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Code Activity

hugetlb: revert use of page_cache_next_miss()

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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: d0ce0e47b3 ("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>
This commit is contained in:
Mike Kravetz 2023-06-21 14:24:03 -07:00 • committed by Andrew Morton
parent 16f8eb3eea
commit fd4aed8d98
2 changed files with 9 additions and 11 deletions
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8
fs/hugetlbfs/inode.c
View file

@ -821,7 +821,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
*/ */
struct folio *folio; struct folio *folio;
unsigned long addr; unsigned long addr;
bool present;
cond_resched(); 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]); mutex_lock(&hugetlb_fault_mutex_table[hash]);
/* See if already present in mapping to avoid alloc/free */ /* See if already present in mapping to avoid alloc/free */
rcu_read_lock(); folio = filemap_get_folio(mapping, index);
present = page_cache_next_miss(mapping, index, 1) != index; if (!IS_ERR(folio)) {
rcu_read_unlock(); folio_put(folio);
if (present) {
mutex_unlock(&hugetlb_fault_mutex_table[hash]); mutex_unlock(&hugetlb_fault_mutex_table[hash]);
continue; continue;
} }

12
mm/hugetlb.c
View file

@ -5728,13 +5728,13 @@ static bool hugetlbfs_pagecache_present(struct hstate *h,
{ {
struct address_space *mapping = vma->vm_file->f_mapping; struct address_space *mapping = vma->vm_file->f_mapping;
pgoff_t idx = vma_hugecache_offset(h, vma, address); pgoff_t idx = vma_hugecache_offset(h, vma, address);
bool present; struct folio *folio;
rcu_read_lock(); folio = filemap_get_folio(mapping, idx);
present = page_cache_next_miss(mapping, idx, 1) != idx; if (IS_ERR(folio))
rcu_read_unlock(); return false;
folio_put(folio);
return present; return true;
} }
int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping, int hugetlb_add_to_page_cache(struct folio *folio, struct address_space *mapping,