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SubjectRe: [PATCH] dm-writecache: fix compilation issue with !DAX


On Tue, 29 May 2018, Ross Zwisler wrote:

> As reported by Arnd (https://lkml.org/lkml/2018/5/28/1697), dm-writecache
> will fail with link errors in configs where DAX isn't present:
>
> drivers/md/dm-writecache.o: In function `writecache_ctr':
> dm-writecache.c:(.text+0x1fdc): undefined reference to `dax_read_lock'
> dm-writecache.c:(.text+0x2004): undefined reference to `dax_direct_access'
> dm-writecache.c:(.text+0x21cc): undefined reference to `dax_read_unlock'
>
> Fix this by following the lead of the other DM modules and wrapping calls
> to the generic DAX code in #if IS_ENABLED(CONFIG_DAX_DRIVER) blocks.
>
> We also expand the failure case for the 'p' (persistent memory) flag so
> that fails on both architectures that don't support persistent memory and
> on kernels that don't have DAX support configured. This prevents us from
> ever hitting the BUG() in the persistent_memory_claim() stub.
>
> Signed-off-by: Ross Zwisler <ross.zwisler@linux.intel.com>
> Reported-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/md/dm-writecache.c | 16 ++++++++++++----
> 1 file changed, 12 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c
> index 92af65fdf4af..1c2b53ae1a96 100644
> --- a/drivers/md/dm-writecache.c
> +++ b/drivers/md/dm-writecache.c
> @@ -253,6 +253,7 @@ static void wc_unlock(struct dm_writecache *wc)
> mutex_unlock(&wc->lock);
> }
>
> +#if IS_ENABLED(CONFIG_DAX_DRIVER)

We already have #if(n)def DM_WRITECACHE_ONLY_SSD

There is no need to use another macro for the same purpose.

Mikulas

> static int persistent_memory_claim(struct dm_writecache *wc)
> {
> int r;
> @@ -337,6 +338,12 @@ static int persistent_memory_claim(struct dm_writecache *wc)
> err1:
> return r;
> }
> +#else
> +static int persistent_memory_claim(struct dm_writecache *wc)
> +{
> + BUG();
> +}
> +#endif
>
> static void persistent_memory_release(struct dm_writecache *wc)
> {
> @@ -1901,16 +1908,17 @@ static int writecache_ctr(struct dm_target *ti, unsigned argc, char **argv)
> if (!strcasecmp(string, "s")) {
> wc->pmem_mode = false;
> } else if (!strcasecmp(string, "p")) {
> -#ifdef CONFIG_ARCH_HAS_PMEM_API
> +#if defined(CONFIG_ARCH_HAS_PMEM_API) && IS_ENABLED(CONFIG_DAX_DRIVER)
> wc->pmem_mode = true;
> wc->writeback_fua = true;
> #else
> /*
> - * If the architecture doesn't support persistent memory, this
> - * driver can only be used in SSD-only mode.
> + * If the architecture doesn't support persistent memory or
> + * the kernel doesn't support any DAX drivers, this driver can
> + * only be used in SSD-only mode.
> */
> r = -EOPNOTSUPP;
> - ti->error = "Persistent memory not supported on this architecture";
> + ti->error = "Persistent memory or DAX not supported on this system";
> goto bad;
> #endif
> } else {
> --
> 2.14.3
>

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