Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>
于2025年7月31日周四 16:49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 <c...@kernel.org>
> ---
> Documentation/ABI/testing/sysfs-fs-f2fs | 9 +++++++++
> fs/f2fs/checkpoint.c | 10 +++++++++-
> fs/f2fs/f2fs.h | 7 +++++++
> fs/f2fs/sysfs.c | 9 +++++++++
> 4 files changed, 34 insertions(+), 1 deletion(-)
>
> 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" <daehoje...@google.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" <c...@kernel.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 bbe07e3a6c75..10cc27158770 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)
> @@ -1606,6 +1608,12 @@ static int do_checkpoint(struct f2fs_sb_info *sbi,
> struct cp_control *cpc)
> f2fs_wait_on_all_pages(sbi, F2FS_WB_CP_DATA);
> stat_cp_time(cpc, CP_TIME_WAIT_LAST_CP);
>
> + if (sbi->flush_policy & BIT(FLUSH_POLICY_CP_NO_FUA)) {
> + err = f2fs_flush_device_cache(sbi);
> + if (err)
> + return err;
> + }
Hi Chao,
sorry for late interruption.
f2fs_flush_device_cache is just used for multi device cases, so this patch will
not be suitable for a single device if the user changes flush_policy
by sysfs, otherwise it
will not use FUA write when committing checkpoint? Is this expected?
Thanks!
> +
> /*
> * invalidate intermediate page cache borrowed from meta inode which
> are
> * used for migration of encrypted, verity or compressed inode's
> blocks.
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 5c0ea60e502e..5bba24ca15c8 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1621,6 +1621,11 @@ 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 */
> @@ -1873,6 +1878,8 @@ 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 */
> 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
>
>
>
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