[patch 050/262] mm/gup: further simplify __gup_device_huge()

Andrew Morton
2021-11-05T20:37:19Z

From: John Hubbard <jhubbard@nvidia.com>
Subject: 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>
---

mm/gup.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)

--- a/mm/gup.c~mm-gup-further-simplify-__gup_device_huge
+++ a/mm/gup.c
@@ -2228,7 +2228,6 @@ static int __gup_device_huge(unsigned lo
{
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 lo
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 lo
} 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,
_