linux-kernel - Re: [patch 3/5] fuse: fix race in llseek

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Message-Id: <E1JqO9C-0003zM-E2@pomaz-ex.szeredi.hu>
Date:	Mon, 28 Apr 2008 09:51:38 +0200
From:	Miklos Szeredi <miklos@...redi.hu>
To:	akpm@...ux-foundation.org
CC:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [patch 3/5] fuse: fix race in llseek

> > +static loff_t fuse_file_llseek(struct file *file, loff_t offset, int origin)
> > +{
> > +	long long retval;
> 
> I switched this to have a type of loff_t.

Ugh, right.  I wonder where that long long came from.  I probably
copied the generic_file_llseek() from some earlier kernel...

> 
> > +	struct inode *inode = file->f_path.dentry->d_inode;
> > +
> > +	mutex_lock(&inode->i_mutex);
> > +	switch (origin) {
> > +	case SEEK_END:
> > +		offset += i_size_read(inode);
> 
> As we hold i_mutex we could directly read inode->i_size here, save a few
> cycles.

No, that's the whole point of the fuse specific function: fuse doesn't
use i_mutex to protect writing i_size, instead it uses a per
filesystem spinlock.

This is probably worth a comment though, so I'll do that.

Thanks,
Miklos
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