linux-kernel - [PATCH v5 23/39] mm: Allow large pages to be added to the page cache

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-Id: <20200529025824.32296-24-willy@infradead.org>
Date:   Thu, 28 May 2020 19:58:08 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     linux-fsdevel@...r.kernel.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: [PATCH v5 23/39] mm: Allow large pages to be added to the page cache

From: "Matthew Wilcox (Oracle)" <willy@...radead.org>

We return -EEXIST if there are any non-shadow entries in the page
cache in the range covered by the large page.  If there are multiple
shadow entries in the range, we set *shadowp to one of them (currently
the one at the highest index).  If that turns out to be the wrong
answer, we can implement something more complex.  This is mostly
modelled after the equivalent function in the shmem code.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 mm/filemap.c | 44 +++++++++++++++++++++++++++++++-------------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/mm/filemap.c b/mm/filemap.c
index 9abba062973a..437484d42b78 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -834,6 +834,7 @@ static int __add_to_page_cache_locked(struct page *page,
 	int huge = PageHuge(page);
 	struct mem_cgroup *memcg;
 	int error;
+	unsigned int nr = 1;
 	void *old;
 
 	VM_BUG_ON_PAGE(!PageLocked(page), page);
@@ -845,31 +846,48 @@ static int __add_to_page_cache_locked(struct page *page,
 					      gfp_mask, &memcg, false);
 		if (error)
 			return error;
+		xas_set_order(&xas, offset, thp_order(page));
+		nr = hpage_nr_pages(page);
 	}
 
-	get_page(page);
+	page_ref_add(page, nr);
 	page->mapping = mapping;
 	page->index = offset;
 
 	do {
+		unsigned long exceptional = 0;
+		unsigned int i = 0;
+
 		xas_lock_irq(&xas);
-		old = xas_load(&xas);
-		if (old && !xa_is_value(old))
-			xas_set_err(&xas, -EEXIST);
-		xas_store(&xas, page);
+		xas_for_each_conflict(&xas, old) {
+			if (!xa_is_value(old)) {
+				xas_set_err(&xas, -EEXIST);
+				break;
+			}
+			exceptional++;
+			if (shadowp)
+				*shadowp = old;
+		}
+		xas_create_range(&xas);
 		if (xas_error(&xas))
 			goto unlock;
 
-		if (xa_is_value(old)) {
-			mapping->nrexceptional--;
-			if (shadowp)
-				*shadowp = old;
+next:
+		xas_store(&xas, page);
+		if (++i < nr) {
+			xas_next(&xas);
+			goto next;
 		}
-		mapping->nrpages++;
+		mapping->nrexceptional -= exceptional;
+		mapping->nrpages += nr;
 
 		/* hugetlb pages do not participate in page cache accounting */
-		if (!huge)
-			__inc_node_page_state(page, NR_FILE_PAGES);
+		if (!huge) {
+			__mod_node_page_state(page_pgdat(page), NR_FILE_PAGES,
+						nr);
+			if (nr > 1)
+				__inc_node_page_state(page, NR_FILE_THPS);
+		}
 unlock:
 		xas_unlock_irq(&xas);
 	} while (xas_nomem(&xas, gfp_mask & GFP_RECLAIM_MASK));
@@ -886,7 +904,7 @@ static int __add_to_page_cache_locked(struct page *page,
 	/* Leave page->index set: truncation relies upon it */
 	if (!huge)
 		mem_cgroup_cancel_charge(page, memcg, false);
-	put_page(page);
+	page_ref_sub(page, nr);
 	return xas_error(&xas);
 }
 ALLOW_ERROR_INJECTION(__add_to_page_cache_locked, ERRNO);
-- 
2.26.2