From 16f8eb3eea9eb2a1568279d64ca4dc977e7aa538 Mon Sep 17 00:00:00 2001 From: Mike Kravetz Date: Wed, 21 Jun 2023 14:24:02 -0700 Subject: [PATCH] Revert "page cache: fix page_cache_next/prev_miss off by one" 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. Link: https://lkml.kernel.org/r/20230621212403.174710-1-mike.kravetz@oracle.com Fixes: 9425c591e06a ("page cache: fix page_cache_next/prev_miss off by one") Signed-off-by: Mike Kravetz Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202306211346.1e9ff03e-oliver.sang@intel.com Reviewed-by: Sidhartha Kumar Cc: Ackerley Tng Cc: Erdem Aktas Cc: Greg Kroah-Hartman Cc: Matthew Wilcox Cc: Muchun Song Cc: Vishal Annapurve Signed-off-by: Andrew Morton --- mm/filemap.c | 26 ++++++++++---------------- 1 file changed, 10 insertions(+), 16 deletions(-) diff --git a/mm/filemap.c b/mm/filemap.c index c20e0b1..758bbdf 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); -- 2.7.4