[f2fs-dev] [PATCH 2/2] f2fs: remove max_atc_write_bio_size

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

From: Chao Yu <chao@kernel.org>

Commit 3de6b8094115 ("f2fs: Run f2fs_write_end_io() asynchronously")
introduced max_atc_write_bio_size to offload the completion of large
write bios to sbi->wq when f2fs_write_end_io() is called in atomic
context.

However, relying on bio->bi_iter.bi_size has two issues:
1. bi_size is not reliable at completion time: on a direct blk-mq path
   (e.g. SCSI or UFS), blk_update_request() consumes the bio iterator
   via bio_advance() before calling bio_endio(), so bi_size is already 0
   in f2fs_write_end_io(), whereas on a DM / zoned path (e.g. dm-linear)
   only the clone bio is advanced and orig_bio->bi_iter.bi_size stays
   intact.
2. With large folios enabled, folio size may be larger than 4KB, so
   bi_size cannot indicate how many folios are in a bio.

Since max_write_bio_{folio,entry}_cnt module parameters have been
introduced to limit the number of folios or cached blocks completed in
atomic context without depending on the bio iterator, let's remove
max_atc_write_bio_size logic and its sysfs entry.

Signed-off-by: Chao Yu <chao@kernel.org>
---
 Documentation/ABI/testing/sysfs-fs-f2fs | 10 ----------
 fs/f2fs/data.c                          |  4 ++--
 fs/f2fs/f2fs.h                          |  2 --
 fs/f2fs/super.c                         |  1 -
 fs/f2fs/sysfs.c                         |  2 --
 5 files changed, 2 insertions(+), 17 deletions(-)

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 3d2e78a8bb7d..3520c29f3b9c 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -1004,16 +1004,6 @@ Description:	It can be used to tune priority of f2fs critical task, e.g. f2fs_ck
 		- it requires user has CAP_SYS_NICE capability.
 		- the range is [100, 139], by default the value is 120.
 
-What:		/sys/fs/f2fs/<disk>/max_atc_write_bio_size
-Date:		June 2026
-Contact:	Bart Van Assche <bvanassche@acm.org>
-Description:	Every time a write operation completes f2fs_write_end_io() is
-		called. This function may be called from an atomic context,
-		e.g. from inside an interrupt handler. This attribute controls
-		the maximum size of a write bio that is completed in atomic
-		(atc) context. The default value for this attribute is UINT_MAX
-		which means that this functionality is disabled by default.
-
 What:		/sys/fs/f2fs/<disk>/pinned_area_max_secno
 Date:		August 2026
 Contact:	"Daeho Jeong" <daehojeong@google.com>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 3caadb30496a..867024c4c72d 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -414,8 +414,8 @@ static void f2fs_write_end_io(struct bio *bio)
 
 	sbi = bio->bi_private;
 
-	if (in_atomic() && (bio->bi_iter.bi_size > sbi->max_atc_write_bio_size ||
-		F2FS_BIO(bio)->entry_cnt > f2fs_max_write_bio_cnt(bio))) {
+	if (in_atomic() &&
+		F2FS_BIO(bio)->entry_cnt > f2fs_max_write_bio_cnt(bio)) {
 		struct work_struct *w;
 
 		w = &container_of(bio, struct f2fs_bio, bio)->work;
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 4333d88cf076..e3ee28f0201f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1806,8 +1806,6 @@ struct f2fs_sb_info {
 	struct f2fs_sm_info *sm_info;		/* segment manager */
 
 	/* for bio operations */
-	/* Largest write bio size completed in atomic context (atc). */
-	u32 max_atc_write_bio_size;
 	struct f2fs_bio_info *write_io[NR_PAGE_TYPE];	/* for write bios */
 	/* keep migration IO order for LFS mode */
 	struct f2fs_rwsem io_order_lock;
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 1664928fedca..10be5888273c 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -5183,7 +5183,6 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc)
 		err = -EINVAL;
 		goto free_sb_buf;
 	}
-	sbi->max_atc_write_bio_size = UINT_MAX;
 
 	INIT_WORK(&sbi->s_error_work, f2fs_record_error_work);
 	memcpy(sbi->errors, raw_super->s_errors, MAX_F2FS_ERRORS);
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index 95f8dc0c4218..67202b7f8293 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -1284,7 +1284,6 @@ F2FS_SBI_RW_ATTR(gc_idle_interval, interval_time[GC_TIME]);
 F2FS_SBI_RW_ATTR(umount_discard_timeout, interval_time[UMOUNT_DISCARD_TIMEOUT]);
 F2FS_SBI_RW_ATTR(gc_pin_file_thresh, gc_pin_file_threshold);
 F2FS_SBI_RW_ATTR(gc_reclaimed_segments, gc_reclaimed_segs);
-F2FS_SBI_RW_ATTR(max_atc_write_bio_size, max_atc_write_bio_size);
 F2FS_SBI_GENERAL_RW_ATTR(max_victim_search);
 F2FS_SBI_GENERAL_RW_ATTR(migration_granularity);
 F2FS_SBI_GENERAL_RW_ATTR(migration_window_granularity);
@@ -1535,7 +1534,6 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(seq_file_ra_mul),
 	ATTR_LIST(gc_segment_mode),
 	ATTR_LIST(gc_reclaimed_segments),
-	ATTR_LIST(max_atc_write_bio_size),
 	ATTR_LIST(max_fragment_chunk),
 	ATTR_LIST(max_fragment_hole),
 	ATTR_LIST(current_atomic_write),
-- 
2.49.0



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