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

[Jaegeuk Kim <jaegeuk@kernel.org>]

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                          |  2 ++
 fs/f2fs/shrinker.c                      | 27 +++++++++++++++++++++++++
 fs/f2fs/sysfs.c                         |  8 ++++++++
 4 files changed, 44 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 951fbc3f94c7..399ddd10a94f 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1637,6 +1637,7 @@ struct f2fs_sb_info {
 
 	/* control donate caches */
 	unsigned int donate_files;
+	unsigned int donate_caches;
 
 	/* basic filesystem units */
 	unsigned int log_sectors_per_block;	/* log2 sectors per block */
@@ -4259,6 +4260,7 @@ 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..22f62813910b 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;
+	struct f2fs_inode_info *fi;
+	int nfiles = sbi->donate_caches;
+
+	while (nfiles--) {
+		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;
+
+		invalidate_inode_pages2_range(inode->i_mapping,
+					fi->donate_start, fi->donate_end);
+		iput(inode);
+	}
+}
+
 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..f81190fabdd3 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->donate_files);
+		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),
-- 
2.48.0.rc2.279.g1de40edade-goog