On Tue, Dec 04, 2007 at 12:06:23PM +0000, Duane Griffin wrote:
> On 04/12/2007, Nick Piggin <[EMAIL PROTECTED]> wrote:
> > +       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);
> 
> I think that should be alloc_page(gfp_flags), no?

Yes. Here is a resend. Andrew, please apply this one (has passed some
testing with ext2 XIP).

--

Support direct_access XIP method with brd.

Signed-off-by: Nick Piggin <[EMAIL PROTECTED]>
---
Index: linux-2.6/drivers/block/Kconfig
===================================================================
--- linux-2.6.orig/drivers/block/Kconfig
+++ linux-2.6/drivers/block/Kconfig
@@ -346,6 +346,16 @@ 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: linux-2.6/drivers/block/brd.c
===================================================================
--- linux-2.6.orig/drivers/block/brd.c
+++ linux-2.6/drivers/block/brd.c
@@ -89,6 +89,7 @@ static struct page *brd_insert_page(stru
 {
        pgoff_t idx;
        struct page *page;
+       gfp_t gfp_flags;
 
        page = brd_lookup_page(brd, sector);
        if (page)
@@ -97,8 +98,17 @@ static struct page *brd_insert_page(stru
        /*
         * 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.
         */
-       page = alloc_page(GFP_NOIO | __GFP_HIGHMEM | __GFP_ZERO);
+       gfp_flags = GFP_NOIO | __GFP_ZERO;
+#ifndef CONFIG_BLK_DEV_XIP
+       gfp_flags |= __GFP_HIGHMEM;
+#endif
+       page = alloc_page(gfp_flags);
        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
 }
 
 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
 };
 
 /*
-
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