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Subject[PATCH 1/5] f2fs: add mount option for segment allocation policy
Date
This patch adds an mount option, "alloc_mode=%s" having two options, "default"
and "reuse".

In "alloc_mode=reuse" case, f2fs starts to allocate segments from 0'th segment
all the time to reassign segments. It'd be useful for small-sized eMMC parts.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
---
fs/f2fs/f2fs.h | 8 ++++++++
fs/f2fs/segment.c | 5 +++++
fs/f2fs/super.c | 24 ++++++++++++++++++++++++
3 files changed, 37 insertions(+)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index 4e79a7b6f2e9..1ed17ec682ef 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -1043,6 +1043,11 @@ enum {
WHINT_MODE_FS, /* pass down hints with F2FS policy */
};

+enum {
+ ALLOC_MODE_DEFAULT, /* stay default */
+ ALLOC_MODE_REUSE, /* reuse segments as much as possible */
+};
+
struct f2fs_sb_info {
struct super_block *sb; /* pointer to VFS super block */
struct proc_dir_entry *s_proc; /* proc entry */
@@ -1229,6 +1234,9 @@ struct f2fs_sb_info {
#endif
/* For which write hints are passed down to block layer */
int whint_mode;
+
+ /* segment allocation policy */
+ int alloc_mode;
};

#ifdef CONFIG_F2FS_FAULT_INJECTION
diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
index 0646d5de8cd0..5e5e2936a26a 100644
--- a/fs/f2fs/segment.c
+++ b/fs/f2fs/segment.c
@@ -2170,6 +2170,11 @@ static unsigned int __get_next_segno(struct f2fs_sb_info *sbi, int type)

if (SIT_I(sbi)->last_victim[ALLOC_NEXT])
return SIT_I(sbi)->last_victim[ALLOC_NEXT];
+
+ /* find segments from 0 to reuse freed segments */
+ if (sbi->alloc_mode == ALLOC_MODE_REUSE)
+ return 0;
+
return CURSEG_I(sbi, type)->segno;
}

diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
index 2e4f5673d65d..b7c0bdd1e532 100644
--- a/fs/f2fs/super.c
+++ b/fs/f2fs/super.c
@@ -130,6 +130,7 @@ enum {
Opt_jqfmt_vfsv0,
Opt_jqfmt_vfsv1,
Opt_whint,
+ Opt_alloc,
Opt_err,
};

@@ -184,6 +185,7 @@ static match_table_t f2fs_tokens = {
{Opt_jqfmt_vfsv0, "jqfmt=vfsv0"},
{Opt_jqfmt_vfsv1, "jqfmt=vfsv1"},
{Opt_whint, "whint_mode=%s"},
+ {Opt_alloc, "alloc_mode=%s"},
{Opt_err, NULL},
};

@@ -700,6 +702,23 @@ static int parse_options(struct super_block *sb, char *options)
}
kfree(name);
break;
+ case Opt_alloc:
+ name = match_strdup(&args[0]);
+ if (!name)
+ return -ENOMEM;
+
+ if (strlen(name) == 7 &&
+ !strncmp(name, "default", 7)) {
+ sbi->alloc_mode = ALLOC_MODE_DEFAULT;
+ } else if (strlen(name) == 5 &&
+ !strncmp(name, "reuse", 5)) {
+ sbi->alloc_mode = ALLOC_MODE_REUSE;
+ } else {
+ kfree(name);
+ return -EINVAL;
+ }
+ kfree(name);
+ break;
default:
f2fs_msg(sb, KERN_ERR,
"Unrecognized mount option \"%s\" or missing value",
@@ -1264,6 +1283,10 @@ static int f2fs_show_options(struct seq_file *seq, struct dentry *root)
else if (sbi->whint_mode == WHINT_MODE_FS)
seq_printf(seq, ",whint_mode=%s", "fs-based");

+ if (sbi->alloc_mode == ALLOC_MODE_DEFAULT)
+ seq_printf(seq, ",alloc_mode=%s", "default");
+ else if (sbi->alloc_mode == ALLOC_MODE_REUSE)
+ seq_printf(seq, ",alloc_mode=%s", "reuse");
return 0;
}

@@ -1273,6 +1296,7 @@ static void default_options(struct f2fs_sb_info *sbi)
sbi->active_logs = NR_CURSEG_TYPE;
sbi->inline_xattr_size = DEFAULT_INLINE_XATTR_ADDRS;
sbi->whint_mode = WHINT_MODE_OFF;
+ sbi->alloc_mode = ALLOC_MODE_DEFAULT;

set_opt(sbi, BG_GC);
set_opt(sbi, INLINE_XATTR);
--
2.15.0.531.g2ccb3012c9-goog
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