From: Mike Kravetz mike.kravetz@oracle.com

commit 16f8eb3eea9eb2a1568279d64ca4dc977e7aa538 upstream

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 mike.kravetz@oracle.com Reported-by: kernel test robot oliver.sang@intel.com Closes: https://lore.kernel.org/oe-lkp/202306211346.1e9ff03e-oliver.sang@intel.com Reviewed-by: Sidhartha Kumar sidhartha.kumar@oracle.com Cc: stable@vger.kernel.org Cc: Thomas Backlund tmb@tmb.nu 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: Andrew Morton akpm@linux-foundation.org ---

As pointed out in [1], this patch was missed in the 6.4 stable tree. Resending this patch with a Cc: stable.

[1]: https://lore.kernel.org/all/20230621212403.174710-1-mike.kravetz@oracle.com/...

mm/filemap.c | 26 ++++++++++---------------- 1 file changed, 10 insertions(+), 16 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c index 8abce63b259c9..a2006936a6ae2 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -1760,9 +1760,7 @@ 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) @@ -1772,13 +1770,12 @@ 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);

@@ -1799,9 +1796,7 @@ 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) @@ -1811,13 +1806,12 @@ 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);