linux-kernel - [PATCH v2] mm: add prototype for __add_to_page_cache

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Date:   Wed, 23 Dec 2020 08:51:42 +0530
From:   Souptick Joarder <jrdr.linux@...il.com>
To:     akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Souptick Joarder <jrdr.linux@...il.com>,
        Alex Shi <alex.shi@...ux.alibaba.com>,
        Matthew Wilcox <willy@...radead.org>
Subject: [PATCH v2] mm: add prototype for __add_to_page_cache_locked()

Otherwise it causes a gcc warning:

../mm/filemap.c:830:14: warning: no previous prototype for
`__add_to_page_cache_locked' [-Wmissing-prototypes]

A previous attempt to make this function static led to compilation
errors when CONFIG_DEBUG_INFO_BTF is enabled because
__add_to_page_cache_locked() is referred to by BPF code.

Adding a prototype will silence the warning.

Signed-off-by: Souptick Joarder <jrdr.linux@...il.com>
Cc: Alex Shi <alex.shi@...ux.alibaba.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Cc: Matthew Wilcox <willy@...radead.org>
---
v2:
	Updated change logs and code comments as per review.
	s/offset/index.

 include/linux/mm.h | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 5299b90a..c1e9081 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -216,6 +216,13 @@ int overcommit_kbytes_handler(struct ctl_table *, int, void *, size_t *,
 		loff_t *);
 int overcommit_policy_handler(struct ctl_table *, int, void *, size_t *,
 		loff_t *);
+/*
+ * Any attempt to mark this function as static leads to build failure
+ * when CONFIG_DEBUG_INFO_BTF is enabled because __add_to_page_cache_locked()
+ * is referred to by BPF code. This must be visible for error injection.
+ */
+int __add_to_page_cache_locked(struct page *page, struct address_space *mapping,
+		pgoff_t index, gfp_t gfp, void **shadowp);
 
 #define nth_page(page,n) pfn_to_page(page_to_pfn((page)) + (n))
 
-- 
1.9.1