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

[Chao Yu <chao@kernel.org>]

On 1/14/25 02:39, 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 3 > /sys/fs/f2fs/blk/donate_caches
> 
> will reclaim 3 page cache ranges, registered by #1, #2, and #3.
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>   Documentation/ABI/testing/sysfs-fs-f2fs |  7 +++++++
>   fs/f2fs/f2fs.h                          |  4 ++++
>   fs/f2fs/shrinker.c                      | 27 +++++++++++++++++++++++++
>   fs/f2fs/sysfs.c                         |  8 ++++++++
>   4 files changed, 46 insertions(+)
> 
> diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
> index 3e1630c70d8a..6f9d8b8889fd 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@kernel.org>
>   Description:	It controls max read extent count for per-inode, the value of threshold
>   		is 10240 by default.
> +
> +What:		/sys/fs/f2fs/<disk>/donate_caches
> +Date:		December 2024
> +Contact:	"Jaegeuk Kim" <jaegeuk@kernel.org>
> +Description:	It reclaims the certian file-backed pages registered by
> +		ioctl(F2FS_IOC_DONATE_RANGE).
> +		For example, writing N tries to drop N address spaces in LRU.
> diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
> index 7ce3e3eab17a..6c434ae94cb1 100644
> --- a/fs/f2fs/f2fs.h
> +++ b/fs/f2fs/f2fs.h
> @@ -1635,6 +1635,9 @@ struct f2fs_sb_info {
>   	unsigned int warm_data_age_threshold;
>   	unsigned int last_age_weight;
>   
> +	/* control donate caches */
> +	unsigned int donate_caches;
> +
>   	/* basic filesystem units */
>   	unsigned int log_sectors_per_block;	/* log2 sectors per block */
>   	unsigned int log_blocksize;		/* log2 block size */
> @@ -4256,6 +4259,7 @@ unsigned long f2fs_shrink_count(struct shrinker *shrink,
>   			struct shrink_control *sc);
>   unsigned long f2fs_shrink_scan(struct shrinker *shrink,
>   			struct shrink_control *sc);
> +void f2fs_donate_caches(struct f2fs_sb_info *sbi);
>   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..a3e2063392a7 100644
> --- a/fs/f2fs/shrinker.c
> +++ b/fs/f2fs/shrinker.c
> @@ -130,6 +130,33 @@ unsigned long f2fs_shrink_scan(struct shrinker *shrink,
>   	return freed;
>   }
>   
> +void f2fs_donate_caches(struct f2fs_sb_info *sbi)
> +{
> +	struct inode *inode = NULL;
> +	struct f2fs_inode_info *fi;
> +	int nfiles = sbi->donate_caches;
> +next:
> +	spin_lock(&sbi->inode_lock[DONATE_INODE]);
> +	if (list_empty(&sbi->inode_list[DONATE_INODE]) || !nfiles) {
> +		spin_unlock(&sbi->inode_lock[DONATE_INODE]);
> +		return;
> +	}
> +
> +	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]);

Not needed to drop it from the global list, right?

Thanks,

> +	inode = igrab(&fi->vfs_inode);
> +	spin_unlock(&sbi->inode_lock[DONATE_INODE]);
> +
> +	if (inode) {
> +		invalidate_inode_pages2_range(inode->i_mapping,
> +			fi->donate_start, fi->donate_end);
> +		iput(inode);
> +	}
> +	if (nfiles--)
> +		goto next;
> +}
> +
>   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 6b99dc49f776..7570580ec3c0 100644
> --- a/fs/f2fs/sysfs.c
> +++ b/fs/f2fs/sysfs.c
> @@ -811,6 +811,12 @@ static ssize_t __sbi_store(struct f2fs_attr *a,
>   		return count;
>   	}
>   
> +	if (!strcmp(a->attr.name, "donate_caches")) {
> +		sbi->donate_caches = min(t, sbi->ndirty_inode[DONATE_INODE]);
> +		f2fs_donate_caches(sbi);
> +		return count;
> +	}
> +
>   	*ui = (unsigned int)t;
>   
>   	return count;
> @@ -1030,6 +1036,7 @@ F2FS_SBI_GENERAL_RW_ATTR(max_victim_search);
>   F2FS_SBI_GENERAL_RW_ATTR(migration_granularity);
>   F2FS_SBI_GENERAL_RW_ATTR(migration_window_granularity);
>   F2FS_SBI_GENERAL_RW_ATTR(dir_level);
> +F2FS_SBI_GENERAL_RW_ATTR(donate_caches);
>   #ifdef CONFIG_F2FS_IOSTAT
>   F2FS_SBI_GENERAL_RW_ATTR(iostat_enable);
>   F2FS_SBI_GENERAL_RW_ATTR(iostat_period_ms);
> @@ -1178,6 +1185,7 @@ static struct attribute *f2fs_attrs[] = {
>   	ATTR_LIST(migration_granularity),
>   	ATTR_LIST(migration_window_granularity),
>   	ATTR_LIST(dir_level),
> +	ATTR_LIST(donate_caches),
>   	ATTR_LIST(ram_thresh),
>   	ATTR_LIST(ra_nid_pages),
>   	ATTR_LIST(dirty_nats_ratio),