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

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Message-ID: <3e95b4e9-aef7-478b-aa16-1fa167182f02@kernel.org>
Date: Wed, 15 Jan 2025 10:17:21 +0800
From: Chao Yu <chao@...nel.org>
To: Jaegeuk Kim <jaegeuk@...nel.org>
Cc: chao@...nel.org, linux-kernel@...r.kernel.org,
 linux-f2fs-devel@...ts.sourceforge.net
Subject: Re: [f2fs-dev] [PATCH 2/2] f2fs: add a sysfs entry to request donate
 file-backed pages

On 1/15/25 01:18, Jaegeuk Kim wrote:
> On 01/14, Chao Yu wrote:
>> 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@...nel.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@...nel.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@...nel.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?
> 
> Yea, there're two paths to drop: 1) waiting for evict_inode, 2) setting a new
> range having len=0.

Second way just relocate entry to list tail, not drop it from list?

Thanks,

> 
>>
>> 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),