The patch titled
Subject: mm: add find_lock_head
has been added to the -mm tree. Its filename is
mm-add-find_lock_head.patch
This patch should soon appear at
https://ozlabs.org/~akpm/mmots/broken-out/mm-add-find_lock_head.patch
and later at
https://ozlabs.org/~akpm/mmotm/broken-out/mm-add-find_lock_head.patch
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx>
Subject: mm: add find_lock_head
Add a new FGP_HEAD flag which avoids calling find_subpage() and add a
convenience wrapper for it.
Link: https://lkml.kernel.org/r/20200910183318.20139-9-willy@xxxxxxxxxxxxx
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Alexey Dobriyan <adobriyan@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Huang Ying <ying.huang@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxxxxxxxx>
Cc: Johannes Weiner <hannes@xxxxxxxxxxx>
Cc: Matthew Auld <matthew.auld@xxxxxxxxx>
Cc: William Kucharski <william.kucharski@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/pagemap.h | 32 ++++++++++++++++++++++++++------
mm/filemap.c | 9 ++++++---
2 files changed, 32 insertions(+), 9 deletions(-)
--- a/include/linux/pagemap.h~mm-add-find_lock_head
+++ a/include/linux/pagemap.h
@@ -278,6 +278,7 @@ pgoff_t page_cache_prev_miss(struct addr
#define FGP_NOFS 0x00000010
#define FGP_NOWAIT 0x00000020
#define FGP_FOR_MMAP 0x00000040
+#define FGP_HEAD 0x00000080
struct page *pagecache_get_page(struct address_space *mapping, pgoff_t offset,
int fgp_flags, gfp_t cache_gfp_mask);
@@ -309,18 +310,37 @@ static inline struct page *find_get_page
* @mapping: the address_space to search
* @offset: the page index
*
- * Looks up the page cache slot at @mapping & @offset. If there is a
+ * Looks up the page cache entry at @mapping & @offset. If there is a
* page cache page, it is returned locked and with an increased
* refcount.
*
- * Otherwise, %NULL is returned.
- *
- * find_lock_page() may sleep.
+ * Context: May sleep.
+ * Return: A struct page or %NULL if there is no page in the cache for this
+ * index.
*/
static inline struct page *find_lock_page(struct address_space *mapping,
- pgoff_t offset)
+ pgoff_t index)
+{
+ return pagecache_get_page(mapping, index, FGP_LOCK, 0);
+}
+
+/**
+ * find_lock_head - Locate, pin and lock a pagecache page.
+ * @mapping: The address_space to search.
+ * @offset: The page index.
+ *
+ * Looks up the page cache entry at @mapping & @offset. If there is a
+ * page cache page, its head page is returned locked and with an increased
+ * refcount.
+ *
+ * Context: May sleep.
+ * Return: A struct page which is !PageTail, or %NULL if there is no page
+ * in the cache for this index.
+ */
+static inline struct page *find_lock_head(struct address_space *mapping,
+ pgoff_t index)
{
- return pagecache_get_page(mapping, offset, FGP_LOCK, 0);
+ return pagecache_get_page(mapping, index, FGP_LOCK | FGP_HEAD, 0);
}
/**
--- a/mm/filemap.c~mm-add-find_lock_head
+++ a/mm/filemap.c
@@ -1639,6 +1639,8 @@ repeat:
*
* * %FGP_ACCESSED - The page will be marked accessed.
* * %FGP_LOCK - The page is returned locked.
+ * * %FGP_HEAD - If the page is present and a THP, return the head page
+ * rather than the exact page specified by the index.
* * %FGP_CREAT - If no page is present then a new page is allocated using
* @gfp_mask and added to the page cache and the VM's LRU list.
* The page is returned locked and with an increased refcount.
@@ -1667,7 +1669,6 @@ repeat:
page = NULL;
if (!page)
goto no_page;
- page = find_subpage(page, index);
if (fgp_flags & FGP_LOCK) {
if (fgp_flags & FGP_NOWAIT) {
@@ -1680,12 +1681,12 @@ repeat:
}
/* Has the page been truncated? */
- if (unlikely(compound_head(page)->mapping != mapping)) {
+ if (unlikely(page->mapping != mapping)) {
unlock_page(page);
put_page(page);
goto repeat;
}
- VM_BUG_ON_PAGE(page->index != index, page);
+ VM_BUG_ON_PAGE(!thp_contains(page, index), page);
}
if (fgp_flags & FGP_ACCESSED)
@@ -1695,6 +1696,8 @@ repeat:
if (page_is_idle(page))
clear_page_idle(page);
}
+ if (!(fgp_flags & FGP_HEAD))
+ page = find_subpage(page, index);
no_page:
if (!page && (fgp_flags & FGP_CREAT)) {
_
Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are
mm-debug-do-not-dereference-i_ino-blindly.patch
mm-factor-find_get_incore_page-out-of-mincore_page.patch
mm-use-find_get_incore_page-in-memcontrol.patch
mm-optimise-madvise-willneed.patch
proc-optimise-smaps-for-shmem-entries.patch
i915-use-find_lock_page-instead-of-find_lock_entry.patch
mm-convert-find_get_entry-to-return-the-head-page.patch
mm-shmem-return-head-page-from-find_lock_entry.patch
mm-add-find_lock_head.patch
mm-account-pmd-tables-like-pte-tables.patch
mm-move-pagedoublemap-bit.patch
mm-simplify-pagedoublemap-with-pf_second-policy.patch
xarray-add-xa_get_order.patch
xarray-add-xas_split.patch
xarray-add-xas_split-fix-2.patch
mm-filemap-fix-storing-to-a-thp-shadow-entry.patch
mm-filemap-fix-page-cache-removal-for-arbitrary-sized-thps.patch
mm-memory-remove-page-fault-assumption-of-compound-page-size.patch
mm-page_owner-change-split_page_owner-to-take-a-count.patch
mm-huge_memory-fix-page_trans_huge_mapcount-assumption-of-thp-size.patch
mm-huge_memory-fix-can_split_huge_page-assumption-of-thp-size.patch
mm-rmap-fix-assumptions-of-thp-size.patch
mm-truncate-fix-truncation-for-pages-of-arbitrary-size.patch
mm-page-writeback-support-tail-pages-in-wait_for_stable_page.patch
mm-vmscan-allow-arbitrary-sized-pages-to-be-paged-out.patch
mm-readahead-add-define_readahead.patch
mm-readahead-make-page_cache_ra_unbounded-take-a-readahead_control.patch
mm-readahead-make-do_page_cache_ra-take-a-readahead_control.patch
mm-readahead-add-page_cache_sync_ra-and-page_cache_async_ra.patch
harden-autofs-ioctl-table.patch
