Commits
Miao Xie committed a7e252af5a8
Btrfs: don't clear the default compression type We met a oops caused by the wrong compression type: [ 556.512356] BUG: unable to handle kernel NULL pointer dereference at (null) [ 556.512370] IP: [<ffffffff811dbaa0>] __list_del_entry+0x1/0x98 [SNIP] [ 556.512490] [<ffffffff811dbb44>] ? list_del+0xd/0x2b [ 556.512539] [<ffffffffa05dd5ce>] find_workspace+0x97/0x175 [btrfs] [ 556.512546] [<ffffffff813c14b5>] ? _raw_spin_lock+0xe/0x10 [ 556.512576] [<ffffffffa05de276>] btrfs_compress_pages+0x2d/0xa2 [btrfs] [ 556.512601] [<ffffffffa05af060>] compress_file_range.constprop.54+0x1f2/0x4e8 [btrfs] [ 556.512627] [<ffffffffa05af388>] async_cow_start+0x32/0x4d [btrfs] [ 556.512655] [<ffffffffa05cc7a1>] worker_loop+0x144/0x4c3 [btrfs] [ 556.512661] [<ffffffff81059404>] ? finish_task_switch+0x80/0xb8 [ 556.512689] [<ffffffffa05cc65d>] ? btrfs_queue_worker+0x244/0x244 [btrfs] [ 556.512695] [<ffffffff8104fa4e>] kthread+0x8d/0x95 [ 556.512699] [<ffffffff81050000>] ? bit_waitqueue+0x34/0x7d [ 556.512704] [<ffffffff8104f9c1>] ? __kthread_parkme+0x65/0x65 [ 556.512709] [<ffffffff813c7eec>] ret_from_fork+0x7c/0xb0 [ 556.512713] [<ffffffff8104f9c1>] ? __kthread_parkme+0x65/0x65 Steps to reproduce: # mkfs.btrfs -f <dev> # mount -o nodatacow <dev> <mnt> # touch <mnt>/<file> # chattr =c <mnt>/<file> # dd if=/dev/zero of=<mnt>/<file> bs=1M count=10 It is because we cleared the default compression type when setting the nodatacow. In fact, we needn't do it because we have used COMPRESS flag to indicate if we need compressed the file data or not, needn't use the variant -- compress_type -- in btrfs_info to do the same thing, and just use it to hold the default compression type. Or we would get a wrong compress type for a file whose own compress flag is set but the compress flag of its filesystem is not set. Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com> Signed-off-by: Miao Xie <miaox@cn.fujitsu.com> Reviewed-by: Liu Bo <bo.li.liu@oracle.com> Signed-off-by: Chris Mason <clm@fb.com>