nilfs2: add missing blkdev_issue_flush() to nilfs_sync_fs()

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.  For convenience the function
nilfs_flush_device() is added, which contains the above logic.

Signed-off-by: Andreas Rohner <andreas.rohner@gmx.net>
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/nilfs2/file.c b/fs/nilfs2/file.c
index 24978153c0c4daefd04f2853576db34aa3e8e0fe..e9e3325f29f30cbe0c01c4433441803ff097df58 100644 (file)
--- a/fs/nilfs2/file.c
+++ b/fs/nilfs2/file.c
@@ -56,11 +56,9 @@ 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)) {
-               err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
-               if (err != -EIO)
-                       err = 0;
-       }
+       if (!err)
+               err = nilfs_flush_device(nilfs);
+
        return err;
 }
 

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 422fb54b73771f04690e16726f9a85a74c4febfd..9a20e513d7eb89ee21228e6af0a723996c4150a5 100644 (file)
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -1022,11 +1022,9 @@ 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)) {
-               ret = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
-               if (ret == -EIO)
-                       return ret;
-       }
+       ret = nilfs_flush_device(nilfs);
+       if (ret < 0)
+               return ret;
 
        if (argp != NULL) {
                down_read(&nilfs->ns_segctor_sem);

diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c
index a1a191634abc1729f94a443ab4eac4cdddaaf54c..0b7d2cad042657c09b7c84bb42b177e2b585fc7a 100644 (file)
--- a/fs/nilfs2/segment.c
+++ b/fs/nilfs2/segment.c
@@ -1833,6 +1833,7 @@ static void nilfs_segctor_complete_write(struct nilfs_sc_info *sci)
        nilfs_set_next_segment(nilfs, segbuf);
 
        if (update_sr) {
+               nilfs->ns_flushed_device = 0;
                nilfs_set_last_segment(nilfs, segbuf->sb_pseg_start,
                                       segbuf->sb_sum.seg_seq, nilfs->ns_cno++);
 
@@ -2216,6 +2217,8 @@ int nilfs_construct_dsync_segment(struct super_block *sb, struct inode *inode,
        sci->sc_dsync_end = end;
 
        err = nilfs_segctor_do_construct(sci, SC_LSEG_DSYNC);
+       if (!err)
+               nilfs->ns_flushed_device = 0;
 
        nilfs_transaction_unlock(sb);
        return err;

diff --git a/fs/nilfs2/super.c b/fs/nilfs2/super.c
index 228f5bdf07721dabae68349461eb1f24f99a2f33..2e5b3ec85b8f62c967e785697449c773fe0e1337 100644 (file)
--- 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 +517,9 @@ static int nilfs_sync_fs(struct super_block *sb, int wait)
        }
        up_write(&nilfs->ns_sem);
 
+       if (!err)
+               err = nilfs_flush_device(nilfs);
+
        return err;
 }
 

diff --git a/fs/nilfs2/the_nilfs.h b/fs/nilfs2/the_nilfs.h
index d01ead1bea9a738a5268908fe321eed19af3cc07..23778d385836f56c9cad3be7aa3cdaca2e7c1e69 100644 (file)
--- a/fs/nilfs2/the_nilfs.h
+++ b/fs/nilfs2/the_nilfs.h
@@ -46,6 +46,7 @@ enum {
 /**
  * struct the_nilfs - struct to supervise multiple nilfs mount points
  * @ns_flags: flags
+ * @ns_flushed_device: flag indicating if all volatile data was flushed
  * @ns_bdev: block device
  * @ns_sem: semaphore for shared states
  * @ns_snapshot_mount_mutex: mutex to protect snapshot mounts
@@ -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;
@@ -371,4 +373,24 @@ static inline int nilfs_segment_is_active(struct the_nilfs *nilfs, __u64 n)
        return n == nilfs->ns_segnum || n == nilfs->ns_nextnum;
 }
 
+static inline int nilfs_flush_device(struct the_nilfs *nilfs)
+{
+       int err;
+
+       if (!nilfs_test_opt(nilfs, BARRIER) || nilfs->ns_flushed_device)
+               return 0;
+
+       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(nilfs->ns_bdev, GFP_KERNEL, NULL);
+       if (err != -EIO)
+               err = 0;
+       return err;
+}
+
 #endif /* _THE_NILFS_H */