linux-kernel - Re: [PATCH 1/2] LSEEK: BTRFS: Avoid i_mutex for SEEK

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Date:	Sat, 5 Nov 2011 11:27:49 -0400
From:	Chris Mason <chris.mason@...cle.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Andres Freund <andres@...razel.de>,
	Andi Kleen <andi@...stfloor.org>, robertmhaas@...il.com,
	viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-btrfs@...r.kernel.org
Subject: Re: [PATCH 1/2] LSEEK: BTRFS: Avoid i_mutex for SEEK_{CUR,SET,END}

On Wed, Nov 02, 2011 at 04:29:15AM -0400, Christoph Hellwig wrote:
> Andres, can you check with Chris that the btrfs changes made it to
> his tree?  The core lseek changes from Andi are in mainline now, but
> I think these bits are better off going through Chrises btrfs tree.

I'm pulling these in, thanks!

-chris

> 
> On Sat, Oct 01, 2011 at 10:49:27PM +0200, Andres Freund wrote:
> > 
> > Don't need the i_mutex for those cases, only for SEEK_HOLE/DATA.
> > 
> > Really-From: Andi Kleen <ak@...ux.intel.com>
> > Signed-off-by: Andi Kleen <ak@...ux.intel.com>
> > Signed-off-by: Andres Freund <andres@...razel.de>
> > ---
> >  fs/btrfs/file.c |   27 +++++++++++----------------
> >  1 files changed, 11 insertions(+), 16 deletions(-)
> > 
> > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
> > index 7a13337..5bc7116 100644
> > --- a/fs/btrfs/file.c
> > +++ b/fs/btrfs/file.c
> > @@ -1809,24 +1809,19 @@ static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int origin)
> >  	struct inode *inode = file->f_mapping->host;
> >  	int ret;
> >  
> > +	if (origin != SEEK_DATA && origin != SEEK_HOLE)
> > +		return generic_file_llseek(file, offset, origin);
> > +
> >  	mutex_lock(&inode->i_mutex);
> > -	switch (origin) {
> > -	case SEEK_END:
> > -	case SEEK_CUR:
> > -		offset = generic_file_llseek(file, offset, origin);
> > -		goto out;
> > -	case SEEK_DATA:
> > -	case SEEK_HOLE:
> > -		if (offset >= i_size_read(inode)) {
> > -			mutex_unlock(&inode->i_mutex);
> > -			return -ENXIO;
> > -		}
> > +	if (offset >= i_size_read(inode)) {
> > +		mutex_unlock(&inode->i_mutex);
> > +		return -ENXIO;
> > +	}
> >  
> > -		ret = find_desired_extent(inode, &offset, origin);
> > -		if (ret) {
> > -			mutex_unlock(&inode->i_mutex);
> > -			return ret;
> > -		}
> > +	ret = find_desired_extent(inode, &offset, origin);
> > +	if (ret) {
> > +		mutex_unlock(&inode->i_mutex);
> > +		return ret;
> >  	}
> >  
> >  	if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET)) {
> > -- 
> > 1.7.6.409.ge7a85.dirty
> > 
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
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> > More majordomo info at  http://vger.kernel.org/majordomo-info.html
> ---end quoted text---
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