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Message-ID: <CAHJ8P3+tT70BLK38ROh_jiZO-OBWGXDSu65Q0w+ppMW0QHSFSA@mail.gmail.com>
Date: Thu, 7 Aug 2025 13:31:30 +0800
From: Zhiguo Niu <niuzhiguo84@...il.com>
To: Chao Yu <chao@...nel.org>
Cc: jaegeuk@...nel.org, linux-kernel@...r.kernel.org,
linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH v3] f2fs: introduce flush_policy sysfs entry
Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@...ts.sourceforge.net>
于2025年8月7日周四 11:50写道：
>
> This patch introduces a new sysfs entry /sys/fs/f2fs/<disk>/flush_policy
> in order to tune performance of f2fs data flush flow.
>
> For example, checkpoint will use REQ_FUA to persist CP metadata, however,
> some kind device has bad performance on REQ_FUA command, result in that
> checkpoint being blocked for long time, w/ this sysfs entry, we can give
> an option to use REQ_PREFLUSH command instead of REQ_FUA during checkpoint,
> it can help to mitigate long latency of checkpoint.
>
> Signed-off-by: Chao Yu <chao@...nel.org>
> ---
> v3:
> - export f2fs_submit_flush_wait()
looks good to me.
Reviewed-by: Zhiguo Niu <zhiguo.niu@...soc.com>
> Documentation/ABI/testing/sysfs-fs-f2fs | 9 +++++++++
> fs/f2fs/checkpoint.c | 11 ++++++++++-
> fs/f2fs/f2fs.h | 9 +++++++++
> fs/f2fs/segment.c | 8 ++++----
> fs/f2fs/sysfs.c | 9 +++++++++
> 5 files changed, 41 insertions(+), 5 deletions(-)
>
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index bc0e7fefc39d..2fedb44b713b 100644
> --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> @@ -883,3 +883,12 @@ Date: June 2025
> Contact: "Daeho Jeong" <daehojeong@...gle.com>
> Description: Control GC algorithm for boost GC. 0: cost benefit, 1: greedy
> Default: 1
> +
> +What: /sys/fs/f2fs/<disk>/flush_policy
> +Date: July 2025
> +Contact: "Chao Yu" <chao@...nel.org>
> +Description: Device has different performance for the same flush methods, this node
> + can be used to tune performance by setting different flush methods.
> +
> + policy value description
> + 0x00000001 Use preflush instead of fua during checkpoint
> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
> index db3831f7f2f5..2450e382fe6b 100644
> --- a/fs/f2fs/checkpoint.c
> +++ b/fs/f2fs/checkpoint.c
> @@ -1419,7 +1419,9 @@ static void commit_checkpoint(struct f2fs_sb_info *sbi,
> f2fs_folio_put(folio, false);
>
> /* submit checkpoint (with barrier if NOBARRIER is not set) */
> - f2fs_submit_merged_write(sbi, META_FLUSH);
> + f2fs_submit_merged_write(sbi,
> + sbi->flush_policy & BIT(FLUSH_POLICY_CP_NO_FUA) ?
> + META : META_FLUSH);
> }
>
> static inline u64 get_sectors_written(struct block_device *bdev)
> @@ -1594,6 +1596,13 @@ static int do_checkpoint(struct f2fs_sb_info *sbi, struct cp_control *cpc)
>
> __set_cp_next_pack(sbi);
>
> + /* flush device cache to make sure last cp pack can be persisted */
> + if (sbi->flush_policy & BIT(FLUSH_POLICY_CP_NO_FUA)) {
> + err = f2fs_submit_flush_wait(sbi, sbi->sb->s_bdev);
> + if (err)
> + return err;
> + }
> +
> /*
> * redirty superblock if metadata like node page or inode cache is
> * updated during writing checkpoint.
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 46be7560548c..e7b866a98c92 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1594,6 +1594,11 @@ struct decompress_io_ctx {
> #define MAX_COMPRESS_LOG_SIZE 8
> #define MAX_COMPRESS_WINDOW_SIZE(log_size) ((PAGE_SIZE) << (log_size))
>
> +enum flush_policy {
> + FLUSH_POLICY_CP_NO_FUA,
> + FLUSH_POLICY_MAX,
> +};
> +
> struct f2fs_sb_info {
> struct super_block *sb; /* pointer to VFS super block */
> struct proc_dir_entry *s_proc; /* proc entry */
> @@ -1845,6 +1850,8 @@ struct f2fs_sb_info {
> /* carve out reserved_blocks from total blocks */
> bool carve_out;
>
> + unsigned int flush_policy; /* flush policy */
> +
> #ifdef CONFIG_F2FS_FS_COMPRESSION
> struct kmem_cache *page_array_slab; /* page array entry */
> unsigned int page_array_slab_size; /* default page array slab size */
> @@ -3821,6 +3828,8 @@ int f2fs_commit_atomic_write(struct inode *inode);
> void f2fs_abort_atomic_write(struct inode *inode, bool clean);
> void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need);
> void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi, bool from_bg);
> +int f2fs_submit_flush_wait(struct f2fs_sb_info *sbi,
> + struct block_device *bdev);
> int f2fs_issue_flush(struct f2fs_sb_info *sbi, nid_t ino);
> int f2fs_create_flush_cmd_control(struct f2fs_sb_info *sbi);
> int f2fs_flush_device_cache(struct f2fs_sb_info *sbi);
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index cc82d42ef14c..d68c903f1ad3 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -544,7 +544,7 @@ void f2fs_balance_fs_bg(struct f2fs_sb_info *sbi, bool from_bg)
> f2fs_sync_fs(sbi->sb, 1);
> }
>
> -static int __submit_flush_wait(struct f2fs_sb_info *sbi,
> +int f2fs_submit_flush_wait(struct f2fs_sb_info *sbi,
> struct block_device *bdev)
> {
> int ret = blkdev_issue_flush(bdev);
> @@ -562,12 +562,12 @@ static int submit_flush_wait(struct f2fs_sb_info *sbi, nid_t ino)
> int i;
>
> if (!f2fs_is_multi_device(sbi))
> - return __submit_flush_wait(sbi, sbi->sb->s_bdev);
> + return f2fs_submit_flush_wait(sbi, sbi->sb->s_bdev);
>
> for (i = 0; i < sbi->s_ndevs; i++) {
> if (!f2fs_is_dirty_device(sbi, ino, i, FLUSH_INO))
> continue;
> - ret = __submit_flush_wait(sbi, FDEV(i).bdev);
> + ret = f2fs_submit_flush_wait(sbi, FDEV(i).bdev);
> if (ret)
> break;
> }
> @@ -748,7 +748,7 @@ int f2fs_flush_device_cache(struct f2fs_sb_info *sbi)
> continue;
>
> do {
> - ret = __submit_flush_wait(sbi, FDEV(i).bdev);
> + ret = f2fs_submit_flush_wait(sbi, FDEV(i).bdev);
> if (ret)
> f2fs_io_schedule_timeout(DEFAULT_IO_TIMEOUT);
> } while (ret && --count);
> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> index f736052dea50..b69015f1dc67 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -852,6 +852,13 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
> return count;
> }
>
> + if (!strcmp(a->attr.name, "flush_policy")) {
> + if (t >= BIT(FLUSH_POLICY_MAX))
> + return -EINVAL;
> + *ui = (unsigned int)t;
> + return count;
> + }
> +
> if (!strcmp(a->attr.name, "gc_boost_gc_multiple")) {
> if (t < 1 || t > SEGS_PER_SEC(sbi))
> return -EINVAL;
> @@ -1175,6 +1182,7 @@ F2FS_SBI_GENERAL_RW_ATTR(blkzone_alloc_policy);
> #endif
> F2FS_SBI_GENERAL_RW_ATTR(carve_out);
> F2FS_SBI_GENERAL_RW_ATTR(reserved_pin_section);
> +F2FS_SBI_GENERAL_RW_ATTR(flush_policy);
>
> /* STAT_INFO ATTR */
> #ifdef CONFIG_F2FS_STAT_FS
> @@ -1371,6 +1379,7 @@ static struct attribute *f2fs_attrs[] = {
> ATTR_LIST(max_read_extent_count),
> ATTR_LIST(carve_out),
> ATTR_LIST(reserved_pin_section),
> + ATTR_LIST(flush_policy),
> NULL,
> };
> ATTRIBUTE_GROUPS(f2fs);
> --
> 2.49.0
>
>
>
> _______________________________________________
> Linux-f2fs-devel mailing list
> Linux-f2fs-devel@...ts.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
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