zram: do not allocate physically contiguous strm buffers

Currently zram allocates 2 physically contiguous pages per-CPU's
compression stream (we may have up to 4 streams per-CPU).  Since those
buffers are per-CPU we allocate them from CPU hotplug path, which may have
higher risks of failed allocations on devices with fragmented memory.

Switch to virtually contiguous allocations - crypto comp does not seem
impose requirements on compression working buffers to be physically
contiguous.

Link: https://lkml.kernel.org/r/20240213065400.6561-1-21cnbao@gmail.comSigned-off-by: Barry Song <v-songbaohua@oppo.com>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/block/zram/zcomp.c

@@ -11,6 +11,7 @@
 #include <linux/sched.h>
 #include <linux/cpu.h>
 #include <linux/crypto.h>
+#include <linux/vmalloc.h>
 
 #include "zcomp.h"
 
@@ -37,7 +38,7 @@ static void zcomp_strm_free(struct zcomp_strm *zstrm)
 {
 	if (!IS_ERR_OR_NULL(zstrm->tfm))
 		crypto_free_comp(zstrm->tfm);
-	free_pages((unsigned long)zstrm->buffer, 1);
+	vfree(zstrm->buffer);
 	zstrm->tfm = NULL;
 	zstrm->buffer = NULL;
 }
@@ -53,7 +54,7 @@ static int zcomp_strm_init(struct zcomp_strm *zstrm, struct zcomp *comp)
 	 * allocate 2 pages. 1 for compressed data, plus 1 extra for the
 	 * case when compressed size is larger than the original one
 	 */
-	zstrm->buffer = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, 1);
+	zstrm->buffer = vzalloc(2 * PAGE_SIZE);
 	if (IS_ERR_OR_NULL(zstrm->tfm) || !zstrm->buffer) {
 		zcomp_strm_free(zstrm);
 		return -ENOMEM;