Re: [f2fs-dev] [PATCH 1/5 v2] f2fs: add mount option for segment allocation policy

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 02/28, Chao Yu wrote:
> On 2018/2/28 13:09, Jaegeuk Kim wrote:
> > Change log from v1:
> >  - add doc :)
> > 
> > This patch adds an mount option, "alloc_mode=%s" having two options, "default"
> > and "reuse".
> > 
> > In "alloc_mode=reuse" case, f2fs starts to allocate segments from 0'th segment
> > all the time to reassign segments. It'd be useful for small-sized eMMC parts.
> 
> We have to restore old alloc_mode if we encounter any failure in ->remount, right?

Yup, done.

> 
> Thanks,
> 
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  Documentation/filesystems/f2fs.txt |  2 ++
> >  fs/f2fs/f2fs.h                     |  8 ++++++++
> >  fs/f2fs/segment.c                  |  5 +++++
> >  fs/f2fs/super.c                    | 24 ++++++++++++++++++++++++
> >  4 files changed, 39 insertions(+)
> > 
> > diff --git a/Documentation/filesystems/f2fs.txt b/Documentation/filesystems/f2fs.txt
> > index 0caf7da0a532..0409c47584ea 100644
> > --- a/Documentation/filesystems/f2fs.txt
> > +++ b/Documentation/filesystems/f2fs.txt
> > @@ -180,6 +180,8 @@ whint_mode=%s          Control which write hints are passed down to block
> >                         down hints. In "user-based" mode, f2fs tries to pass
> >                         down hints given by users. And in "fs-based" mode, f2fs
> >                         passes down hints with its policy.
> > +alloc_mode=%s          Adjust block allocation policy, which supports "reuse"
> > +                       and "default".
> >  
> >  ================================================================================
> >  DEBUGFS ENTRIES
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index f68ece08b5a2..d1bfdf691afc 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -1043,6 +1043,11 @@ enum {
> >  	WHINT_MODE_FS,		/* pass down hints with F2FS policy */
> >  };
> >  
> > +enum {
> > +	ALLOC_MODE_DEFAULT,	/* stay default */
> > +	ALLOC_MODE_REUSE,	/* reuse segments as much as possible */
> > +};
> > +
> >  struct f2fs_sb_info {
> >  	struct super_block *sb;			/* pointer to VFS super block */
> >  	struct proc_dir_entry *s_proc;		/* proc entry */
> > @@ -1229,6 +1234,9 @@ struct f2fs_sb_info {
> >  #endif
> >  	/* For which write hints are passed down to block layer */
> >  	int whint_mode;
> > +
> > +	/* segment allocation policy */
> > +	int alloc_mode;
> >  };
> >  
> >  #ifdef CONFIG_F2FS_FAULT_INJECTION
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 0646d5de8cd0..5e5e2936a26a 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -2170,6 +2170,11 @@ static unsigned int __get_next_segno(struct f2fs_sb_info *sbi, int type)
> >  
> >  	if (SIT_I(sbi)->last_victim[ALLOC_NEXT])
> >  		return SIT_I(sbi)->last_victim[ALLOC_NEXT];
> > +
> > +	/* find segments from 0 to reuse freed segments */
> > +	if (sbi->alloc_mode == ALLOC_MODE_REUSE)
> > +		return 0;
> > +
> >  	return CURSEG_I(sbi, type)->segno;
> >  }
> >  
> > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
> > index 2d832866720c..1345ef167140 100644
> > --- a/fs/f2fs/super.c
> > +++ b/fs/f2fs/super.c
> > @@ -130,6 +130,7 @@ enum {
> >  	Opt_jqfmt_vfsv0,
> >  	Opt_jqfmt_vfsv1,
> >  	Opt_whint,
> > +	Opt_alloc,
> >  	Opt_err,
> >  };
> >  
> > @@ -184,6 +185,7 @@ static match_table_t f2fs_tokens = {
> >  	{Opt_jqfmt_vfsv0, "jqfmt=vfsv0"},
> >  	{Opt_jqfmt_vfsv1, "jqfmt=vfsv1"},
> >  	{Opt_whint, "whint_mode=%s"},
> > +	{Opt_alloc, "alloc_mode=%s"},
> >  	{Opt_err, NULL},
> >  };
> >  
> > @@ -700,6 +702,23 @@ static int parse_options(struct super_block *sb, char *options)
> >  			}
> >  			kfree(name);
> >  			break;
> > +		case Opt_alloc:
> > +			name = match_strdup(&args[0]);
> > +			if (!name)
> > +				return -ENOMEM;
> > +
> > +			if (strlen(name) == 7 &&
> > +					!strncmp(name, "default", 7)) {
> > +				sbi->alloc_mode = ALLOC_MODE_DEFAULT;
> > +			} else if (strlen(name) == 5 &&
> > +					!strncmp(name, "reuse", 5)) {
> > +				sbi->alloc_mode = ALLOC_MODE_REUSE;
> > +			} else {
> > +				kfree(name);
> > +				return -EINVAL;
> > +			}
> > +			kfree(name);
> > +			break;
> >  		default:
> >  			f2fs_msg(sb, KERN_ERR,
> >  				"Unrecognized mount option \"%s\" or missing value",
> > @@ -1264,6 +1283,10 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
> >  	else if (sbi->whint_mode == WHINT_MODE_FS)
> >  		seq_printf(seq, ",whint_mode=%s", "fs-based");
> >  
> > +	if (sbi->alloc_mode == ALLOC_MODE_DEFAULT)
> > +		seq_printf(seq, ",alloc_mode=%s", "default");
> > +	else if (sbi->alloc_mode == ALLOC_MODE_REUSE)
> > +		seq_printf(seq, ",alloc_mode=%s", "reuse");
> >  	return 0;
> >  }
> >  
> > @@ -1273,6 +1296,7 @@ static void default_options(struct f2fs_sb_info *sbi)
> >  	sbi->active_logs = NR_CURSEG_TYPE;
> >  	sbi->inline_xattr_size = DEFAULT_INLINE_XATTR_ADDRS;
> >  	sbi->whint_mode = WHINT_MODE_OFF;
> > +	sbi->alloc_mode = ALLOC_MODE_DEFAULT;
> >  
> >  	set_opt(sbi, BG_GC);
> >  	set_opt(sbi, INLINE_XATTR);
> >