On Sat, 13 Sep 2014 16:37:53 +0200, Andreas Rohner wrote:
> 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@xxxxxxx>
Applied, thank you!
Ryusuke Konishi
> ---
> fs/nilfs2/file.c | 8 +++-----
> fs/nilfs2/ioctl.c | 8 +++-----
> fs/nilfs2/segment.c | 3 +++
> fs/nilfs2/super.c | 6 ++++++
> fs/nilfs2/the_nilfs.h | 22 ++++++++++++++++++++++
> 5 files changed, 37 insertions(+), 10 deletions(-)
>
> diff --git a/fs/nilfs2/file.c b/fs/nilfs2/file.c
> index 2497815..e9e3325 100644
> --- 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 422fb54..9a20e51 100644
> --- 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 a1a1916..0b7d2ca 100644
> --- 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 228f5bd..2e5b3ec 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 +517,9 @@ 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 d01ead1..23778d3 100644
> --- 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 */
> --
> 2.1.0
>
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