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authorMike Kravetz <mike.kravetz@oracle.com>2022-09-14 15:18:10 -0700
committerAndrew Morton <akpm@linux-foundation.org>2022-10-03 14:03:17 -0700
commitfa27759af4a6d7494c986c44695b13bcd6eaf46b (patch)
treed20a218f389abd1703c69b002c7d9ae3a5830407 /fs/hugetlbfs
parent40549ba8f8e0ed1f8b235979563f619e9aa34fdf (diff)
downloadlinux-fa27759af4a6d7494c986c44695b13bcd6eaf46b.tar.bz2
hugetlb: clean up code checking for fault/truncation races
With the new hugetlb vma lock in place, it can also be used to handle page fault races with file truncation. The lock is taken at the beginning of the code fault path in read mode. During truncation, it is taken in write mode for each vma which has the file mapped. The file's size (i_size) is modified before taking the vma lock to unmap. How are races handled? The page fault code checks i_size early in processing after taking the vma lock. If the fault is beyond i_size, the fault is aborted. If the fault is not beyond i_size the fault will continue and a new page will be added to the file. It could be that truncation code modifies i_size after the check in fault code. That is OK, as truncation code will soon remove the page. The truncation code will wait until the fault is finished, as it must obtain the vma lock in write mode. This patch cleans up/removes late checks in the fault paths that try to back out pages racing with truncation. As noted above, we just let the truncation code remove the pages. [mike.kravetz@oracle.com: fix reserve_alloc set but not used compiler warning] Link: https://lkml.kernel.org/r/Yyj7HsJWfHDoU24U@monkey Link: https://lkml.kernel.org/r/20220914221810.95771-10-mike.kravetz@oracle.com Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> Cc: Axel Rasmussen <axelrasmussen@google.com> Cc: David Hildenbrand <david@redhat.com> Cc: Davidlohr Bueso <dave@stgolabs.net> Cc: James Houghton <jthoughton@google.com> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> Cc: Miaohe Lin <linmiaohe@huawei.com> Cc: Michal Hocko <mhocko@suse.com> Cc: Mina Almasry <almasrymina@google.com> Cc: Muchun Song <songmuchun@bytedance.com> Cc: Naoya Horiguchi <naoya.horiguchi@linux.dev> Cc: Pasha Tatashin <pasha.tatashin@soleen.com> Cc: Peter Xu <peterx@redhat.com> Cc: Prakash Sangappa <prakash.sangappa@oracle.com> Cc: Sven Schnelle <svens@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'fs/hugetlbfs')
-rw-r--r--fs/hugetlbfs/inode.c31
1 files changed, 12 insertions, 19 deletions
diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 009ae539b9b2..ed57a029eab0 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -568,26 +568,19 @@ static bool remove_inode_single_folio(struct hstate *h, struct inode *inode,
folio_lock(folio);
/*
- * After locking page, make sure mapping is the same.
- * We could have raced with page fault populate and
- * backout code.
+ * We must remove the folio from page cache before removing
+ * the region/ reserve map (hugetlb_unreserve_pages). In
+ * rare out of memory conditions, removal of the region/reserve
+ * map could fail. Correspondingly, the subpool and global
+ * reserve usage count can need to be adjusted.
*/
- if (folio_mapping(folio) == mapping) {
- /*
- * We must remove the folio from page cache before removing
- * the region/ reserve map (hugetlb_unreserve_pages). In
- * rare out of memory conditions, removal of the region/reserve
- * map could fail. Correspondingly, the subpool and global
- * reserve usage count can need to be adjusted.
- */
- VM_BUG_ON(HPageRestoreReserve(&folio->page));
- hugetlb_delete_from_page_cache(&folio->page);
- ret = true;
- if (!truncate_op) {
- if (unlikely(hugetlb_unreserve_pages(inode, index,
- index + 1, 1)))
- hugetlb_fix_reserve_counts(inode);
- }
+ VM_BUG_ON(HPageRestoreReserve(&folio->page));
+ hugetlb_delete_from_page_cache(&folio->page);
+ ret = true;
+ if (!truncate_op) {
+ if (unlikely(hugetlb_unreserve_pages(inode, index,
+ index + 1, 1)))
+ hugetlb_fix_reserve_counts(inode);
}
folio_unlock(folio);