linux-kernel - Re: [PATCH -mm] rescue large xfs preferred iosize from the inode diet patch

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Date:	Fri, 22 Sep 2006 12:03:30 +1000
From:	Timothy Shimmin <tes@....com>
To:	Eric Sandeen <sandeen@...deen.net>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	xfs mailing list <xfs@....sgi.com>
Subject: Re: [PATCH -mm] rescue large xfs preferred iosize from the inode
 diet patch

Hi Eric,

Eric Sandeen wrote:
> The inode diet patch in -mm unhooked xfs_preferred_iosize from the stat call:
> 
> --- a/fs/xfs/linux-2.6/xfs_vnode.c
> +++ b/fs/xfs/linux-2.6/xfs_vnode.c
> @@ -122,7 +122,6 @@ vn_revalidate_core(
>         inode->i_blocks     = vap->va_nblocks;
>         inode->i_mtime      = vap->va_mtime;
>         inode->i_ctime      = vap->va_ctime;
> -       inode->i_blksize    = vap->va_blocksize;
>         if (vap->va_xflags & XFS_XFLAG_IMMUTABLE)
> 
> This in turn breaks the largeio mount option for xfs:
> 
>   largeio/nolargeio
>         If "nolargeio" is specified, the optimal I/O reported in
>         st_blksize by stat(2) will be as small as possible to allow user
>         applications to avoid inefficient read/modify/write I/O.
>         If "largeio" specified, a filesystem that has a "swidth" specified
>         will return the "swidth" value (in bytes) in st_blksize. If the
>         filesystem does not have a "swidth" specified but does specify
>         an "allocsize" then "allocsize" (in bytes) will be returned
>         instead.
>         If neither of these two options are specified, then filesystem
>         will behave as if "nolargeio" was specified.
> 
> and the (undocumented?) allocsize mount option as well.
> 
> For a filesystem like this with sunit/swidth specified,
> 
> meta-data=/dev/sda1              isize=512    agcount=32, agsize=7625840 blks
>          =                       sectsz=512   attr=0
> data     =                       bsize=4096   blocks=244026880, imaxpct=25
>          =                       sunit=16     swidth=16 blks, unwritten=1
> naming   =version 2              bsize=4096
> log      =internal               bsize=4096   blocks=32768, version=1
>          =                       sectsz=512   sunit=0 blks
> realtime =none                   extsz=65536  blocks=0, rtextents=0
> 
> stat on a stock FC6 kernel w/ the largeio mount option returns only the page size:
> 
> [root@...k-07]# mount -o largeio /dev/sda1 /mnt/test/
> [root@...k-07]# stat -c %o /mnt/test/foo
> 4096
> 
> with the following patch, it does what it should:
> 
> [root@...k-07]# mount -o largeio /dev/sda1 /mnt/test/
> [root@...k-07]# stat -c %o /mnt/test/foo
> 65536
> 
> same goes for filesystems w/o sunit,swidth but with the allocsize mount option.
> 
> stock:
> [root@...k-07]# mount -o largeio,allocsize=32768 /dev/sda1 /mnt/test/
> [root@...k-07]# stat -c %o /mnt/test/foo
> 4096
> 
> w/ patch:
> [root@...k-07# mount -o largeio,allocsize=32768 /dev/sda1 /mnt/test/
> [root@...k-07]# stat -c %o /mnt/test/foo
> 32768
> 
> Signed-off-by: Eric Sandeen <sandeen@...deen.net>
> 
> XFS guys, does this look ok?
> 
> Index: linux-2.6.18/fs/xfs/linux-2.6/xfs_iops.c
> ===================================================================
> --- linux-2.6.18.orig/fs/xfs/linux-2.6/xfs_iops.c
> +++ linux-2.6.18/fs/xfs/linux-2.6/xfs_iops.c
> @@ -623,12 +623,16 @@ xfs_vn_getattr(
>  {
>  	struct inode	*inode = dentry->d_inode;
>  	bhv_vnode_t	*vp = vn_from_inode(inode);
> +	xfs_inode_t	*ip;
>  	int		error = 0;
>  
>  	if (unlikely(vp->v_flag & VMODIFIED))
>  		error = vn_revalidate(vp);
> -	if (!error)
> +	if (!error) {
>  		generic_fillattr(inode, stat);
> +		ip = xfs_vtoi(vp);
> +		stat->blksize = xfs_preferred_iosize(ip->i_mount);
> +	}
>  	return -error;
>  }
>  

Looked at your patch and then at our xfs code in the tree and
the existing code is different than what yours is based on.
I then noticed in the logs Nathan has actually made changes for this:

----------------------------
revision 1.254
date: 2006/07/17 10:46:05;  author: nathans;  state: Exp;  lines: +20 -5
modid: xfs-linux-melb:xfs-kern:26565a
Update XFS for i_blksize removal from generic inode structure
----------------------------
I even reviewed the change (and I don't remember it - getting old).

I looked at the mods scheduled for 2.6.19 and this is one of them.

So the fix for this is coming soon (and the fix is different from the
one above).

Cheers,
Tim.
-
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