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Message-ID: <7e5f3327-59c6-4c40-a3bf-3b847183f30d@kernel.org>
Date: Thu, 12 Jun 2025 22:07:17 +0800
From: Chao Yu <chao@...nel.org>
To: wangzijie <wangzijie1@...or.com>, linux-f2fs-devel@...ts.sourceforge.net
Cc: chao@...nel.org, bo.wu@...o.com, jaegeuk@...nel.org,
linux-kernel@...r.kernel.org, bintian.wang@...or.com, feng.han@...or.com
Subject: Re: [f2fs-dev] [PATCH] f2fs: continue to allocate pinned section when
gc happens EAGAIN
On 2025/6/12 20:34, wangzijie wrote:
>> On 6/12/25 11:27, wangzijie wrote:
>>> Wu Bo once mentioned a fallocate fail scenario in this link[1].
>>> After commit 3fdd89b452c2("f2fs: prevent writing without fallocate()
>>> for pinned files"), we cannot directly generate 4K size file and
>>> pin it, but we can still generate non-segment aligned pinned file:
>>>
>>> touch test_file
>>> ./f2fs_io pinfile set test_file
>>> ./f2fs_io fallocate 0 0 8192 test_file
>>> truncate -s 4096 test_file
>>
>> Well, shouldn't we avoid such case by adding check condition in setattr?
>
> Maybe like this?
>
> ---
> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> index 6bd3de64f..2f6537d9c 100644
> --- a/fs/f2fs/file.c
> +++ b/fs/f2fs/file.c
> @@ -1027,6 +1027,8 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> struct inode *inode = d_inode(dentry);
> struct f2fs_inode_info *fi = F2FS_I(inode);
> int err;
> + struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> + block_t sec_blks = CAP_BLKS_PER_SEC(sbi);
>
> if (unlikely(f2fs_cp_error(F2FS_I_SB(inode))))
> return -EIO;
> @@ -1047,6 +1049,11 @@ int f2fs_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
> !IS_ALIGNED(attr->ia_size,
> F2FS_BLK_TO_BYTES(fi->i_cluster_size)))
> return -EINVAL;
> + if (f2fs_is_pinned_file(inode) &&
> + attr->ia_size < i_size_read(inode) &&
> + !IS_ALIGNED(attr->ia_size,
> + F2FS_BLK_TO_BYTES(sec_blks)));
> + return -EINVAL;
> }
I think so, can you please send a formal patch?
>
> err = setattr_prepare(idmap, dentry, attr);
> ---
>
>>>
>>> By doing this, pin+fallocate failure(gc happens EAGAIN but f2fs shows
>>> enough spare space) may occurs.
>>>
>>> From message in commit 2e42b7f817ac("f2fs: stop allocating pinned sections
>>> if EAGAIN happens"), gc EAGAIN doesn't guarantee a free section, so we stop
>>> allocating. But after commit 48ea8b200414 ("f2fs: fix to avoid panic once
>>> fallocation fails for pinfile"), we have a way to avoid panic caused by
>>> concurrent pinfile allocation run out of free section, so I think that we
>>> can continue to allocate pinned section when gc happens EAGAIN. Even if we
>>> don't have free section, f2fs_allocate_pinning_section() can fail with ENOSPC.
>>
>> What do you think of introduce /sys/fs/f2fs/<dev>/reserved_pin_section to
>> tune @needed parameter of has_not_enough_free_secs()? If we configure it
>> w/ zero, it can avoid f2fs_gc() before preallocation.
>>
>> ---
>> fs/f2fs/f2fs.h | 3 +++
>> fs/f2fs/file.c | 5 ++---
>> fs/f2fs/super.c | 3 +++
>> fs/f2fs/sysfs.c | 9 +++++++++
>> 4 files changed, 17 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
>> index 785537576aa8..ffb15da570d7 100644
>> --- a/fs/f2fs/f2fs.h
>> +++ b/fs/f2fs/f2fs.h
>> @@ -1731,6 +1731,9 @@ struct f2fs_sb_info {
>> /* for skip statistic */
>> unsigned long long skipped_gc_rwsem; /* FG_GC only */
>>
>> + /* free sections reserved for pinned file */
>> + unsigned int reserved_pin_section;
>> +
>> /* threshold for gc trials on pinned files */
>> unsigned short gc_pin_file_threshold;
>> struct f2fs_rwsem pin_sem;
>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>> index 696131e655ed..a909f79db178 100644
>> --- a/fs/f2fs/file.c
>> +++ b/fs/f2fs/file.c
>> @@ -1887,9 +1887,8 @@ static int f2fs_expand_inode_data(struct inode *inode, loff_t offset,
>> }
>> }
>>
>> - if (has_not_enough_free_secs(sbi, 0, f2fs_sb_has_blkzoned(sbi) ?
>> - ZONED_PIN_SEC_REQUIRED_COUNT :
>> - GET_SEC_FROM_SEG(sbi, overprovision_segments(sbi)))) {
>> + if (has_not_enough_free_secs(sbi, 0,
>> + sbi->reserved_pin_section)) {
>> f2fs_down_write(&sbi->gc_lock);
>> stat_inc_gc_call_count(sbi, FOREGROUND);
>> err = f2fs_gc(sbi, &gc_control);
>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>> index 57adeff5ef25..48b97a95fd63 100644
>> --- a/fs/f2fs/super.c
>> +++ b/fs/f2fs/super.c
>> @@ -4975,6 +4975,9 @@ static int f2fs_fill_super(struct super_block *sb, struct fs_context *fc)
>> sbi->last_valid_block_count = sbi->total_valid_block_count;
>> sbi->reserved_blocks = 0;
>> sbi->current_reserved_blocks = 0;
>> + sbi->reserved_pin_section = f2fs_sb_has_blkzoned(sbi) ?
>> + ZONED_PIN_SEC_REQUIRED_COUNT :
>> + GET_SEC_FROM_SEG(sbi, overprovision_segments(sbi));
>> limit_reserve_root(sbi);
>> adjust_unusable_cap_perc(sbi);
>>
>> diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
>> index 75134d69a0bd..51be7ffb38c5 100644
>> --- a/fs/f2fs/sysfs.c
>> +++ b/fs/f2fs/sysfs.c
>> @@ -824,6 +824,13 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
>> return count;
>> }
>>
>> + if (!strcmp(a->attr.name, "reserved_pin_section")) {
>> + if (t > GET_SEC_FROM_SEG(sbi, overprovision_segments(sbi)))
>> + return -EINVAL;
>> + *ui = (unsigned int)t;
>> + return count;
>> + }
>> +
>> *ui = (unsigned int)t;
>>
>> return count;
>> @@ -1130,6 +1137,7 @@ F2FS_SBI_GENERAL_RO_ATTR(unusable_blocks_per_sec);
>> F2FS_SBI_GENERAL_RW_ATTR(blkzone_alloc_policy);
>> #endif
>> F2FS_SBI_GENERAL_RW_ATTR(carve_out);
>> +F2FS_SBI_GENERAL_RW_ATTR(reserved_pin_section);
>>
>> /* STAT_INFO ATTR */
>> #ifdef CONFIG_F2FS_STAT_FS
>> @@ -1323,6 +1331,7 @@ static struct attribute *f2fs_attrs[] = {
>> ATTR_LIST(last_age_weight),
>> ATTR_LIST(max_read_extent_count),
>> ATTR_LIST(carve_out),
>> + ATTR_LIST(reserved_pin_section),
>> NULL,
>> };
>> ATTRIBUTE_GROUPS(f2fs);
>> --
>> 2.49.0
>
> I think it's a good way to solve this problem. Thank you!
Sent a formal patch w/ below link. :)
https://lore.kernel.org/linux-f2fs-devel/20250612140526.6435-1-chao@kernel.org
Thanks,
>
>
>>>
>>> [1] https://lore.kernel.org/linux-f2fs-devel/20231030094024.263707-1-bo.wu@vivo.com/t/#u
>>>
>>> Signed-off-by: wangzijie <wangzijie1@...or.com>
>>> ---
>>> fs/f2fs/file.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
>>> index 6bd3de64f..05c80d2b5 100644
>>> --- a/fs/f2fs/file.c
>>> +++ b/fs/f2fs/file.c
>>> @@ -1859,7 +1859,7 @@ static int f2fs_expand_inode_data(struct inode *inode, loff_t offset,
>>> f2fs_down_write(&sbi->gc_lock);
>>> stat_inc_gc_call_count(sbi, FOREGROUND);
>>> err = f2fs_gc(sbi, &gc_control);
>>> - if (err && err != -ENODATA) {
>>> + if (err && err != -ENODATA && err != -EAGAIN) {
>>> f2fs_up_write(&sbi->pin_sem);
>>> goto out_err;
>>> }
>>
>>
>>
>> _______________________________________________
>> Linux-f2fs-devel mailing list
>> Linux-f2fs-devel@...ts.sourceforge.net
>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>
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