On Sat, 16 Feb 2013 14:47:45 +0800, Liu Bo wrote:
> What about this patch(UNTESTED)?
>
> thanks,
> liubo
>
> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
> index ca7ace7..dac9d4b 100644
> --- a/fs/btrfs/inode.c
> +++ b/fs/btrfs/inode.c
> @@ -4142,9 +4142,14 @@ static void inode_tree_del(struct inode *inode)
> * root_refs of 0, so this could end up dropping the tree root as a
> * snapshot, so we need the extra !root->fs_info->tree_root check to
> * make sure we don't drop it.
> + *
> + * Inode cache's inodes may be iput and add root back to dead roots
> + * list during killing super, which leads to use-after-free, so
> + * we need to check fs_info->closing to keep us from use-after-free.
> */
> if (empty && btrfs_root_refs(&root->root_item) == 0 &&
> - root != root->fs_info->tree_root) {
> + root != root->fs_info->tree_root &&
> + btrfs_fs_closing(root->fs_info) > 1) {
> synchronize_srcu(&root->fs_info->subvol_srcu);
> spin_lock(&root->inode_lock);
> empty = RB_EMPTY_ROOT(&root->inode_tree);
No improvement with this patch. The inode_cache causes a crash in __list_add.
I tested it on the latest cmason/for-linus with and without your patch.
This script is an 100% reproducer on my test box:
mkfs.btrfs -d single -m raid1 /dev/sdc /dev/sdj /dev/sds /dev/sdt /dev/sdu
/dev/sdv
mount /dev/sdc /mnt -o compress=lzo,space_cache,inode_cache
btrfs subv create /mnt/src
(cd ~/git/btrfs/fs/btrfs && tar cf - .) | (cd /mnt/src && tar xf -)
for i in `seq 2000`; do btrfs subv create /mnt/${i}; (cd /mnt/src && tar cf -
.) | (cd /mnt/${i} && tar xf -); done
for i in /mnt/[0-9]*; do btrfs subv dele ${i}; done
sleep 45
umount /mnt
BUG: unable to handle kernel paging request at ffff88023517d830
IP: [<ffffffff814415f7>] __list_add+0x17/0xd0
PGD 1e0c063 PUD bf58e067 PMD bf737067 PTE 800000023517d160
Oops: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC
Modules linked in: btrfs raid1 mpt2sas scsi_transport_sas raid_class
CPU 2
Pid: 18503, comm: umount Not tainted 3.7.0+ #44 Supermicro X8SIL/X8SIL
RIP: 0010:[<ffffffff814415f7>] [<ffffffff814415f7>] __list_add+0x17/0xd0
RSP: 0018:ffff88019e1abbd8 EFLAGS: 00010286
RAX: ffff8802353aa290 RBX: ffff880229e38828 RCX: 0000000000000001
RDX: ffff88023517d828 RSI: ffff8802327214c0 RDI: ffff880229e38828
RBP: ffff88019e1abbf8 R08: 000000000006e130 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000001 R12: ffff880229e38000
R13: ffff880229e38898 R14: 0000000000000000 R15: ffff88019e1abd30
FS: 00007f75eabc4740(0000) GS:ffff880236a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: ffff88023517d830 CR3: 000000019e17e000 CR4: 00000000000007e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process umount (pid: 18503, threadinfo ffff88019e1aa000, task ffff8802353aa290)
Stack:
ffffffffa008619f ffff880229e38000 ffff880229e38000 ffff880229e38898
ffff88019e1abc18 ffffffffa00861c0 ffff88012760dc38 ffff88012760dc38
ffff88019e1abc48 ffffffffa0095358 ffff88012760dc38 ffff88012760dcc0
Call Trace:
[<ffffffffa008619f>] ? btrfs_add_dead_root+0x1f/0x60 [btrfs]
[<ffffffffa00861c0>] btrfs_add_dead_root+0x40/0x60 [btrfs]
[<ffffffffa0095358>] btrfs_destroy_inode+0x1d8/0x2d0 [btrfs]
[<ffffffff811af9c7>] destroy_inode+0x37/0x60
[<ffffffff811afafd>] evict+0x10d/0x1a0
[<ffffffff811b02a5>] iput+0x105/0x190
[<ffffffffa007dda8>] free_fs_root+0x18/0x90 [btrfs]
[<ffffffffa00811eb>] btrfs_free_fs_root+0x7b/0x90 [btrfs]
[<ffffffffa00812af>] del_fs_roots+0xaf/0xf0 [btrfs]
[<ffffffffa0082c16>] close_ctree+0x1c6/0x300 [btrfs]
[<ffffffff811b072c>] ? evict_inodes+0xec/0x100
[<ffffffffa00583a4>] btrfs_put_super+0x14/0x20 [btrfs]
[<ffffffff8119805c>] generic_shutdown_super+0x5c/0xe0
[<ffffffff81198171>] kill_anon_super+0x11/0x20
[<ffffffffa005c3a5>] btrfs_kill_super+0x15/0x90 [btrfs]
[<ffffffff811991a1>] ? deactivate_super+0x41/0x70
[<ffffffff8119856d>] deactivate_locked_super+0x3d/0x70
[<ffffffff811991a9>] deactivate_super+0x49/0x70
[<ffffffff811b4332>] mntput_no_expire+0xd2/0x130
[<ffffffff811b52e1>] sys_umount+0x71/0x390
[<ffffffff81956992>] system_call_fastpath+0x16/0x1b
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