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

Jaegeuk Kim
2025-01-17T16:43:59Z

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