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Message-ID: <bf744801-96a1-bdf1-79b5-5e8a21c05be3@tmb.nu>
Date: Mon, 24 Jul 2023 12:15:17 +0000
From: Thomas Backlund <tmb@....nu>
To: Mike Kravetz <mike.kravetz@...cle.com>,
linux-kernel@...r.kernel.org, linux-mm@...ck.org,
linux-fsdevel@...r.kernel.org
Cc: Matthew Wilcox <willy@...radead.org>,
Ackerley Tng <ackerleytng@...gle.com>,
Sidhartha Kumar <sidhartha.kumar@...cle.com>,
Muchun Song <songmuchun@...edance.com>,
Vishal Annapurve <vannapurve@...gle.com>,
Erdem Aktas <erdemaktas@...gle.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
kernel test robot <oliver.sang@...el.com>
Subject: Re: [PATCH 1/2] Revert "page cache: fix page_cache_next/prev_miss off by one"
Den 2023-06-22 kl. 00:24, skrev Mike Kravetz:
> 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@...el.com>
> Closes: https://lore.kernel.org/oe-lkp/202306211346.1e9ff03e-oliver.sang@intel.com
> Fixes: 9425c591e06a ("page cache: fix page_cache_next/prev_miss off by one")
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>
Should not this one be submitted to 6.4 stable branch too ?
git describe --contains 9425c591e06a
v6.4-rc7~29^2~1
The other one (hugetlb: revert use of page_cache_next_miss()) of this
patch series landed in 6.4.2
Or am I missing something ?
--
Thomas
> ---
> 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);
>
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