mm/zswap: enable zswap_ever_enabled in zswap_pool_create()

If zswap is enabled by default at boot and pool creation fails, then a
pool is later created by updating the compressor, data written to zswap is
corrupted on swapin.

Enable the static key in zswap_pool_create(), covering boot-time and
runtime pool creation with a single site.

Verified with fault injection on a stock kernel (compressor builtin,
CONFIG_ZSWAP_DEFAULT_ON=n):

  1. Boot with zswap.enabled=1; pool creation fails, init completes
     pool-less (static key off).
  2. Echo an available compressor name to zswap.compressor.
  3. Enable zswap.
  4. madvise(MADV_PAGEOUT) a pattern-verified 512 MiB region, then
     fault it back in and verify.

Step 4 reads back 131072/131072 zeroed pages (zswpin=0, zswpout=131072)
without this patch; all pages intact (zswpin=131072) with it.

Link: https://lore.kernel.org/20260906135938.3568108-1-xialonglong2025@163.com
Fixes: 2d4d2b1cfb85 ("mm: zswap: add zswap_never_enabled()")
Signed-off-by: Longlong Xia <xialonglong@kylinos.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Suggested-by: Yosry Ahmed <yosry@kernel.org>
Acked-by: Yosry Ahmed <yosry@kernel.org>
Assisted-by: Zcode:GLM-5.3
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: <stable@vger.kernel.org>

0 files changed, 0 insertions, 0 deletions