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f2fs: support resizable tail section and unify pinned allocation

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Currently, zoned block devices restrict pinned file allocations to
conventional zones at the beginning of the storage (before
first_seq_zone_segno), triggering range GC when conventional space is
exhausted.

On regular block devices, when preparing for future online filesystem
resizing (e.g. partition shrinking), pinned files must not be allocated
in the tail area that will be truncated, as pinned files cannot be
relocated by GC. Specifying the resizable tail area size (in sections)
allows uniform mount configuration across devices of different storage
capacities.

To support this, introduce a unified `pinned_area_max_secno` boundary
abstraction in `f2fs_sb_info`:
1. Add `-o resizable_tail_secno=%u` mount option to specify the number
   of sections at the tail of the filesystem reserved for resizing.
2. In `f2fs_fill_super()`, initialize `sbi->pinned_area_max_secno` as:
   min(MAIN_SECS(sbi) - resizable_tail_sec, zoned_max_sec).
3. In `get_new_segment()`, restrict segment allocation for pinned files
   (`pinning == true`) to `0 .. sbi->pinned_area_max_secno - 1`. If no
   free section is available in the pinned area, return -EAGAIN.
4. In `f2fs_allocate_pinning_section()`, unify the range GC trigger to
   run `f2fs_gc_range()` up to `sbi->pinned_area_max_secno` whenever
   `sbi->pinned_area_max_secno < MAIN_SECS(sbi)` and allocation
   returns -EAGAIN.
5. Expose `/sys/fs/f2fs/<dev>/pinned_area_max_secno` as a read-only
   sysfs node.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
Signed-off-by: Sunmin Jeong <s_min.jeong@samsung.com>
Reviewed-by: Wenjie Qi <qiwenjie@xiaomi.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
This commit is contained in:
Daeho Jeong 2026-08-26 08:36:44 -07:00 committed by Jaegeuk Kim
parent 24c1a47f1e
commit c966d29e01
7 changed files with 73 additions and 18 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

7
Documentation/ABI/testing/sysfs-fs-f2fs
View File

@ -1013,3 +1013,10 @@ Description: Every time a write operation completes f2fs_write_end_io() is
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>
Description: This is a read-only entry to show the upper bound section number
for pinned files. Pinned files will only be allocated within
sections 0 to pinned_area_max_secno - 1.

8
Documentation/filesystems/f2fs.rst
View File

@ -417,7 +417,13 @@ lookup_mode=%s Control the directory lookup behavior for casefolded
auto F2FS determines the mode based on the
on-disk `SB_ENC_NO_COMPAT_FALLBACK_FL`
flag.
================== ========================================
resizable_tail_secno=%u Control the number of sections at the tail of the
filesystem reserved for online resizing. Pinned files
will only be allocated within sections 0 to
(MAIN_SECS - resizable_tail_secno) - 1. If set to 0
(default), there is no tail restriction unless running
on a zoned block device where conventional zones are
used.
======================== ============================================================
Debugfs Entries

2
fs/f2fs/f2fs.h
View File

@ -255,6 +255,7 @@ struct f2fs_mount_info {
block_t unusable_cap; /* Amount of space allowed to be
* unusable when disabling checkpoint
*/
unsigned int resizable_tail_secno; /* number of resizable tail sections */
/* For compression */
unsigned char compress_algorithm; /* algorithm type */
@ -2005,6 +2006,7 @@ struct f2fs_sb_info {
spinlock_t dev_lock; /* protect dirty_device */
bool aligned_blksize; /* all devices has the same logical blksize */
unsigned int first_seq_zone_segno; /* first segno in sequential zone */
unsigned int pinned_area_max_secno; /* upper bound section for pinned files */
unsigned int bggc_io_aware; /* For adjust the BG_GC priority when pending IO */
unsigned int allocate_section_hint; /* the boundary position between devices */
unsigned int allocate_section_policy; /* determine the section writing priority */

35
fs/f2fs/segment.c
View File

@ -2877,6 +2877,7 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
unsigned int old_zoneno = GET_ZONE_FROM_SEG(sbi, *newseg);
unsigned int alloc_policy = sbi->allocate_section_policy;
unsigned int alloc_hint = sbi->allocate_section_hint;
unsigned int max_secno = MAIN_SECS(sbi);
bool init = true;
bool looped = false;
int i, devi;
@ -2908,7 +2909,7 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
*/
if (f2fs_sb_has_blkzoned(sbi)) {
/* Prioritize writing to conventional zones */
if (sbi->blkzone_alloc_policy == BLKZONE_ALLOC_PRIOR_CONV || pinning)
if (sbi->blkzone_alloc_policy == BLKZONE_ALLOC_PRIOR_CONV)
segno = 0;
else
segno = max(sbi->first_seq_zone_segno, *newseg);
@ -2924,19 +2925,24 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
alloc_hint > MAIN_SECS(sbi))
alloc_hint = MAIN_SECS(sbi);
if (alloc_policy == ALLOCATE_FORWARD_FROM_HINT &&
hint < alloc_hint)
hint = alloc_hint;
else if (alloc_policy == ALLOCATE_FORWARD_WITHIN_HINT &&
hint >= alloc_hint)
if (pinning) {
max_secno = sbi->pinned_area_max_secno;
hint = 0;
} else if (alloc_policy == ALLOCATE_FORWARD_FROM_HINT &&
hint < alloc_hint) {
hint = alloc_hint;
} else if (alloc_policy == ALLOCATE_FORWARD_WITHIN_HINT &&
hint >= alloc_hint) {
hint = 0;
}
find_other_zone:
secno = find_next_zero_bit(free_i->free_secmap, MAIN_SECS(sbi), hint);
secno = find_next_zero_bit(free_i->free_secmap, max_secno, hint);
if (secno >= MAIN_SECS(sbi)) {
if (secno >= max_secno) {
if (looped) {
ret = -ENOSPC;
ret = (pinning && has_unpinned_area(sbi)) ?
-EAGAIN : -ENOSPC;
f2fs_bug_on(sbi, !pinning);
goto out_unlock;
}
@ -3001,12 +3007,6 @@ static int get_new_segment(struct f2fs_sb_info *sbi,
goto out_unlock;
}
/* no free section in conventional device or conventional zone */
if (new_sec && pinning &&
f2fs_is_sequential_zone_area(sbi, START_BLOCK(sbi, segno))) {
ret = -EAGAIN;
goto out_unlock;
}
__set_inuse(sbi, segno);
*newseg = segno;
out_unlock:
@ -3472,8 +3472,9 @@ int f2fs_allocate_pinning_section(struct f2fs_sb_info *sbi)
err = f2fs_allocate_new_section(sbi, CURSEG_COLD_DATA_PINNED, false);
f2fs_unlock_op(sbi, &lc);
if (f2fs_sb_has_blkzoned(sbi) && err == -EAGAIN && gc_required) {
err = f2fs_gc_range(sbi, 0, sbi->first_seq_zone_segno - 1,
if (has_unpinned_area(sbi) && err == -EAGAIN && gc_required) {
err = f2fs_gc_range(sbi, 0,
sbi->pinned_area_max_secno * SEGS_PER_SEC(sbi) - 1,
true, ZONED_PIN_SEC_REQUIRED_COUNT, true);
if (err)
return err;

1
fs/f2fs/segment.h
View File

@ -43,6 +43,7 @@ static inline void sanity_check_seg_type(struct f2fs_sb_info *sbi,
#define MAIN_SEGS(sbi) (SM_I(sbi)->main_segments)
#define MAIN_SECS(sbi) ((sbi)->total_sections)
#define has_unpinned_area(sbi) ((sbi)->pinned_area_max_secno < MAIN_SECS(sbi))
#define TOTAL_SEGS(sbi) \
(SM_I(sbi) ? SM_I(sbi)->segment_count : \

36
fs/f2fs/super.c
View File

@ -235,6 +235,7 @@ enum {
Opt_jqfmt,
Opt_checkpoint,
Opt_lookup_mode,
Opt_resizable_tail_secno,
Opt_err,
};
@ -366,6 +367,7 @@ static const struct fs_parameter_spec f2fs_param_specs[] = {
fsparam_flag("age_extent_cache", Opt_age_extent_cache),
fsparam_enum("errors", Opt_errors, f2fs_param_errors),
fsparam_enum("lookup_mode", Opt_lookup_mode, f2fs_param_lookup_mode),
fsparam_u32("resizable_tail_secno", Opt_resizable_tail_secno),
{}
};
@ -404,6 +406,7 @@ static match_table_t f2fs_checkpoint_tokens = {
#define F2FS_SPEC_errors (1 << 23)
#define F2FS_SPEC_lookup_mode (1 << 24)
#define F2FS_SPEC_reserve_node (1 << 25)
#define F2FS_SPEC_resizable_tail_secno (1 << 26)
struct f2fs_fs_context {
struct f2fs_mount_info info;
@ -551,6 +554,17 @@ static inline void adjust_unusable_cap_perc(struct f2fs_sb_info *sbi)
F2FS_OPTION(sbi).unusable_cap_perc);
}
static inline void adjust_pinned_area_boundary(struct f2fs_sb_info *sbi)
{
sbi->pinned_area_max_secno = MAIN_SECS(sbi);
if (f2fs_sb_has_blkzoned(sbi) && sbi->first_seq_zone_segno != NULL_SEGNO)
sbi->pinned_area_max_secno = min(sbi->pinned_area_max_secno,
GET_SEC_FROM_SEG(sbi, sbi->first_seq_zone_segno));
if (F2FS_OPTION(sbi).resizable_tail_secno)
sbi->pinned_area_max_secno = min(sbi->pinned_area_max_secno,
MAIN_SECS(sbi) - F2FS_OPTION(sbi).resizable_tail_secno);
}
static void init_once(void *foo)
{
struct f2fs_inode_info *fi = (struct f2fs_inode_info *) foo;
@ -1235,6 +1249,10 @@ static int f2fs_parse_param(struct fs_context *fc, struct fs_parameter *param)
F2FS_CTX_INFO(ctx).lookup_mode = result.uint_32;
ctx->spec_mask |= F2FS_SPEC_lookup_mode;
break;
case Opt_resizable_tail_secno:
F2FS_CTX_INFO(ctx).resizable_tail_secno = result.uint_32;
ctx->spec_mask |= F2FS_SPEC_resizable_tail_secno;
break;
}
return 0;
}
@ -1763,6 +1781,9 @@ static void f2fs_apply_options(struct fs_context *fc, struct super_block *sb)
F2FS_OPTION(sbi).errors = F2FS_CTX_INFO(ctx).errors;
if (ctx->spec_mask & F2FS_SPEC_lookup_mode)
F2FS_OPTION(sbi).lookup_mode = F2FS_CTX_INFO(ctx).lookup_mode;
if (ctx->spec_mask & F2FS_SPEC_resizable_tail_secno)
F2FS_OPTION(sbi).resizable_tail_secno =
F2FS_CTX_INFO(ctx).resizable_tail_secno;
f2fs_apply_compression(fc, sb);
f2fs_apply_test_dummy_encryption(fc, sb);
@ -1771,6 +1792,13 @@ static void f2fs_apply_options(struct fs_context *fc, struct super_block *sb)
static int f2fs_sanity_check_options(struct f2fs_sb_info *sbi, bool remount)
{
unsigned int total_sections = le32_to_cpu(sbi->raw_super->section_count);
if (F2FS_OPTION(sbi).resizable_tail_secno >= total_sections) {
f2fs_err(sbi, "Option resizable_tail_secno is larger than or equal to total sections (%u >= %u)",
F2FS_OPTION(sbi).resizable_tail_secno, total_sections);
return -EINVAL;
}
if (f2fs_sb_has_device_alias(sbi) &&
!test_opt(sbi, READ_EXTENT_CACHE)) {
f2fs_err(sbi, "device aliasing requires extent cache");
@ -2544,6 +2572,10 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
else if (F2FS_OPTION(sbi).lookup_mode == LOOKUP_AUTO)
seq_show_option(seq, "lookup_mode", "auto");
if (F2FS_OPTION(sbi).resizable_tail_secno)
seq_printf(seq, ",resizable_tail_secno=%u",
F2FS_OPTION(sbi).resizable_tail_secno);
return 0;
}
@ -2586,6 +2618,7 @@ static void default_options(struct f2fs_sb_info *sbi, bool remount)
F2FS_OPTION(sbi).bggc_mode = BGGC_MODE_ON;
F2FS_OPTION(sbi).memory_mode = MEMORY_MODE_NORMAL;
F2FS_OPTION(sbi).errors = MOUNT_ERRORS_CONTINUE;
F2FS_OPTION(sbi).resizable_tail_secno = 0;
set_opt(sbi, INLINE_XATTR);
set_opt(sbi, INLINE_DATA);
@ -3045,6 +3078,7 @@ static int __f2fs_remount(struct fs_context *fc, struct super_block *sb)
sb->s_flags = (sb->s_flags & ~SB_POSIXACL) |
(test_opt(sbi, POSIX_ACL) ? SB_POSIXACL : 0);
adjust_pinned_area_boundary(sbi);
limit_reserve_root(sbi);
fc->sb_flags = (flags & ~SB_LAZYTIME) | (sb->s_flags & SB_LAZYTIME);
@ -5287,6 +5321,8 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc)
/* get segno of first zoned block device */
sbi->first_seq_zone_segno = get_first_seq_zone_segno(sbi);
adjust_pinned_area_boundary(sbi);
sbi->reserved_pin_section = f2fs_sb_has_blkzoned(sbi) ?
ZONED_PIN_SEC_REQUIRED_COUNT :
GET_SEC_FROM_SEG(sbi, overprovision_segments(sbi));

2
fs/f2fs/sysfs.c
View File

@ -1313,6 +1313,7 @@ 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_RO_ATTR(pinned_area_max_secno);
F2FS_SBI_GENERAL_RW_ATTR(bggc_io_aware);
F2FS_SBI_GENERAL_RW_ATTR(max_lock_elapsed_time);
F2FS_SBI_GENERAL_RW_ATTR(lock_duration_priority);
@ -1525,6 +1526,7 @@ static struct attribute *f2fs_attrs[] = {
ATTR_LIST(max_read_extent_count),
ATTR_LIST(carve_out),
ATTR_LIST(reserved_pin_section),
ATTR_LIST(pinned_area_max_secno),
ATTR_LIST(allocate_section_hint),
ATTR_LIST(allocate_section_policy),
ATTR_LIST(max_lock_elapsed_time),