mm/gup: further simplify __gup_device_huge()

Commit 6401c4eb57f9 ("mm: gup: fix potential pgmap refcnt leak in
__gup_device_huge()") simplified the return paths, but didn't go quite
far enough, as discussed in [1].

Remove the "ret" variable entirely, because there is enough information
already available to provide the return value.

[1] https://lore.kernel.org/r/CAHk-=wgQTRX=5SkCmS+zfmpqubGHGJvXX_HgnPG8JSpHKHBMeg@mail.gmail.com

Link: https://lkml.kernel.org/r/20210904004224.86391-1-jhubbard@nvidia.com
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/gup.c b/mm/gup.c
index 886d614..48c7a5a 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -2228,7 +2228,6 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
 {
        int nr_start = *nr;
        struct dev_pagemap *pgmap = NULL;
-       int ret = 1;
 
        do {
                struct page *page = pfn_to_page(pfn);
@@ -2236,14 +2235,12 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
                pgmap = get_dev_pagemap(pfn, pgmap);
                if (unlikely(!pgmap)) {
                        undo_dev_pagemap(nr, nr_start, flags, pages);
-                       ret = 0;
                        break;
                }
                SetPageReferenced(page);
                pages[*nr] = page;
                if (unlikely(!try_grab_page(page, flags))) {
                        undo_dev_pagemap(nr, nr_start, flags, pages);
-                       ret = 0;
                        break;
                }
                (*nr)++;
@@ -2251,7 +2248,7 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
        } while (addr += PAGE_SIZE, addr != end);
 
        put_dev_pagemap(pgmap);
-       return ret;
+       return addr == end;
 }
 
 static int __gup_device_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,