block: Fix blk_validate_atomic_write_limits() build for arm32

For arm32, we get the following build warning:
 In file included from /tmp/next/build/include/linux/printk.h:10,
                  from /tmp/next/build/include/linux/kernel.h:31,
                  from /tmp/next/build/block/blk-settings.c:5:
 /tmp/next/build/block/blk-settings.c: In function 'blk_validate_atomic_write_limits':
 /tmp/next/build/include/asm-generic/div64.h:222:35: warning: comparison of distinct pointer types lacks a cast
   222 |         (void)(((typeof((n)) *)0) == ((uint64_t *)0));  \
       |                                   ^~

The divident for do_div() should be 64b, which it is not. Since we want to
check 2x unsigned ints, just use % operator. This allows us to drop the
chunk_sectors variable.

Fixes: 9da3d1e ("block: Add core atomic write support")
Reported-by: Mark Brown <[email protected]>
Closes: https://lore.kernel.org/linux-next/[email protected]/T/#mbf067b1edd89c7f9d7dac6e258c516199953a108
Signed-off-by: John Garry <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

Author: johnpgarry

block/blk-settings.c

@@ -175,7 +175,6 @@ static void blk_atomic_writes_update_limits(struct queue_limits *lim)
 
 static void blk_validate_atomic_write_limits(struct queue_limits *lim)
 {
-	unsigned int chunk_sectors = lim->chunk_sectors;
 	unsigned int boundary_sectors;
 
 	if (!lim->atomic_write_hw_max)
@@ -197,7 +196,7 @@ static void blk_validate_atomic_write_limits(struct queue_limits *lim)
 		 * Devices which do not conform to these rules can be dealt
 		 * with if and when they show up.
 		 */
-		if (WARN_ON_ONCE(do_div(chunk_sectors, boundary_sectors)))
+		if (WARN_ON_ONCE(lim->chunk_sectors % boundary_sectors))
 			goto unsupported;
 
 		/*