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Subject[PATCH 04/10] mm/rmap: share the i_mmap_rwsem
Date
Similarly to the anon memory counterpart, we can share
the mapping's lock ownership as the interval tree is
not modified when doing doing the walk, only the file
page.

Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Acked-by: Rik van Riel <riel@redhat.com>
---
include/linux/fs.h | 10 ++++++++++
mm/rmap.c | 6 +++---
2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index b183792..1059be0 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -465,6 +465,16 @@ static inline void i_mmap_unlock_write(struct address_space *mapping)
up_write(&mapping->i_mmap_rwsem);
}

+static inline void i_mmap_lock_read(struct address_space *mapping)
+{
+ down_read(&mapping->i_mmap_rwsem);
+}
+
+static inline void i_mmap_unlock_read(struct address_space *mapping)
+{
+ up_read(&mapping->i_mmap_rwsem);
+}
+
/*
* Might pages of this file be mapped into userspace?
*/
diff --git a/mm/rmap.c b/mm/rmap.c
index f234bc6..a77726f 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1674,7 +1674,8 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)

if (!mapping)
return ret;
- i_mmap_lock_write(mapping);
+
+ i_mmap_lock_read(mapping);
vma_interval_tree_foreach(vma, &mapping->i_mmap, pgoff, pgoff) {
unsigned long address = vma_address(page, vma);

@@ -1695,9 +1696,8 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
goto done;

ret = rwc->file_nonlinear(page, mapping, rwc->arg);
-
done:
- i_mmap_unlock_write(mapping);
+ i_mmap_unlock_read(mapping);
return ret;
}

--
1.8.4.5


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