| Message ID | 1524033714-20063-1-git-send-email-nborisov@suse.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Wed, Apr 18, 2018 at 09:41:54AM +0300, Nikolay Borisov wrote: > 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") > Suggested-by: Omar Sandoval <osandov@osandov.com> > Signed-off-by: Nikolay Borisov <nborisov@suse.com> Added to next, thanks. > @@ -550,8 +550,10 @@ 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) At some point we might want to peel of a few arguments of that function. It now has 14. The fs_info/trans should work and the action/is_data/is_system could be merged to a bitmask. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 18.04.2018 23:47, David Sterba wrote: > On Wed, Apr 18, 2018 at 09:41:54AM +0300, Nikolay Borisov wrote: >> 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") >> Suggested-by: Omar Sandoval <osandov@osandov.com> >> Signed-off-by: Nikolay Borisov <nborisov@suse.com> > > Added to next, thanks. > >> @@ -550,8 +550,10 @@ 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) > > At some point we might want to peel of a few arguments of that function. > It now has 14. The fs_info/trans should work and the > action/is_data/is_system could be merged to a bitmask. Yes, I sent a series which splits the delayed ref initialisation + addition. It will conflicts with this patch but I intend to rebase. I'm talking about [PATCH 0/8] Delayed refs cleanups/streamlining > -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c index 5ac2d7909782..20fa7b4c132d 100644 --- a/fs/btrfs/delayed-ref.c +++ b/fs/btrfs/delayed-ref.c @@ -550,8 +550,10 @@ 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; @@ -595,6 +597,7 @@ 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); @@ -782,6 +785,7 @@ 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); @@ -810,8 +814,8 @@ 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); @@ -878,7 +882,7 @@ 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, @@ -908,9 +912,14 @@ 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 cdf4a94ce5c1..7e7bf4e66d48 100644 --- a/fs/btrfs/delayed-ref.h +++ b/fs/btrfs/delayed-ref.h @@ -139,6 +139,7 @@ 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 133a131c12d0..eb98f943bbed 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -2616,13 +2616,19 @@ 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);
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") Suggested-by: Omar Sandoval <osandov@osandov.com> Signed-off-by: Nikolay Borisov <nborisov@suse.com> --- V3: * Use the logic in the if to set a 'flags' variable and call __find_space_info just once. v2: * Collapsed the if/else logic in cleanup_ref_head fs/btrfs/delayed-ref.c | 19 ++++++++++++++----- fs/btrfs/delayed-ref.h | 1 + fs/btrfs/extent-tree.c | 16 +++++++++++----- 3 files changed, 26 insertions(+), 10 deletions(-)