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Subject[PATCH 21/49] ext4: Make the length of the mb_history file tunable
Date
From: Curt Wohlgemuth <curtw@google.com>

In memory-constrained systems with many partitions, the ~68K for each
partition for the mb_history buffer can be excessive.

This patch adds a new mount option, mb_history_length, as well as a
way of setting the default via a module parameter (or via a sysfs
parameter in /sys/module/ext4/parameter/default_mb_history_length).
If the mb_history_length is set to zero, the mb_history facility is
disabled entirely.

Signed-off-by: Curt Wohlgemuth <curtw@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/ext4/mballoc.c | 13 +++++++------
fs/ext4/super.c | 18 +++++++++++++++++-
2 files changed, 24 insertions(+), 7 deletions(-)
diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index dbd47ea..df75855 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2413,7 +2413,8 @@ static void ext4_mb_history_release(struct super_block *sb)

if (sbi->s_proc != NULL) {
remove_proc_entry("mb_groups", sbi->s_proc);
- remove_proc_entry("mb_history", sbi->s_proc);
+ if (sbi->s_mb_history_max)
+ remove_proc_entry("mb_history", sbi->s_proc);
}
kfree(sbi->s_mb_history);
}
@@ -2424,17 +2425,17 @@ static void ext4_mb_history_init(struct super_block *sb)
int i;

if (sbi->s_proc != NULL) {
- proc_create_data("mb_history", S_IRUGO, sbi->s_proc,
- &ext4_mb_seq_history_fops, sb);
+ if (sbi->s_mb_history_max)
+ proc_create_data("mb_history", S_IRUGO, sbi->s_proc,
+ &ext4_mb_seq_history_fops, sb);
proc_create_data("mb_groups", S_IRUGO, sbi->s_proc,
&ext4_mb_seq_groups_fops, sb);
}

- sbi->s_mb_history_max = 1000;
sbi->s_mb_history_cur = 0;
spin_lock_init(&sbi->s_mb_history_lock);
i = sbi->s_mb_history_max * sizeof(struct ext4_mb_history);
- sbi->s_mb_history = kzalloc(i, GFP_KERNEL);
+ sbi->s_mb_history = i ? kzalloc(i, GFP_KERNEL) : NULL;
/* if we can't allocate history, then we simple won't use it */
}

@@ -2444,7 +2445,7 @@ ext4_mb_store_history(struct ext4_allocation_context *ac)
struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
struct ext4_mb_history h;

- if (unlikely(sbi->s_mb_history == NULL))
+ if (sbi->s_mb_history == NULL)
return;

if (!(ac->ac_op & sbi->s_mb_history_filter))
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7903f20..39223a5 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -47,6 +47,13 @@
#include "xattr.h"
#include "acl.h"

+static int default_mb_history_length = 1000;
+
+module_param_named(default_mb_history_length, default_mb_history_length,
+ int, 0644);
+MODULE_PARM_DESC(default_mb_history_length,
+ "Default number of entries saved for mb_history");
+
struct proc_dir_entry *ext4_proc_root;
static struct kset *ext4_kset;

@@ -1042,7 +1049,7 @@ enum {
Opt_journal_update, Opt_journal_dev,
Opt_journal_checksum, Opt_journal_async_commit,
Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
- Opt_data_err_abort, Opt_data_err_ignore,
+ Opt_data_err_abort, Opt_data_err_ignore, Opt_mb_history_length,
Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
Opt_ignore, Opt_barrier, Opt_nobarrier, Opt_err, Opt_resize,
@@ -1088,6 +1095,7 @@ static const match_table_t tokens = {
{Opt_data_writeback, "data=writeback"},
{Opt_data_err_abort, "data_err=abort"},
{Opt_data_err_ignore, "data_err=ignore"},
+ {Opt_mb_history_length, "mb_history_length=%u"},
{Opt_offusrjquota, "usrjquota="},
{Opt_usrjquota, "usrjquota=%s"},
{Opt_offgrpjquota, "grpjquota="},
@@ -1329,6 +1337,13 @@ static int parse_options(char *options, struct super_block *sb,
case Opt_data_err_ignore:
clear_opt(sbi->s_mount_opt, DATA_ERR_ABORT);
break;
+ case Opt_mb_history_length:
+ if (match_int(&args[0], &option))
+ return 0;
+ if (option < 0)
+ return 0;
+ sbi->s_mb_history_max = option;
+ break;
#ifdef CONFIG_QUOTA
case Opt_usrjquota:
qtype = USRQUOTA;
@@ -2345,6 +2360,7 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
sbi->s_commit_interval = JBD2_DEFAULT_MAX_COMMIT_AGE * HZ;
sbi->s_min_batch_time = EXT4_DEF_MIN_BATCH_TIME;
sbi->s_max_batch_time = EXT4_DEF_MAX_BATCH_TIME;
+ sbi->s_mb_history_max = default_mb_history_length;

set_opt(sbi->s_mount_opt, BARRIER);

--
1.6.3.2.1.gb9f7d.dirty


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