From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Robert W. Fuller" Subject: Re: nobh option to ext2 Date: Sat, 01 Jan 2005 19:10:33 -0500 Message-ID: <41D73BF9.5050509@sbcglobal.net> References: <41D73636.4080405@sbcglobal.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from smtp814.mail.sc5.yahoo.com ([66.163.170.84]:851 "HELO smtp814.mail.sc5.yahoo.com") by vger.kernel.org with SMTP id S261189AbVABAKf (ORCPT ); Sat, 1 Jan 2005 19:10:35 -0500 To: linux-fsdevel@vger.kernel.org In-Reply-To: <41D73636.4080405@sbcglobal.net> Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org http://www.tldp.org/LDP/lki/lki-4.html helped some, but I need more information! Robert W. Fuller wrote: > I must first admit I'm a bit of a newbie. That having been said, what > exactly does the nobh option to ext2 do? Perhaps you can recommend > resources to me that detail the interaction between the memory manager > and the file systems? I'm looking for something that means more to me > than: > > "Implements a new set of block address_space_operations which will never > attach buffer_heads to file pagecache. These can be turned on for ext2 > with the `nobh' mount option. > > During write-intensive testing on a 7G machine, total buffer_head > storage remained below 0.3 megabytes. And those buffer_heads are > against ZONE_NORMAL pagecache and will be reclaimed by ZONE_NORMAL > memory pressure. > > This work is, of course, a special for the huge highmem machines. > Possibly it obsoletes the buffer_heads_over_limit stuff (which doesn't > work terribly well), but that code is simple, and will provide relief > for other filesystems. > > > It should be noted that the nobh_prepare_write() function and the > PageMappedToDisk() infrastructure is what is needed to solve the > problem of user data corruption when the filesystem which backs a > sparse MAP_SHARED mapping runs out of space. We can use this code in > filemap_nopage() to ensure that all mapped pages have space allocated > on-disk. Deliver SIGBUS on ENOSPC." > > Regards, > > Rob > - > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >