Under normal circumstances nilfs_sync_fs() writes out the super block,
which causes a flush of the underlying block device. But this depends on
the THE_NILFS_SB_DIRTY flag, which is only set if the pointer to the
last segment crosses a segment boundary. So if only a small amount of
data is written before the call to nilfs_sync_fs(), no flush of the
block device occurs.
In the above case an additional call to blkdev_issue_flush() is needed.
To prevent unnecessary overhead, the new flag nilfs->ns_flushed_device
is introduced, which is cleared whenever new logs are written and set
whenever the block device is flushed.
Signed-off-by: Andreas Rohner <andreas.rohner@xxxxxxx>
---
fs/nilfs2/file.c | 10 +++++++++-
fs/nilfs2/ioctl.c | 10 +++++++++-
fs/nilfs2/segment.c | 4 ++++
fs/nilfs2/super.c | 17 +++++++++++++++++
fs/nilfs2/the_nilfs.h | 2 ++
5 files changed, 41 insertions(+), 2 deletions(-)
diff --git a/fs/nilfs2/file.c b/fs/nilfs2/file.c
index 2497815..16375c2 100644
--- a/fs/nilfs2/file.c
+++ b/fs/nilfs2/file.c
@@ -56,7 +56,15 @@ int nilfs_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
mutex_unlock(&inode->i_mutex);
nilfs = inode->i_sb->s_fs_info;
- if (!err && nilfs_test_opt(nilfs, BARRIER)) {
+ if (!err && nilfs_test_opt(nilfs, BARRIER) &&
+ !nilfs->ns_flushed_device) {
+ nilfs->ns_flushed_device = 1;
+ /*
+ * the store to ns_flushed_device must not be reordered after
+ * blkdev_issue_flush
+ */
+ smp_wmb();
+
err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
if (err != -EIO)
err = 0;
diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 422fb54..9444d5d 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -1022,7 +1022,15 @@ static int nilfs_ioctl_sync(struct inode *inode, struct file *filp,
return ret;
nilfs = inode->i_sb->s_fs_info;
- if (nilfs_test_opt(nilfs, BARRIER)) {
+ if (nilfs_test_opt(nilfs, BARRIER) &&
+ !nilfs->ns_flushed_device) {
+ nilfs->ns_flushed_device = 1;
+ /*
+ * the store to ns_flushed_device must not be reordered after
+ * blkdev_issue_flush
+ */
+ smp_wmb();
+
ret = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
if (ret == -EIO)
return ret;
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index a1a1916..379da1b 100644
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1997,6 +1997,10 @@ static int nilfs_segctor_do_construct(struct nilfs_sc_info *sci, int mode)
err = nilfs_segctor_wait(sci);
if (err)
goto failed_to_write;
+
+ if (test_bit(NILFS_SC_SUPER_ROOT, &sci->sc_flags) ||
+ mode == SC_LSEG_DSYNC)
+ nilfs->ns_flushed_device = 0;
}
} while (sci->sc_stage.scnt != NILFS_ST_DONE);
diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 228f5bd..33aafbd 100644
--- a/fs/nilfs2/super.c
+++ b/fs/nilfs2/super.c
@@ -310,6 +310,9 @@ int nilfs_commit_super(struct super_block *sb, int flag)
nilfs->ns_sbsize));
}
clear_nilfs_sb_dirty(nilfs);
+ nilfs->ns_flushed_device = 1;
+ /* make sure store to ns_flushed_device cannot be reordered */
+ smp_wmb();
return nilfs_sync_super(sb, flag);
}
@@ -514,6 +517,20 @@ static int nilfs_sync_fs(struct super_block *sb, int wait)
}
up_write(&nilfs->ns_sem);
+ if (wait && !err && nilfs_test_opt(nilfs, BARRIER) &&
+ !nilfs->ns_flushed_device) {
+ nilfs->ns_flushed_device = 1;
+ /*
+ * the store to ns_flushed_device must not be reordered after
+ * blkdev_issue_flush
+ */
+ smp_wmb();
+
+ err = blkdev_issue_flush(sb->s_bdev, GFP_KERNEL, NULL);
+ if (err != -EIO)
+ err = 0;
+ }
+
return err;
}
diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index d01ead1..dabb02c 100644
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -45,6 +45,7 @@ enum {
/**
* struct the_nilfs - struct to supervise multiple nilfs mount points
+ * @ns_flushed_device: flag indicating if all volatile data was flushed
* @ns_flags: flags
* @ns_bdev: block device
* @ns_sem: semaphore for shared states
@@ -103,6 +104,7 @@ enum {
*/
struct the_nilfs {
unsigned long ns_flags;
+ int ns_flushed_device;
struct block_device *ns_bdev;
struct rw_semaphore ns_sem;
--
2.1.0
--
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