From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx3-rdu2.redhat.com ([66.187.233.73]:36500 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755212AbeFRRik (ORCPT ); Mon, 18 Jun 2018 13:38:40 -0400 Date: Mon, 18 Jun 2018 13:38:38 -0400 From: Brian Foster To: Christoph Hellwig Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: Re: [PATCH 11/24] xfs: remove xfs_map_cow Message-ID: <20180618173837.GA40796@bfoster> References: <20180615130209.1970-1-hch@lst.de> <20180615130209.1970-12-hch@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180615130209.1970-12-hch@lst.de> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Fri, Jun 15, 2018 at 03:01:56PM +0200, Christoph Hellwig wrote: > We can handle the existing cow mapping case as a special case directly > in xfs_writepage_map, and share code for allocating delalloc blocks > with regular I/O in xfs_map_blocks. This means we need to always > call xfs_map_blocks for reflink inodes, but we can still skip most of > the work if it turns out that there is no COW mapping overlapping the > current block. > > As a subtle detail we need to start caching holes in the wpc to deal > with the case of COW reservations between EOF. But we'll need that > infrastructure later anyway, so this is no big deal. > > Based on a patch from Dave Chinner. > > Signed-off-by: Christoph Hellwig > --- > fs/xfs/xfs_aops.c | 186 ++++++++++++++++++++++------------------------ > fs/xfs/xfs_aops.h | 4 +- > 2 files changed, 92 insertions(+), 98 deletions(-) > > diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c > index c8fc6786b06c..ff27bdcc49a1 100644 > --- a/fs/xfs/xfs_aops.c > +++ b/fs/xfs/xfs_aops.c ... > @@ -887,22 +877,24 @@ xfs_writepage_map( > if (wpc->imap_valid) > wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap, > offset); > - if (!wpc->imap_valid) { > - error = xfs_map_blocks(inode, offset, &wpc->imap, > - wpc->io_type); A comment would be nice here just so the purpose of the logic is clear at a glance. E.g: /* * COW fork blocks can overlap data fork blocks even if the * blocks aren't shared. COW I/O always takes precedent, so we * must always check for overlap on reflink inodes unless the * mapping is already COW. */ With something like that, this now looks pretty good to me: Reviewed-by: Brian Foster Note: I see that this code ends up shifted into xfs_map_blocks(). If it's easier to add the comment in whatever patch touches that last, that's fine too. Brian > + if (!wpc->imap_valid || > + (xfs_is_reflink_inode(XFS_I(inode)) && > + wpc->io_type != XFS_IO_COW)) { > + error = xfs_map_blocks(wpc, inode, offset); > if (error) > goto out; > wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap, > offset); > } > - if (wpc->imap_valid) { > - lock_buffer(bh); > - if (wpc->io_type != XFS_IO_OVERWRITE) > - xfs_map_at_offset(inode, bh, &wpc->imap, offset); > - xfs_add_to_ioend(inode, bh, offset, wpc, wbc, &submit_list); > - count++; > - } > > + if (!wpc->imap_valid || wpc->io_type == XFS_IO_HOLE) > + continue; > + > + lock_buffer(bh); > + if (wpc->io_type != XFS_IO_OVERWRITE) > + xfs_map_at_offset(inode, bh, &wpc->imap, offset); > + xfs_add_to_ioend(inode, bh, offset, wpc, wbc, &submit_list); > + count++; > } while (offset += len, ((bh = bh->b_this_page) != head)); > > ASSERT(wpc->ioend || list_empty(&submit_list)); > diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h > index 694c85b03813..466d22e5bc36 100644 > --- a/fs/xfs/xfs_aops.h > +++ b/fs/xfs/xfs_aops.h > @@ -29,6 +29,7 @@ enum { > XFS_IO_UNWRITTEN, /* covers allocated but uninitialized data */ > XFS_IO_OVERWRITE, /* covers already allocated extent */ > XFS_IO_COW, /* covers copy-on-write extent */ > + XFS_IO_HOLE, /* covers region without any block allocation */ > }; > > #define XFS_IO_TYPES \ > @@ -36,7 +37,8 @@ enum { > { XFS_IO_DELALLOC, "delalloc" }, \ > { XFS_IO_UNWRITTEN, "unwritten" }, \ > { XFS_IO_OVERWRITE, "overwrite" }, \ > - { XFS_IO_COW, "CoW" } > + { XFS_IO_COW, "CoW" }, \ > + { XFS_IO_HOLE, "hole" } > > /* > * Structure for buffered I/O completions. > -- > 2.17.1 > > -- > 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