mm: userfaultfd: combine 'mode' and 'wp_copy' arguments

Many userfaultfd ioctl functions take both a 'mode' and a 'wp_copy'
argument.  In future commits we plan to plumb the flags through to more
places, so we'd be proliferating the very long argument list even further.

Let's take the time to simplify the argument list.  Combine the two
arguments into one - and generalize, so when we add more flags in the
future, it doesn't imply more function arguments.

Since the modes (copy, zeropage, continue) are mutually exclusive, store
them as an integer value (0, 1, 2) in the low bits.  Place combine-able
flag bits in the high bits.

This is quite similar to an earlier patch proposed by Nadav Amit
("userfaultfd: introduce uffd_flags" [1]).  The main difference is that
patch only handled flags, whereas this patch *also* combines the "mode"
argument into the same type to shorten the argument list.

[1]: https://lore.kernel.org/all/20220619233449.181323-2-namit@vmware.com/

Link: https://lkml.kernel.org/r/20230314221250.682452-4-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Acked-by: James Houghton <jthoughton@google.com>
Acked-by: Peter Xu <peterx@redhat.com>
Acked-by: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 3 insertions, 4 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 9d13b9a64144d..b185c1db30091 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -76,7 +76,6 @@ static struct vfsmount *shm_mnt;
 #include <linux/syscalls.h>
 #include <linux/fcntl.h>
 #include <uapi/linux/memfd.h>
-#include <linux/userfaultfd_k.h>
 #include <linux/rmap.h>
 #include <linux/uuid.h>
 
@@ -2433,7 +2432,7 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
 			   struct vm_area_struct *dst_vma,
 			   unsigned long dst_addr,
 			   unsigned long src_addr,
-			   bool zeropage, bool wp_copy,
+			   uffd_flags_t flags,
 			   struct page **pagep)
 {
 	struct inode *inode = file_inode(dst_vma->vm_file);
@@ -2465,7 +2464,7 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
 		if (!folio)
 			goto out_unacct_blocks;
 
-		if (!zeropage) {	/* COPY */
+		if (uffd_flags_mode_is(flags, MFILL_ATOMIC_COPY)) {
 			page_kaddr = kmap_local_folio(folio, 0);
 			/*
 			 * The read mmap_lock is held here.  Despite the
@@ -2524,7 +2523,7 @@ int shmem_mfill_atomic_pte(pmd_t *dst_pmd,
 		goto out_release;
 
 	ret = mfill_atomic_install_pte(dst_pmd, dst_vma, dst_addr,
-				       &folio->page, true, wp_copy);
+				       &folio->page, true, flags);
 	if (ret)
 		goto out_delete_from_cache;