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 <djw...@kernel.org>
Reviewed-by: Christoph Hellwig <h...@lst.de>
Signed-off-by: Jan Kara <j...@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 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 f7f9b87d2cd0..0fad08331cf4 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
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