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Date:   Wed, 1 Jun 2022 11:05:07 +0800
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Subject: Re: [PATCH v4] f2fs: separate NOCoW and pinfile semantics
Content-Language: en-US
To:     Jaegeuk Kim <jaegeuk@kernel.org>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, Chao Yu <chao.yu@oppo.com>
References: <20220517032410.3564033-1-chao@kernel.org>
 <YoPZh+vl68IH5loV@google.com>
 <fa3cbe36-1738-a811-ce03-dd5aaf8ea3d4@kernel.org>
 <YpZ4MxH3bkWbTPvI@google.com>
From:   Chao Yu <chao@kernel.org>
In-Reply-To: <YpZ4MxH3bkWbTPvI@google.com>
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On 2022/6/1 4:18, Jaegeuk Kim wrote:
> On 05/31, Chao Yu wrote:
>> On 2022/5/18 1:21, Jaegeuk Kim wrote:
>>> On 05/17, Chao Yu wrote:
>>>> Pinning a file is heavy, because skipping pinned files make GC
>>>> running with heavy load or no effect.
>>>>
>>>> So that this patch proposes to separate nocow and pinfile semantics:
>>>> - NOCoW flag can only be set on regular file.
>>>> - NOCoW file will only trigger IPU at common writeback/flush.
>>>> - NOCow file will do OPU during GC.
>>>
>>> How about adding
>>>    - NOCow file will allocate 2MB-aligned space via fallocate.
>>>
>>> So, it'd be same as file pinning except allowing GCs. wdyt?
>>
>> Well, it seems the segment-aligned allocation feature should not couple with
>> pin_file or NoCow flag, what about introducing another ioctl for that? something
>> like: F2FS_IOC_ALIGNMENT_PREALLOCATION w/ arg.alignment_start, arg.alignment_len,
>> arg.total_len?
> 
> We should allocate 2MB to pin the file, since android is using it.

I mean we can use nocow + new ioctl instead of pinfile, thoughts?

Thanks,

> 
>>
>> Thanks,
>>
>>>
>>>>
>>>> This flag can satisfying the demand of:
>>>> 1) avoiding fragment of file's physical block
>>>> 2) userspace doesn't want to pin file's physical address
>>>>
>>>> After commit 5d539245cb18 ("f2fs: export FS_NOCOW_FL flag to user"),
>>>> Pin_file and NOCoW flags have already been twined closely. e.g.
>>>> once we set pinfile flag in file, nocow flag will be shown; and after
>>>> clearing pinfile flag, nocow flag will disappear.
>>>>
>>>> So, in order to keep backward compatibility, let use below semantics:
>>>>
>>>> f2fs_ioc_set_pin_file/f2fs_fileattr_set logic:
>>>> 		pinfile			nocow
>>>> set		set pinfile | nocow	set nocow
>>>> clear		clear pinfile | nocow	clear nocow
>>>>
>>>> File Behaviors:
>>>> w/ pinfile, w/ nocow:		use pinfile semantics
>>>> w/ pinfile, w/o nocow:		use pinfile semantics
>>>> w/o pinfile, w/ nocow:		use nocow semantics
>>>> w/o pinfile, w/o nocow:		no pinfile or nocow semantics
>>>>
>>>> NOCoW can also be set on directory, and it will have no effect on
>>>> directory, however, new files created in nocow directory will have the
>>>> flag set.
>>>>
>>>> Signed-off-by: Chao Yu <chao.yu@oppo.com>
>>>> ---
>>>> v4:
>>>> - allow IPU only for NoCowed regular inode.
>>>>    fs/f2fs/data.c |  3 +++
>>>>    fs/f2fs/f2fs.h | 13 +++++++++++--
>>>>    fs/f2fs/file.c | 18 +++++++++++++++++-
>>>>    3 files changed, 31 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>>>> index 54a7a8ad994d..42d95ac6b508 100644
>>>> --- a/fs/f2fs/data.c
>>>> +++ b/fs/f2fs/data.c
>>>> @@ -2498,6 +2498,9 @@ bool f2fs_should_update_inplace(struct inode *inode, struct f2fs_io_info *fio)
>>>>    	if (f2fs_is_pinned_file(inode))
>>>>    		return true;
>>>> +	if (S_ISREG(inode->i_mode) && F2FS_I(inode)->i_flags & F2FS_NOCOW_FL)
>>>> +		return true;
>>>> +
>>>>    	/* if this is cold file, we should overwrite to avoid fragmentation */
>>>>    	if (file_is_cold(inode))
>>>>    		return true;
>>>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>>>> index 492af5b96de1..5c67736000a7 100644
>>>> --- a/fs/f2fs/f2fs.h
>>>> +++ b/fs/f2fs/f2fs.h
>>>> @@ -2916,13 +2916,15 @@ static inline void f2fs_change_bit(unsigned int nr, char *addr)
>>>>    #define F2FS_NOCOMP_FL			0x00000400 /* Don't compress */
>>>>    #define F2FS_INDEX_FL			0x00001000 /* hash-indexed directory */
>>>>    #define F2FS_DIRSYNC_FL			0x00010000 /* dirsync behaviour (directories only) */
>>>> +#define F2FS_NOCOW_FL			0x00800000 /* Do not cow file */
>>>>    #define F2FS_PROJINHERIT_FL		0x20000000 /* Create with parents projid */
>>>>    #define F2FS_CASEFOLD_FL		0x40000000 /* Casefolded file */
>>>>    /* Flags that should be inherited by new inodes from their parent. */
>>>>    #define F2FS_FL_INHERITED (F2FS_SYNC_FL | F2FS_NODUMP_FL | F2FS_NOATIME_FL | \
>>>>    			   F2FS_DIRSYNC_FL | F2FS_PROJINHERIT_FL | \
>>>> -			   F2FS_CASEFOLD_FL | F2FS_COMPR_FL | F2FS_NOCOMP_FL)
>>>> +			   F2FS_CASEFOLD_FL | F2FS_COMPR_FL | F2FS_NOCOMP_FL | \
>>>> +			   F2FS_NOCOW_FL)
>>>>    /* Flags that are appropriate for regular files (all but dir-specific ones). */
>>>>    #define F2FS_REG_FLMASK		(~(F2FS_DIRSYNC_FL | F2FS_PROJINHERIT_FL | \
>>>> @@ -2954,9 +2956,16 @@ static inline void __mark_inode_dirty_flag(struct inode *inode,
>>>>    		fallthrough;
>>>>    	case FI_DATA_EXIST:
>>>>    	case FI_INLINE_DOTS:
>>>> -	case FI_PIN_FILE:
>>>>    	case FI_COMPRESS_RELEASED:
>>>>    		f2fs_mark_inode_dirty_sync(inode, true);
>>>> +		break;
>>>> +	case FI_PIN_FILE:
>>>> +		if (set)
>>>> +			F2FS_I(inode)->i_flags |= F2FS_NOCOW_FL;
>>>> +		else
>>>> +			F2FS_I(inode)->i_flags &= ~F2FS_NOCOW_FL;
>>>> +		f2fs_mark_inode_dirty_sync(inode, true);
>>>> +		break;
>>>>    	}
>>>>    }
>>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>>> index 216081ea8c81..9e71ce8601f9 100644
>>>> --- a/fs/f2fs/file.c
>>>> +++ b/fs/f2fs/file.c
>>>> @@ -1851,6 +1851,20 @@ static int f2fs_setflags_common(struct inode *inode, u32 iflags, u32 mask)
>>>>    	if (IS_NOQUOTA(inode))
>>>>    		return -EPERM;
>>>> +	if ((iflags ^ masked_flags) & F2FS_NOCOW_FL) {
>>>> +		int ret;
>>>> +
>>>> +		if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
>>>> +			return -EINVAL;
>>>> +		if (S_ISREG(inode->i_mode)) {
>>>> +			if (f2fs_should_update_outplace(inode, NULL))
>>>> +				return -EINVAL;
>>>> +			ret = f2fs_convert_inline_inode(inode);
>>>> +			if (ret)
>>>> +				return ret;
>>>> +		}
>>>> +	}
>>>> +
>>>>    	if ((iflags ^ masked_flags) & F2FS_CASEFOLD_FL) {
>>>>    		if (!f2fs_sb_has_casefold(F2FS_I_SB(inode)))
>>>>    			return -EOPNOTSUPP;
>>>> @@ -1926,6 +1940,7 @@ static const struct {
>>>>    	{ F2FS_NOCOMP_FL,	FS_NOCOMP_FL },
>>>>    	{ F2FS_INDEX_FL,	FS_INDEX_FL },
>>>>    	{ F2FS_DIRSYNC_FL,	FS_DIRSYNC_FL },
>>>> +	{ F2FS_NOCOW_FL,	FS_NOCOW_FL },
>>>>    	{ F2FS_PROJINHERIT_FL,	FS_PROJINHERIT_FL },
>>>>    	{ F2FS_CASEFOLD_FL,	FS_CASEFOLD_FL },
>>>>    };
>>>> @@ -1957,7 +1972,8 @@ static const struct {
>>>>    		FS_NOCOMP_FL |		\
>>>>    		FS_DIRSYNC_FL |		\
>>>>    		FS_PROJINHERIT_FL |	\
>>>> -		FS_CASEFOLD_FL)
>>>> +		FS_CASEFOLD_FL |	\
>>>> +		FS_NOCOW_FL)
>>>>    /* Convert f2fs on-disk i_flags to FS_IOC_{GET,SET}FLAGS flags */
>>>>    static inline u32 f2fs_iflags_to_fsflags(u32 iflags)
>>>> -- 
>>>> 2.25.1