linux-kernel - [PATCH] btrfs: fix cannot use the loop device

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Date:	Mon, 07 Jun 2010 11:38:51 +0800
From:	Miao Xie <miaox@...fujitsu.com>
To:	Chris Mason <chris.mason@...cle.com>
CC:	Linux Btrfs <linux-btrfs@...r.kernel.org>,
	Linux-Kernel <linux-kernel@...r.kernel.org>
Subject: [PATCH] btrfs: fix cannot use the loop device

we cannot use the loop device which has been connected to a file in the btrf

The reproduce steps is following:
 # dd if=/dev/zero of=vdev0 bs=1M count=1024
 # losetup /dev/loop0 vdev0
 # mkfs.btrfs /dev/loop0
 ...
 failed to zero device start -5

The reason is that the btrfs don't implement either ->write_begin or ->write
the VFS API, so we fix it by setting ->write to do_sync_write().

Signed-off-by: Miao Xie <miaox@...fujitsu.com>
---
 fs/btrfs/file.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 79437c5..abcb918 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1197,6 +1197,7 @@ static int btrfs_file_mmap(struct file	*filp, struct vm_area_struct *vma)
 const struct file_operations btrfs_file_operations = {
 	.llseek		= generic_file_llseek,
 	.read		= do_sync_read,
+	.write		= do_sync_write,
 	.aio_read       = generic_file_aio_read,
 	.splice_read	= generic_file_splice_read,
 	.aio_write	= btrfs_file_aio_write,
-- 
1.6.5.2


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