[PATCH 4/5] mm/rmap: share the i_mmap_rwsem

Davidlohr Bueso
2014-05-23T03:34:10Z

Similarly to rmap_walk_anon() and collect_procs_anon(),
there is opportunity to share the lock in rmap_walk_file()
and collect_procs_file() for file backed pages.

Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
---
include/linux/fs.h | 10 ++++++++++
mm/memory-failure.c | 4 ++--
mm/rmap.c | 4 ++--
3 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 60a1d7d..4c2c228 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -467,6 +467,16 @@ 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/memory-failure.c b/mm/memory-failure.c
index 1389a28..acbcd8e 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -434,7 +434,7 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
struct task_struct *tsk;
struct address_space *mapping = page->mapping;

- i_mmap_lock_write(mapping);
+ i_mmap_lock_read(mapping);
read_lock(&tasklist_lock);
for_each_process(tsk) {
pgoff_t pgoff = page_pgoff(page);
@@ -456,7 +456,7 @@ static void collect_procs_file(struct page *page, struct list_head *to_kill,
}
}
read_unlock(&tasklist_lock);
- i_mmap_unlock_write(mapping);
+ i_mmap_unlock_read(mapping);
}

/*
diff --git a/mm/rmap.c b/mm/rmap.c
index 9a56e4f..5841dcb 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1685,7 +1685,7 @@ 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);

@@ -1708,7 +1708,7 @@ static int rmap_walk_file(struct page *page, struct rmap_walk_control *rwc)
ret = rwc->file_nonlinear(page, mapping, rwc->arg);

done:
- i_mmap_unlock_write(mapping);
+ i_mmap_unlock_read(mapping);
return ret;
}

--
1.8.1.4