Commit 16f8eb3e authored by Mike Kravetz's avatar Mike Kravetz Committed by Andrew Morton
Browse files

Revert "page cache: fix page_cache_next/prev_miss off by one" 

This reverts commit 9425c591

The reverted commit fixed up routines primarily used by readahead code
such that they could also be used by hugetlb.  Unfortunately, this
caused a performance regression as pointed out by the Closes: tag.

The hugetlb code which uses page_cache_next_miss will be addressed in
a subsequent patch.

Link: https://lkml.kernel.org/r/20230621212403.174710-1-mike.kravetz@oracle.com


Fixes: 9425c591 ("page cache: fix page_cache_next/prev_miss off by one")
Signed-off-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
Closes: https://lore.kernel.org/oe-lkp/202306211346.1e9ff03e-oliver.sang@intel.com


Reviewed-by: default avatarSidhartha Kumar <sidhartha.kumar@oracle.com>
Cc: Ackerley Tng <ackerleytng@google.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 1bc545bf

mm/filemap.c

+10 −16
Original line number Diff line number Diff line
@@ -1728,9 +1728,7 @@ bool __folio_lock_or_retry(struct folio *folio, struct mm_struct *mm, 
 *

 * Return: The index of the gap if found, otherwise an index outside the

 * range specified (in which case 'return - index >= max_scan' will be true).

 * In the rare case of index wrap-around, 0 will be returned.  0 will also

 * be returned if index == 0 and there is a gap at the index.  We can not

 * wrap-around if passed index == 0.

 * In the rare case of index wrap-around, 0 will be returned.

 */

pgoff_t page_cache_next_miss(struct address_space *mapping,

			     pgoff_t index, unsigned long max_scan)
@@ -1740,13 +1738,12 @@ pgoff_t page_cache_next_miss(struct address_space *mapping, 
	while (max_scan--) {

		void *entry = xas_next(&xas);

		if (!entry || xa_is_value(entry))

			return xas.xa_index;

		if (xas.xa_index == 0 && index != 0)

			return xas.xa_index;

			break;

		if (xas.xa_index == 0)

			break;

	}



	/* No gaps in range and no wrap-around, return index beyond range */

	return xas.xa_index + 1;

	return xas.xa_index;

}

EXPORT_SYMBOL(page_cache_next_miss);
@@ -1767,9 +1764,7 @@ EXPORT_SYMBOL(page_cache_next_miss); 
 *

 * Return: The index of the gap if found, otherwise an index outside the

 * range specified (in which case 'index - return >= max_scan' will be true).

 * In the rare case of wrap-around, ULONG_MAX will be returned.  ULONG_MAX

 * will also be returned if index == ULONG_MAX and there is a gap at the

 * index.  We can not wrap-around if passed index == ULONG_MAX.

 * In the rare case of wrap-around, ULONG_MAX will be returned.

 */

pgoff_t page_cache_prev_miss(struct address_space *mapping,

			     pgoff_t index, unsigned long max_scan)
@@ -1779,13 +1774,12 @@ pgoff_t page_cache_prev_miss(struct address_space *mapping, 
	while (max_scan--) {

		void *entry = xas_prev(&xas);

		if (!entry || xa_is_value(entry))

			return xas.xa_index;

		if (xas.xa_index == ULONG_MAX && index != ULONG_MAX)

			return xas.xa_index;

			break;

		if (xas.xa_index == ULONG_MAX)

			break;

	}



	/* No gaps in range and no wrap-around, return index beyond range */

	return xas.xa_index - 1;

	return xas.xa_index;

}

EXPORT_SYMBOL(page_cache_prev_miss);