From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:37590 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933359AbdEON2j (ORCPT ); Mon, 15 May 2017 09:28:39 -0400 Date: Mon, 15 May 2017 09:28:37 -0400 From: Brian Foster Subject: Re: [PATCH 2/2] xfs: Move handling of missing page into one place in xfs_find_get_desired_pgoff() Message-ID: <20170515132834.GB27809@bfoster.bfoster> References: <20170511165023.29887-1-jack@suse.cz> <20170511165023.29887-2-jack@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170511165023.29887-2-jack@suse.cz> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Jan Kara Cc: "Darrick J . Wong" , linux-xfs@vger.kernel.org On Thu, May 11, 2017 at 06:50:23PM +0200, Jan Kara wrote: > Currently several places in xfs_find_get_desired_pgoff() handle the case > of a missing page. Make them all handled in one place after the loop has > terminated. > > Signed-off-by: Jan Kara > --- > fs/xfs/xfs_file.c | 24 ++++++++---------------- > 1 file changed, 8 insertions(+), 16 deletions(-) > > diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c > index df51c025adfe..719923b99ba1 100644 > --- a/fs/xfs/xfs_file.c > +++ b/fs/xfs/xfs_file.c > @@ -1069,10 +1069,6 @@ xfs_find_get_desired_pgoff( > break; > > ASSERT(type == HOLE_OFF); > - if (lastoff == startoff || lastoff < endoff) { > - found = true; > - *offset = lastoff; > - } > break; > } > > @@ -1080,11 +1076,8 @@ xfs_find_get_desired_pgoff( > * At least we found one page. If the current offset is smaller > * than the first page offset, a hole was found. > */ > - if (type == HOLE_OFF && lastoff < page_offset(pvec.pages[0])) { > - found = true; > - *offset = lastoff; > + if (type == HOLE_OFF && lastoff < page_offset(pvec.pages[0])) > break; > - } > > for (i = 0; i < nr_pages; i++) { > struct page *page = pvec.pages[i]; FWIW, it looks like there's still a bug here that the first patch doesn't address: # xfs_io -fc "truncate 0" -c "falloc 0 32k" -c "pwrite 0 4k" -c "pwrite 32k 4k" -c "seek -h 0" /mnt/file wrote 4096/4096 bytes at offset 0 4 KiB, 1 ops; 0.0000 sec (126.008 MiB/sec and 32258.0645 ops/sec) wrote 4096/4096 bytes at offset 32768 4 KiB, 1 ops; 0.0000 sec (102.796 MiB/sec and 26315.7895 ops/sec) Whence Result HOLE 36864 # xfs_io -c fsync -c "seek -h 0" /mnt/file Whence Result HOLE 4096 I initially thought this patch might fix it, but on further digging it doesn't appear to. What looks like is going on here is that the 'page->index > end' check doesn't actually catch this case of the page being just beyond the current unwritten extent (perhaps the check should be 'page->index >= end'), so lastoff is set beyond end and we skip the hole. Brian > @@ -1150,21 +1143,20 @@ xfs_find_get_desired_pgoff( > > /* > * The number of returned pages less than our desired, search > - * done. In this case, nothing was found for searching data, > - * but we found a hole behind the last offset. > + * done. > */ > - if (nr_pages < want) { > - if (type == HOLE_OFF) { > - *offset = lastoff; > - found = true; > - } > + if (nr_pages < want) > break; > - } > > index = pvec.pages[i - 1]->index + 1; > pagevec_release(&pvec); > } while (index <= end); > > + /* No page at lastoff and we are not done - we found a hole. */ > + if (type == HOLE_OFF && lastoff < endoff) { > + *offset = lastoff; > + found = true; > + } > out: > pagevec_release(&pvec); > return found; > -- > 2.12.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-xfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html