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Date:   Sun, 28 Jul 2019 22:57:38 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <yuchao0@huawei.com>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, chao@kernel.org
Subject: Re: [PATCH v2] f2fs: separate NOCoW and pinfile semantics
Message-ID: <20190729055738.GA95664@jaegeuk-macbookpro.roam.corp.google.com>
References: <20190719073903.9138-1-yuchao0@huawei.com>
 <20190723023640.GC60778@jaegeuk-macbookpro.roam.corp.google.com>
 <d4d064a2-2b3c-3536-6488-39e7cfdb1ea4@huawei.com>
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On 07/23, Chao Yu wrote:
> On 2019/7/23 10:36, Jaegeuk Kim wrote:
> > On 07/19, Chao Yu wrote:
> >> Pinning a file is heavy, because skipping pinned files make GC
> >> running with heavy load or no effect.
> > 
> > Pinned file is a part of NOCOW files, so I don't think we can simply drop it
> > for backward compatibility.
> 
> Yes,
> 
> But what I concerned is that pin file is too heavy, so in order to satisfy below
> demand, how about introducing pin_file_2 flag to triggering IPU only during
> flush/writeback.

That can be done by cold files?

> 
> > 
> >>
> >> So that this patch propose 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.
> >>
> >> For the demand of 1) avoid fragment of file's physical block and
> >> 2) userspace don't care about file's specific physical address,
> >> tagging file as NOCoW will be cheaper than pinned one.
> 
> ^^^
> 
> Thanks,
> 
> >>
> >> Signed-off-by: Chao Yu <yuchao0@huawei.com>
> >> ---
> >> v2:
> >> - rebase code to fix compile error.
> >>  fs/f2fs/data.c |  3 ++-
> >>  fs/f2fs/f2fs.h |  1 +
> >>  fs/f2fs/file.c | 22 +++++++++++++++++++---
> >>  3 files changed, 22 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> >> index a2a28bb269bf..15fb8954c363 100644
> >> --- a/fs/f2fs/data.c
> >> +++ b/fs/f2fs/data.c
> >> @@ -1884,7 +1884,8 @@ static inline bool check_inplace_update_policy(struct inode *inode,
> >>  
> >>  bool f2fs_should_update_inplace(struct inode *inode, struct f2fs_io_info *fio)
> >>  {
> >> -	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 596ab3e1dd7b..f6c5a3d2e659 100644
> >> --- a/fs/f2fs/f2fs.h
> >> +++ b/fs/f2fs/f2fs.h
> >> @@ -2374,6 +2374,7 @@ static inline void f2fs_change_bit(unsigned int nr, char *addr)
> >>  #define F2FS_NOATIME_FL			0x00000080 /* do not update atime */
> >>  #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 */
> >>  
> >>  /* Flags that should be inherited by new inodes from their parent. */
> >> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> >> index 7ca545874060..ae0fec54cac6 100644
> >> --- a/fs/f2fs/file.c
> >> +++ b/fs/f2fs/file.c
> >> @@ -1692,6 +1692,7 @@ static const struct {
> >>  	{ F2FS_NOATIME_FL,	FS_NOATIME_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 },
> >>  };
> >>  
> >> @@ -1715,7 +1716,8 @@ static const struct {
> >>  		FS_NODUMP_FL |		\
> >>  		FS_NOATIME_FL |		\
> >>  		FS_DIRSYNC_FL |		\
> >> -		FS_PROJINHERIT_FL)
> >> +		FS_PROJINHERIT_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)
> >> @@ -1753,8 +1755,6 @@ static int f2fs_ioc_getflags(struct file *filp, unsigned long arg)
> >>  		fsflags |= FS_ENCRYPT_FL;
> >>  	if (f2fs_has_inline_data(inode) || f2fs_has_inline_dentry(inode))
> >>  		fsflags |= FS_INLINE_DATA_FL;
> >> -	if (is_inode_flag_set(inode, FI_PIN_FILE))
> >> -		fsflags |= FS_NOCOW_FL;
> >>  
> >>  	fsflags &= F2FS_GETTABLE_FS_FL;
> >>  
> >> @@ -1794,6 +1794,22 @@ static int f2fs_ioc_setflags(struct file *filp, unsigned long arg)
> >>  	if (ret)
> >>  		goto out;
> >>  
> >> +	if ((fsflags ^ old_fsflags) & FS_NOCOW_FL) {
> >> +		if (!S_ISREG(inode->i_mode)) {
> >> +			ret = -EINVAL;
> >> +			goto out;
> >> +		}
> >> +
> >> +		if (f2fs_should_update_outplace(inode, NULL)) {
> >> +			ret = -EINVAL;
> >> +			goto out;
> >> +		}
> >> +
> >> +		ret = f2fs_convert_inline_inode(inode);
> >> +		if (ret)
> >> +			goto out;
> >> +	}
> >> +
> >>  	ret = f2fs_setflags_common(inode, iflags,
> >>  			f2fs_fsflags_to_iflags(F2FS_SETTABLE_FS_FL));
> >>  out:
> >> -- 
> >> 2.18.0.rc1
> > .
> >