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Date: Fri, 19 Apr 2024 17:53:31 +0000
From: Jaegeuk Kim <jaegeuk@kernel.org>
To: Chao Yu <chao@kernel.org>
Cc: linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH] f2fs: assign the write hint per stream by
 default
Message-ID: <ZiKvm57zbjq_ZpZj@google.com>
References: <20240417211201.3919770-1-jaegeuk@kernel.org>
 <afe91331-92a5-4ccf-b5b3-095a2d65f0d0@kernel.org>
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In-Reply-To: <afe91331-92a5-4ccf-b5b3-095a2d65f0d0@kernel.org>

On 04/18, Chao Yu wrote:
> On 2024/4/18 5:12, Jaegeuk Kim wrote:
> > This reverts commit 930e2607638d ("f2fs: remove obsolete whint_mode"), as we
> > decide to pass write hints to the disk.
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >   Documentation/filesystems/f2fs.rst | 29 +++++++++++++++
> >   fs/f2fs/data.c                     |  2 +
> >   fs/f2fs/f2fs.h                     |  2 +
> >   fs/f2fs/segment.c                  | 59 ++++++++++++++++++++++++++++++
> >   4 files changed, 92 insertions(+)
> > 
> > diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
> > index efc3493fd6f8..68a0885fb5e6 100644
> > --- a/Documentation/filesystems/f2fs.rst
> > +++ b/Documentation/filesystems/f2fs.rst
> > @@ -774,6 +774,35 @@ In order to identify whether the data in the victim segment are valid or not,
> >   F2FS manages a bitmap. Each bit represents the validity of a block, and the
> >   bitmap is composed of a bit stream covering whole blocks in main area.
> > +Write-hint Policy
> > +-----------------
> > +
> > +F2FS sets the whint all the time with the below policy.
> 
> No user-based mode?

Not anymore, as there's no user.

> 
> Thanks,
> 
> > +
> > +===================== ======================== ===================
> > +User                  F2FS                     Block
> > +===================== ======================== ===================
> > +N/A                   META                     WRITE_LIFE_NONE|REQ_META
> > +N/A                   HOT_NODE                 WRITE_LIFE_NONE
> > +N/A                   WARM_NODE                WRITE_LIFE_MEDIUM
> > +N/A                   COLD_NODE                WRITE_LIFE_LONG
> > +ioctl(COLD)           COLD_DATA                WRITE_LIFE_EXTREME
> > +extension list        "                        "
> > +
> > +-- buffered io
> > +N/A                   COLD_DATA                WRITE_LIFE_EXTREME
> > +N/A                   HOT_DATA                 WRITE_LIFE_SHORT
> > +N/A                   WARM_DATA                WRITE_LIFE_NOT_SET
> > +
> > +-- direct io
> > +WRITE_LIFE_EXTREME    COLD_DATA                WRITE_LIFE_EXTREME
> > +WRITE_LIFE_SHORT      HOT_DATA                 WRITE_LIFE_SHORT
> > +WRITE_LIFE_NOT_SET    WARM_DATA                WRITE_LIFE_NOT_SET
> > +WRITE_LIFE_NONE       "                        WRITE_LIFE_NONE
> > +WRITE_LIFE_MEDIUM     "                        WRITE_LIFE_MEDIUM
> > +WRITE_LIFE_LONG       "                        WRITE_LIFE_LONG
> > +===================== ======================== ===================
> > +
> >   Fallocate(2) Policy
> >   -------------------
> > diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
> > index 5d641fac02ba..ed7d08785fcf 100644
> > --- a/fs/f2fs/data.c
> > +++ b/fs/f2fs/data.c
> > @@ -465,6 +465,8 @@ static struct bio *__bio_alloc(struct f2fs_io_info *fio, int npages)
> >   	} else {
> >   		bio->bi_end_io = f2fs_write_end_io;
> >   		bio->bi_private = sbi;
> > +		bio->bi_write_hint = f2fs_io_type_to_rw_hint(sbi,
> > +						fio->type, fio->temp);
> >   	}
> >   	iostat_alloc_and_bind_ctx(sbi, bio, NULL);
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index dd530dc70005..b3b878acc86b 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -3745,6 +3745,8 @@ void f2fs_destroy_segment_manager(struct f2fs_sb_info *sbi);
> >   int __init f2fs_create_segment_manager_caches(void);
> >   void f2fs_destroy_segment_manager_caches(void);
> >   int f2fs_rw_hint_to_seg_type(enum rw_hint hint);
> > +enum rw_hint f2fs_io_type_to_rw_hint(struct f2fs_sb_info *sbi,
> > +			enum page_type type, enum temp_type temp);
> >   unsigned int f2fs_usable_segs_in_sec(struct f2fs_sb_info *sbi,
> >   			unsigned int segno);
> >   unsigned int f2fs_usable_blks_in_seg(struct f2fs_sb_info *sbi,
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index f0da516ba8dc..daa94669f7ee 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -3364,6 +3364,65 @@ int f2fs_rw_hint_to_seg_type(enum rw_hint hint)
> >   	}
> >   }
> > +/*
> > + * This returns write hints for each segment type. This hints will be
> > + * passed down to block layer as below by default.
> > + *
> > + * User                  F2FS                     Block
> > + * ----                  ----                     -----
> > + *                       META                     WRITE_LIFE_NONE|REQ_META
> > + *                       HOT_NODE                 WRITE_LIFE_NONE
> > + *                       WARM_NODE                WRITE_LIFE_MEDIUM
> > + *                       COLD_NODE                WRITE_LIFE_LONG
> > + * ioctl(COLD)           COLD_DATA                WRITE_LIFE_EXTREME
> > + * extension list        "                        "
> > + *
> > + * -- buffered io
> > + *                       COLD_DATA                WRITE_LIFE_EXTREME
> > + *                       HOT_DATA                 WRITE_LIFE_SHORT
> > + *                       WARM_DATA                WRITE_LIFE_NOT_SET
> > + *
> > + * -- direct io
> > + * WRITE_LIFE_EXTREME    COLD_DATA                WRITE_LIFE_EXTREME
> > + * WRITE_LIFE_SHORT      HOT_DATA                 WRITE_LIFE_SHORT
> > + * WRITE_LIFE_NOT_SET    WARM_DATA                WRITE_LIFE_NOT_SET
> > + * WRITE_LIFE_NONE       "                        WRITE_LIFE_NONE
> > + * WRITE_LIFE_MEDIUM     "                        WRITE_LIFE_MEDIUM
> > + * WRITE_LIFE_LONG       "                        WRITE_LIFE_LONG
> > + */
> > +enum rw_hint f2fs_io_type_to_rw_hint(struct f2fs_sb_info *sbi,
> > +				enum page_type type, enum temp_type temp)
> > +{
> > +	switch (type) {
> > +	case DATA:
> > +		switch (temp) {
> > +		case WARM:
> > +			return WRITE_LIFE_NOT_SET;
> > +		case HOT:
> > +			return WRITE_LIFE_SHORT;
> > +		case COLD:
> > +			return WRITE_LIFE_EXTREME;
> > +		default:
> > +			return WRITE_LIFE_NONE;
> > +		}
> > +	case NODE:
> > +		switch (temp) {
> > +		case WARM:
> > +			return WRITE_LIFE_MEDIUM;
> > +		case HOT:
> > +			return WRITE_LIFE_NONE;
> > +		case COLD:
> > +			return WRITE_LIFE_LONG;
> > +		default:
> > +			return WRITE_LIFE_NONE;
> > +		}
> > +	case META:
> > +		return WRITE_LIFE_NONE;
> > +	default:
> > +		return WRITE_LIFE_NONE;
> > +	}
> > +}
> > +
> >   static int __get_segment_type_2(struct f2fs_io_info *fio)
> >   {
> >   	if (fio->type == DATA)