dm-integrity, dm-verity: reduce stack usage for recheck

dm-integrity, dm-verity: reduce stack usage for recheck

The newly added integrity_recheck() function has another larger stack
allocation, just like its caller integrity_metadata(). When it gets
inlined, the combination of the two exceeds the warning limit for 32-bit
architectures and possibly risks an overflow when this is called from
a deep call chain through a file system:

drivers/md/dm-integrity.c:1767:13: error: stack frame size (1048) exceeds limit (1024) in 'integrity_metadata' [-Werror,-Wframe-larger-than]
 1767 | static void integrity_metadata(struct work_struct *w)

Since the caller at this point is done using its checksum buffer,
just reuse the same buffer in the new function to avoid the double
allocation.

[Mikulas: add "noinline" to integrity_recheck and verity_recheck.
These functions are only called on error, so they shouldn't bloat the
stack frame or code size of the caller.]

Fixes: c88f5e553fe3 ("dm-integrity: recheck the integrity tag after a failure")
Fixes: 9177f3c0dea6 ("dm-verity: recheck the hash after a failure")
Cc: stable@vger.kernel.org
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>