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Date:   Tue, 31 May 2022 13:18:59 -0700
From:   Jaegeuk Kim <jaegeuk@kernel.org>
To:     Chao Yu <chao@kernel.org>
Cc:     linux-f2fs-devel@lists.sourceforge.net,
        linux-kernel@vger.kernel.org, Chao Yu <chao.yu@oppo.com>
Subject: Re: [PATCH v4] f2fs: separate NOCoW and pinfile semantics
Message-ID: <YpZ4MxH3bkWbTPvI@google.com>
References: <20220517032410.3564033-1-chao@kernel.org>
 <YoPZh+vl68IH5loV@google.com>
 <fa3cbe36-1738-a811-ce03-dd5aaf8ea3d4@kernel.org>
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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.

> 
> 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