linux-kernel - Re: [PATCH v4] f2fs: separate NOCoW and pinfile semantics

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Message-ID: <fa3cbe36-1738-a811-ce03-dd5aaf8ea3d4@kernel.org>
Date:   Tue, 31 May 2022 16:01:01 +0800
From:   Chao Yu <chao@...nel.org>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, Chao Yu <chao.yu@...o.com>
Subject: Re: [PATCH v4] f2fs: separate NOCoW and pinfile semantics

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?

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@...o.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