hugetlb: revert use of page_cache_next_miss()

Ackerley Tng reported an issue with hugetlbfs fallocate as noted in the
Closes tag.  The issue showed up after the conversion of hugetlb page
cache lookup code to use page_cache_next_miss.  User visible effects are:

- hugetlbfs fallocate incorrectly returns -EEXIST if pages are presnet
  in the file.
- hugetlb pages will not be included in core dumps if they need to be
  brought in via GUP.
- userfaultfd UFFDIO_COPY will not notice pages already present in the
  cache.  It may try to allocate a new page and potentially return
  ENOMEM as opposed to EEXIST.

Revert the use page_cache_next_miss() in hugetlb code.

IMPORTANT NOTE FOR STABLE BACKPORTS:
This patch will apply cleanly to v6.3.  However, due to the change of
filemap_get_folio() return values, it will not function correctly.  This
patch must be modified for stable backports.

[dan.carpenter@linaro.org: fix hugetlbfs_pagecache_present()]
Link: https://lkml.kernel.org/r/efa86091-6a2c-4064-8f55-9b44e1313015@moroto.mountain
Link: https://lkml.kernel.org/r/20230621212403.174710-2-mike.kravetz@oracle.com
Fixes: d0ce0e47b323 ("mm/hugetlb: convert hugetlb fault paths to use alloc_hugetlb_folio()")
Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reported-by: Ackerley Tng <ackerleytng@google.com>
Closes: https://lore.kernel.org/linux-mm/cover.1683069252.git.ackerleytng@google.com
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Vishal Annapurve <vannapurve@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 90361a9..7b17ccf 100644 (file)
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -821,7 +821,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
                 */
                struct folio *folio;
                unsigned long addr;
-               bool present;
 
                cond_resched();
 
@@ -842,10 +841,9 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
                mutex_lock(&hugetlb_fault_mutex_table[hash]);
 
                /* See if already present in mapping to avoid alloc/free */
-               rcu_read_lock();
-               present = page_cache_next_miss(mapping, index, 1) != index;
-               rcu_read_unlock();
-               if (present) {
+               folio = filemap_get_folio(mapping, index);
+               if (!IS_ERR(folio)) {
+                       folio_put(folio);
                        mutex_unlock(&hugetlb_fault_mutex_table[hash]);
                        continue;
                }

diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index d765744..bce28cc 100644 (file)
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -5728,13 +5728,13 @@ static bool hugetlbfs_pagecache_present(struct hstate *h,
 {
        struct address_space *mapping = vma->vm_file->f_mapping;
        pgoff_t idx = vma_hugecache_offset(h, vma, address);
-       bool present;
-
-       rcu_read_lock();
-       present = page_cache_next_miss(mapping, idx, 1) != idx;
-       rcu_read_unlock();
+       struct folio *folio;
 
-       return present;
+       folio = filemap_get_folio(mapping, idx);
+       if (IS_ERR(folio))
+               return false;
+       folio_put(folio);
+       return true;
 }
 
 int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping,