linux-ext4 - [PATCH 04/14] mm: Add functions to lock invalidate

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Date:   Mon, 12 Jul 2021 18:55:55 +0200
From:   Jan Kara <jack@...e.cz>
To:     <linux-fsdevel@...r.kernel.org>
Cc:     <linux-ext4@...r.kernel.org>,
        Christoph Hellwig <hch@...radead.org>,
        "Darrick J. Wong" <djwong@...nel.org>, Ted Tso <tytso@....edu>,
        Dave Chinner <david@...morbit.com>,
        Matthew Wilcox <willy@...radead.org>, <linux-mm@...ck.org>,
        <linux-xfs@...r.kernel.org>,
        linux-f2fs-devel@...ts.sourceforge.net, linux-cifs@...r.kernel.org,
        ceph-devel@...r.kernel.org, Jan Kara <jack@...e.cz>,
        Christoph Hellwig <hch@....de>
Subject: [PATCH 04/14] mm: Add functions to lock invalidate_lock for two mappings

Some operations such as reflinking blocks among files will need to lock
invalidate_lock for two mappings. Add helper functions to do that.

Reviewed-by: Darrick J. Wong <djwong@...nel.org>
Reviewed-by: Christoph Hellwig <hch@....de>
Signed-off-by: Jan Kara <jack@...e.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 90a80de37ad4..894ff2451793 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -849,6 +849,12 @@ static inline void filemap_invalidate_unlock_shared(
 void lock_two_nondirectories(struct inode *, struct inode*);
 void unlock_two_nondirectories(struct inode *, struct inode*);
 
+void filemap_invalidate_lock_two(struct address_space *mapping1,
+				 struct address_space *mapping2);
+void filemap_invalidate_unlock_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 56988c4e655d..fd3f94d36c49 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_lock_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_lock_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_lock_two);
+
+/*
+ * filemap_invalidate_unlock_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_unlock_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_unlock_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