From: =?ISO-8859-15?Q?Luk=E1=A8_Czerner?= Subject: Re: ext4_wait_block_bitmap() and ext4_read_block_bitmap_nowait() handle bitmap verification differently Date: Mon, 7 Oct 2013 14:45:49 +0200 (CEST) Message-ID: References: Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: "linux-ext4@vger.kernel.org List" To: jon ernst Return-path: Received: from mx1.redhat.com ([209.132.183.28]:5622 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751520Ab3JGMp5 (ORCPT ); Mon, 7 Oct 2013 08:45:57 -0400 In-Reply-To: Sender: linux-ext4-owner@vger.kernel.org List-ID: On Thu, 3 Oct 2013, jon ernst wrote: > Date: Thu, 3 Oct 2013 22:45:06 -0400 > From: jon ernst > To: "linux-ext4@vger.kernel.org List" > Subject: ext4_wait_block_bitmap() and ext4_read_block_bitmap_nowait() handle > bitmap verification differently > > Hi, Hi Jon, Btw the patch has some issues and it seems to be badly formatted, or even corrupted. You're also missing some Signed-off-by line and the subject is not good either. Please see Documentation/SubmittingPatches, use git to create patches and use email client which does not automatically wrap your lines. > > I found that ext4_wait_block_bitmap() and > ext4_read_block_bitmap_nowait() handle bitmap verification > differently. > wait_block_bitmap() calls ext4_validate_block_bitmap() all the time. > But read_block_bitmap_nowait() checks EXT4_BG_BLOCK_UNINIT, if it > meets, it will skip ext4_validate_block_bitmap() > > In my opinion, they'd better do same thing. Why ? > In that way, we can also return "fail" in ext4_valid_block_bitmap() > method when we meet FLEX_BG. This does not make sense at all. Why do you suggest that we should "fail" in the case that we have FLEG_BG feature enabled (which is default btw) ? > > > > diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c > index dc5d572..366807a 100644 > --- a/fs/ext4/balloc.c > +++ b/fs/ext4/balloc.c > @@ -319,7 +319,7 @@ static ext4_fsblk_t ext4_valid_block_bitmap(struct > super_block *sb, > * or it has to also read the block group where the bitmaps > * are located to verify they are set. > */ > - return 0; > + return 1; > } > group_first_block = ext4_group_first_block_no(sb, block_group); > > @@ -472,8 +472,12 @@ int ext4_wait_block_bitmap(struct super_block > *sb, ext4_group_t block_group, > return 1; > } > clear_buffer_new(bh); > - /* Panic or remount fs read-only if block bitmap is invalid */ > - ext4_validate_block_bitmap(sb, desc, block_group, bh); > + > + if (desc->bg_flags & cpu_to_le16(EXT4_BG_BLOCK_UNINIT)) { > + return 0; This is wrong from multiple reasons. First of all you're not holding group lock so what is preventing others to actually initialize the bitmap before you return 0 ? Secondly, uninit group will never get that far, because it'll be initialized in ext4_read_block_bitmap_nowait() and we will not actually need to wait for the buffer. Thanks! -Lukas > + } > + /* Panic or remount fs read-only if block bitmap is invalid */ > + ext4_validate_block_bitmap(sb, desc, block_group, bh); > /* ...but check for error just in case errors=continue. */ > return !buffer_verified(bh); > } > -- > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >