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@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 90a80de37ad40f181daab3c0bcb1fe900d6f92ff..894ff2451793478360ebd7bd02ebf6be83535c22 100644 (file)
--- 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 f7f9b87d2cd000e043c85e36c9dbfcfa9fdd3a1d..0fad08331cf441a22323e54fefdeb4608720e4fa 100644 (file)
--- 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