SECTOR_TO_BLOCK(inode->i_blocks) + 1);
>>>>> -
>>>>> - if (!f2fs_is_atomic_file(inode) ||
>>>>> - is_inode_flag_set(inode, FI_ATOMIC_COMMITTED))
>>>>> - ri->i_size = cpu_to_le64(i_size_read(inode));
>>>>> + ri->i_size = cpu_to_le64(i_size_read(inode));
>>>>>
>>>>> if (et) {
>>>>> read_lock(&et->lock);
>>>>> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
>>>>> index 78c3198a6308..2b5391b229a8 100644
>>>>> --- a/fs/f2fs/segment.c
>>>>> +++ b/fs/f2fs/segment.c
>>>>> @@ -196,9 +196,12 @@ void f2fs_abort_atomic_write(struct inode *inode, bool clean)
>>>>> truncate_inode_pages_final(inode->i_mapping);
>>>>>
>>>>> release_atomic_write_cnt(inode);
>>>>> - clear_inode_flag(inode, FI_ATOMIC_COMMITTED);
>>>>> clear_inode_flag(inode, FI_ATOMIC_REPLACE);
>>>>> clear_inode_flag(inode, FI_ATOMIC_FILE);
>>>>> + if (is_inode_flag_set(inode, FI_ATOMIC_DIRTIED)) {
>>>>> + clear_inode_flag(inode, FI_ATOMIC_DIRTIED);
>>>>> + f2fs_mark_inode_dirty_sync(inode, true);
>>>>> + }
>>>>> stat_dec_atomic_inode(inode);
>>>>>
>>>>> F2FS_I(inode)->atomic_write_task = NULL;
>>>>> @@ -365,7 +368,10 @@ static int __f2fs_commit_atomic_write(struct inode *inode)
>>>>> sbi->revoked_atomic_block += fi->atomic_write_cnt;
>>>>> } else {
>>>>> sbi->committed_atomic_block += fi->atomic_write_cnt;
>>>>> - set_inode_flag(inode, FI_ATOMIC_COMMITTED);
>>>>> + if (is_inode_flag_set(inode, FI_ATOMIC_DIRTIED)) {
>>>>> + clear_inode_flag(inode, FI_ATOMIC_DIRTIED);
>>>>> + f2fs_mark_inode_dirty_sync(inode, true);
>>>>> + }
>>>>> }
>>>>>
>>>>> __complete_revoke_list(inode, &revoke_list, ret ? true : false);
>>>>
>>
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