Re: [PATCH v8 04/22] Change direct_access calling convention

[Matthew Wilcox]

On Wed, Jul 30, 2014 at 07:12:44PM +0300, Boaz Harrosh wrote:
> Off course I was wrong here size is in bytes not in sectors. Which points
> out that maybe this API needs to be in sectors.
> 
> [Actually it needs to be in pages both size and offset, because of return of
> pfn, but its your call.]

I considered a number of options here.  The VM wants things to be in pages.
The filesystem wants things to be in block size.  The block device wants
things to be in sectors.  It's all a mess when you try and converge.
Everybody understands bytes.

Here's what I've come up with on top of patch 4/22.  Let me know what
you think.


diff --git a/arch/powerpc/sysdev/axonram.c b/arch/powerpc/sysdev/axonram.c
index 3ee1c08..741293f 100644
--- a/arch/powerpc/sysdev/axonram.c
+++ b/arch/powerpc/sysdev/axonram.c
@@ -146,11 +146,6 @@ axon_ram_direct_access(struct block_device *device, sector_t sector,
 	struct axon_ram_bank *bank = device->bd_disk->private_data;
 	loff_t offset = (loff_t)sector << AXON_RAM_SECTOR_SHIFT;
 
-	if (offset >= bank->size) {
-		dev_err(&bank->device->dev, "Access outside of address space\n");
-		return -ERANGE;
-	}
-
 	*kaddr = (void *)(bank->ph_addr + offset);
 	*pfn = virt_to_phys(*kaddr) >> PAGE_SHIFT;
 
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 33a39e7..3483458 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -378,10 +378,6 @@ static long brd_direct_access(struct block_device *bdev, sector_t sector,
 
 	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 -ENOSPC;
diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index 58958d1..2ee5556 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -877,11 +877,7 @@ dcssblk_direct_access (struct block_device *bdev, sector_t secnum,
 	if (!dev_info)
 		return -ENODEV;
 	dev_sz = dev_info->end - dev_info->start;
-	if (secnum % (PAGE_SIZE/512))
-		return -EINVAL;
 	offset = secnum * 512;
-	if (offset > dev_sz)
-		return -ERANGE;
 	*kaddr = (void *) (dev_info->start + offset);
 	*pfn = virt_to_phys(*kaddr) >> PAGE_SHIFT;
 
diff --git a/fs/block_dev.c b/fs/block_dev.c
index f1a158e..93ebdd53 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -450,8 +450,14 @@ long bdev_direct_access(struct block_device *bdev, sector_t sector,
 	const struct block_device_operations *ops = bdev->bd_disk->fops;
 	if (!ops->direct_access)
 		return -EOPNOTSUPP;
-	return ops->direct_access(bdev, sector + get_start_sect(bdev), addr,
-					pfn, size);
+	if ((sector + DIV_ROUND_UP(size, 512)) >
+					part_nr_sects_read(bdev->bd_part))
+		return -ERANGE;
+	sector += get_start_sect(bdev);
+	if (sector % (PAGE_SIZE / 512))
+		return -EINVAL;
+	size = ops->direct_access(bdev, sector, addr, pfn, size);
+	return size ? size : -ERANGE;
 }
 EXPORT_SYMBOL_GPL(bdev_direct_access);
 
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