Patch "f2fs: introduce memory mode" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    f2fs: introduce memory mode

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     f2fs-introduce-memory-mode.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit c9b88216941edab0e607dea249f4d4d0df4776c3
Author: Daeho Jeong <daehojeong@xxxxxxxxxx>
Date:   Mon Jun 20 10:38:42 2022 -0700

    f2fs: introduce memory mode
    
    [ Upstream commit 7a8fc586180d8c57db5cc1e2acb32bb9986f642b ]
    
    Introduce memory mode to supports "normal" and "low" memory modes.
    "low" mode is to support low memory devices. Because of the nature of
    low memory devices, in this mode, f2fs will try to save memory sometimes
    by sacrificing performance. "normal" mode is the default mode and same
    as before.
    
    Signed-off-by: Daeho Jeong <daehojeong@xxxxxxxxxx>
    Reviewed-by: Chao Yu <chao@xxxxxxxxxx>
    Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
    Stable-dep-of: b0327c84e91a ("f2fs: compress: fix to avoid use-after-free on dic")
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/Documentation/filesystems/f2fs.rst b/Documentation/filesystems/f2fs.rst
index 7fe50b0bccde9..415bba41597c3 100644
--- a/Documentation/filesystems/f2fs.rst
+++ b/Documentation/filesystems/f2fs.rst
@@ -323,6 +323,11 @@ discard_unit=%s		 Control discard unit, the argument can be "block", "segment"
 			 default, it is helpful for large sized SMR or ZNS devices to
 			 reduce memory cost by getting rid of fs metadata supports small
 			 discard.
+memory=%s		 Control memory mode. This supports "normal" and "low" modes.
+			 "low" mode is introduced to support low memory devices.
+			 Because of the nature of low memory devices, in this mode, f2fs
+			 will try to save memory sometimes by sacrificing performance.
+			 "normal" mode is the default mode and same as before.
 ======================== ============================================================
 
 Debugfs Entries
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 835ef98643bd4..fb53a35f31b04 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -142,6 +142,7 @@ struct f2fs_mount_info {
 	int fsync_mode;			/* fsync policy */
 	int fs_mode;			/* fs mode: LFS or ADAPTIVE */
 	int bggc_mode;			/* bggc mode: off, on or sync */
+	int memory_mode;		/* memory mode */
 	int discard_unit;		/*
 					 * discard command's offset/size should
 					 * be aligned to this unit: block,
@@ -1330,6 +1331,13 @@ enum {
 	DISCARD_UNIT_SECTION,	/* basic discard unit is section */
 };
 
+enum {
+	MEMORY_MODE_NORMAL,	/* memory mode for normal devices */
+	MEMORY_MODE_LOW,	/* memory mode for low memry devices */
+};
+
+
+
 static inline int f2fs_test_bit(unsigned int nr, char *addr);
 static inline void f2fs_set_bit(unsigned int nr, char *addr);
 static inline void f2fs_clear_bit(unsigned int nr, char *addr);
@@ -4294,6 +4302,11 @@ static inline bool f2fs_lfs_mode(struct f2fs_sb_info *sbi)
 	return F2FS_OPTION(sbi).fs_mode == FS_MODE_LFS;
 }
 
+static inline bool f2fs_low_mem_mode(struct f2fs_sb_info *sbi)
+{
+	return F2FS_OPTION(sbi).memory_mode == MEMORY_MODE_LOW;
+}
+
 static inline bool f2fs_may_compress(struct inode *inode)
 {
 	if (IS_SWAPFILE(inode) || f2fs_is_pinned_file(inode) ||
diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 5c0b2b300aa1b..4b862e4a6a110 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -159,6 +159,7 @@ enum {
 	Opt_gc_merge,
 	Opt_nogc_merge,
 	Opt_discard_unit,
+	Opt_memory_mode,
 	Opt_err,
 };
 
@@ -236,6 +237,7 @@ static match_table_t f2fs_tokens = {
 	{Opt_gc_merge, "gc_merge"},
 	{Opt_nogc_merge, "nogc_merge"},
 	{Opt_discard_unit, "discard_unit=%s"},
+	{Opt_memory_mode, "memory=%s"},
 	{Opt_err, NULL},
 };
 
@@ -1241,6 +1243,22 @@ static int parse_options(struct super_block *sb, char *options, bool is_remount)
 			}
 			kfree(name);
 			break;
+		case Opt_memory_mode:
+			name = match_strdup(&args[0]);
+			if (!name)
+				return -ENOMEM;
+			if (!strcmp(name, "normal")) {
+				F2FS_OPTION(sbi).memory_mode =
+						MEMORY_MODE_NORMAL;
+			} else if (!strcmp(name, "low")) {
+				F2FS_OPTION(sbi).memory_mode =
+						MEMORY_MODE_LOW;
+			} else {
+				kfree(name);
+				return -EINVAL;
+			}
+			kfree(name);
+			break;
 		default:
 			f2fs_err(sbi, "Unrecognized mount option \"%s\" or missing value",
 				 p);
@@ -2012,6 +2030,11 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
 	else if (F2FS_OPTION(sbi).discard_unit == DISCARD_UNIT_SECTION)
 		seq_printf(seq, ",discard_unit=%s", "section");
 
+	if (F2FS_OPTION(sbi).memory_mode == MEMORY_MODE_NORMAL)
+		seq_printf(seq, ",memory=%s", "normal");
+	else if (F2FS_OPTION(sbi).memory_mode == MEMORY_MODE_LOW)
+		seq_printf(seq, ",memory=%s", "low");
+
 	return 0;
 }
 
@@ -2034,6 +2057,7 @@ static void default_options(struct f2fs_sb_info *sbi)
 	F2FS_OPTION(sbi).compress_ext_cnt = 0;
 	F2FS_OPTION(sbi).compress_mode = COMPR_MODE_FS;
 	F2FS_OPTION(sbi).bggc_mode = BGGC_MODE_ON;
+	F2FS_OPTION(sbi).memory_mode = MEMORY_MODE_NORMAL;
 
 	sbi->sb->s_flags &= ~SB_INLINECRYPT;