| From 140250b24c254918a7b4cfa97f93a1459ae58587 Mon Sep 17 00:00:00 2001 |
| From: Josef Bacik <josef@toxicpanda.com> |
| Date: Mon, 9 Sep 2019 10:12:04 -0400 |
| Subject: [PATCH] btrfs: allocate new inode in NOFS context |
| |
| commit 11a19a90870ea5496a8ded69b86f5b476b6d3355 upstream. |
| |
| A user reported a lockdep splat |
| |
| ====================================================== |
| WARNING: possible circular locking dependency detected |
| 5.2.11-gentoo #2 Not tainted |
| ------------------------------------------------------ |
| kswapd0/711 is trying to acquire lock: |
| 000000007777a663 (sb_internal){.+.+}, at: start_transaction+0x3a8/0x500 |
| |
| but task is already holding lock: |
| 000000000ba86300 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 |
| |
| which lock already depends on the new lock. |
| |
| the existing dependency chain (in reverse order) is: |
| |
| -> #1 (fs_reclaim){+.+.}: |
| kmem_cache_alloc+0x1f/0x1c0 |
| btrfs_alloc_inode+0x1f/0x260 |
| alloc_inode+0x16/0xa0 |
| new_inode+0xe/0xb0 |
| btrfs_new_inode+0x70/0x610 |
| btrfs_symlink+0xd0/0x420 |
| vfs_symlink+0x9c/0x100 |
| do_symlinkat+0x66/0xe0 |
| do_syscall_64+0x55/0x1c0 |
| entry_SYSCALL_64_after_hwframe+0x49/0xbe |
| |
| -> #0 (sb_internal){.+.+}: |
| __sb_start_write+0xf6/0x150 |
| start_transaction+0x3a8/0x500 |
| btrfs_commit_inode_delayed_inode+0x59/0x110 |
| btrfs_evict_inode+0x19e/0x4c0 |
| evict+0xbc/0x1f0 |
| inode_lru_isolate+0x113/0x190 |
| __list_lru_walk_one.isra.4+0x5c/0x100 |
| list_lru_walk_one+0x32/0x50 |
| prune_icache_sb+0x36/0x80 |
| super_cache_scan+0x14a/0x1d0 |
| do_shrink_slab+0x131/0x320 |
| shrink_node+0xf7/0x380 |
| balance_pgdat+0x2d5/0x640 |
| kswapd+0x2ba/0x5e0 |
| kthread+0x147/0x160 |
| ret_from_fork+0x24/0x30 |
| |
| other info that might help us debug this: |
| |
| Possible unsafe locking scenario: |
| |
| CPU0 CPU1 |
| ---- ---- |
| lock(fs_reclaim); |
| lock(sb_internal); |
| lock(fs_reclaim); |
| lock(sb_internal); |
| *** DEADLOCK *** |
| |
| 3 locks held by kswapd0/711: |
| #0: 000000000ba86300 (fs_reclaim){+.+.}, at: __fs_reclaim_acquire+0x0/0x30 |
| #1: 000000004a5100f8 (shrinker_rwsem){++++}, at: shrink_node+0x9a/0x380 |
| #2: 00000000f956fa46 (&type->s_umount_key#30){++++}, at: super_cache_scan+0x35/0x1d0 |
| |
| stack backtrace: |
| CPU: 7 PID: 711 Comm: kswapd0 Not tainted 5.2.11-gentoo #2 |
| Hardware name: Dell Inc. Precision Tower 3620/0MWYPT, BIOS 2.4.2 09/29/2017 |
| Call Trace: |
| dump_stack+0x85/0xc7 |
| print_circular_bug.cold.40+0x1d9/0x235 |
| __lock_acquire+0x18b1/0x1f00 |
| lock_acquire+0xa6/0x170 |
| ? start_transaction+0x3a8/0x500 |
| __sb_start_write+0xf6/0x150 |
| ? start_transaction+0x3a8/0x500 |
| start_transaction+0x3a8/0x500 |
| btrfs_commit_inode_delayed_inode+0x59/0x110 |
| btrfs_evict_inode+0x19e/0x4c0 |
| ? var_wake_function+0x20/0x20 |
| evict+0xbc/0x1f0 |
| inode_lru_isolate+0x113/0x190 |
| ? discard_new_inode+0xc0/0xc0 |
| __list_lru_walk_one.isra.4+0x5c/0x100 |
| ? discard_new_inode+0xc0/0xc0 |
| list_lru_walk_one+0x32/0x50 |
| prune_icache_sb+0x36/0x80 |
| super_cache_scan+0x14a/0x1d0 |
| do_shrink_slab+0x131/0x320 |
| shrink_node+0xf7/0x380 |
| balance_pgdat+0x2d5/0x640 |
| kswapd+0x2ba/0x5e0 |
| ? __wake_up_common_lock+0x90/0x90 |
| kthread+0x147/0x160 |
| ? balance_pgdat+0x640/0x640 |
| ? __kthread_create_on_node+0x160/0x160 |
| ret_from_fork+0x24/0x30 |
| |
| This is because btrfs_new_inode() calls new_inode() under the |
| transaction. We could probably move the new_inode() outside of this but |
| for now just wrap it in memalloc_nofs_save(). |
| |
| Reported-by: Zdenek Sojka <zsojka@seznam.cz> |
| Fixes: 712e36c5f2a7 ("btrfs: use GFP_KERNEL in btrfs_alloc_inode") |
| CC: stable@vger.kernel.org # 4.16+ |
| Reviewed-by: Filipe Manana <fdmanana@suse.com> |
| Signed-off-by: Josef Bacik <josef@toxicpanda.com> |
| Reviewed-by: David Sterba <dsterba@suse.com> |
| Signed-off-by: David Sterba <dsterba@suse.com> |
| Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com> |
| |
| diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c |
| index 4bdc43e1e53c..40ac00730695 100644 |
| --- a/fs/btrfs/inode.c |
| +++ b/fs/btrfs/inode.c |
| @@ -6255,13 +6255,16 @@ static struct inode *btrfs_new_inode(struct btrfs_trans_handle *trans, |
| u32 sizes[2]; |
| int nitems = name ? 2 : 1; |
| unsigned long ptr; |
| + unsigned int nofs_flag; |
| int ret; |
| |
| path = btrfs_alloc_path(); |
| if (!path) |
| return ERR_PTR(-ENOMEM); |
| |
| + nofs_flag = memalloc_nofs_save(); |
| inode = new_inode(fs_info->sb); |
| + memalloc_nofs_restore(nofs_flag); |
| if (!inode) { |
| btrfs_free_path(path); |
| return ERR_PTR(-ENOMEM); |
| -- |
| 2.7.4 |
| |
