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

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Date:   Fri, 13 May 2022 11:20:18 +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] f2fs: separate NOCoW and pinfile semantics

On 2022/5/13 5:57, Jaegeuk Kim wrote:
> On 05/12, 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.
>>
>> 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
>>
>> Signed-off-by: Chao Yu <chao.yu@...o.com>
>> ---
>>   fs/f2fs/data.c |  3 ++-
>>   fs/f2fs/f2fs.h |  1 +
>>   fs/f2fs/file.c | 25 ++++++++++++++++++++++++-
>>   3 files changed, 27 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
>> index 54a7a8ad994d..c8eab78f7d89 100644
>> --- a/fs/f2fs/data.c
>> +++ b/fs/f2fs/data.c
>> @@ -2495,7 +2495,8 @@ bool f2fs_should_update_inplace(struct inode *inode, struct f2fs_io_info *fio)
>>   	if (is_inode_flag_set(inode, FI_ALIGNED_WRITE))
>>   		return false;
>>   
>> -	if (f2fs_is_pinned_file(inode))
>> +	if (f2fs_is_pinned_file(inode) ||
>> +			F2FS_I(inode)->i_flags & F2FS_NOCOW_FL)
>>   		return true;
>>   
>>   	/* if this is cold file, we should overwrite to avoid fragmentation */
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 492af5b96de1..e91ece55f5e8 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -2916,6 +2916,7 @@ 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 */
>>   
>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>> index 09287876dbb7..7f92a3a157f7 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))
>> +			return -EINVAL;
>> +		if (f2fs_should_update_outplace(inode, NULL))
>> +			return -EINVAL;
>> +		if (f2fs_is_pinned_file(inode))
>> +			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)
>> @@ -3081,6 +3097,13 @@ static int f2fs_ioc_set_pin_file(struct file *filp, unsigned long arg)
>>   
>>   	inode_lock(inode);
>>   
>> +	if (F2FS_I(inode)->i_flags & F2FS_NOCOW_FL) {
>> +		f2fs_info(F2FS_I_SB(inode), "inode (%lu) is already NOCOW one",
>> +			inode->i_ino);
>> +		ret = -EINVAL;
> 
> Why rejecting this? We can pin the file to get 2MB-aligned allocation on the
> NOCOW file.

I try to separate these two flag completely, but, seems it can't, because after
commit 5d539245cb18 ("f2fs: export FS_NOCOW_FL flag to user"), these two flags
have already been twined closely....

@@ -1651,6 +1651,8 @@ static int f2fs_ioc_getflags(struct file *filp, unsigned long arg)
  		flags |= F2FS_ENCRYPT_FL;
  	if (f2fs_has_inline_data(inode) || f2fs_has_inline_dentry(inode))
  		flags |= F2FS_INLINE_DATA_FL;
+	if (is_inode_flag_set(inode, FI_PIN_FILE))
+		flags |= F2FS_NOCOW_FL;

How about:

f2fs_ioc_set_pin_file/f2fs_fileattr_set logic:
		pinfile			nocow
set		set pinfile | nocow	set nocow
clear		clear pinfile | nocow	clear nocow

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

Thanks,

> 
>> +		goto out;
>> +	}
>> +
>>   	if (!pin) {
>>   		clear_inode_flag(inode, FI_PIN_FILE);
>>   		f2fs_i_gc_failures_write(inode, 0);
>> -- 
>> 2.25.1