On Tue, Nov 28, 2017 at 6:40 AM, Chengguang Xu <cgxu@xxxxxxxxxxxx> wrote:
> Executes filesystem sync or umount on overlayfs, dirty data does not be synced as expected on upper filesystem.
> This patch fixes sync filesystem method to keep data consistency for overlayfs.
>
> Signed-off-by: Chengguang Xu <cgxu@xxxxxxxxxxxx>
> ---
> fs/overlayfs/super.c | 24 ++++++++++++++++++++----
> 1 file changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
> index f5738e9..9c54345 100644
> --- a/fs/overlayfs/super.c
> +++ b/fs/overlayfs/super.c
> @@ -17,6 +17,7 @@
> #include <linux/statfs.h>
> #include <linux/seq_file.h>
> #include <linux/posix_acl_xattr.h>
> +#include <linux/writeback.h>
> #include "overlayfs.h"
> #include "ovl_entry.h"
>
> @@ -231,6 +232,7 @@ static void ovl_put_super(struct super_block *sb)
> kfree(ufs);
> }
>
> +/* Sync real dirty inodes in upper filesystem (if it exists) */
> static int ovl_sync_fs(struct super_block *sb, int wait)
> {
> struct ovl_fs *ufs = sb->s_fs_info;
> @@ -240,12 +242,26 @@ static int ovl_sync_fs(struct super_block *sb, int wait)
> if (!ufs->upper_mnt)
> return 0;
> upper_sb = ufs->upper_mnt->mnt_sb;
> - if (!upper_sb->s_op->sync_fs)
> - return 0;
>
> - /* real inodes have already been synced by sync_filesystem(ovl_sb) */
> down_read(&upper_sb->s_umount);
> - ret = upper_sb->s_op->sync_fs(upper_sb, wait);
> + if (wait)
> + sync_inodes_sb(upper_sb);
> + else
> + writeback_inodes_sb(upper_sb, WB_REASON_SYNC);
> +
> + if (upper_sb->s_op->sync_fs)
> + upper_sb->s_op->sync_fs(upper_sb, wait);
> +
> + if (!upper_sb->s_bdev) {
> + up_read(&upper_sb->s_umount);
> + return 0;
> + }
> +
> + if (wait)
> + ret = filemap_write_and_wait(upper_sb->s_bdev->bd_inode->i_mapping);
> + else
> + ret = filemap_flush(upper_sb->s_bdev->bd_inode->i_mapping);
> +
> up_read(&upper_sb->s_umount);
> return ret;
> }
Unless I am missing something subtle here, you should export vfs
__sync_filesystem and call it from here instead of duplicating it.
Any technical reason not to do it?
Amir.
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