xip: support non-struct page backed memory

Convert XIP to support non-struct page backed memory, using VM_MIXEDMAP for
the user mappings.

This requires the get_xip_page API to be changed to an address based one.
Improve the API layering a little bit too, while we're here.

This is required in order to support XIP filesystems on memory that isn't
backed with struct page (but memory with struct page is still supported too).

Signed-off-by: Nick Piggin <npiggin@suse.de>
Acked-by: Carsten Otte <cotte@de.ibm.com>
Cc: Jared Hulbert <jaredeh@gmail.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 21 insertions, 27 deletions

diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c
index b8a2990..687023b 100644
--- a/fs/ext2/inode.c
+++ b/fs/ext2/inode.c
@@ -796,7 +796,7 @@ const struct address_space_operations ext2_aops = {
 
 const struct address_space_operations ext2_aops_xip = {
 	.bmap			= ext2_bmap,
-	.get_xip_page		= ext2_get_xip_page,
+	.get_xip_mem		= ext2_get_xip_mem,
 };
 
 const struct address_space_operations ext2_nobh_aops = {
diff --git a/fs/ext2/xip.c b/fs/ext2/xip.c
index 430b4c8..233f7fd 100644
--- a/fs/ext2/xip.c
+++ b/fs/ext2/xip.c
@@ -15,26 +15,28 @@
 #include "xip.h"
 
 static inline int
-__inode_direct_access(struct inode *inode, sector_t sector,
+__inode_direct_access(struct inode *inode, sector_t block,
 		      void **kaddr, unsigned long *pfn)
 {
 	struct block_device *bdev = inode->i_sb->s_bdev;
 	struct block_device_operations *ops = bdev->bd_disk->fops;
+	sector_t sector;
+
+	sector = block * (PAGE_SIZE / 512); /* ext2 block to bdev sector */
 
 	BUG_ON(!ops->direct_access);
 	return ops->direct_access(bdev, sector, kaddr, pfn);
 }
 
 static inline int
-__ext2_get_sector(struct inode *inode, sector_t offset, int create,
+__ext2_get_block(struct inode *inode, pgoff_t pgoff, int create,
 		   sector_t *result)
 {
 	struct buffer_head tmp;
 	int rc;
 
 	memset(&tmp, 0, sizeof(struct buffer_head));
-	rc = ext2_get_block(inode, offset/ (PAGE_SIZE/512), &tmp,
-			    create);
+	rc = ext2_get_block(inode, pgoff, &tmp, create);
 	*result = tmp.b_blocknr;
 
 	/* did we get a sparse block (hole in the file)? */
@@ -47,14 +49,13 @@ __ext2_get_sector(struct inode *inode, sector_t offset, int create,
 }
 
 int
-ext2_clear_xip_target(struct inode *inode, int block)
+ext2_clear_xip_target(struct inode *inode, sector_t block)
 {
-	sector_t sector = block * (PAGE_SIZE/512);
 	void *kaddr;
 	unsigned long pfn;
 	int rc;
 
-	rc = __inode_direct_access(inode, sector, &kaddr, &pfn);
+	rc = __inode_direct_access(inode, block, &kaddr, &pfn);
 	if (!rc)
 		clear_page(kaddr);
 	return rc;
@@ -72,26 +73,18 @@ void ext2_xip_verify_sb(struct super_block *sb)
 	}
 }
 
-struct page *
-ext2_get_xip_page(struct address_space *mapping, sector_t offset,
-		   int create)
+int ext2_get_xip_mem(struct address_space *mapping, pgoff_t pgoff, int create,
+				void **kmem, unsigned long *pfn)
 {
 	int rc;
-	void *kaddr;
-	unsigned long pfn;
-	sector_t sector;
+	sector_t block;
 
 	/* first, retrieve the sector number */
-	rc = __ext2_get_sector(mapping->host, offset, create, &sector);
+	rc = __ext2_get_block(mapping->host, pgoff, create, &block);
 	if (rc)
-		goto error;
+		return rc;
 
 	/* retrieve address of the target data */
-	rc = __inode_direct_access
-		(mapping->host, sector * (PAGE_SIZE/512), &kaddr, &pfn);
-	if (!rc)
-		return pfn_to_page(pfn);
-
- error:
-	return ERR_PTR(rc);
+	rc = __inode_direct_access(mapping->host, block, kmem, pfn);
+	return rc;
 }
diff --git a/fs/ext2/xip.h b/fs/ext2/xip.h
index aa85331..18b34d2 100644
--- a/fs/ext2/xip.h
+++ b/fs/ext2/xip.h
@@ -7,19 +7,20 @@
 
 #ifdef CONFIG_EXT2_FS_XIP
 extern void ext2_xip_verify_sb (struct super_block *);
-extern int ext2_clear_xip_target (struct inode *, int);
+extern int ext2_clear_xip_target (struct inode *, sector_t);
 
 static inline int ext2_use_xip (struct super_block *sb)
 {
 	struct ext2_sb_info *sbi = EXT2_SB(sb);
 	return (sbi->s_mount_opt & EXT2_MOUNT_XIP);
 }
-struct page* ext2_get_xip_page (struct address_space *, sector_t, int);
-#define mapping_is_xip(map) unlikely(map->a_ops->get_xip_page)
+int ext2_get_xip_mem(struct address_space *, pgoff_t, int,
+				void **, unsigned long *);
+#define mapping_is_xip(map) unlikely(map->a_ops->get_xip_mem)
 #else
 #define mapping_is_xip(map)			0
 #define ext2_xip_verify_sb(sb)			do { } while (0)
 #define ext2_use_xip(sb)			0
 #define ext2_clear_xip_target(inode, chain)	0
-#define ext2_get_xip_page			NULL
+#define ext2_get_xip_mem			NULL
 #endif