[PATCH 14/14] Pramfs: XIP operations

[PATCH 14/14] Pramfs: XIP operations

[Marco]

From: Marco Stornelli <marco.stornelli@gmail.com>

XIP operations.

Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>
---

diff -uprN linux-2.6.30-orig/fs/pramfs/xip.c linux-2.6.30/fs/pramfs/xip.c
--- linux-2.6.30-orig/fs/pramfs/xip.c	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.30/fs/pramfs/xip.c	2009-06-13 12:54:26.000000000 +0200
@@ -0,0 +1,90 @@
+/*
+ * FILE NAME fs/pramfs/xip.c
+ *
+ * BRIEF DESCRIPTION
+ *
+ * XIP operations.
+ *
+ * Copyright 2009 Marco Stornelli <marco.stornelli@gmail.com>
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#include <linux/mm.h>
+#include <linux/fs.h>
+#include <linux/genhd.h>
+#include <linux/buffer_head.h>
+#include "pram_fs.h"
+#include "xip.h"
+
+static int pram_find_and_alloc_blocks(struct inode *inode, sector_t iblock,
+				     sector_t *data_block, int create)
+{
+	int err = -EIO;
+	off_t block;
+
+	lock_kernel();
+
+	block = pram_find_data_block(inode, iblock);
+
+	if (!block) {
+		if (!create) {
+			err = -ENODATA;
+			goto err;
+		}
+
+		err = pram_alloc_blocks(inode, iblock, 1);
+		if (err)
+			goto err;
+
+		block = pram_find_data_block(inode, iblock);
+		if (!block) {
+			err = -ENODATA;
+			goto err;
+		}
+	}
+
+	*data_block = block;
+	err = 0;
+
+ err:
+	unlock_kernel();
+	return err;
+}
+
+
+static int __pram_get_block(struct inode *inode, pgoff_t pgoff, int create,
+		   sector_t *result)
+{
+	int rc = 0;
+	sector_t iblock;
+
+	/* find starting block number to access */
+	iblock = (sector_t)pgoff << (PAGE_CACHE_SHIFT - inode->i_blkbits);
+
+	rc = pram_find_and_alloc_blocks(inode, iblock, result, create);
+
+	if (rc == -ENODATA)
+		BUG_ON(create);
+
+	return rc;
+}
+
+int pram_get_xip_mem(struct address_space *mapping, pgoff_t pgoff, int create,
+				void **kmem, unsigned long *pfn)
+{
+	int rc;
+	sector_t block;
+
+	/* first, retrieve the block */
+	rc = __pram_get_block(mapping->host, pgoff, create, &block);
+	if (rc)
+		goto exit;
+
+	*kmem = pram_get_block(mapping->host->i_sb, block);
+	*pfn = page_to_pfn(virt_to_page((unsigned long)*kmem));
+
+exit:
+	return rc;
+}
diff -uprN linux-2.6.30-orig/fs/pramfs/xip.h linux-2.6.30/fs/pramfs/xip.h
--- linux-2.6.30-orig/fs/pramfs/xip.h	1970-01-01 01:00:00.000000000 +0100
+++ linux-2.6.30/fs/pramfs/xip.h	2009-03-28 14:59:13.000000000 +0100
@@ -0,0 +1,25 @@
+/*
+ * FILE NAME fs/pramfs/xip.h
+ *
+ * BRIEF DESCRIPTION
+ *
+ * XIP operations.
+ *
+ * Author: Marco Stornelli <marco.stornelli@gmail.com>
+ *
+ * This file is licensed under the terms of the GNU General Public
+ * License version 2. This program is licensed "as is" without any
+ * warranty of any kind, whether express or implied.
+ */
+
+#ifdef CONFIG_PRAMFS_XIP
+
+int pram_get_xip_mem(struct address_space *, pgoff_t, int, void **,
+							      unsigned long *);
+
+#else
+
+#define pram_get_xip_mem NULL
+
+#endif
+

Re: [PATCH 14/14] Pramfs: XIP operations

[Sam Ravnborg]

On Sat, Jun 13, 2009 at 03:23:13PM +0200, Marco wrote:
> From: Marco Stornelli <marco.stornelli@gmail.com>
> 
> XIP operations.
> 
> Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>
> ---
> 
> diff -uprN linux-2.6.30-orig/fs/pramfs/xip.c linux-2.6.30/fs/pramfs/xip.c
> --- linux-2.6.30-orig/fs/pramfs/xip.c	1970-01-01 01:00:00.000000000 +0100
> +++ linux-2.6.30/fs/pramfs/xip.c	2009-06-13 12:54:26.000000000 +0200
> @@ -0,0 +1,90 @@
> +/*
> + * FILE NAME fs/pramfs/xip.c
> + *
> + * BRIEF DESCRIPTION
> + *
> + * XIP operations.
> + *
> + * Copyright 2009 Marco Stornelli <marco.stornelli@gmail.com>
> + * This file is licensed under the terms of the GNU General Public
> + * License version 2. This program is licensed "as is" without any
> + * warranty of any kind, whether express or implied.
> + */
> +
> +#include <linux/mm.h>
> +#include <linux/fs.h>
> +#include <linux/genhd.h>
> +#include <linux/buffer_head.h>
> +#include "pram_fs.h"
> +#include "xip.h"
> +
> +static int pram_find_and_alloc_blocks(struct inode *inode, sector_t iblock,
> +				     sector_t *data_block, int create)
> +{
> +	int err = -EIO;
> +	off_t block;
> +
> +	lock_kernel();

Can we find other solutions than taking the BKL?
We are trying to get rid of it.

> +
> +	block = pram_find_data_block(inode, iblock);
> +
> +	if (!block) {
> +		if (!create) {
> +			err = -ENODATA;
> +			goto err;
> +		}
> +
> +		err = pram_alloc_blocks(inode, iblock, 1);
> +		if (err)
> +			goto err;
> +
> +		block = pram_find_data_block(inode, iblock);
> +		if (!block) {
> +			err = -ENODATA;
> +			goto err;
> +		}
> +	}
> +
> +	*data_block = block;
> +	err = 0;
> +
> + err:
> +	unlock_kernel();
> +	return err;
> +}
> +

Re: [PATCH 14/14] Pramfs: XIP operations

[Marco]

Sam Ravnborg wrote:
> On Sat, Jun 13, 2009 at 03:23:13PM +0200, Marco wrote:
>> From: Marco Stornelli <marco.stornelli@gmail.com>
>>
>> XIP operations.
>>
>> Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>
>> ---
>>
>> diff -uprN linux-2.6.30-orig/fs/pramfs/xip.c linux-2.6.30/fs/pramfs/xip.c
>> --- linux-2.6.30-orig/fs/pramfs/xip.c	1970-01-01 01:00:00.000000000 +0100
>> +++ linux-2.6.30/fs/pramfs/xip.c	2009-06-13 12:54:26.000000000 +0200
>> @@ -0,0 +1,90 @@
>> +/*
>> + * FILE NAME fs/pramfs/xip.c
>> + *
>> + * BRIEF DESCRIPTION
>> + *
>> + * XIP operations.
>> + *
>> + * Copyright 2009 Marco Stornelli <marco.stornelli@gmail.com>
>> + * This file is licensed under the terms of the GNU General Public
>> + * License version 2. This program is licensed "as is" without any
>> + * warranty of any kind, whether express or implied.
>> + */
>> +
>> +#include <linux/mm.h>
>> +#include <linux/fs.h>
>> +#include <linux/genhd.h>
>> +#include <linux/buffer_head.h>
>> +#include "pram_fs.h"
>> +#include "xip.h"
>> +
>> +static int pram_find_and_alloc_blocks(struct inode *inode, sector_t iblock,
>> +				     sector_t *data_block, int create)
>> +{
>> +	int err = -EIO;
>> +	off_t block;
>> +
>> +	lock_kernel();
> 
> Can we find other solutions than taking the BKL?
> We are trying to get rid of it.
> 

I know. It wasn't my intention to introduce it but as I said in my first
patch I've done a porting of this code from 2.6.10 and to remove it I
need time to analyze well the code to avoid deadlock and so on. If
someone would like to help me I'd really appreciate it. However I see
the use of BKL even in other recent "mainlined" fs as ext4, so I
preferred to move the porting effort on other areas. However it's the
first item on my todo list.

Re: [PATCH 14/14] Pramfs: XIP operations

[Jared Hulbert]

> I know. It wasn't my intention to introduce it but as I said in my first
> patch I've done a porting of this code from 2.6.10 and to remove it I
> need time to analyze well the code to avoid deadlock and so on. If
> someone would like to help me I'd really appreciate it. However I see
> the use of BKL even in other recent "mainlined" fs as ext4, so I
> preferred to move the porting effort on other areas. However it's the
> first item on my todo list.


Why do you need the lock in pram_find_and_alloc_blocks() to begin
with?  Why wouldn't a mutex work?