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Message-ID: <4BDB00BE.7040600@redhat.com>
Date: Fri, 30 Apr 2010 11:09:34 -0500
From: Eric Sandeen <sandeen@...hat.com>
To: ext4 development <linux-ext4@...r.kernel.org>
CC: Jan Kara <jack@...e.cz>
Subject: [PATCH] ext3: make barrier options consistent with ext4
ext4 was updated to accept barrier/nobarrier mount options
in addition to the older barrier=0/1. The barrier story
is complex enough, we should help people by making the options
the same at least, even if the defaults are different.
This patch allows the barrier/nobarrier mount options for ext3,
while keeping nobarrier the default.
It also unconditionally displays barrier status in show_options,
and prints a message at mount time if barriers are not enabled,
just as ext4 does.
Signed-off-by: Eric Sandeen <sandeen@...hat.com>
---
diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt
index 867c5b5..272f80d 100644
--- a/Documentation/filesystems/ext3.txt
+++ b/Documentation/filesystems/ext3.txt
@@ -59,8 +59,19 @@ commit=nrsec (*) Ext3 can be told to sync all its data and metadata
Setting it to very large values will improve
performance.
-barrier=1 This enables/disables barriers. barrier=0 disables
- it, barrier=1 enables it.
+barrier=<0(*)|1> This enables/disables the use of write barriers in
+barrier the jbd code. barrier=0 disables, barrier=1 enables.
+nobarrier (*) This also requires an IO stack which can support
+ barriers, and if jbd gets an error on a barrier
+ write, it will disable again with a warning.
+ Write barriers enforce proper on-disk ordering
+ of journal commits, making volatile disk write caches
+ safe to use, at some performance penalty. If
+ your disks are battery-backed in one way or another,
+ disabling barriers may safely improve performance.
+ The mount options "barrier" and "nobarrier" can
+ also be used to enable or disable barriers, for
+ consistency with other ext3 mount options.
orlov (*) This enables the new Orlov block allocator. It is
enabled by default.
diff --git a/fs/ext3/super.c b/fs/ext3/super.c
index 1bee604..5e7463d 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -653,8 +653,12 @@ static int ext3_show_options(struct seq_file *seq, struct vfsmount *vfs)
seq_printf(seq, ",commit=%u",
(unsigned) (sbi->s_commit_interval / HZ));
}
- if (test_opt(sb, BARRIER))
- seq_puts(seq, ",barrier=1");
+
+ /*
+ * Always display barrier state so it's clear what the status is.
+ */
+ seq_puts(seq, ",barrier=");
+ seq_puts(seq, test_opt(sb, BARRIER) ? "1" : "0");
if (test_opt(sb, NOBH))
seq_puts(seq, ",nobh");
@@ -810,8 +814,8 @@ enum {
Opt_data_err_abort, Opt_data_err_ignore,
Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_jqfmt_vfsv1, Opt_quota,
- Opt_noquota, Opt_ignore, Opt_barrier, Opt_err, Opt_resize,
- Opt_usrquota, Opt_grpquota
+ Opt_noquota, Opt_ignore, Opt_barrier, Opt_nobarrier, Opt_err,
+ Opt_resize, Opt_usrquota, Opt_grpquota
};
static const match_table_t tokens = {
@@ -865,6 +869,8 @@ static const match_table_t tokens = {
{Opt_quota, "quota"},
{Opt_usrquota, "usrquota"},
{Opt_barrier, "barrier=%u"},
+ {Opt_barrier, "barrier"},
+ {Opt_nobarrier, "nobarrier"},
{Opt_resize, "resize"},
{Opt_err, NULL},
};
@@ -967,7 +973,11 @@ static int parse_options (char *options, struct super_block *sb,
int token;
if (!*p)
continue;
-
+ /*
+ * Initialize args struct so we know whether arg was
+ * found; some options take optional arguments.
+ */
+ args[0].to = args[0].from = 0;
token = match_token(p, tokens, args);
switch (token) {
case Opt_bsd_df:
@@ -1215,9 +1225,15 @@ set_qf_format:
case Opt_abort:
set_opt(sbi->s_mount_opt, ABORT);
break;
+ case Opt_nobarrier:
+ clear_opt(sbi->s_mount_opt, BARRIER);
+ break;
case Opt_barrier:
- if (match_int(&args[0], &option))
- return 0;
+ if (args[0].from) {
+ if (match_int(&args[0], &option))
+ return 0;
+ } else
+ option = 1; /* No argument, default to 1 */
if (option)
set_opt(sbi->s_mount_opt, BARRIER);
else
@@ -2278,6 +2294,9 @@ static int ext3_load_journal(struct super_block *sb,
return -EINVAL;
}
+ if (!(journal->j_flags & JFS_BARRIER))
+ printk(KERN_INFO "EXT3-fs: barriers not enabled\n");
+
if (!really_read_only && test_opt(sb, UPDATE_JOURNAL)) {
err = journal_update_format(journal);
if (err) {
--
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