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Subject[PATCH 1/2] shmem: export shmem_unlock_mapping
Date
By exporting this function, drivers can mark/unmark a shmemfs address
space as unevictable in the following way: 1. mark an address space as
unevictable with mapping_set_unevictable(), pages in the address space
will be moved to unevictable list in vmscan. 2. mark an address space
evictable with mapping_clear_unevictable(), and move these pages back to
evictable list with shmem_unlock_mapping().

Signed-off-by: Kuo-Hsin Yang <vovoy@chromium.org>
---
Documentation/vm/unevictable-lru.rst | 4 +++-
mm/shmem.c | 2 ++
2 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/Documentation/vm/unevictable-lru.rst b/Documentation/vm/unevictable-lru.rst
index fdd84cb8d511..a812fb55136d 100644
--- a/Documentation/vm/unevictable-lru.rst
+++ b/Documentation/vm/unevictable-lru.rst
@@ -143,7 +143,7 @@ using a number of wrapper functions:
Query the address space, and return true if it is completely
unevictable.

-These are currently used in two places in the kernel:
+These are currently used in three places in the kernel:

(1) By ramfs to mark the address spaces of its inodes when they are created,
and this mark remains for the life of the inode.
@@ -154,6 +154,8 @@ These are currently used in two places in the kernel:
swapped out; the application must touch the pages manually if it wants to
ensure they're in memory.

+ (3) By the i915 driver to mark pinned address space until it's unpinned.
+

Detecting Unevictable Pages
---------------------------
diff --git a/mm/shmem.c b/mm/shmem.c
index 446942677cd4..d1ce34c09df6 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -786,6 +786,7 @@ void shmem_unlock_mapping(struct address_space *mapping)
cond_resched();
}
}
+EXPORT_SYMBOL_GPL(shmem_unlock_mapping);

/*
* Remove range of pages and swap entries from radix tree, and free them.
@@ -3874,6 +3875,7 @@ int shmem_lock(struct file *file, int lock, struct user_struct *user)
void shmem_unlock_mapping(struct address_space *mapping)
{
}
+EXPORT_SYMBOL_GPL(shmem_unlock_mapping);

#ifdef CONFIG_MMU
unsigned long shmem_get_unmapped_area(struct file *file,
--
2.19.1.331.ge82ca0e54c-goog
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