2011-05-19 02:11:45

by Robin Dong

Subject: [PATCH] ext4: fix the incorrect info of /proc/mounts after mount no-journal fs

After mkfs without journal:

# mkfs.ext4 -O ^has_journal /dev/sda
# mount -t ext4 /dev/sda /test

the /proc/mounts will show:
"/dev/sda /test ext4 rw,relatime,user_xattr,acl,barrier=1,data=writeback 0 0"
which usually make users think the fs is using writeback-mode.

Signed-off-by: Robin Dong <[email protected]>
---
fs/ext4/super.c | 3 ++-
1 files changed, 2 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 8553dfb..4ea1e85 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3474,7 +3474,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
goto failed_mount_wq;
} else {
clear_opt(sb, DATA_FLAGS);
- set_opt(sb, WRITEBACK_DATA);
+ if (EXT4_HAS_COMPAT_FEATURE(sb, EXT4_FEATURE_COMPAT_HAS_JOURNAL))
+ set_opt(sb, WRITEBACK_DATA);
sbi->s_journal = NULL;
needs_recovery = 0;
goto no_journal;
--
1.7.1

2011-05-22 20:12:24

by Theodore Ts'o

Subject: Re: [PATCH] ext4: fix the incorrect info of /proc/mounts after mount no-journal fs

On Thu, May 19, 2011 at 10:11:34AM +0800, Robin Dong wrote:
> After mkfs without journal:
>
> # mkfs.ext4 -O ^has_journal /dev/sda
> # mount -t ext4 /dev/sda /test
>
> the /proc/mounts will show:
> "/dev/sda /test ext4 rw,relatime,user_xattr,acl,barrier=1,data=writeback 0 0"
> which usually make users think the fs is using writeback-mode.
>
> Signed-off-by: Robin Dong <[email protected]>

It's actually better to simply always not set WRITEBACK_DATA() if we
are not journaling (either because of a noload mount option or because
the file systme doesn't have a journal).

- Ted

commit d0e5cab82ecbe5578d3d17b90ba3515918ea0b9f
Author: Theodore Ts'o <[email protected]>
Date: Sun May 22 16:10:01 2011 -0400

ext4: don't show mount options in /proc/mounts if there is no journal

After creating an ext4 file system without a journal:

# mke2fs -t ext4 -O ^has_journal /dev/sda
# mount -t ext4 /dev/sda /test

the /proc/mounts will show:
"/dev/sda /test ext4 rw,relatime,user_xattr,acl,barrier=1,data=writeback 0 0"
which can fool users into thinking that the fs is using writeback mode.

So don't set the writeback option when the journal has not been
enabled; we don't depend on the writeback option being set, since
ext4_should_writeback_data() in ext4_jbd2.h tests to see if the
journal is not present before returning true.

Reported-by: Robin Dong <[email protected]>
Signed-off-by: "Theodore Ts'o" <[email protected]>

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index ed5e80e..fdce4ee 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -3485,7 +3485,6 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
goto failed_mount_wq;
} else {
clear_opt(sb, DATA_FLAGS);
- set_opt(sb, WRITEBACK_DATA);
sbi->s_journal = NULL;
needs_recovery = 0;
goto no_journal;