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Message-ID: <20250612123444.1779509-1-wangzijie1@honor.com>
Date: Thu, 12 Jun 2025 20:34:44 +0800
From: wangzijie <wangzijie1@...or.com>
To: <linux-f2fs-devel@...ts.sourceforge.net>
CC: <bo.wu@...o.com>, <chao@...nel.org>, <jaegeuk@...nel.org>,
<linux-kernel@...r.kernel.org>, <bintian.wang@...or.com>,
<feng.han@...or.com>, <wangzijie1@...or.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: continue to allocate pinned section when gc happens EAGAIN
> 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;
}
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!
> >
> > [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;
> > }
>
>
>
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> Linux-f2fs-devel@...ts.sourceforge.net
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