Re: [f2fs-dev] [PATCH 2/2] f2fs: add a sysfs entry to request donate file-backed pages

[Jaegeuk Kim]

On 02/06, Chao Yu wrote:
> On 2/1/25 06:27, Jaegeuk Kim via Linux-f2fs-devel wrote:
> > 1. ioctl(fd1, F2FS_IOC_DONATE_RANGE, {0,3});
> > 2. ioctl(fd2, F2FS_IOC_DONATE_RANGE, {1,2});
> > 3. ioctl(fd3, F2FS_IOC_DONATE_RANGE, {3,1});
> > 4. echo 1024 > /sys/fs/f2fs/tuning/reclaim_caches_kb
> > 
> > This gives a way to reclaim file-backed pages by iterating all f2fs mounts until
> > reclaiming 1MB page cache ranges, registered by #1, #2, and #3.
> > 
> > 5. cat /sys/fs/f2fs/tuning/reclaim_caches_kb
> > -> gives total number of registered file ranges.
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > ---
> >  Documentation/ABI/testing/sysfs-fs-f2fs |  7 ++
> >  fs/f2fs/f2fs.h                          |  2 +
> >  fs/f2fs/shrinker.c                      | 90 +++++++++++++++++++++++++
> >  fs/f2fs/sysfs.c                         | 63 +++++++++++++++++
> >  4 files changed, 162 insertions(+)
> > 
> > diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> > index 3e1630c70d8a..81deae2af84d 100644
> > --- a/Documentation/ABI/testing/sysfs-fs-f2fs
> > +++ b/Documentation/ABI/testing/sysfs-fs-f2fs
> > @@ -828,3 +828,10 @@ Date:		November 2024
> >  Contact:	"Chao Yu" <chao@xxxxxxxxxx>
> >  Description:	It controls max read extent count for per-inode, the value of threshold
> >  		is 10240 by default.
> > +
> > +What:		/sys/fs/f2fs/tuning/reclaim_caches_kb
> > +Date:		February 2025
> > +Contact:	"Jaegeuk Kim" <jaegeuk@xxxxxxxxxx>
> > +Description:	It reclaims the given KBs of file-backed pages registered by
> > +		ioctl(F2FS_IOC_DONATE_RANGE).
> > +		For example, writing N tries to drop N KBs spaces in LRU.
> > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> > index 805585a7d2b6..bd0d8138b71d 100644
> > --- a/fs/f2fs/f2fs.h
> > +++ b/fs/f2fs/f2fs.h
> > @@ -4241,6 +4241,8 @@ unsigned long f2fs_shrink_count(struct shrinker *shrink,
> >  			struct shrink_control *sc);
> >  unsigned long f2fs_shrink_scan(struct shrinker *shrink,
> >  			struct shrink_control *sc);
> > +unsigned int f2fs_donate_files(void);
> > +void f2fs_reclaim_caches(unsigned int reclaim_caches_kb);
> >  void f2fs_join_shrinker(struct f2fs_sb_info *sbi);
> >  void f2fs_leave_shrinker(struct f2fs_sb_info *sbi);
> >  
> > diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c
> > index 83d6fb97dcae..45efff635d8e 100644
> > --- a/fs/f2fs/shrinker.c
> > +++ b/fs/f2fs/shrinker.c
> > @@ -130,6 +130,96 @@ unsigned long f2fs_shrink_scan(struct shrinker *shrink,
> >  	return freed;
> >  }
> >  
> > +unsigned int f2fs_donate_files(void)
> > +{
> > +	struct f2fs_sb_info *sbi;
> > +	struct list_head *p;
> > +	unsigned int donate_files = 0;
> > +
> > +	spin_lock(&f2fs_list_lock);
> > +	p = f2fs_list.next;
> > +	while (p != &f2fs_list) {
> > +		sbi = list_entry(p, struct f2fs_sb_info, s_list);
> > +
> > +		/* stop f2fs_put_super */
> > +		if (!mutex_trylock(&sbi->umount_mutex)) {
> > +			p = p->next;
> > +			continue;
> > +		}
> > +		spin_unlock(&f2fs_list_lock);
> > +
> > +		donate_files += sbi->donate_files;
> > +
> > +		spin_lock(&f2fs_list_lock);
> > +		p = p->next;
> > +		mutex_unlock(&sbi->umount_mutex);
> > +	}
> > +	spin_unlock(&f2fs_list_lock);
> > +
> > +	return donate_files;
> > +}
> > +
> > +static unsigned int do_reclaim_caches(struct f2fs_sb_info *sbi,
> > +				unsigned int reclaim_caches_kb)
> > +{
> > +	struct inode *inode;
> > +	struct f2fs_inode_info *fi;
> > +	unsigned int nfiles = sbi->donate_files;
> > +	pgoff_t npages = reclaim_caches_kb >> (PAGE_SHIFT - 10);
> > +
> > +	while (npages && nfiles--) {
> > +		pgoff_t len;
> > +
> > +		spin_lock(&sbi->inode_lock[DONATE_INODE]);
> > +		if (list_empty(&sbi->inode_list[DONATE_INODE])) {
> > +			spin_unlock(&sbi->inode_lock[DONATE_INODE]);
> > +			break;
> > +		}
> > +		fi = list_first_entry(&sbi->inode_list[DONATE_INODE],
> > +					struct f2fs_inode_info, gdonate_list);
> > +		list_move_tail(&fi->gdonate_list, &sbi->inode_list[DONATE_INODE]);
> > +		inode = igrab(&fi->vfs_inode);
> > +		spin_unlock(&sbi->inode_lock[DONATE_INODE]);
> > +
> > +		if (!inode)
> > +			continue;
> > +
> > +		len = fi->donate_end - fi->donate_start + 1;
> > +		npages = npages < len ? 0 : npages - len;
> > +		invalidate_inode_pages2_range(inode->i_mapping,
> > +					fi->donate_start, fi->donate_end);
> > +		iput(inode);
> > +		cond_resched();
> > +	}
> > +	return npages << (PAGE_SHIFT - 10);
> > +}
> > +
> > +void f2fs_reclaim_caches(unsigned int reclaim_caches_kb)
> > +{
> > +	struct f2fs_sb_info *sbi;
> > +	struct list_head *p;
> > +
> > +	spin_lock(&f2fs_list_lock);
> > +	p = f2fs_list.next;
> > +	while (p != &f2fs_list && reclaim_caches_kb) {
> > +		sbi = list_entry(p, struct f2fs_sb_info, s_list);
> > +
> > +		/* stop f2fs_put_super */
> > +		if (!mutex_trylock(&sbi->umount_mutex)) {
> > +			p = p->next;
> > +			continue;
> > +		}
> > +		spin_unlock(&f2fs_list_lock);
> > +
> > +		reclaim_caches_kb = do_reclaim_caches(sbi, reclaim_caches_kb);
> > +
> > +		spin_lock(&f2fs_list_lock);
> > +		p = p->next;
> > +		mutex_unlock(&sbi->umount_mutex);
> > +	}
> > +	spin_unlock(&f2fs_list_lock);
> > +}
> > +
> >  void f2fs_join_shrinker(struct f2fs_sb_info *sbi)
> >  {
> >  	spin_lock(&f2fs_list_lock);
> > diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
> > index 4bd7b17a20c8..579226a05a69 100644
> > --- a/fs/f2fs/sysfs.c
> > +++ b/fs/f2fs/sysfs.c
> > @@ -916,6 +916,39 @@ static struct f2fs_base_attr f2fs_base_attr_##_name = {		\
> >  	.show	= f2fs_feature_show,				\
> >  }
> >  
> > +static ssize_t f2fs_tune_show(struct f2fs_base_attr *a, char *buf)
> > +{
> > +	unsigned int res;
> > +
> > +	if (!strcmp(a->attr.name, "reclaim_caches_kb"))
> > +		res = f2fs_donate_files();
> > +
> > +	return sysfs_emit(buf, "%u\n", res);
> > +}
> > +
> > +static ssize_t f2fs_tune_store(struct f2fs_base_attr *a,
> > +			const char *buf, size_t count)
> > +{
> > +	unsigned long t;
> > +	int ret;
> > +
> > +	ret = kstrtoul(skip_spaces(buf), 0, &t);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (!strcmp(a->attr.name, "reclaim_caches_kb"))
> > +		f2fs_reclaim_caches(t);
> > +
> > +	return ret ? ret : count;
> 
> return count;

Applied. Thanks,

> 
> Thanks,
> 
> > +}
> > +
> > +#define F2FS_TUNE_RW_ATTR(_name)				\
> > +static struct f2fs_base_attr f2fs_base_attr_##_name = {		\
> > +	.attr = {.name = __stringify(_name), .mode = 0644 },	\
> > +	.show	= f2fs_tune_show,				\
> > +	.store	= f2fs_tune_store,				\
> > +}
> > +
> >  static ssize_t f2fs_sb_feature_show(struct f2fs_attr *a,
> >  		struct f2fs_sb_info *sbi, char *buf)
> >  {
> > @@ -1368,6 +1401,14 @@ static struct attribute *f2fs_sb_feat_attrs[] = {
> >  };
> >  ATTRIBUTE_GROUPS(f2fs_sb_feat);
> >  
> > +F2FS_TUNE_RW_ATTR(reclaim_caches_kb);
> > +
> > +static struct attribute *f2fs_tune_attrs[] = {
> > +	BASE_ATTR_LIST(reclaim_caches_kb),
> > +	NULL,
> > +};
> > +ATTRIBUTE_GROUPS(f2fs_tune);
> > +
> >  static const struct sysfs_ops f2fs_attr_ops = {
> >  	.show	= f2fs_attr_show,
> >  	.store	= f2fs_attr_store,
> > @@ -1401,6 +1442,20 @@ static struct kobject f2fs_feat = {
> >  	.kset	= &f2fs_kset,
> >  };
> >  
> > +static const struct sysfs_ops f2fs_tune_attr_ops = {
> > +	.show	= f2fs_base_attr_show,
> > +	.store	= f2fs_base_attr_store,
> > +};
> > +
> > +static const struct kobj_type f2fs_tune_ktype = {
> > +	.default_groups = f2fs_tune_groups,
> > +	.sysfs_ops	= &f2fs_tune_attr_ops,
> > +};
> > +
> > +static struct kobject f2fs_tune = {
> > +	.kset	= &f2fs_kset,
> > +};
> > +
> >  static ssize_t f2fs_stat_attr_show(struct kobject *kobj,
> >  				struct attribute *attr, char *buf)
> >  {
> > @@ -1637,6 +1692,11 @@ int __init f2fs_init_sysfs(void)
> >  	if (ret)
> >  		goto unregister_out;
> >  
> > +	ret = kobject_init_and_add(&f2fs_tune, &f2fs_tune_ktype,
> > +				   NULL, "tuning");
> > +	if (ret)
> > +		goto put_feat;
> > +
> >  	f2fs_proc_root = proc_mkdir("fs/f2fs", NULL);
> >  	if (!f2fs_proc_root) {
> >  		ret = -ENOMEM;
> > @@ -1645,6 +1705,8 @@ int __init f2fs_init_sysfs(void)
> >  
> >  	return 0;
> >  put_kobject:
> > +	kobject_put(&f2fs_tune);
> > +put_feat:
> >  	kobject_put(&f2fs_feat);
> >  unregister_out:
> >  	kset_unregister(&f2fs_kset);
> > @@ -1653,6 +1715,7 @@ int __init f2fs_init_sysfs(void)
> >  
> >  void f2fs_exit_sysfs(void)
> >  {
> > +	kobject_put(&f2fs_tune);
> >  	kobject_put(&f2fs_feat);
> >  	kset_unregister(&f2fs_kset);
> >  	remove_proc_entry("fs/f2fs", NULL);