linux.git/fs/f2fs/segment.c, branch v6.16

f2fs: fix to skip f2fs_balance_fs() if checkpoint is disabled

2025-05-28T16:04:15+00:00

Syzbot reports a f2fs bug as below:

INFO: task syz-executor328:5856 blocked for more than 144 seconds.
      Not tainted 6.15.0-rc6-syzkaller-00208-g3c21441eeffc #0
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
task:syz-executor328 state:D stack:24392 pid:5856  tgid:5832  ppid:5826   task_flags:0x400040 flags:0x00004006
Call Trace:
 
 context_switch kernel/sched/core.c:5382 [inline]
 __schedule+0x168f/0x4c70 kernel/sched/core.c:6767
 __schedule_loop kernel/sched/core.c:6845 [inline]
 schedule+0x165/0x360 kernel/sched/core.c:6860
 io_schedule+0x81/0xe0 kernel/sched/core.c:7742
 f2fs_balance_fs+0x4b4/0x780 fs/f2fs/segment.c:444
 f2fs_map_blocks+0x3af1/0x43b0 fs/f2fs/data.c:1791
 f2fs_expand_inode_data+0x653/0xaf0 fs/f2fs/file.c:1872
 f2fs_fallocate+0x4f5/0x990 fs/f2fs/file.c:1975
 vfs_fallocate+0x6a0/0x830 fs/open.c:338
 ioctl_preallocate fs/ioctl.c:290 [inline]
 file_ioctl fs/ioctl.c:-1 [inline]
 do_vfs_ioctl+0x1b8f/0x1eb0 fs/ioctl.c:885
 __do_sys_ioctl fs/ioctl.c:904 [inline]
 __se_sys_ioctl+0x82/0x170 fs/ioctl.c:892
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xf6/0x210 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The root cause is after commit 84b5bb8bf0f6 ("f2fs: modify
f2fs_is_checkpoint_ready logic to allow more data to be written with the
CP disable"), we will get chance to allow f2fs_is_checkpoint_ready() to
return true once below conditions are all true:
1. checkpoint is disabled
2. there are not enough free segments
3. there are enough free blocks

Then it will cause f2fs_balance_fs() to trigger foreground GC.

void f2fs_balance_fs(struct f2fs_sb_info *sbi, bool need)
...
	if (!f2fs_is_checkpoint_ready(sbi))
		return;

And the testcase mounts f2fs image w/ gc_merge,checkpoint=disable, so deadloop
will happen through below race condition:

- f2fs_do_shutdown		- vfs_fallocate				- gc_thread_func
				 - file_start_write
				  - __sb_start_write(SB_FREEZE_WRITE)
				 - f2fs_fallocate
				  - f2fs_expand_inode_data
				   - f2fs_map_blocks
				    - f2fs_balance_fs
				     - prepare_to_wait
				     - wake_up(gc_wait_queue_head)
				     - io_schedule
 - bdev_freeze
  - freeze_super
   - sb->s_writers.frozen = SB_FREEZE_WRITE;
   - sb_wait_write(sb, SB_FREEZE_WRITE);
									 - if (sbi->sb->s_writers.frozen >= SB_FREEZE_WRITE) continue;
									 : cause deadloop

This patch fix to add check condition in f2fs_balance_fs(), so that if
checkpoint is disabled, we will just skip trigger foreground GC to
avoid such deadloop issue.

Meanwhile let's remove f2fs_is_checkpoint_ready() check condition in
f2fs_balance_fs(), since it's redundant, due to the main logic in the
function is to check:
a) whether checkpoint is disabled
b) there is enough free segments

f2fs_balance_fs() still has all logics after f2fs_is_checkpoint_ready()'s
removal.

Reported-by: syzbot+aa5bb5f6860e08a60450@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/linux-f2fs-devel/682d743a.a00a0220.29bc26.0289.GAE@google.com
Fixes: 84b5bb8bf0f6 ("f2fs: modify f2fs_is_checkpoint_ready logic to allow more data to be written with the CP disable")
Cc: Qi Han 
Signed-off-by: Chao Yu 
Reviewed-by: Zhiguo Niu 
Signed-off-by: Jaegeuk Kim

f2fs: add ckpt_valid_blocks to the section entry

2025-05-28T15:58:49+00:00

when performing buffered writes in a large section,
overhead is incurred due to the iteration through
ckpt_valid_blocks within the section.
when SEGS_PER_SEC is 128, this overhead accounts for 20% within
the f2fs_write_single_data_page routine.
as the size of the section increases, the overhead also grows.
to handle this problem ckpt_valid_blocks is
added within the section entries.

Test
insmod null_blk.ko nr_devices=1 completion_nsec=1  submit_queues=8
hw_queue_depth=64 max_sectors=512 bs=4096 memory_backed=1
make_f2fs /dev/block/nullb0
make_f2fs -s 128 /dev/block/nullb0
fio --bs=512k --size=1536M --rw=write --name=1
--filename=/mnt/test_dir/seq_write
--ioengine=io_uring --iodepth=64 --end_fsync=1

before
SEGS_PER_SEC 1
2556MiB/s
SEGS_PER_SEC 128
2145MiB/s

after
SEGS_PER_SEC 1
2556MiB/s
SEGS_PER_SEC 128
2556MiB/s

Signed-off-by: yohan.joung 
Reviewed-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: support FAULT_TIMEOUT

2025-05-06T15:46:55+00:00

Support to inject a timeout fault into function, currently it only
support to inject timeout to commit_atomic_write flow to reproduce
inconsistent bug, like the bug fixed by commit f098aeba04c9 ("f2fs:
fix to avoid atomicity corruption of atomic file").

By default, the new type fault will inject 1000ms timeout, and the
timeout process can be interrupted by SIGKILL.

Signed-off-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: fix to bail out in get_new_segment()

2025-05-06T15:46:54+00:00

------------[ cut here ]------------
WARNING: CPU: 3 PID: 579 at fs/f2fs/segment.c:2832 new_curseg+0x5e8/0x6dc
pc : new_curseg+0x5e8/0x6dc
Call trace:
 new_curseg+0x5e8/0x6dc
 f2fs_allocate_data_block+0xa54/0xe28
 do_write_page+0x6c/0x194
 f2fs_do_write_node_page+0x38/0x78
 __write_node_page+0x248/0x6d4
 f2fs_sync_node_pages+0x524/0x72c
 f2fs_write_checkpoint+0x4bc/0x9b0
 __checkpoint_and_complete_reqs+0x80/0x244
 issue_checkpoint_thread+0x8c/0xec
 kthread+0x114/0x1bc
 ret_from_fork+0x10/0x20

get_new_segment() detects inconsistent status in between free_segmap
and free_secmap, let's record such error into super block, and bail
out get_new_segment() instead of continue using the segment.

Signed-off-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: zone: fix to calculate first_zoned_segno correctly

2025-04-28T15:26:48+00:00

A zoned device can has both conventional zones and sequential zones,
so we should not treat first segment of zoned device as first_zoned_segno,
instead, we need to check zone type for each zone during traversing zoned
device to find first_zoned_segno.

Otherwise, for below case, first_zoned_segno will be 0, which could be
wrong.

create_null_blk 512 2 1024 1024
mkfs.f2fs -m /dev/nullb0

Testcase:

export SCRIPTS_PATH=/share/git/scripts

test multiple devices w/ zoned device
for ((i=0;i<8;i++)) do {
	zonesize=$((2<<$i))
	conzone=$((4096/$zonesize))
	seqzone=$((4096/$zonesize))
	$SCRIPTS_PATH/nullblk_create.sh 512 $zonesize $conzone $seqzone
	mkfs.f2fs -f -m /dev/vdb -c /dev/nullb0
	mount /dev/vdb /mnt/f2fs
	touch /mnt/f2fs/file
	f2fs_io pinfile set /mnt/f2fs/file $((8589934592*2))
	stat /mnt/f2fs/file
	df
	cat /proc/fs/f2fs/vdb/segment_info
	umount /mnt/f2fs
	$SCRIPTS_PATH/nullblk_remove.sh 0
} done

test single zoned device
for ((i=0;i<8;i++)) do {
	zonesize=$((2<<$i))
	conzone=$((4096/$zonesize))
	seqzone=$((4096/$zonesize))
	$SCRIPTS_PATH/nullblk_create.sh 512 $zonesize $conzone $seqzone
	mkfs.f2fs -f -m /dev/nullb0
	mount /dev/nullb0 /mnt/f2fs
	touch /mnt/f2fs/file
	f2fs_io pinfile set /mnt/f2fs/file $((8589934592*2))
	stat /mnt/f2fs/file
	df
	cat /proc/fs/f2fs/nullb0/segment_info
	umount /mnt/f2fs
	$SCRIPTS_PATH/nullblk_remove.sh 0
} done

Fixes: 9703d69d9d15 ("f2fs: support file pinning for zoned devices")
Cc: Daeho Jeong 
Signed-off-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: Convert fsync_node_entry->page to folio

2025-04-28T15:26:47+00:00

Convert all callers to set/get a folio instead of a page.  Removes
five calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: Convert dnode_of_data->node_page to node_folio

2025-04-28T15:26:47+00:00

All assignments to this struct member are conversions from a folio
so convert it to be a folio and convert all users.  At the same time,
convert data_blkaddr() to take a folio as all callers now have a folio.
Remove eight calls to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: Use a folio in f2fs_wait_on_block_writeback()

2025-04-28T15:26:46+00:00

Fetch a folio from the pagecache and use it.  Removes two calls
to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: Use a folio in change_curseg()

2025-04-28T15:26:31+00:00

Get a folio and use it.  Saves a call to compound_head().

Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Chao Yu 
Signed-off-by: Jaegeuk Kim

f2fs: Add f2fs_get_sum_folio()

2025-04-28T15:26:31+00:00

Convert f2fs_get_sum_page() to f2fs_get_sum_folio() and add a
f2fs_get_sum_page() wrapper.

Signed-off-by: Matthew Wilcox (Oracle) 
Reviewed-by: Chao Yu 
Signed-off-by: Jaegeuk Kim