hugetlb: create remove_inode_single_folio to remove single file folio

Create the new routine remove_inode_single_folio that will remove a single
folio from a file.  This is refactored code from remove_inode_hugepages.
It checks for the uncommon case in which the folio is still mapped and
unmaps.

No functional change.  This refactoring will be put to use and expanded
upon in a subsequent patches.

Link: https://lkml.kernel.org/r/20220914221810.95771-5-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: Miaohe Lin <linmiaohe@huawei.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: 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>

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index edd69cc..7112a9a 100644 (file)
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -412,17 +412,70 @@ hugetlb_vmdelete_list(struct rb_root_cached *root, pgoff_t start, pgoff_t end,
 }
 
 /*
+ * Called with hugetlb fault mutex held.
+ * Returns true if page was actually removed, false otherwise.
+ */
+static bool remove_inode_single_folio(struct hstate *h, struct inode *inode,
+                                       struct address_space *mapping,
+                                       struct folio *folio, pgoff_t index,
+                                       bool truncate_op)
+{
+       bool ret = false;
+
+       /*
+        * If folio is mapped, it was faulted in after being
+        * unmapped in caller.  Unmap (again) while holding
+        * the fault mutex.  The mutex will prevent faults
+        * until we finish removing the folio.
+        */
+       if (unlikely(folio_mapped(folio))) {
+               i_mmap_lock_write(mapping);
+               hugetlb_vmdelete_list(&mapping->i_mmap,
+                       index * pages_per_huge_page(h),
+                       (index + 1) * pages_per_huge_page(h),
+                       ZAP_FLAG_DROP_MARKER);
+               i_mmap_unlock_write(mapping);
+       }
+
+       folio_lock(folio);
+       /*
+        * After locking page, make sure mapping is the same.
+        * We could have raced with page fault populate and
+        * backout code.
+        */
+       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);
+               }
+       }
+
+       folio_unlock(folio);
+       return ret;
+}
+
+/*
  * remove_inode_hugepages handles two distinct cases: truncation and hole
  * punch.  There are subtle differences in operation for each case.
  *
  * truncation is indicated by end of range being LLONG_MAX
  *     In this case, we first scan the range and release found pages.
  *     After releasing pages, hugetlb_unreserve_pages cleans up region/reserve
- *     maps and global counts.  Page faults can not race with truncation
- *     in this routine.  hugetlb_no_page() prevents page faults in the
- *     truncated range.  It checks i_size before allocation, and again after
- *     with the page table lock for the page held.  The same lock must be
- *     acquired to unmap a page.
+ *     maps and global counts.  Page faults can race with truncation.
+ *     During faults, hugetlb_no_page() checks i_size before page allocation,
+ *     and again after obtaining page table lock.  It will 'back out'
+ *     allocations in the truncated range.
  * hole punch is indicated if end is not LLONG_MAX
  *     In the hole punch case we scan the range and release found pages.
  *     Only when releasing a page is the associated region/reserve map
@@ -456,44 +509,12 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
                        mutex_lock(&hugetlb_fault_mutex_table[hash]);
 
                        /*
-                        * If folio is mapped, it was faulted in after being
-                        * unmapped in caller.  Unmap (again) now after taking
-                        * the fault mutex.  The mutex will prevent faults
-                        * until we finish removing the folio.
-                        *
-                        * This race can only happen in the hole punch case.
-                        * Getting here in a truncate operation is a bug.
+                        * Remove folio that was part of folio_batch.
                         */
-                       if (unlikely(folio_mapped(folio))) {
-                               BUG_ON(truncate_op);
-
-                               i_mmap_lock_write(mapping);
-                               hugetlb_vmdelete_list(&mapping->i_mmap,
-                                       index * pages_per_huge_page(h),
-                                       (index + 1) * pages_per_huge_page(h),
-                                       ZAP_FLAG_DROP_MARKER);
-                               i_mmap_unlock_write(mapping);
-                       }
-
-                       folio_lock(folio);
-                       /*
-                        * We must free the huge page and remove 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);
-                       freed++;
-                       if (!truncate_op) {
-                               if (unlikely(hugetlb_unreserve_pages(inode,
-                                                       index, index + 1, 1)))
-                                       hugetlb_fix_reserve_counts(inode);
-                       }
-
-                       folio_unlock(folio);
+                       if (remove_inode_single_folio(h, inode, mapping, folio,
+                                                       index, truncate_op))
+                               freed++;
+
                        mutex_unlock(&hugetlb_fault_mutex_table[hash]);
                }
                folio_batch_release(&fbatch);