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Message-ID: <20250807034838.3829794-1-chao@kernel.org>
Date: Thu, 7 Aug 2025 11:48:38 +0800
From: Chao Yu <chao@...nel.org>
To: jaegeuk@...nel.org
Cc: linux-f2fs-devel@...ts.sourceforge.net,
linux-kernel@...r.kernel.org,
Chao Yu <chao@...nel.org>
Subject: [PATCH v3] f2fs: introduce flush_policy sysfs entry
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()
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
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