On Fri, Nov 22, 2013 at 06:47:59PM +0800, Miao Xie wrote:
> 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.
A good candidate for upstream and stable tree.
Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
-liubo
>
> Reported-by: Tsutomu Itoh <t-itoh@xxxxxxxxxxxxxx>
> Signed-off-by: Miao Xie <miaox@xxxxxxxxxxxxxx>
> ---
> fs/btrfs/super.c | 5 ++---
> 1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/fs/btrfs/super.c b/fs/btrfs/super.c
> index fb62c45..fd05d7a 100644
> --- a/fs/btrfs/super.c
> +++ b/fs/btrfs/super.c
> @@ -432,7 +432,6 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
> } else {
> printk(KERN_INFO "btrfs: setting nodatacow\n");
> }
> - info->compress_type = BTRFS_COMPRESS_NONE;
> btrfs_clear_opt(info->mount_opt, COMPRESS);
> btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
> btrfs_set_opt(info->mount_opt, NODATACOW);
> @@ -461,7 +460,6 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
> btrfs_set_fs_incompat(info, COMPRESS_LZO);
> } else if (strncmp(args[0].from, "no", 2) == 0) {
> compress_type = "no";
> - info->compress_type = BTRFS_COMPRESS_NONE;
> btrfs_clear_opt(info->mount_opt, COMPRESS);
> btrfs_clear_opt(info->mount_opt, FORCE_COMPRESS);
> compress_force = false;
> @@ -474,9 +472,10 @@ int btrfs_parse_options(struct btrfs_root *root, char *options)
> btrfs_set_opt(info->mount_opt, FORCE_COMPRESS);
> pr_info("btrfs: force %s compression\n",
> compress_type);
> - } else
> + } else if (btrfs_test_opt(root, COMPRESS)) {
> pr_info("btrfs: use %s compression\n",
> compress_type);
> + }
> break;
> case Opt_ssd:
> printk(KERN_INFO "btrfs: use ssd allocation scheme\n");
> --
> 1.8.3.1
>
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