On 02/24/2018 06:55 AM, David Sterba wrote:
On Tue, Feb 20, 2018 at 10:46:25PM +0800, Anand Jain wrote:
The replace target device can be missing in which case we don't
allocate a missing btrfs_device when mounted with the -o degraded.
So check the device before access.
BUG: unable to handle kernel NULL pointer dereference at 00000000000000b0
Please don't use uncommon acronyms, NPD is quite confusing, null pointer
deref should be fine.
Ok, sent v2.
IP: btrfs_destroy_dev_replace_tgtdev+0x43/0xf0 [btrfs]
Call Trace:
btrfs_dev_replace_cancel+0x15f/0x180 [btrfs]
btrfs_ioctl+0x2216/0x2590 [btrfs]
do_vfs_ioctl+0x625/0x650
SyS_ioctl+0x4e/0x80
do_syscall_64+0x5d/0x160
entry_SYSCALL64_slow_path+0x25/0x25
Do you have a reproducer for that?
For now, I used a tweaked btrfs.ko [1], then
mkfs.btrfs -fq /dev/sdb && mount /dev/sdb /btrfs
btrfs rep start -B /dev/sdb /dev/sdc
after reboot, we have the replace target device
and now use non-tweaked btrfs.ko
mount -o degraded /dev/sdb /btrfs
[1]
-----------
diff --git a/fs/btrfs/dev-replace.c b/fs/btrfs/dev-replace.c
index 476981c2cf55..8ea4856b6368 100644
--- a/fs/btrfs/dev-replace.c
+++ b/fs/btrfs/dev-replace.c
@@ -25,6 +25,7 @@
#include <linux/capability.h>
#include <linux/kthread.h>
#include <linux/math64.h>
+#include <linux/reboot.h>
#include <asm/div64.h>
#include "ctree.h"
#include "extent_map.h"
@@ -419,6 +420,8 @@ int btrfs_dev_replace_start(struct btrfs_fs_info
*fs_info,
btrfs_device_get_total_bytes(src_device),
&dev_replace->scrub_progress, 0, 1);
+ emergency_restart();
+
ret = btrfs_dev_replace_finishing(fs_info, ret);
if (ret == -EINPROGRESS) {
ret = BTRFS_IOCTL_DEV_REPLACE_RESULT_SCRUB_INPROGRESS;
------------
Thanks, Anand
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