From mboxrd@z Thu Jan 1 00:00:00 1970 From: =?ISO-8859-15?Q?Luk=E1=A8_Czerner?= Subject: Re: [PATCH] ext4: Allocate entire range in zero range Date: Thu, 5 Mar 2015 12:43:58 +0100 (CET) Message-ID: References: <1424278168-13711-1-git-send-email-lczerner@redhat.com> Mime-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: esandeen@redhat.com, tytso@mit.edu To: linux-ext4@vger.kernel.org Return-path: Received: from mx1.redhat.com ([209.132.183.28]:39128 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755252AbbCELoF (ORCPT ); Thu, 5 Mar 2015 06:44:05 -0500 In-Reply-To: <1424278168-13711-1-git-send-email-lczerner@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: Eric, can I get some review on this one ? Ted, I think this is quite critical, could you please ACK this one so we know whether it's going in or not ? Thanks! -Lukas On Wed, 18 Feb 2015, Lukas Czerner wrote: > Date: Wed, 18 Feb 2015 17:49:28 +0100 > From: Lukas Czerner > To: linux-ext4@vger.kernel.org > Cc: Lukas Czerner > Subject: [PATCH] ext4: Allocate entire range in zero range > > Currently there is a bug in zero range code which causes zero range > calls to only allocate block aligned portion of the range, while > ignoring the rest in some cases. > > In some cases, namely if the end of the range is past isize, we do > attempt to preallocate the last nonaligned block. However this might > cause kernel to BUG() in some carefully designed zero range requests on > setups where page size > block size. > > Fix this problem by first preallocating the entire range, including the > nonaligned edges and converting the written extents to unwritten in the > next step. This approach will also give us the advantage of having the > range to be as linearly contiguous as possible. > > Signed-off-by: Lukas Czerner > --- > fs/ext4/extents.c | 31 +++++++++++++++++++------------ > 1 file changed, 19 insertions(+), 12 deletions(-) > > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c > index bed4308..aa52242 100644 > --- a/fs/ext4/extents.c > +++ b/fs/ext4/extents.c > @@ -4803,12 +4803,6 @@ static long ext4_zero_range(struct file *file, loff_t offset, > else > max_blocks -= lblk; > > - flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT | > - EXT4_GET_BLOCKS_CONVERT_UNWRITTEN | > - EXT4_EX_NOCACHE; > - if (mode & FALLOC_FL_KEEP_SIZE) > - flags |= EXT4_GET_BLOCKS_KEEP_SIZE; > - > mutex_lock(&inode->i_mutex); > > /* > @@ -4825,15 +4819,28 @@ static long ext4_zero_range(struct file *file, loff_t offset, > ret = inode_newsize_ok(inode, new_size); > if (ret) > goto out_mutex; > - /* > - * If we have a partial block after EOF we have to allocate > - * the entire block. > - */ > - if (partial_end) > - max_blocks += 1; > } > > + flags = EXT4_GET_BLOCKS_CREATE_UNWRIT_EXT; > + if (mode & FALLOC_FL_KEEP_SIZE) > + flags |= EXT4_GET_BLOCKS_KEEP_SIZE; > + > + /* Preallocate the range including the unaligned edges */ > + if (partial_begin || partial_end) { > + ret = ext4_alloc_file_blocks(file, > + round_down(offset, 1 << blkbits) >> blkbits, > + (round_up((offset + len), 1 << blkbits) - > + round_down(offset, 1 << blkbits)) >> blkbits, > + new_size, flags, mode); > + if (ret) > + goto out_mutex; > + > + } > + > + /* Zero range excluding the unaligned edges */ > if (max_blocks > 0) { > + flags |= (EXT4_GET_BLOCKS_CONVERT_UNWRITTEN | > + EXT4_EX_NOCACHE); > > /* Now release the pages and zero block aligned part of pages*/ > truncate_pagecache_range(inode, start, end - 1); >