The patch below does not apply to the 4.14-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 5e388e95815408c27f3612190d089afc0774b870 Mon Sep 17 00:00:00 2001
From: Nikolay Borisov nborisov@suse.com Date: Wed, 18 Apr 2018 09:41:54 +0300 Subject: [PATCH] btrfs: Fix race condition between delayed refs and blockgroup removal
When the delayed refs for a head are all run, eventually cleanup_ref_head is called which (in case of deletion) obtains a reference for the relevant btrfs_space_info struct by querying the bg for the range. This is problematic because when the last extent of a bg is deleted a race window emerges between removal of that bg and the subsequent invocation of cleanup_ref_head. This can result in cache being null and either a null pointer dereference or assertion failure.
task: ffff8d04d31ed080 task.stack: ffff9e5dc10cc000 RIP: 0010:assfail.constprop.78+0x18/0x1a [btrfs] RSP: 0018:ffff9e5dc10cfbe8 EFLAGS: 00010292 RAX: 0000000000000044 RBX: 0000000000000000 RCX: 0000000000000000 RDX: ffff8d04ffc1f868 RSI: ffff8d04ffc178c8 RDI: ffff8d04ffc178c8 RBP: ffff8d04d29e5ea0 R08: 00000000000001f0 R09: 0000000000000001 R10: ffff9e5dc0507d58 R11: 0000000000000001 R12: ffff8d04d29e5ea0 R13: ffff8d04d29e5f08 R14: ffff8d04efe29b40 R15: ffff8d04efe203e0 FS: 00007fbf58ead500(0000) GS:ffff8d04ffc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe6c6975648 CR3: 0000000013b2a000 CR4: 00000000000006f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: __btrfs_run_delayed_refs+0x10e7/0x12c0 [btrfs] btrfs_run_delayed_refs+0x68/0x250 [btrfs] btrfs_should_end_transaction+0x42/0x60 [btrfs] btrfs_truncate_inode_items+0xaac/0xfc0 [btrfs] btrfs_evict_inode+0x4c6/0x5c0 [btrfs] evict+0xc6/0x190 do_unlinkat+0x19c/0x300 do_syscall_64+0x74/0x140 entry_SYSCALL_64_after_hwframe+0x3d/0xa2 RIP: 0033:0x7fbf589c57a7
To fix this, introduce a new flag "is_system" to head_ref structs, which is populated at insertion time. This allows to decouple the querying for the spaceinfo from querying the possibly deleted bg.
Fixes: d7eae3403f46 ("Btrfs: rework delayed ref total_bytes_pinned accounting") CC: stable@vger.kernel.org # 4.14+ Suggested-by: Omar Sandoval osandov@osandov.com Signed-off-by: Nikolay Borisov nborisov@suse.com Reviewed-by: Omar Sandoval osandov@fb.com Signed-off-by: David Sterba dsterba@suse.com
diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c index 9e98295de7ce..e1b0651686f7 100644 --- a/fs/btrfs/delayed-ref.c +++ b/fs/btrfs/delayed-ref.c @@ -540,8 +540,10 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info, struct btrfs_delayed_ref_head *head_ref, struct btrfs_qgroup_extent_record *qrecord, u64 bytenr, u64 num_bytes, u64 ref_root, u64 reserved, - int action, int is_data, int *qrecord_inserted_ret, + int action, int is_data, int is_system, + int *qrecord_inserted_ret, int *old_ref_mod, int *new_ref_mod) + { struct btrfs_delayed_ref_head *existing; struct btrfs_delayed_ref_root *delayed_refs; @@ -585,6 +587,7 @@ add_delayed_ref_head(struct btrfs_fs_info *fs_info, head_ref->ref_mod = count_mod; head_ref->must_insert_reserved = must_insert_reserved; head_ref->is_data = is_data; + head_ref->is_system = is_system; head_ref->ref_tree = RB_ROOT; INIT_LIST_HEAD(&head_ref->ref_add_list); RB_CLEAR_NODE(&head_ref->href_node); @@ -772,6 +775,7 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info, struct btrfs_delayed_ref_root *delayed_refs; struct btrfs_qgroup_extent_record *record = NULL; int qrecord_inserted; + int is_system = (ref_root == BTRFS_CHUNK_TREE_OBJECTID);
BUG_ON(extent_op && extent_op->is_data); ref = kmem_cache_alloc(btrfs_delayed_tree_ref_cachep, GFP_NOFS); @@ -800,8 +804,8 @@ int btrfs_add_delayed_tree_ref(struct btrfs_fs_info *fs_info, */ head_ref = add_delayed_ref_head(fs_info, trans, head_ref, record, bytenr, num_bytes, 0, 0, action, 0, - &qrecord_inserted, old_ref_mod, - new_ref_mod); + is_system, &qrecord_inserted, + old_ref_mod, new_ref_mod);
add_delayed_tree_ref(fs_info, trans, head_ref, &ref->node, bytenr, num_bytes, parent, ref_root, level, action); @@ -868,7 +872,7 @@ int btrfs_add_delayed_data_ref(struct btrfs_fs_info *fs_info, */ head_ref = add_delayed_ref_head(fs_info, trans, head_ref, record, bytenr, num_bytes, ref_root, reserved, - action, 1, &qrecord_inserted, + action, 1, 0, &qrecord_inserted, old_ref_mod, new_ref_mod);
add_delayed_data_ref(fs_info, trans, head_ref, &ref->node, bytenr, @@ -898,9 +902,14 @@ int btrfs_add_delayed_extent_op(struct btrfs_fs_info *fs_info, delayed_refs = &trans->transaction->delayed_refs; spin_lock(&delayed_refs->lock);
+ /* + * extent_ops just modify the flags of an extent and they don't result + * in ref count changes, hence it's safe to pass false/0 for is_system + * argument + */ add_delayed_ref_head(fs_info, trans, head_ref, NULL, bytenr, num_bytes, 0, 0, BTRFS_UPDATE_DELAYED_HEAD, - extent_op->is_data, NULL, NULL, NULL); + extent_op->is_data, 0, NULL, NULL, NULL);
spin_unlock(&delayed_refs->lock); return 0; diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h index 741869dbc316..7f00db50bd24 100644 --- a/fs/btrfs/delayed-ref.h +++ b/fs/btrfs/delayed-ref.h @@ -127,6 +127,7 @@ struct btrfs_delayed_ref_head { */ unsigned int must_insert_reserved:1; unsigned int is_data:1; + unsigned int is_system:1; unsigned int processing:1; };
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 055494ddcace..f99102063366 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -2601,13 +2601,19 @@ static int cleanup_ref_head(struct btrfs_trans_handle *trans, trace_run_delayed_ref_head(fs_info, head, 0);
if (head->total_ref_mod < 0) { - struct btrfs_block_group_cache *cache; + struct btrfs_space_info *space_info; + u64 flags;
- cache = btrfs_lookup_block_group(fs_info, head->bytenr); - ASSERT(cache); - percpu_counter_add(&cache->space_info->total_bytes_pinned, + if (head->is_data) + flags = BTRFS_BLOCK_GROUP_DATA; + else if (head->is_system) + flags = BTRFS_BLOCK_GROUP_SYSTEM; + else + flags = BTRFS_BLOCK_GROUP_METADATA; + space_info = __find_space_info(fs_info, flags); + ASSERT(space_info); + percpu_counter_add(&space_info->total_bytes_pinned, -head->num_bytes); - btrfs_put_block_group(cache);
if (head->is_data) { spin_lock(&delayed_refs->lock);