From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Holden Karau" Subject: Re: [PATCH 1/1] fat: improve sync performance by grouping writes revised Date: Tue, 31 Oct 2006 22:10:39 -0500 Message-ID: References: <454765AC.1050905@xandros.com> <20061031162825.GD26964@parisc-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: "Holden Karau" , "Josef Sipek" , hirofumi@mail.parknet.co.jp, linux-kernel@vger.kernel.org, "akpm@osdl.org" , linux-fsdevel@vger.kernel.org, "Nick Piggin" , "J?rn Engel" Return-path: Received: from nf-out-0910.google.com ([64.233.182.187]:29682 "EHLO nf-out-0910.google.com") by vger.kernel.org with ESMTP id S1423850AbWKADKq (ORCPT ); Tue, 31 Oct 2006 22:10:46 -0500 Received: by nf-out-0910.google.com with SMTP id c2so587910nfe for ; Tue, 31 Oct 2006 19:10:45 -0800 (PST) To: "Matthew Wilcox" In-Reply-To: Content-Disposition: inline Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org I was thinking about the issue of running out of memory, while its not particularly likely to happen except on devices with huge disks and tiney amount of memory, it is a possibility. I can make it fall-through to the previous way of doing things, does that sound like a reasonable idea? On 10/31/06, Holden Karau wrote: > On 10/31/06, Matthew Wilcox wrote: > > On Tue, Oct 31, 2006 at 10:03:08AM -0500, Holden Karau wrote: > > > @@ -343,52 +344,65 @@ int fat_ent_read(struct inode *inode, st > > > return ops->ent_get(fatent); > > > } > > > > > > -/* FIXME: We can write the blocks as more big chunk. */ > > > -static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs, > > > - int nr_bhs) > > > + > > > +static int fat_mirror_bhs_optw(struct super_block *sb, struct buffer_head **bhs, > > > + int nr_bhs , int wait) > > > { > > > struct msdos_sb_info *sbi = MSDOS_SB(sb); > > > - struct buffer_head *c_bh; > > > + struct buffer_head *c_bh[nr_bhs*(sbi->fats)]; > > > int err, n, copy; > > > > > > + /* Always wait if mounted -o sync */ > > > + if (sb->s_flags & MS_SYNCHRONOUS ) > > > + wait = 1; > > > err = 0; > > > for (copy = 1; copy < sbi->fats; copy++) { > > > sector_t backup_fat = sbi->fat_length * copy; > > > - > > > - for (n = 0; n < nr_bhs; n++) { > > > - c_bh = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr); > > > - if (!c_bh) { > > > + for (n = 0 ; n < nr_bhs ; n++ ) { > > > + c_bh[(copy-1)*nr_bhs+n] = sb_getblk(sb, backup_fat + bhs[n]->b_blocknr); > > > + if (!c_bh[(copy-1)*nr_bhs+n]) { > > > + printk(KERN_CRIT "fat: out of memory while copying backup fat. possible data loss\n"); > > > > I don't like that at all. > Not much to be done about that. The amount of memory required is > fairly small, but if its not there its not there. > > > > > err = -ENOMEM; > > > goto error; > > > } > > > - memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize); > > > - set_buffer_uptodate(c_bh); > > > - mark_buffer_dirty(c_bh); > > > - if (sb->s_flags & MS_SYNCHRONOUS) > > > - err = sync_dirty_buffer(c_bh); > > > - brelse(c_bh); > > > - if (err) > > > - goto error; > > > + memcpy(c_bh[(copy-1)*nr_bhs+n]->b_data, bhs[n]->b_data, sb->s_blocksize); > > > + set_buffer_uptodate(c_bh[(copy-1)*nr_bhs+n]); > > > + mark_buffer_dirty(c_bh[(copy-1)*nr_bhs+n]); > > > } > > > } > > > + > > > + if (wait) { > > > + for (n = 0 ; n < nr_bhs ; n++) { > > > + printk("copying to %d to %d\n" ,n, nr_bhs*(sbi->fats-1)+n); > > > > Is this the right version of the patch? The printk should never be left in. > > Plus, as far as I can tell, that whole loop is actually just memcpy(). > whoops. That was in for debugging, I thought I took that out. The loop > structure is how it was before, but I don't see a way to get rid of > it, do you have an idea? > > > > > -- > Cell: 613-276-1645 > -- Cell: 613-276-1645