Commit fd4aed8d authored by Mike Kravetz's avatar Mike Kravetz Committed by Andrew Morton
Browse files

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: d0ce0e47 ("mm/hugetlb: convert hugetlb fault paths to use alloc_hugetlb_folio()")
Signed-off-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: default avatarDan Carpenter <dan.carpenter@linaro.org>
Reported-by: default avatarAckerley Tng <ackerleytng@google.com>
Closes: https://lore.kernel.org/linux-mm/cover.1683069252.git.ackerleytng@google.com


Reviewed-by: default avatarSidhartha 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 16f8eb3e

fs/hugetlbfs/inode.c

+3 −5
Original line number Diff line number Diff line
@@ -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;

		}

mm/hugetlb.c

+6 −6
Original line number Diff line number Diff line
@@ -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,