rd: support XIP
Nick Piggin [Fri, 8 Feb 2008 12:19:50 +0000 (04:19 -0800)]
Support direct_access XIP method with brd.

Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/block/Kconfig
drivers/block/brd.c

index 8be67cd..b6d230b 100644 (file)
@@ -357,6 +357,16 @@ config BLK_DEV_RAM_SIZE
          The default value is 4096 kilobytes. Only change this if you know
          what you are doing.
 
+config BLK_DEV_XIP
+       bool "Support XIP filesystems on RAM block device"
+       depends on BLK_DEV_RAM
+       default n
+       help
+         Support XIP filesystems (such as ext2 with XIP support on) on
+         top of block ram device. This will slightly enlarge the kernel, and
+         will prevent RAM block device backing store memory from being
+         allocated from highmem (only a problem for highmem systems).
+
 config CDROM_PKTCDVD
        tristate "Packet writing on CD/DVD media"
        depends on !UML
index 50b659b..8536480 100644 (file)
@@ -89,6 +89,7 @@ static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
 {
        pgoff_t idx;
        struct page *page;
+       gfp_t gfp_flags;
 
        page = brd_lookup_page(brd, sector);
        if (page)
@@ -97,7 +98,16 @@ static struct page *brd_insert_page(struct brd_device *brd, sector_t sector)
        /*
         * Must use NOIO because we don't want to recurse back into the
         * block or filesystem layers from page reclaim.
+        *
+        * Cannot support XIP and highmem, because our ->direct_access
+        * routine for XIP must return memory that is always addressable.
+        * If XIP was reworked to use pfns and kmap throughout, this
+        * restriction might be able to be lifted.
         */
+       gfp_flags = GFP_NOIO | __GFP_ZERO;
+#ifndef CONFIG_BLK_DEV_XIP
+       gfp_flags |= __GFP_HIGHMEM;
+#endif
        page = alloc_page(GFP_NOIO | __GFP_HIGHMEM | __GFP_ZERO);
        if (!page)
                return NULL;
@@ -307,6 +317,28 @@ out:
        return 0;
 }
 
+#ifdef CONFIG_BLK_DEV_XIP
+static int brd_direct_access (struct block_device *bdev, sector_t sector,
+                       unsigned long *data)
+{
+       struct brd_device *brd = bdev->bd_disk->private_data;
+       struct page *page;
+
+       if (!brd)
+               return -ENODEV;
+       if (sector & (PAGE_SECTORS-1))
+               return -EINVAL;
+       if (sector + PAGE_SECTORS > get_capacity(bdev->bd_disk))
+               return -ERANGE;
+       page = brd_insert_page(brd, sector);
+       if (!page)
+               return -ENOMEM;
+       *data = (unsigned long)page_address(page);
+
+       return 0;
+}
+#endif
+
 static int brd_ioctl(struct inode *inode, struct file *file,
                        unsigned int cmd, unsigned long arg)
 {
@@ -342,8 +374,11 @@ static int brd_ioctl(struct inode *inode, struct file *file,
 }
 
 static struct block_device_operations brd_fops = {
-       .owner =        THIS_MODULE,
-       .ioctl =        brd_ioctl,
+       .owner =                THIS_MODULE,
+       .ioctl =                brd_ioctl,
+#ifdef CONFIG_BLK_DEV_XIP
+       .direct_access =        brd_direct_access,
+#endif
 };
 
 /*