On 6/21/23 2:24 PM, Mike Kravetz wrote:
This reverts commit 9425c591e06a9ab27a145ba655fb50532cf0bcc9
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.
Reported-by: kernel test robot <oliver.sang@xxxxxxxxx>
Closes: https://lore.kernel.org/oe-lkp/202306211346.1e9ff03e-oliver.sang@xxxxxxxxx
Fixes: 9425c591e06a ("page cache: fix page_cache_next/prev_miss off by one")
Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
---
mm/filemap.c | 26 ++++++++++----------------
1 file changed, 10 insertions(+), 16 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 3b73101f9f86..9e44a49bbd74 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -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);
Reviewed-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
