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From:   Jan Kara <jack@suse.cz>
To:     <linux-fsdevel@vger.kernel.org>
Cc:     Christoph Hellwig <hch@infradead.org>,
        Dave Chinner <david@fromorbit.com>, ceph-devel@vger.kernel.org,
        Chao Yu <yuchao0@huawei.com>,
        Damien Le Moal <damien.lemoal@wdc.com>,
        "Darrick J. Wong" <darrick.wong@oracle.com>,
        Jaegeuk Kim <jaegeuk@kernel.org>,
        Jeff Layton <jlayton@kernel.org>,
        Johannes Thumshirn <jth@kernel.org>,
        linux-cifs@vger.kernel.org, <linux-ext4@vger.kernel.org>,
        linux-f2fs-devel@lists.sourceforge.net, <linux-mm@kvack.org>,
        <linux-xfs@vger.kernel.org>, Miklos Szeredi <miklos@szeredi.hu>,
        Steve French <sfrench@samba.org>, Ted Tso <tytso@mit.edu>,
        Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>
Subject: [PATCH 04/13] mm: Add functions to lock invalidate_lock for two mappings
Date:   Tue, 25 May 2021 15:50:41 +0200
Message-Id: <20210525135100.11221-4-jack@suse.cz>
In-Reply-To: <20210525125652.20457-1-jack@suse.cz>
References: <20210525125652.20457-1-jack@suse.cz>
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Some operations such as reflinking blocks among files will need to lock
invalidate_lock for two mappings. Add helper functions to do that.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 include/linux/fs.h |  6 ++++++
 mm/filemap.c       | 38 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 897238d9f1e0..e6f7447505f5 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -822,6 +822,12 @@ static inline void inode_lock_shared_nested(struct inode *inode, unsigned subcla
 void lock_two_nondirectories(struct inode *, struct inode*);
 void unlock_two_nondirectories(struct inode *, struct inode*);
 
+void filemap_invalidate_down_write_two(struct address_space *mapping1,
+				       struct address_space *mapping2);
+void filemap_invalidate_up_write_two(struct address_space *mapping1,
+				     struct address_space *mapping2);
+
+
 /*
  * NOTE: in a 32bit arch with a preemptable kernel and
  * an UP compile the i_size_read/write must be atomic
diff --git a/mm/filemap.c b/mm/filemap.c
index 4d9ec4c6cc34..d3801a9739aa 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1009,6 +1009,44 @@ struct page *__page_cache_alloc(gfp_t gfp)
 EXPORT_SYMBOL(__page_cache_alloc);
 #endif
 
+/*
+ * filemap_invalidate_down_write_two - lock invalidate_lock for two mappings
+ *
+ * Lock exclusively invalidate_lock of any passed mapping that is not NULL.
+ *
+ * @mapping1: the first mapping to lock
+ * @mapping2: the second mapping to lock
+ */
+void filemap_invalidate_down_write_two(struct address_space *mapping1,
+				       struct address_space *mapping2)
+{
+	if (mapping1 > mapping2)
+		swap(mapping1, mapping2);
+	if (mapping1)
+		down_write(&mapping1->invalidate_lock);
+	if (mapping2 && mapping1 != mapping2)
+		down_write_nested(&mapping2->invalidate_lock, 1);
+}
+EXPORT_SYMBOL(filemap_invalidate_down_write_two);
+
+/*
+ * filemap_invalidate_up_write_two - unlock invalidate_lock for two mappings
+ *
+ * Unlock exclusive invalidate_lock of any passed mapping that is not NULL.
+ *
+ * @mapping1: the first mapping to unlock
+ * @mapping2: the second mapping to unlock
+ */
+void filemap_invalidate_up_write_two(struct address_space *mapping1,
+				     struct address_space *mapping2)
+{
+	if (mapping1)
+		up_write(&mapping1->invalidate_lock);
+	if (mapping2 && mapping1 != mapping2)
+		up_write(&mapping2->invalidate_lock);
+}
+EXPORT_SYMBOL(filemap_invalidate_up_write_two);
+
 /*
  * In order to wait for pages to become available there must be
  * waitqueues associated with pages. By using a hash table of
-- 
2.26.2