A collection of patches to make ext3 & 4 use barriers by
default, and to call blkdev_issue_flush on fsync if they
are enabled.
To ensure that bits are truly on-disk after an fsync,
ext3 should call blkdev_issue_flush if barriers are supported.
Inspired by an old thread on barriers, by reiserfs & xfs
which do the same, and by a patch SuSE ships with their kernel
Signed-off-by: Eric Sandeen <[email protected]>
---
fs/ext3/fsync.c | 5 +++++
1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/fs/ext3/fsync.c b/fs/ext3/fsync.c
index d336341..f6167ec 100644
--- a/fs/ext3/fsync.c
+++ b/fs/ext3/fsync.c
@@ -27,6 +27,7 @@
#include <linux/sched.h>
#include <linux/writeback.h>
#include <linux/jbd.h>
+#include <linux/blkdev.h>
#include <linux/ext3_fs.h>
#include <linux/ext3_jbd.h>
@@ -45,6 +46,7 @@
int ext3_sync_file(struct file * file, struct dentry *dentry, int datasync)
{
struct inode *inode = dentry->d_inode;
+ journal_t *journal = EXT3_SB(inode->i_sb)->s_journal;
int ret = 0;
J_ASSERT(ext3_journal_current_handle() == NULL);
@@ -85,6 +87,9 @@ int ext3_sync_file(struct file * file, struct dentry *dentry, int datasync)
.nr_to_write = 0, /* sys_fsync did this */
};
ret = sync_inode(inode, &wbc);
+
+ if (journal && (journal->j_flags & JFS_BARRIER))
+ blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
}
out:
return ret;
--
1.5.3.6
I can't think of any valid reason for ext4 to not use barriers when
they are available; I believe this is necessary for filesystem
integrity in the face of a volatile write cache on storage.
An administrator who trusts that the cache is sufficiently battery-
backed (and power supplies are sufficiently redundant, etc...)
can always turn it back off again.
SuSE has carried such a patch for ext3 for quite some time now.
Also document the mount option while we're at it.
Signed-off-by: Eric Sandeen <[email protected]>
---
Documentation/filesystems/ext4.txt | 12 ++++++++++--
fs/ext4/super.c | 11 +++++++++--
2 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 560f88d..0c5086d 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -139,8 +139,16 @@ commit=nrsec (*) Ext4 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
+ the jbd code. barrier=0 disables, barrier=1 enables.
+ 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.
orlov (*) This enables the new Orlov block allocator. It is
enabled by default.
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 52dd067..77b036a 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -671,6 +671,7 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs)
unsigned long def_mount_opts;
struct super_block *sb = vfs->mnt_sb;
struct ext4_sb_info *sbi = EXT4_SB(sb);
+ journal_t *journal = sbi->s_journal;
struct ext4_super_block *es = sbi->s_es;
def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
@@ -729,8 +730,13 @@ static int ext4_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");
+ /*
+ * jbd2 inherits the barrier flag from ext4, and may actually
+ * turn off barriers if a write fails, so it's the real test.
+ */
+ if (!test_opt(sb, BARRIER) ||
+ (journal && !(journal->j_flags & JBD2_BARRIER)))
+ seq_puts(seq, ",barrier=0");
if (test_opt(sb, NOBH))
seq_puts(seq, ",nobh");
if (!test_opt(sb, EXTENTS))
@@ -1890,6 +1896,7 @@ static int ext4_fill_super (struct super_block *sb, void *data, int silent)
sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
set_opt(sbi->s_mount_opt, RESERVATION);
+ set_opt(sbi->s_mount_opt, BARRIER);
/*
* turn on extents feature by default in ext4 filesystem
--
1.5.3.6
To ensure that bits are truly on-disk after an fsync,
we should call blkdev_issue_flush if barriers are supported.
Inspired by an old thread on barriers, by reiserfs & xfs
which do the same, and by a patch SuSE ships with their kernel
Signed-off-by: Eric Sandeen <[email protected]>
---
fs/ext4/fsync.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
index 1c8ba48..a45c373 100644
--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -27,6 +27,7 @@
#include <linux/sched.h>
#include <linux/writeback.h>
#include <linux/jbd2.h>
+#include <linux/blkdev.h>
#include "ext4.h"
#include "ext4_jbd2.h"
@@ -45,6 +46,7 @@
int ext4_sync_file(struct file * file, struct dentry *dentry, int datasync)
{
struct inode *inode = dentry->d_inode;
+ journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
int ret = 0;
J_ASSERT(ext4_journal_current_handle() == NULL);
@@ -85,6 +87,8 @@ int ext4_sync_file(struct file * file, struct dentry *dentry, int datasync)
.nr_to_write = 0, /* sys_fsync did this */
};
ret = sync_inode(inode, &wbc);
+ if (journal && (journal->j_flags & JBD2_BARRIER))
+ blkdev_issue_flush(inode->i_sb->s_bdev, NULL);
}
out:
return ret;
--
1.5.3.6
I can't think of any valid reason for ext3 to not use barriers when
they are available; I believe this is necessary for filesystem
integrity in the face of a volatile write cache on storage.
An administrator who trusts that the cache is sufficiently battery-
backed (and power supplies are sufficiently redundant, etc...)
can always turn it back off again.
SuSE has carried such a patch for quite some time now.
Also document the mount option while we're at it.
Signed-off-by: Eric Sandeen <[email protected]>
Acked-by: Jan Kara <[email protected]>
---
Documentation/filesystems/ext3.txt | 12 ++++++++++--
fs/ext3/super.c | 11 +++++++++--
2 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt
index b45f3c1..daab1f5 100644
--- a/Documentation/filesystems/ext3.txt
+++ b/Documentation/filesystems/ext3.txt
@@ -52,8 +52,16 @@ 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
+ the jbd code. barrier=0 disables, barrier=1 enables.
+ 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.
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 fe3119a..9c30dc7 100644
--- a/fs/ext3/super.c
+++ b/fs/ext3/super.c
@@ -555,6 +555,7 @@ static int ext3_show_options(struct seq_file *seq, struct vfsmount *vfs)
struct super_block *sb = vfs->mnt_sb;
struct ext3_sb_info *sbi = EXT3_SB(sb);
struct ext3_super_block *es = sbi->s_es;
+ journal_t *journal = sbi->s_journal;
unsigned long def_mount_opts;
def_mount_opts = le32_to_cpu(es->s_default_mount_opts);
@@ -613,8 +614,13 @@ 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");
+ /*
+ * jbd inherits the barrier flag from ext3, and may actually
+ * turn off barriers if a write fails, so it's the real test.
+ */
+ if (!test_opt(sb, BARRIER) ||
+ (journal && !(journal->j_flags & JFS_BARRIER)))
+ seq_puts(seq, ",barrier=0");
if (test_opt(sb, NOBH))
seq_puts(seq, ",nobh");
@@ -1589,6 +1595,7 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent)
sbi->s_resgid = le16_to_cpu(es->s_def_resgid);
set_opt(sbi->s_mount_opt, RESERVATION);
+ set_opt(sbi->s_mount_opt, BARRIER);
if (!parse_options ((char *) data, sb, &journal_inum, &journal_devnum,
NULL, 0))
--
1.5.3.6