From a7e252af5a819eb71c9494e62b2bfca982e92f84 Mon Sep 17 00:00:00 2001 From: Miao Xie Date: Fri, 22 Nov 2013 18:47:59 +0800 Subject: [PATCH] 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: [] __list_del_entry+0x1/0x98 [SNIP] [ 556.512490] [] ? list_del+0xd/0x2b [ 556.512539] [] find_workspace+0x97/0x175 [btrfs] [ 556.512546] [] ? _raw_spin_lock+0xe/0x10 [ 556.512576] [] btrfs_compress_pages+0x2d/0xa2 [btrfs] [ 556.512601] [] compress_file_range.constprop.54+0x1f2/0x4e8 [btrfs] [ 556.512627] [] async_cow_start+0x32/0x4d [btrfs] [ 556.512655] [] worker_loop+0x144/0x4c3 [btrfs] [ 556.512661] [] ? finish_task_switch+0x80/0xb8 [ 556.512689] [] ? btrfs_queue_worker+0x244/0x244 [btrfs] [ 556.512695] [] kthread+0x8d/0x95 [ 556.512699] [] ? bit_waitqueue+0x34/0x7d [ 556.512704] [] ? __kthread_parkme+0x65/0x65 [ 556.512709] [] ret_from_fork+0x7c/0xb0 [ 556.512713] [] ? __kthread_parkme+0x65/0x65 Steps to reproduce: # mkfs.btrfs -f # mount -o nodatacow # touch / # chattr =c / # dd if=/dev/zero of=/ 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 Signed-off-by: Miao Xie Reviewed-by: Liu Bo Signed-off-by: Chris Mason --- 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 2d8ac1bf0cf9..d71a11d13dfa 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"); -- 2.20.1