linux-kernel - [PATCH 2/2] fs: Do not update nr_thps for mappings which support THPs

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Message-Id: <20200916032717.22917-2-willy@infradead.org>
Date:   Wed, 16 Sep 2020 04:27:17 +0100
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     Alexander Viro <viro@...iv.linux.org.uk>
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-fsdevel@...r.kernel.org, Hugh Dickins <hughd@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Song Liu <songliubraving@...com>,
        Rik van Riel <riel@...riel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Dave Chinner <dchinner@...hat.com>
Subject: [PATCH 2/2] fs: Do not update nr_thps for mappings which support THPs

The nr_thps counter is to support THPs in the page cache when the
filesystem doesn't understand THPs.  Eventually it will be removed, but
we should still support filesystems which do not understand THPs yet.
Move the nr_thp manipulation functions to filemap.h since they're
page-cache specific.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 include/linux/fs.h      | 27 ---------------------------
 include/linux/pagemap.h | 29 +++++++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 27 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index f10190b22d5a..83d8f3ba17a5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2701,33 +2701,6 @@ static inline errseq_t file_sample_sb_err(struct file *file)
 	return errseq_sample(&file->f_path.dentry->d_sb->s_wb_err);
 }
 
-static inline int filemap_nr_thps(struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
-	return atomic_read(&mapping->nr_thps);
-#else
-	return 0;
-#endif
-}
-
-static inline void filemap_nr_thps_inc(struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
-	atomic_inc(&mapping->nr_thps);
-#else
-	WARN_ON_ONCE(1);
-#endif
-}
-
-static inline void filemap_nr_thps_dec(struct address_space *mapping)
-{
-#ifdef CONFIG_READ_ONLY_THP_FOR_FS
-	atomic_dec(&mapping->nr_thps);
-#else
-	WARN_ON_ONCE(1);
-#endif
-}
-
 extern int vfs_fsync_range(struct file *file, loff_t start, loff_t end,
 			   int datasync);
 extern int vfs_fsync(struct file *file, int datasync);
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index ecb03e1b3555..2b637960be3a 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -130,6 +130,35 @@ static inline bool mapping_thp_support(struct address_space *mapping)
 	return test_bit(AS_THP_SUPPORT, &mapping->flags);
 }
 
+static inline int filemap_nr_thps(struct address_space *mapping)
+{
+#ifdef CONFIG_READ_ONLY_THP_FOR_FS
+	return atomic_read(&mapping->nr_thps);
+#else
+	return 0;
+#endif
+}
+
+static inline void filemap_nr_thps_inc(struct address_space *mapping)
+{
+#ifdef CONFIG_READ_ONLY_THP_FOR_FS
+	if (!mapping_thp_support(mapping))
+		atomic_inc(&mapping->nr_thps);
+#else
+	WARN_ON_ONCE(1);
+#endif
+}
+
+static inline void filemap_nr_thps_dec(struct address_space *mapping)
+{
+#ifdef CONFIG_READ_ONLY_THP_FOR_FS
+	if (!mapping_thp_support(mapping))
+		atomic_dec(&mapping->nr_thps);
+#else
+	WARN_ON_ONCE(1);
+#endif
+}
+
 void release_pages(struct page **pages, int nr);
 
 /*
-- 
2.28.0