[PATCH] iomap: fsync swap files before iterating mappings

[PATCH] iomap: fsync swap files before iterating mappings

[Darrick J. Wong]

From: Darrick J. Wong <darrick.wong@oracle.com>

Swap files require that all the file mapping metadata be stable on disk.
It is insufficient to flush dirty pages in the page cache because that
won't necessarily result in filesystems pushing all their metadata out
to disk.  Therefore, call fsync from iomap_swapfile_activate.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
 fs/iomap.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/iomap.c b/fs/iomap.c
index 206539d369a8..48622bbbd751 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -1387,7 +1387,11 @@ int iomap_swapfile_activate(struct swap_info_struct *sis,
 	loff_t len = ALIGN_DOWN(i_size_read(inode), PAGE_SIZE);
 	loff_t ret;
 
-	ret = filemap_write_and_wait(inode->i_mapping);
+	/*
+	 * Persist all file mapping metadata so that we won't have any
+	 * IOMAP_F_DIRTY iomaps.
+	 */
+	ret = vfs_fsync(swap_file, 0);
 	if (ret)
 		return ret;
 

Re: [PATCH] iomap: fsync swap files before iterating mappings

[Christoph Hellwig]

On Tue, Jun 05, 2018 at 09:16:05AM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@oracle.com>
> 
> Swap files require that all the file mapping metadata be stable on disk.
> It is insufficient to flush dirty pages in the page cache because that
> won't necessarily result in filesystems pushing all their metadata out
> to disk.  Therefore, call fsync from iomap_swapfile_activate.
> 
> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
> ---
>  fs/iomap.c |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 206539d369a8..48622bbbd751 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -1387,7 +1387,11 @@ int iomap_swapfile_activate(struct swap_info_struct *sis,
>  	loff_t len = ALIGN_DOWN(i_size_read(inode), PAGE_SIZE);
>  	loff_t ret;
>  
> -	ret = filemap_write_and_wait(inode->i_mapping);
> +	/*
> +	 * Persist all file mapping metadata so that we won't have any
> +	 * IOMAP_F_DIRTY iomaps.
> +	 */
> +	ret = vfs_fsync(swap_file, 0);

datasync semantics should be more than enough, so you can pass 1 here..