[Cluster-devel] [PATCH 3/3] gfs2: Add a crc field to resource group headers

[Steven Whitehouse]

On 07/12/17 11:52, Andrew Price wrote:
> Add the rg_crc field to store a crc32 of the gfs2_rgrp structure. This
> allows us to check resource group headers' integrity and removes the
> requirement to check them against the rindex entries in fsck. If this
> field is found to be zero, it should be ignored (or updated with an
> accurate value).
>
> Signed-off-by: Andrew Price <anprice at redhat.com>
> ---
>   fs/gfs2/rgrp.c                   | 5 +++++
>   include/uapi/linux/gfs2_ondisk.h | 3 ++-
>   2 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
> index 9a6fa21a2f5a..80e020fc117f 100644
> --- a/fs/gfs2/rgrp.c
> +++ b/fs/gfs2/rgrp.c
> @@ -34,6 +34,7 @@
>   #include "log.h"
>   #include "inode.h"
>   #include "trace_gfs2.h"
> +#include "dir.h"
>   
>   #define BFITNOENT ((u32)~0)
>   #define NO_BLOCK ((u64)~0)
> @@ -1047,6 +1048,7 @@ static void gfs2_rgrp_out(struct gfs2_rgrpd *rgd, void *buf)
>   {
>   	struct gfs2_rgrpd *next = gfs2_rgrpd_get_next(rgd);
>   	struct gfs2_rgrp *str = buf;
> +	u32 crc;
>   
>   	str->rg_flags = cpu_to_be32(rgd->rd_flags & ~GFS2_RDF_MASK);
>   	str->rg_free = cpu_to_be32(rgd->rd_free);
> @@ -1057,6 +1059,9 @@ static void gfs2_rgrp_out(struct gfs2_rgrpd *rgd, void *buf)
>   	str->rg_data0 = cpu_to_be64(rgd->rd_data0);
>   	str->rg_data = cpu_to_be64(rgd->rd_data);
>   	str->rg_bitbytes = cpu_to_be64(rgd->rd_bitbytes);
> +	str->rg_crc = 0;
> +	crc = gfs2_disk_hash(buf, sizeof(struct gfs2_rgrp));
> +	str->rg_crc = cpu_to_be32(crc);
>   
>   	memset(&str->rg_reserved, 0, sizeof(str->rg_reserved));
>   }
> diff --git a/include/uapi/linux/gfs2_ondisk.h b/include/uapi/linux/gfs2_ondisk.h
> index 648e0cbca574..09f0920f07e9 100644
> --- a/include/uapi/linux/gfs2_ondisk.h
> +++ b/include/uapi/linux/gfs2_ondisk.h
> @@ -197,8 +197,9 @@ struct gfs2_rgrp {
>   	__be64 rg_data0;     /* First data location */
>   	__be32 rg_data;      /* Number of data blocks in rgrp */
>   	__be32 rg_bitbytes;  /* Number of bytes in data bitmaps */
> +	__be32 rg_crc;       /* crc32 of the structure with this field 0 */
In this case because rg_crc is followed by another structure element, if 
that element is 64 bit aligned, then there might be a gap here. Worth 
checking that the overall structure size has not changed, and might be 
worth adding an explicit 32 bit pad field to pair up with the crc too, 
and reducing the reserved field by another 4 bytes.
>   
> -	__u8 rg_reserved[64]; /* Several fields from gfs1 now reserved */
> +	__u8 rg_reserved[60]; /* Several fields from gfs1 now reserved */
>   };
>   
>   /*

Otherwise the patches look good, and this should be a major step forward 
for fsck in due course,

Steve.