[Devel] [RFC v14-rc2][PATCH 20/29] Prepare to support shared memory

[Oren Laadan]

Export functionality to retrieve specific pages from shared memory
given an inode in shmem-fs; this will be used in the next two patches
to provide support for c/r of shared memory.

Handling of shared memory depends on the type of a vma; to classify a
vma we extend the 'struct vma_operations_struct' with a new function
- 'cr_vma_type()' - through which a vma will report an integer that
reflects its type.

mm/shmem.c:
- shmem_getpage() and 'enum sgp_type' moved to linux/mm.h
- 'struct vm_operations_struct' extended with '->cr_vma_type' function

Changelog[v14]:
  - Introduce patch

Signed-off-by: Oren Laadan <orenl at cs.columbia.edu>
---
 include/linux/mm.h |   14 ++++++++++++++
 mm/shmem.c         |   15 ++-------------
 2 files changed, 16 insertions(+), 13 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index 065cdf8..e9bdc00 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -218,6 +218,9 @@ struct vm_operations_struct {
 	int (*migrate)(struct vm_area_struct *vma, const nodemask_t *from,
 		const nodemask_t *to, unsigned long flags);
 #endif
+#ifdef CONFIG_CHECKPOINT
+	int (*cr_vma_type)(struct vm_area_struct *vma);
+#endif
 };
 
 struct mmu_gather;
@@ -323,6 +326,17 @@ void put_pages_list(struct list_head *pages);
 
 void split_page(struct page *page, unsigned int order);
 
+/* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
+enum sgp_type {
+	SGP_READ,	/* don't exceed i_size, don't allocate page */
+	SGP_CACHE,	/* don't exceed i_size, may allocate page */
+	SGP_DIRTY,	/* like SGP_CACHE, but set new page dirty */
+	SGP_WRITE,	/* may exceed i_size, may allocate page */
+};
+
+extern int shmem_getpage(struct inode *inode, unsigned long idx,
+			 struct page **pagep, enum sgp_type sgp, int *type);
+
 /*
  * Compound pages have a destructor function.  Provide a
  * prototype for that function and accessor functions.
diff --git a/mm/shmem.c b/mm/shmem.c
index 4103a23..53118f0 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -83,14 +83,6 @@ static struct vfsmount *shm_mnt;
 /* Pretend that each entry is of this size in directory's i_size */
 #define BOGO_DIRENT_SIZE 20
 
-/* Flag allocation requirements to shmem_getpage and shmem_swp_alloc */
-enum sgp_type {
-	SGP_READ,	/* don't exceed i_size, don't allocate page */
-	SGP_CACHE,	/* don't exceed i_size, may allocate page */
-	SGP_DIRTY,	/* like SGP_CACHE, but set new page dirty */
-	SGP_WRITE,	/* may exceed i_size, may allocate page */
-};
-
 #ifdef CONFIG_TMPFS
 static unsigned long shmem_default_max_blocks(void)
 {
@@ -103,9 +95,6 @@ static unsigned long shmem_default_max_inodes(void)
 }
 #endif
 
-static int shmem_getpage(struct inode *inode, unsigned long idx,
-			 struct page **pagep, enum sgp_type sgp, int *type);
-
 static inline struct page *shmem_dir_alloc(gfp_t gfp_mask)
 {
 	/*
@@ -1187,8 +1176,8 @@ static inline struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
  * vm. If we swap it in we mark it dirty since we also free the swap
  * entry since a page cannot live in both the swap and page cache
  */
-static int shmem_getpage(struct inode *inode, unsigned long idx,
-			struct page **pagep, enum sgp_type sgp, int *type)
+int shmem_getpage(struct inode *inode, unsigned long idx,
+		  struct page **pagep, enum sgp_type sgp, int *type)
 {
 	struct address_space *mapping = inode->i_mapping;
 	struct shmem_inode_info *info = SHMEM_I(inode);
-- 
1.5.4.3

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