From: Mike Kravetz <mike.kravetz@xxxxxxxxxx> 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@xxxxxxxxxx Fixes: 9425c591e06a ("page cache: fix page_cache_next/prev_miss off by one") Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx> Reported-by: kernel test robot <oliver.sang@xxxxxxxxx> Closes: https://lore.kernel.org/oe-lkp/202306211346.1e9ff03e-oliver.sang@xxxxxxxxx Reviewed-by: Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Cc: Thomas Backlund <tmb@xxxxxx> Cc: Ackerley Tng <ackerleytng@xxxxxxxxxx> Cc: Erdem Aktas <erdemaktas@xxxxxxxxxx> Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Cc: Muchun Song <songmuchun@xxxxxxxxxxxxx> Cc: Vishal Annapurve <vannapurve@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- 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@xxxxxxxxxx/T/#m9e33a9ccb76e4db123279b371cff57d4e1a1ed3a 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); -- 2.41.0
