linux-kernel - Re: [PATCH 4/11] eCryptfs: Replace encrypt, decrypt, and inode size write

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Date:	Thu, 20 Sep 2007 19:35:57 -0400
From:	Erez Zadok <ezk@...sunysb.edu>
To:	Michael Halcrow <mhalcrow@...ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	ecryptfs-devel@...ts.sourceforge.net
Subject: Re: [PATCH 4/11] eCryptfs: Replace encrypt, decrypt, and inode size write 

In message <20070920214447.GB8496@...crow.austin.ibm.com>, Michael Halcrow writes:
> On Wed, Sep 19, 2007 at 10:46:26PM -0700, Andrew Morton wrote:
> (from ecryptfs_encrypt_page()):
> > > +	enc_extent_virt = kmalloc(PAGE_CACHE_SIZE, GFP_USER);
> > 
> > I'd have thought that alloc_page() would be nicer.  After all, we _are_
> > treating it as a page, and not as a random piece of memry.
> >
> > > +	if (!enc_extent_virt) {
> > > +		rc = -ENOMEM;
> > > +		ecryptfs_printk(KERN_ERR, "Error allocating memory for "
> > > +				"encrypted extent\n");
> > > +		goto out;
> > > +	}
> > > +	enc_extent_page = virt_to_page(enc_extent_virt);
> > 
> > And then we don't need this.
> 
> If neither kmap() nor kmap_atomic() can be safely used to get a
> virtual address to pass to vfs_write(), then I do not know what my
> other options are here.

kmap_atomic is intended for short-lived code sections, where you may not
sleep, so you can't do a vfs_read/write in b/t kmap/kunmap_atomic.

Erez.
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