The patch titled
Subject: Revert "page cache: fix page_cache_next/prev_miss off by one"
has been added to the -mm mm-unstable branch. Its filename is
revert-page-cache-fix-page_cache_next-prev_miss-off-by-one.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/revert-page-cache-fix-page_cache_next-prev_miss-off-by-one.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Subject: Revert "page cache: fix page_cache_next/prev_miss off by one"
Date: Wed, 21 Jun 2023 14:24:02 -0700
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
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: Reviewed-by Sidhartha Kumar <sidhartha.kumar@xxxxxxxxxx>
Cc: Vishal Annapurve <vannapurve@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/filemap.c | 26 ++++++++++----------------
1 file changed, 10 insertions(+), 16 deletions(-)
--- a/mm/filemap.c~revert-page-cache-fix-page_cache_next-prev_miss-off-by-one
+++ a/mm/filemap.c
@@ -1728,9 +1728,7 @@ bool __folio_lock_or_retry(struct folio
*
* 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 addr
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 addr
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);
_
Patches currently in -mm which might be from mike.kravetz@xxxxxxxxxx are
revert-page-cache-fix-page_cache_next-prev_miss-off-by-one.patch
hugetlb-revert-use-of-page_cache_next_miss.patch
