From: Greg KH <greg@kroah.com>
To: Anand Jain <anand.jain@oracle.com>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
wqu@suse.com, fdmanana@suse.com, dsterba@suse.com,
linux-btrfs@vger.kernel.org
Subject: Re: [PATCH stable-5.4 6/6] btrfs: allow btrfs_truncate_block() to fallback to nocow for data space reservation
Date: Fri, 9 Oct 2020 16:06:48 +0200 [thread overview]
Message-ID: <20201009140648.GB573779@kroah.com> (raw)
In-Reply-To: <9df7b36688030028271fe5d4265512328534f9b6.1599750901.git.anand.jain@oracle.com>
On Thu, Oct 08, 2020 at 06:59:54PM +0800, Anand Jain wrote:
> From: Qu Wenruo <wqu@suse.com>
>
> commit 6d4572a9d71d5fc2affee0258d8582d39859188c upstream.
>
> [BUG]
> When the data space is exhausted, even if the inode has NOCOW attribute,
> we will still refuse to truncate unaligned range due to ENOSPC.
>
> The following script can reproduce it pretty easily:
> #!/bin/bash
>
> dev=/dev/test/test
> mnt=/mnt/btrfs
>
> umount $dev &> /dev/null
> umount $mnt &> /dev/null
>
> mkfs.btrfs -f $dev -b 1G
> mount -o nospace_cache $dev $mnt
> touch $mnt/foobar
> chattr +C $mnt/foobar
>
> xfs_io -f -c "pwrite -b 4k 0 4k" $mnt/foobar > /dev/null
> xfs_io -f -c "pwrite -b 4k 0 1G" $mnt/padding &> /dev/null
> sync
>
> xfs_io -c "fpunch 0 2k" $mnt/foobar
> umount $mnt
>
> Currently this will fail at the fpunch part.
>
> [CAUSE]
> Because btrfs_truncate_block() always reserves space without checking
> the NOCOW attribute.
>
> Since the writeback path follows NOCOW bit, we only need to bother the
> space reservation code in btrfs_truncate_block().
>
> [FIX]
> Make btrfs_truncate_block() follow btrfs_buffered_write() to try to
> reserve data space first, and fall back to NOCOW check only when we
> don't have enough space.
>
> Such always-try-reserve is an optimization introduced in
> btrfs_buffered_write(), to avoid expensive btrfs_check_can_nocow() call.
>
> This patch will export check_can_nocow() as btrfs_check_can_nocow(), and
> use it in btrfs_truncate_block() to fix the problem.
>
> Reported-by: Martin Doucha <martin.doucha@suse.com>
> Reviewed-by: Filipe Manana <fdmanana@suse.com>
> Reviewed-by: Anand Jain <anand.jain@oracle.com>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> Reviewed-by: David Sterba <dsterba@suse.com>
> Signed-off-by: David Sterba <dsterba@suse.com>
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> Conflicts:
> fs/btrfs/ctree.h
> fs/btrfs/file.c
> fs/btrfs/inode.c
Why are these Conflicts: lines here?
Anyway, fixed up, and all queued up now, thansk!
greg k-h
prev parent reply other threads:[~2020-10-09 14:06 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-08 10:59 [PATCH stable-5.4 0/6] backport fixes for xfstests btrfs/199,200,203,204 Anand Jain
2020-10-08 10:59 ` [PATCH stable-5.4 1/6] Btrfs: send, allow clone operations within the same file Anand Jain
2020-10-08 10:59 ` [PATCH stable-5.4 2/6] Btrfs: send, fix emission of invalid " Anand Jain
2020-10-08 10:59 ` [PATCH stable-5.4 3/6] btrfs: volumes: Use more straightforward way to calculate map length Anand Jain
2020-10-08 10:59 ` [PATCH stable-5.4 4/6] btrfs: Ensure we trim ranges across block group boundary Anand Jain
2020-10-08 10:59 ` [PATCH stable-5.4 5/6] btrfs: fix RWF_NOWAIT write not failling when we need to cow Anand Jain
2020-10-08 10:59 ` [PATCH stable-5.4 6/6] btrfs: allow btrfs_truncate_block() to fallback to nocow for data space reservation Anand Jain
2020-10-09 14:06 ` Greg KH [this message]
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