[PATCH] f2fs: add carve_out sysfs node

[Daeho Jeong <daeho43@gmail.com>]

From: Daeho Jeong <daehojeong@google.com>

For several zoned storage devices, vendors will provide extra space
which was used for device level GC than specs and F2FS can use this
space for filesystem level GC. To do that, we can reserve the space
using reserved_blocks. However, it is not enough, since this extra
space should not be shown to users. So, with this new sysfs node,
we can hide the space by substracting reserved_blocks from total
bytes.

Signed-off-by: Daeho Jeong <daehojeong@google.com>
---
 Documentation/ABI/testing/sysfs-fs-f2fs | 10 ++++++++++
 fs/f2fs/f2fs.h                          |  3 +++
 fs/f2fs/super.c                         |  3 ++-
 fs/f2fs/sysfs.c                         |  2 ++
 4 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Documentation/ABI/testing/sysfs-fs-f2fs b/Documentation/ABI/testing/sysfs-fs-f2fs
index 3e1630c70d8a..6e327fdc6ef4 100644
--- a/Documentation/ABI/testing/sysfs-fs-f2fs
+++ b/Documentation/ABI/testing/sysfs-fs-f2fs
@@ -828,3 +828,13 @@ 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>/carve_out
+Date:		March 2025
+Contact:	"Daeho Jeong" <daehojeong@google.com>
+Description:	For several zoned storage devices, vendors will provide extra space which
+		was used for device level GC than specs and F2FS can use this space for
+		filesystem level GC. To do that, we can reserve the space using
+		reserved_blocks. However, it is not enough, since this extra space should
+		not be shown to users. So, with this new sysfs node, we can hide the space
+		by substracting reserved_blocks from total bytes.
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 1afa7be16e7d..5718996c42a8 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1800,6 +1800,9 @@ struct f2fs_sb_info {
 	u64 committed_atomic_block;
 	u64 revoked_atomic_block;
 
+	/* carve out reserved_blocks from total blocks */
+	bool carve_out;
+
 #ifdef CONFIG_F2FS_FS_COMPRESSION
 	struct kmem_cache *page_array_slab;	/* page array entry */
 	unsigned int page_array_slab_size;	/* default page array slab size */
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 19b67828ae32..42651ec824f9 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -1836,7 +1836,8 @@ static int f2fs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_blocks = total_count - start_count;
 
 	spin_lock(&sbi->stat_lock);
-
+	if (sbi->carve_out)
+		buf->f_blocks -= sbi->current_reserved_blocks;
 	user_block_count = sbi->user_block_count;
 	total_valid_node_count = valid_node_count(sbi);
 	avail_node_count = sbi->total_node_count - F2FS_RESERVED_NODE_NUM;
diff --git a/fs/f2fs/sysfs.c b/fs/f2fs/sysfs.c
index d15c68b28952..a50f5cfe9fa9 100644
--- a/fs/f2fs/sysfs.c
+++ b/fs/f2fs/sysfs.c
@@ -1065,6 +1065,7 @@ F2FS_SBI_GENERAL_RW_ATTR(max_read_extent_count);
 F2FS_SBI_GENERAL_RO_ATTR(unusable_blocks_per_sec);
 F2FS_SBI_GENERAL_RW_ATTR(blkzone_alloc_policy);
 #endif
+F2FS_SBI_GENERAL_RW_ATTR(carve_out);
 
 /* STAT_INFO ATTR */
 #ifdef CONFIG_F2FS_STAT_FS
@@ -1252,6 +1253,7 @@ static struct attribute *f2fs_attrs[] = {
 	ATTR_LIST(warm_data_age_threshold),
 	ATTR_LIST(last_age_weight),
 	ATTR_LIST(max_read_extent_count),
+	ATTR_LIST(carve_out),
 	NULL,
 };
 ATTRIBUTE_GROUPS(f2fs);
-- 
2.49.0.rc0.332.g42c0ae87b1-goog