From patchwork Wed May 30 10:00:01 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christoph Hellwig X-Patchwork-Id: 10438231 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 05B79601E9 for ; Wed, 30 May 2018 10:01:04 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EA7D3288EF for ; Wed, 30 May 2018 10:01:03 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DBE90288B7; Wed, 30 May 2018 10:01:03 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.8 required=2.0 tests=BAYES_00,DKIM_SIGNED, MAILING_LIST_MULTI, RCVD_IN_DNSWL_NONE, T_DKIM_INVALID autolearn=unavailable version=3.3.1 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 91D63288B7 for ; Wed, 30 May 2018 10:01:02 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id EB1506B027E; Wed, 30 May 2018 06:00:48 -0400 (EDT) Delivered-To: linux-mm-outgoing@kvack.org Received: by kanga.kvack.org (Postfix, from userid 40) id E63576B027F; Wed, 30 May 2018 06:00:48 -0400 (EDT) X-Original-To: int-list-linux-mm@kvack.org X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D28F66B0280; Wed, 30 May 2018 06:00:48 -0400 (EDT) X-Original-To: linux-mm@kvack.org X-Delivered-To: linux-mm@kvack.org Received: from mail-pl0-f71.google.com (mail-pl0-f71.google.com [209.85.160.71]) by kanga.kvack.org (Postfix) with ESMTP id 816266B027E for ; Wed, 30 May 2018 06:00:48 -0400 (EDT) Received: by mail-pl0-f71.google.com with SMTP id c6-v6so942830pll.4 for ; Wed, 30 May 2018 03:00:48 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:dkim-signature:from:to:cc:subject:date :message-id:in-reply-to:references; bh=rrCtBPH3QqluC9AbB2OnGJOZgUzqOyVKgMqZJ6WfOIE=; b=DVn3sBiVn1bndzJwzu9tLaSPBMmBBUDIFwgSyZCxen/Ge7lECtKogTCM8ZjQbA4q9v +heez/SbNBwABcADJSmOtzDHp2jYhBwdzdB27I0ApwyliWwg6vadGJwcEVr0sI3y7E3O L+7Y1DHkn7stKJ509p/Ang0v/7tCgWIfHtKGrLSUYl4M+IJ1zeTfJyDsPT+hsvJXy/+L lUyCQLLUX+vrF723BJ/6NZtqMj/NWkesisApurtGGSbu8Bhq+rXej/mjeUO4+TKJCr4Y oOoWr03y4sN0x3cs8Zqf3BIRoKcd7fE6q0l5DRj0/UyPHP7lZpIR8CdP+JB+Uzr6SDfr jZhQ== X-Gm-Message-State: ALKqPweYKC0sbT3n2xqXnBcPPXnDn1sCzO0vybRFsNYrf7cmkZ1JTlZs Jk0CcPMPSRS3sa3b/SNA6IljoYYtyr83AnCYCAwp34lovNWKz21ym5r0rPw36eHku3b/KA2Fj+q GDUOn3JMSs5HywjWQi53FdkACHQod8bVaJkisVJPKUoVw/TZs6PL0KHpRNYCBdHk= X-Received: by 2002:a63:79ce:: with SMTP id u197-v6mr1699688pgc.284.1527674448119; Wed, 30 May 2018 03:00:48 -0700 (PDT) X-Google-Smtp-Source: ADUXVKJMn1CVJhg/Fx44JN7iaXhHMkdLKLEVz5AxiYE9qrZub9Fmv/KlrfW+8R0Q/EvXqaQaFHu5 X-Received: by 2002:a63:79ce:: with SMTP id u197-v6mr1699580pgc.284.1527674446383; Wed, 30 May 2018 03:00:46 -0700 (PDT) ARC-Seal: i=1; a=rsa-sha256; t=1527674446; cv=none; d=google.com; s=arc-20160816; b=s6VFLrVJH44s9NNFnfvE1ycLUU4yGBuc9kLwDzPapIFyCYZaBF02T9+8FWOi+a1C72 ap0GmgphSpZK1OgA5T2YiWdrWxjzZT7RWd6ijpShvh64eFErU0ifVnIfTYr86nhWtPnE qCYmnfpknDqK2IXw17MBkv8/TLAVf76QprpextIQqyA7qzcKqSOtyASJ+2Ehc1UNOY0L 0AxjhzYUfPaHmHEKTLvgKKtN0LUhqJQk0OImm5CU9rNLfLsQronyRV7rbb6rzBoUyHD5 do391IxBJMrsXsDEiYZIEQEOEl6pbd4nbS4QlRagxU75QxwTgQ3wV5T1dWuiHWM0WW3j H+uA== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816; h=references:in-reply-to:message-id:date:subject:cc:to:from :dkim-signature:arc-authentication-results; bh=rrCtBPH3QqluC9AbB2OnGJOZgUzqOyVKgMqZJ6WfOIE=; b=wG87TKAI3kbcyElBak6ekDUWx2sMpk7obkLTfPxp9+J5HoafHt5gT8lPb5U2J1Ea8w 3OU1QaFE/QUuEtDXBxy3XSZtImPI1fmzYrATFkpCtMC2uz90ecXHEXEylG6BDS38OHKM ppxv8a4kILNcJz/Z7zxfwwyj55M/vTn6WgRVrCM+np614zIrN1ifbNp092qFM30X0DoN 9M4iCctdyK1SuyxlxoyHgDHFau6/RmvZqvC12CVQT3BE4NBhu96OgqZ1oISxGirzO6oz e0MX1zzR5nAXzypRPPSqYVM8cj29DDPBa1jAwCXxfpc83tsQGE44udvFWg+M02Z9EHwq DVKQ== ARC-Authentication-Results: i=1; mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=jbWNApjT; spf=pass (google.com: best guess record for domain of batv+1f4557cc97fec8e307c5+5393+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=BATV+1f4557cc97fec8e307c5+5393+infradead.org+hch@bombadil.srs.infradead.org Received: from bombadil.infradead.org (bombadil.infradead.org. [2607:7c80:54:e::133]) by mx.google.com with ESMTPS id l13-v6si18576163pls.45.2018.05.30.03.00.46 for (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Wed, 30 May 2018 03:00:46 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of batv+1f4557cc97fec8e307c5+5393+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) client-ip=2607:7c80:54:e::133; Authentication-Results: mx.google.com; dkim=pass header.i=@infradead.org header.s=bombadil.20170209 header.b=jbWNApjT; spf=pass (google.com: best guess record for domain of batv+1f4557cc97fec8e307c5+5393+infradead.org+hch@bombadil.srs.infradead.org designates 2607:7c80:54:e::133 as permitted sender) smtp.mailfrom=BATV+1f4557cc97fec8e307c5+5393+infradead.org+hch@bombadil.srs.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=References:In-Reply-To:Message-Id: Date:Subject:Cc:To:From:Sender:Reply-To:MIME-Version:Content-Type: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=rrCtBPH3QqluC9AbB2OnGJOZgUzqOyVKgMqZJ6WfOIE=; b=jbWNApjTUZl3PORiUuhOI92Am ic2NjhX00Lcug0M11M2wQ1Jv1JgZN0azk38UMyQKP9z0l+QJsrtifnqnBh+uChcju8SxwrJvhAySO qzIQeJt6TsbuSRmB181Y0wi35sPypgrPApl8LvkuhJeNjXg3u8XNJPpACqJ9cwqO7aHkG6kfefl4X 9GwGWMkV/8Hl327jN42ov4c1o4J24jlM0FuTr2J466mJM2QHKOpgIeru7u01GRuboboTvV4+oNMWP +jYCRzleoMHgQtjArpJwZf5KUjzV9is8LnsxuhYBC3DtEQkU8Dticx+aNwkEvQiV5otJPMS8pGKnJ y3nOs9PDQ==; Received: from 213-225-38-123.nat.highway.a1.net ([213.225.38.123] helo=localhost) by bombadil.infradead.org with esmtpsa (Exim 4.90_1 #2 (Red Hat Linux)) id 1fNxuM-0008Iu-4F; Wed, 30 May 2018 10:00:42 +0000 From: Christoph Hellwig To: linux-xfs@vger.kernel.org Cc: linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, Dave Chinner Subject: [PATCH 06/18] xfs: make xfs_writepage_map extent map centric Date: Wed, 30 May 2018 12:00:01 +0200 Message-Id: <20180530100013.31358-7-hch@lst.de> X-Mailer: git-send-email 2.17.0 In-Reply-To: <20180530100013.31358-1-hch@lst.de> References: <20180530100013.31358-1-hch@lst.de> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: X-Virus-Scanned: ClamAV using ClamSMTP From: Dave Chinner xfs_writepage_map() iterates over the bufferheads on a page to decide what sort of IO to do and what actions to take. However, when it comes to reflink and deciding when it needs to execute a COW operation, we no longer look at the bufferhead state but instead we ignore than and look up internal state held in teh COW fork extent list. This means xfs_writepage_map() is somewhat confused. It does stuff, then ignores it, then tries to handle the impedence mismatch by shovelling the results inside the existing mapping code. It works, but it's a bit of a mess and it makes it hard to fix the cached map bug that the writepage code currently has. To unify the two different mechanisms, we first have to choose a direction. That's already been set - we're de-emphasising bufferheads so they are no longer a control structure as we need to do taht to allow for eventual removal. Hence we need to move away from looking at bufferhead state to determine what operations we need to perform. We can't completely get rid of bufferheads yet - they do contain some state that is absolutely necessary, such as whether that part of the page contains valid data or not (buffer_uptodate()). Other state in the bufferhead is redundant: BH_dirty - the page is dirty, so we can ignore this and just write it BH_delay - we have delalloc extent info in the DATA fork extent tree BH_unwritten - same as BH_delay BH_mapped - indicates we've already used it once for IO and it is mapped to a disk address. Needs to be ignored for COW blocks. The BH_mapped flag is an interesting case - it's supposed to indicate that it's already mapped to disk and so we can just use it "as is". In theory, we don't even have to do an extent lookup to find where to write it too, but we have to do that anyway to determine we are actually writing over a valid extent. Hence it's not even serving the purpose of avoiding a an extent lookup during writeback, and so we can pretty much ignore it. Especially as we have to ignore it for COW operations... Therefore, use the extent map as the source of information to tell us what actions we need to take and what sort of IO we should perform. The first step is integration xfs_map_blocks() and xfs_map_cow() and have xfs_map_blocks() set the io type according to what it looks up. This means it can easily handle both normal overwrite and COW cases. The only thing we also need to add is the ability to return hole mappings. We need to return and cache hole mappings now for the case of multiple blocks per page. We no longer use the BH_mapped to indicate a block over a hole, so we have to get that info from xfs_map_blocks(). We cache it so that holes that span two pages don't need separate lookups. This allows us to avoid ever doing write IO over a hole, too. Further, we need to drop the XFS_BMAPI_IGSTATE flag so that we don't combine contiguous written and unwritten extents into a single map. The io type needs to match the extent type we are writing to so that we run the correct IO completion routine for the IO. There is scope for optimisation that would allow us to re-instate the XFS_BMAPI_IGSTATE flag, but this requires tweaks to code outside the scope of this change. Now that we have xfs_map_blocks() returning both a cached map and the type of IO we need to perform, we can rewrite xfs_writepage_map() to drop all the bufferhead control. It's also much simplified because it doesn't need to explicitly handle COW operations. Instead of iterating bufferheads, it iterates blocks within the page and then looks up what per-block state is required from the appropriate bufferhead. It then validates the cached map, and if it's not valid, we get a new map. If we don't get a valid map or it's over a hole, we skip the block. At this point, we have to remap the bufferhead via xfs_map_at_offset(). As previously noted, we had to do this even if the buffer was already mapped as the mapping would be stale for XFS_IO_DELALLOC, XFS_IO_UNWRITTEN and XFS_IO_COW IO types. With xfs_map_blocks() now controlling the type, even XFS_IO_OVERWRITE types need remapping, as converted-but-not-yet- written delalloc extents beyond EOF can be reported at XFS_IO_OVERWRITE. Bufferheads that span such regions still need their BH_Delay flags cleared and their block numbers calculated, so we now unconditionally map each bufferhead before submission. But wait! There's more - remember the old "treat unwritten extents as holes on read" hack? Yeah, that means we can have a dirty page with unmapped, unwritten bufferheads that contain data! What makes these so special is that the unwritten "hole" bufferheads do not have a valid block device pointer, so if we attempt to write them xfs_add_to_ioend() blows up. So we make xfs_map_at_offset() do the "realtime or data device" lookup from the inode and ignore what was or wasn't put into the bufferhead when the buffer was instantiated. The astute reader will have realised by now that this code treats unwritten extents in multiple-blocks-per-page situations differently. If we get any combination of unwritten blocks on a dirty page that contain valid data in the page, we're going to convert them to real extents. This can actually be a win, because it means that pages with interleaving unwritten and written blocks will get converted to a single written extent with zeros replacing the interspersed unwritten blocks. This is actually good for reducing extent list and conversion overhead, and it means we issue a contiguous IO instead of lots of little ones. The downside is that we use up a little extra IO bandwidth. Neither of these seem like a bad thing given that spinning disks are seek sensitive, and SSDs/pmem have bandwidth to burn and the lower Io latency/CPU overhead of fewer, larger IOs will result in better performance on them... As a result of all this, the only state we actually care about from the bufferhead is a single flag - BH_Uptodate. We still use the bufferhead to pass some information to the bio via xfs_add_to_ioend(), but that is trivial to separate and pass explicitly. This means we really only need 1 bit of state per block per page from the buffered write path in the writeback path. Everything else we do with the bufferhead is purely to make the buffered IO front end continue to work correctly. i.e we've pretty much marginalised bufferheads in the writeback path completely. Signed-Off-By: Dave Chinner [hch: forward port + slight refactoring] Signed-off-by: Christoph Hellwig Reviewed-by: Darrick J. Wong --- fs/xfs/xfs_aops.c | 273 ++++++++++++++++++++-------------------------- fs/xfs/xfs_aops.h | 4 +- 2 files changed, 124 insertions(+), 153 deletions(-) diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c index 5dd09e83c81c..8cc41a786b5e 100644 --- a/fs/xfs/xfs_aops.c +++ b/fs/xfs/xfs_aops.c @@ -378,78 +378,93 @@ xfs_map_blocks( struct inode *inode, loff_t offset, struct xfs_bmbt_irec *imap, - int type) + int *type) { struct xfs_inode *ip = XFS_I(inode); struct xfs_mount *mp = ip->i_mount; ssize_t count = i_blocksize(inode); xfs_fileoff_t offset_fsb, end_fsb; + int whichfork = XFS_DATA_FORK; int error = 0; - int bmapi_flags = XFS_BMAPI_ENTIRE; int nimaps = 1; if (XFS_FORCED_SHUTDOWN(mp)) return -EIO; - /* - * Truncate can race with writeback since writeback doesn't take the - * iolock and truncate decreases the file size before it starts - * truncating the pages between new_size and old_size. Therefore, we - * can end up in the situation where writeback gets a CoW fork mapping - * but the truncate makes the mapping invalid and we end up in here - * trying to get a new mapping. Bail out here so that we simply never - * get a valid mapping and so we drop the write altogether. The page - * truncation will kill the contents anyway. - */ - if (type == XFS_IO_COW && offset > i_size_read(inode)) - return 0; - - ASSERT(type != XFS_IO_COW); - if (type == XFS_IO_UNWRITTEN) - bmapi_flags |= XFS_BMAPI_IGSTATE; - xfs_ilock(ip, XFS_ILOCK_SHARED); ASSERT(ip->i_d.di_format != XFS_DINODE_FMT_BTREE || (ip->i_df.if_flags & XFS_IFEXTENTS)); ASSERT(offset <= mp->m_super->s_maxbytes); + if (xfs_is_reflink_inode(ip) && + xfs_reflink_find_cow_mapping(ip, offset, imap)) { + xfs_iunlock(ip, XFS_ILOCK_SHARED); + /* + * Truncate can race with writeback since writeback doesn't + * take the iolock and truncate decreases the file size before + * it starts truncating the pages between new_size and old_size. + * Therefore, we can end up in the situation where writeback + * gets a CoW fork mapping but the truncate makes the mapping + * invalid and we end up in here trying to get a new mapping. + * bail out here so that we simply never get a valid mapping + * and so we drop the write altogether. The page truncation + * will kill the contents anyway. + */ + if (offset > i_size_read(inode)) + return 0; + whichfork = XFS_COW_FORK; + *type = XFS_IO_COW; + goto allocate_blocks; + } + if (offset > mp->m_super->s_maxbytes - count) count = mp->m_super->s_maxbytes - offset; end_fsb = XFS_B_TO_FSB(mp, (xfs_ufsize_t)offset + count); offset_fsb = XFS_B_TO_FSBT(mp, offset); error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, - imap, &nimaps, bmapi_flags); - /* - * Truncate an overwrite extent if there's a pending CoW - * reservation before the end of this extent. This forces us - * to come back to writepage to take care of the CoW. - */ - if (nimaps && type == XFS_IO_OVERWRITE) + imap, &nimaps, XFS_BMAPI_ENTIRE); + if (!nimaps) { + /* + * Lookup returns no match? Beyond eof? regardless, + * return it as a hole so we don't write it + */ + imap->br_startoff = offset_fsb; + imap->br_blockcount = end_fsb - offset_fsb; + imap->br_startblock = HOLESTARTBLOCK; + *type = XFS_IO_HOLE; + } else if (imap->br_startblock == HOLESTARTBLOCK) { + /* landed in a hole */ + *type = XFS_IO_HOLE; + } else { + if (isnullstartblock(imap->br_startblock)) { + /* got a delalloc extent */ + *type = XFS_IO_DELALLOC; + goto allocate_blocks; + } + + /* + * Got an existing extent for overwrite. Truncate it if there + * is a pending CoW reservation before the end of this extent, + * so that we pick up the COW extents in the next iteration. + */ xfs_reflink_trim_irec_to_next_cow(ip, offset_fsb, imap); + if (imap->br_state == XFS_EXT_UNWRITTEN) + *type = XFS_IO_UNWRITTEN; + else + *type = XFS_IO_OVERWRITE; + } xfs_iunlock(ip, XFS_ILOCK_SHARED); - if (error) - return error; - - if (type == XFS_IO_DELALLOC && - (!nimaps || isnullstartblock(imap->br_startblock))) { - error = xfs_iomap_write_allocate(ip, XFS_DATA_FORK, offset, - imap); - if (!error) - trace_xfs_map_blocks_alloc(ip, offset, count, type, imap); - return error; - } + trace_xfs_map_blocks_found(ip, offset, count, *type, imap); + return error; -#ifdef DEBUG - if (type == XFS_IO_UNWRITTEN) { - ASSERT(nimaps); - ASSERT(imap->br_startblock != HOLESTARTBLOCK); - ASSERT(imap->br_startblock != DELAYSTARTBLOCK); - } -#endif - if (nimaps) - trace_xfs_map_blocks_found(ip, offset, count, type, imap); - return 0; +allocate_blocks: + xfs_iunlock(ip, XFS_ILOCK_SHARED); + if (!error) + error = xfs_iomap_write_allocate(ip, whichfork, offset, imap); + if (!error) + trace_xfs_map_blocks_alloc(ip, offset, count, *type, imap); + return error; } STATIC bool @@ -709,6 +724,14 @@ xfs_map_at_offset( set_buffer_mapped(bh); clear_buffer_delay(bh); clear_buffer_unwritten(bh); + + /* + * If this is a realtime file, data may be on a different device. + * to that pointed to from the buffer_head b_bdev currently. We can't + * trust that the bufferhead has a already been mapped correctly, so + * set the bdev now. + */ + bh->b_bdev = xfs_find_bdev_for_inode(inode); } STATIC void @@ -769,56 +792,6 @@ xfs_aops_discard_page( xfs_vm_invalidatepage(page, 0, PAGE_SIZE); } -static int -xfs_map_cow( - struct xfs_writepage_ctx *wpc, - struct inode *inode, - loff_t offset, - unsigned int *new_type) -{ - struct xfs_inode *ip = XFS_I(inode); - struct xfs_bmbt_irec imap; - bool is_cow = false; - int error; - - /* - * If we already have a valid COW mapping keep using it. - */ - if (wpc->io_type == XFS_IO_COW) { - wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap, offset); - if (wpc->imap_valid) { - *new_type = XFS_IO_COW; - return 0; - } - } - - /* - * Else we need to check if there is a COW mapping at this offset. - */ - xfs_ilock(ip, XFS_ILOCK_SHARED); - is_cow = xfs_reflink_find_cow_mapping(ip, offset, &imap); - xfs_iunlock(ip, XFS_ILOCK_SHARED); - - if (!is_cow) - return 0; - - /* - * And if the COW mapping has a delayed extent here we need to - * allocate real space for it now. - */ - if (isnullstartblock(imap.br_startblock)) { - error = xfs_iomap_write_allocate(ip, XFS_COW_FORK, offset, - &imap); - if (error) - return error; - } - - wpc->io_type = *new_type = XFS_IO_COW; - wpc->imap_valid = true; - wpc->imap = imap; - return 0; -} - /* * We implement an immediate ioend submission policy here to avoid needing to * chain multiple ioends and hence nest mempool allocations which can violate @@ -845,85 +818,81 @@ xfs_writepage_map( { LIST_HEAD(submit_list); struct xfs_ioend *ioend, *next; - struct buffer_head *bh, *head; + struct buffer_head *bh; ssize_t len = i_blocksize(inode); - uint64_t offset; int error = 0; int count = 0; - int uptodate = 1; - unsigned int new_type; + bool uptodate = true; + loff_t file_offset; /* file offset of page */ + unsigned poffset; /* offset into page */ - bh = head = page_buffers(page); - offset = page_offset(page); - do { - if (offset >= end_offset) + /* + * Walk the blocks on the page, and we we run off then end of the + * current map or find the current map invalid, grab a new one. + * We only use bufferheads here to check per-block state - they no + * longer control the iteration through the page. This allows us to + * replace the bufferhead with some other state tracking mechanism in + * future. + */ + file_offset = page_offset(page); + bh = page_buffers(page); + for (poffset = 0; + poffset < PAGE_SIZE; + poffset += len, file_offset += len, bh = bh->b_this_page) { + /* past the range we are writing, so nothing more to write. */ + if (file_offset >= end_offset) break; - if (!buffer_uptodate(bh)) - uptodate = 0; /* - * set_page_dirty dirties all buffers in a page, independent - * of their state. The dirty state however is entirely - * meaningless for holes (!mapped && uptodate), so skip - * buffers covering holes here. + * Block does not contain valid data, skip it, mark the current + * map as invalid because we have a discontiguity. This ensures + * we put subsequent writeable buffers into a new ioend. */ - if (!buffer_mapped(bh) && buffer_uptodate(bh)) { - wpc->imap_valid = false; - continue; - } - - if (buffer_unwritten(bh)) - new_type = XFS_IO_UNWRITTEN; - else if (buffer_delay(bh)) - new_type = XFS_IO_DELALLOC; - else if (buffer_uptodate(bh)) - new_type = XFS_IO_OVERWRITE; - else { + if (!buffer_uptodate(bh)) { if (PageUptodate(page)) ASSERT(buffer_mapped(bh)); - /* - * This buffer is not uptodate and will not be - * written to disk. Ensure that we will put any - * subsequent writeable buffers into a new - * ioend. - */ + uptodate = false; wpc->imap_valid = false; continue; } - if (xfs_is_reflink_inode(XFS_I(inode))) { - error = xfs_map_cow(wpc, inode, offset, &new_type); - if (error) - goto out; - } - - if (wpc->io_type != new_type) { - wpc->io_type = new_type; - wpc->imap_valid = false; - } - + /* Check to see if current map spans this file offset */ if (wpc->imap_valid) wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap, - offset); + file_offset); + /* + * If we don't have a valid map, now it's time to get a new one + * for this offset. This will convert delayed allocations + * (including COW ones) into real extents. If we return without + * a valid map, it means we landed in a hole and we skip the + * block. + */ if (!wpc->imap_valid) { - error = xfs_map_blocks(inode, offset, &wpc->imap, - wpc->io_type); + error = xfs_map_blocks(inode, file_offset, &wpc->imap, + &wpc->io_type); if (error) goto out; wpc->imap_valid = xfs_imap_valid(inode, &wpc->imap, - offset); + file_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) { + /* + * set_page_dirty dirties all buffers in a page, independent + * of their state. The dirty state however is entirely + * meaningless for holes (!mapped && uptodate), so check we did + * have a buffer covering a hole here and continue. + */ + continue; } - } while (offset += len, ((bh = bh->b_this_page) != head)); + lock_buffer(bh); + xfs_map_at_offset(inode, bh, &wpc->imap, file_offset); + xfs_add_to_ioend(inode, bh, file_offset, wpc, wbc, &submit_list); + count++; + } - if (uptodate && bh == head) + if (uptodate && poffset == PAGE_SIZE) SetPageUptodate(page); ASSERT(wpc->ioend || list_empty(&submit_list)); diff --git a/fs/xfs/xfs_aops.h b/fs/xfs/xfs_aops.h index 69346d460dfa..b2ef5b661761 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.