From: "Satyam Sharma" Subject: Re: [PATCH 2/5] jffs2: Add LZO compression support to jffs2 Date: Fri, 4 May 2007 14:36:16 +0530 Message-ID: References: <1178030823.5883.54.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: LKML , "David Woodhouse" , herbert@gondor.apana.org.au, linux-mtd , linux-crypto@vger.kernel.org To: "Richard Purdie" Return-path: Received: from wr-out-0506.google.com ([64.233.184.235]:40105 "EHLO wr-out-0506.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1767744AbXEDJGS (ORCPT ); Fri, 4 May 2007 05:06:18 -0400 Received: by wr-out-0506.google.com with SMTP id 76so829243wra for ; Fri, 04 May 2007 02:06:17 -0700 (PDT) In-Reply-To: <1178030823.5883.54.camel@localhost.localdomain> Content-Disposition: inline Sender: linux-crypto-owner@vger.kernel.org List-Id: linux-crypto.vger.kernel.org Hi Richard, On 5/1/07, Richard Purdie wrote: > Add LZO1X compression/decompression support to jffs2. > > LZO's interface doesn't entirely match that required by jffs2 so a > buffer and memcpy is unavoidable. > > Signed-off-by: Richard Purdie > --- > [...] > +++ b/fs/jffs2/compr_lzo.c > [...] > +static void *lzo_mem; > +static void *lzo_compress_buf; > +static DEFINE_MUTEX(deflate_mutex); > + > +static void free_workspace(void) > +{ > + vfree(lzo_mem); > + vfree(lzo_compress_buf); > +} > + > +static int __init alloc_workspace(void) > +{ > + lzo_mem = vmalloc(LZO1X_MEM_COMPRESS); > + lzo_compress_buf = vmalloc(lzo1x_worst_compress(PAGE_SIZE)); > + > + if (!lzo_mem || !lzo_compress_buf) { > + printk(KERN_WARNING "Failed to allocate lzo deflate workspace\n"); > + free_workspace(); > + return -ENOMEM; > + } > + > + return 0; > +} > + > +static int jffs2_lzo_compress(unsigned char *data_in, unsigned char *cpage_out, > + uint32_t *sourcelen, uint32_t *dstlen, void *model) > +{ > + unsigned long compress_size; > + int ret; > + > + mutex_lock(&deflate_mutex); > + ret = lzo1x_1_compress(data_in, *sourcelen, lzo_compress_buf, &compress_size, lzo_mem); > + mutex_unlock(&deflate_mutex); Considering we do have to memcpy() the entire compressed result to the destination output buffer later anyway (note that fs/jffs2/compr_zlib.c doesn't need to do that), do we really gain much by avoiding vmalloc() and vfree() in jffs2_lzo_compress() itself and keeping the workspace buffers pre-allocated? I ask because I always found these global static workspace buffers ugly, and all the associated code + mutex could go away if we make them local to jffs2_lzo_compress() -- as long as it doesn't hurt performance terribly, of course. Thanks, Satyam