On Mon, 2022-01-31 at 17:52 +0000, David Howells wrote:
> Fix the cache volume coherency attribute check. It was copied from the
> file coherency check which uses as struct to lay out the xattr, and so
> needs to add a bit on to find the coherency data - but the volume coherency
> attribute only contains the coherency data, so we shouldn't be using the
> layout struct for it.
>
> This has passed unnoticed so far because it only affects cifs at the
> moment, and cifs had its fscache component disabled.
>
> This can now be checked by enabling CONFIG_CIFS_FSCACHE, enabling the
> following tracepoint:
>
> /sys/kernel/debug/tracing/events/cachefiles/cachefiles_vol_coherency/enable
>
> and making a cifs mount. Without this change, the trace shows a
> cachefiles_vol_coherency line with "VOL BAD cmp" in it; with this change it
> shows "VOL OK" instead.
>
> Fixes: 32e150037dce ("fscache, cachefiles: Store the volume coherency data")
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> cc: Jeff Layton <jlayton@xxxxxxxxxx>
> cc: Steve French <smfrench@xxxxxxxxx>
> cc: linux-cifs@xxxxxxxxxxxxxxx
> cc: linux-cachefs@xxxxxxxxxx
> ---
>
> fs/cachefiles/xattr.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/cachefiles/xattr.c b/fs/cachefiles/xattr.c
> index 83f41bd0c3a9..c6171e818a7c 100644
> --- a/fs/cachefiles/xattr.c
> +++ b/fs/cachefiles/xattr.c
> @@ -218,10 +218,10 @@ bool cachefiles_set_volume_xattr(struct cachefiles_volume *volume)
> */
> int cachefiles_check_volume_xattr(struct cachefiles_volume *volume)
> {
> - struct cachefiles_xattr *buf;
> struct dentry *dentry = volume->dentry;
> unsigned int len = volume->vcookie->coherency_len;
> const void *p = volume->vcookie->coherency;
> + void *buf;
> enum cachefiles_coherency_trace why;
> ssize_t xlen;
> int ret = -ESTALE;
> @@ -245,7 +245,7 @@ int cachefiles_check_volume_xattr(struct cachefiles_volume *volume)
> "Failed to read xattr with error %zd", xlen);
> }
> why = cachefiles_coherency_vol_check_xattr;
> - } else if (memcmp(buf->data, p, len) != 0) {
> + } else if (memcmp(buf, p, len) != 0) {
> why = cachefiles_coherency_vol_check_cmp;
> } else {
> why = cachefiles_coherency_vol_check_ok;
>
>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
