mm/hugetlb: simplify refs in memfd_alloc_folio

The folio_try_get in memfd_alloc_folio is not necessary.  Delete it, and
delete the matching folio_put in memfd_pin_folios.  This also avoids
leaking a ref if the memfd_alloc_folio call to hugetlb_add_to_page_cache
fails.  That error path is also broken in a second way -- when its
folio_put causes the ref to become 0, it will implicitly call
free_huge_folio, but then the path *explicitly* calls free_huge_folio.
Delete the latter.

This is a continuation of the fix
  "mm/hugetlb: fix memfd_pin_folios free_huge_pages leak"

[steven.sistare@oracle.com: remove explicit call to free_huge_folio(), per Matthew]
Link: https://lkml.kernel.org/r/Zti-7nPVMcGgpcbi@casper.infradead.org
Link: https://lkml.kernel.org/r/1725481920-82506-1-git-send-email-steven.sistare@oracle.com
Link: https://lkml.kernel.org/r/1725478868-61732-1-git-send-email-steven.sistare@oracle.com
Fixes: 89c1905d9c14 ("mm/gup: introduce memfd_pin_folios() for pinning memfd folios")
Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
Suggested-by: Vivek Kasireddy <vivek.kasireddy@intel.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/gup.c b/mm/gup.c
index 8d9b560a0fec2f8e29a380139a3a2ddf68cb50f7..a82890b46a36505136acea09009c8314e22bd0de 100644 (file)
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -3615,7 +3615,7 @@ long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end,
        pgoff_t start_idx, end_idx, next_idx;
        struct folio *folio = NULL;
        struct folio_batch fbatch;
-       struct hstate *h = NULL;
+       struct hstate *h;
        long ret = -EINVAL;
 
        if (start < 0 || start > end || !max_folios)
@@ -3659,8 +3659,6 @@ long memfd_pin_folios(struct file *memfd, loff_t start, loff_t end,
                                                             &fbatch);
                        if (folio) {
                                folio_put(folio);
-                               if (h)
-                                       folio_put(folio);
                                folio = NULL;
                        }
 

diff --git a/mm/memfd.c b/mm/memfd.c
index bcb131db829d4d6c1d2dcab1365ed2c584380f5c..c17c3ea701a17e9f3a652e77ba60ca9c58b0ca8e 100644 (file)
--- a/mm/memfd.c
+++ b/mm/memfd.c
@@ -89,13 +89,12 @@ struct folio *memfd_alloc_folio(struct file *memfd, pgoff_t idx)
                                                    numa_node_id(),
                                                    NULL,
                                                    gfp_mask);
-               if (folio && folio_try_get(folio)) {
+               if (folio) {
                        err = hugetlb_add_to_page_cache(folio,
                                                        memfd->f_mapping,
                                                        idx);
                        if (err) {
                                folio_put(folio);
-                               free_huge_folio(folio);
                                return ERR_PTR(err);
                        }
                        folio_unlock(folio);