[patch?] RAMFS

[patch?] RAMFS

[Mike Galbraith]

Hi,

With the patch below, ramfs will withstand make -j20 (binutils)
even while an iozone is running, and cp /dev/zero zero.  These
fail as is.  The problem seems to be in the way writepage() is
called.. ClearPageDirty(); writepage().  That screws up ramfs's
beancounting and makes it wipe pages and do double accounting.
(df;cp /dev/zero zero;rm zero;df to see accounting woes).

Accounting only from ramfs_prepare_write() seems to be enough for
the page limit to function (whodathunkit;)

	-Mike

--- linux-2.4.1.ac2/fs/ramfs/inode.c.org	Sat Feb  3 10:29:54 2001
+++ linux-2.4.1.ac2/fs/ramfs/inode.c	Sat Feb  3 19:22:08 2001
@@ -173,11 +173,8 @@
 	       (inode->i_data.nrpages <= rsb->max_file_pages) ) ) {
 		inode->i_blocks += IBLOCKS_PER_PAGE;
 		rsb->free_pages--;
-		SetPageDirty(page);
-	} else {
-		ClearPageUptodate(page);
+	} else
 		ret = 0;
-	}
 	
 	unlock_rsb(rsb);
 
@@ -259,13 +256,7 @@
  */
 static int ramfs_writepage(struct page *page)
 {
-	struct inode *inode = (struct inode *)page->mapping->host;
-
-	if (! ramfs_alloc_page(inode, page))
-	{
-		UnlockPage(page);
-		return -ENOSPC;
-	}
+	SetPageDirty(page);
 	UnlockPage(page);
 	return 0;
 }
@@ -275,9 +266,8 @@
 	struct inode *inode = (struct inode *)page->mapping->host;
 	void *addr;
 	
-	if (! ramfs_alloc_page(inode, page)) {
+	if (! ramfs_alloc_page(inode, page))
 		return -ENOSPC;
-	}
 
 	addr = (void *) kmap(page);
 	if (!Page_Uptodate(page)) {
@@ -285,6 +275,7 @@
 		flush_dcache_page(page);
 		SetPageUptodate(page);
 	}
+	SetPageDirty(page);
 	return 0;
 }
 

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Re: [patch?] RAMFS

[Mike Galbraith]

On Sat, 3 Feb 2001, Mike Galbraith wrote:

> Hi,
> 
> With the patch below...

However, tmpfs appears to cover the functionality provided by ramfs.
Are there any uses for ramfs which can't be handled by tmpfs?

The only thing I could think of was "what if you don't have a
swap device up and running".  Seems it doesn't need one :))

	-Mike

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Re: [patch?] RAMFS

[Christoph Rohland]

Mike Galbraith <mikeg@wen-online.de> writes:

> However, tmpfs appears to cover the functionality provided by ramfs.
> Are there any uses for ramfs which can't be handled by tmpfs?

Nothing I know of.

> The only thing I could think of was "what if you don't have a
> swap device up and running".  Seems it doesn't need one :))

Yes and no. tmpfs has a little bit overhead for the noswap case but
this overhead is in the kernel anyways for shared anon mappings. The
whole vm is using swap unconditionally.

Greetings
                Christoph



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Re: [patch?] RAMFS

[David Woodhouse]

On 4 Feb 2001, Christoph Rohland wrote:

> Yes and no. tmpfs has a little bit overhead for the noswap case but
> this overhead is in the kernel anyways for shared anon mappings. The
> whole vm is using swap unconditionally.

I'm hoping that'll end up conditional on CONFIG_BLK_DEV or CONFIG_SWAP. 

-- 
dwmw2


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