[PATCH] f2fs: control nat_bits feature via mount option

[Chao Yu]

Introduce a new mount option "nat_bits" to control nat_bits feature,
by default nat_bits feature is disabled.

Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
 Documentation/filesystems/f2fs.rst |  2 ++
 fs/f2fs/f2fs.h                     |  1 +
 fs/f2fs/node.c                     |  3 +++
 fs/f2fs/super.c                    | 15 +++++++++++++++
 4 files changed, 21 insertions(+)

diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
index 42f28dbf2410..e15c4275862a 100644
--- a/Documentation/filesystems/f2fs.rst
+++ b/Documentation/filesystems/f2fs.rst
@@ -366,6 +366,8 @@ errors=%s		 Specify f2fs behavior on critical errors. This supports modes:
 			 pending node write	drop		keep		N/A
 			 pending meta write	keep		keep		N/A
 			 ====================== =============== =============== ========
+nat_bits		 Enable nat_bits feature to enhance full/empty nat blocks access,
+			 by default it's disabled.
 ======================== ============================================================
 
 Debugfs Entries
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 8d8917b92b5d..99ded6512d8b 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -115,6 +115,7 @@ extern const char *f2fs_fault_name[FAULT_MAX];
 #define	F2FS_MOUNT_GC_MERGE		0x02000000
 #define F2FS_MOUNT_COMPRESS_CACHE	0x04000000
 #define F2FS_MOUNT_AGE_EXTENT_CACHE	0x08000000
+#define F2FS_MOUNT_NAT_BITS		0x10000000
 
 #define F2FS_OPTION(sbi)	((sbi)->mount_opt)
 #define clear_opt(sbi, option)	(F2FS_OPTION(sbi).opt &= ~F2FS_MOUNT_##option)
diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 24085fa8493b..579955c6e03c 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -3278,6 +3278,9 @@ static int init_node_manager(struct f2fs_sb_info *sbi)
 	if (!nm_i->nat_bitmap)
 		return -ENOMEM;
 
+	if (!test_opt(sbi, NAT_BITS))
+		disable_nat_bits(sbi, true);
+
 	err = __get_nat_bitmaps(sbi);
 	if (err)
 		return err;
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 079c5d4b60b6..1b8ca7d63afe 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -191,6 +191,7 @@ enum {
 	Opt_memory_mode,
 	Opt_age_extent_cache,
 	Opt_errors,
+	Opt_nat_bits,
 	Opt_err,
 };
 
@@ -270,6 +271,7 @@ static match_table_t f2fs_tokens = {
 	{Opt_memory_mode, "memory=%s"},
 	{Opt_age_extent_cache, "age_extent_cache"},
 	{Opt_errors, "errors=%s"},
+	{Opt_nat_bits, "nat_bits"},
 	{Opt_err, NULL},
 };
 
@@ -1323,6 +1325,9 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
 			}
 			kfree(name);
 			break;
+		case Opt_nat_bits:
+			set_opt(sbi, NAT_BITS);
+			break;
 		default:
 			f2fs_err(sbi, "Unrecognized mount option \"%s\" or missing value",
 				 p);
@@ -2135,6 +2140,9 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 	else if (F2FS_OPTION(sbi).errors == MOUNT_ERRORS_PANIC)
 		seq_printf(seq, ",errors=%s", "panic");
 
+	if (test_opt(sbi, NAT_BITS))
+		seq_puts(seq, ",nat_bits");
+
 	return 0;
 }
 
@@ -2325,6 +2333,7 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 	bool no_discard = !test_opt(sbi, DISCARD);
 	bool no_compress_cache = !test_opt(sbi, COMPRESS_CACHE);
 	bool block_unit_discard = f2fs_block_unit_discard(sbi);
+	bool no_nat_bits = !test_opt(sbi, NAT_BITS);
 #ifdef CONFIG_QUOTA
 	int i, j;
 #endif
@@ -2453,6 +2462,12 @@ static int f2fs_remount(struct super_block *sb, int *flags, char *data)
 		goto restore_opts;
 	}
 
+	if (no_nat_bits == !!test_opt(sbi, NAT_BITS)) {
+		err = -EINVAL;
+		f2fs_warn(sbi, "switch nat_bits option is not allowed");
+		goto restore_opts;
+	}
+
 	if ((*flags & SB_RDONLY) && test_opt(sbi, DISABLE_CHECKPOINT)) {
 		err = -EINVAL;
 		f2fs_warn(sbi, "disabling checkpoint not compatible with read-only");
-- 
2.40.1