mm, shmem: fix handling /sys/kernel/mm/transparent_hugepage/shmem_ena…

…bled

/sys/kernel/mm/transparent_hugepage/shmem_enabled controls if we want
to allocate huge pages when allocate pages for private in-kernel shmem
mount.

Unfortunately, as Dan noticed, I've screwed it up and the only way to
make kernel allocate huge page for the mount is to use "force" there.
All other values will be effectively ignored.

Link: http://lkml.kernel.org/r/[email protected]
Fixes: 5a6e75f ("shmem: prepare huge= mount option and sysfs knob")
Signed-off-by: Kirill A. Shutemov <[email protected]>
Reported-by: Dan Carpenter <[email protected]>
Cc: stable <[email protected]> [4.8+]
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/shmem.c

@@ -3967,7 +3967,7 @@ int __init shmem_init(void)
 	}
 
 #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
-	if (has_transparent_hugepage() && shmem_huge < SHMEM_HUGE_DENY)
+	if (has_transparent_hugepage() && shmem_huge > SHMEM_HUGE_DENY)
 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
 	else
 		shmem_huge = 0; /* just in case it was patched */
@@ -4028,7 +4028,7 @@ static ssize_t shmem_enabled_store(struct kobject *kobj,
 		return -EINVAL;
 
 	shmem_huge = huge;
-	if (shmem_huge < SHMEM_HUGE_DENY)
+	if (shmem_huge > SHMEM_HUGE_DENY)
 		SHMEM_SB(shm_mnt->mnt_sb)->huge = shmem_huge;
 	return count;
 }