btrfs: qgroup: Move reserved data accounting from btrfs_delayed_ref_head to btrfs_qgroup_extent_record

adam900710 · kdave · commit 1418bae1c229 · 2019-02-25T14:13:39.000+01:00
[BUG] Btrfs/139 will fail with a high probability if the testing machine (VM) has only 2G RAM. Resulting the final write success while it should fail due to EDQUOT, and the fs will have quota exceeding the limit by 16K. The simplified reproducer will be: (needs a 2G ram VM) $ mkfs.btrfs -f $dev $ mount $dev $mnt $ btrfs subv create $mnt/subv $ btrfs quota enable $mnt $ btrfs quota rescan -w $mnt $ btrfs qgroup limit -e 1G $mnt/subv $ for i in $(seq -w 1 8); do xfs_io -f -c "pwrite 0 128M" $mnt/subv/file_$i > /dev/null echo "file $i written" > /dev/kmsg done $ sync $ btrfs qgroup show -pcre --raw $mnt The last pwrite will not trigger EDQUOT and final 'qgroup show' will show something like: qgroupid rfer excl max_rfer max_excl parent child -------- ---- ---- -------- -------- ------ ----- 0/5 16384 16384 none none --- --- 0/256 1073758208 1073758208 none 1073741824 --- --- And 1073758208 is larger than > 1073741824. [CAUSE] It's a bug in btrfs qgroup data reserved space management. For quota limit, we must ensure that: reserved (data + metadata) + rfer/excl <= limit Since rfer/excl is only updated at transaction commmit time, reserved space needs to be taken special care. One important part of reserved space is data, and for a new data extent written to disk, we still need to take the reserved space until rfer/excl numbers get updated. Originally when an ordered extent finishes, we migrate the reserved qgroup data space from extent_io tree to delayed ref head of the data extent, expecting delayed ref will only be cleaned up at commit transaction time. However for small RAM machine, due to memory pressure dirty pages can be flushed back to disk without committing a transaction. The related events will be something like: file 1 written btrfs_finish_ordered_io: ino=258 ordered offset=0 len=54947840 btrfs_finish_ordered_io: ino=258 ordered offset=54947840 len=5636096 btrfs_finish_ordered_io: ino=258 ordered offset=61153280 len=57344 btrfs_finish_ordered_io: ino=258 ordered offset=61210624 len=8192 btrfs_finish_ordered_io: ino=258 ordered offset=60583936 len=569344 cleanup_ref_head: num_bytes=54947840 cleanup_ref_head: num_bytes=5636096 cleanup_ref_head: num_bytes=569344 cleanup_ref_head: num_bytes=57344 cleanup_ref_head: num_bytes=8192 ^^^^^^^^^^^^^^^^ This will free qgroup data reserved space file 2 written ... file 8 written cleanup_ref_head: num_bytes=8192 ... btrfs_commit_transaction <<< the only transaction committed during the test When file 2 is written, we have already freed 128M reserved qgroup data space for ino 258. Thus later write won't trigger EDQUOT. This allows us to write more data beyond qgroup limit. In my 2G ram VM, it could reach about 1.2G before hitting EDQUOT. [FIX] By moving reserved qgroup data space from btrfs_delayed_ref_head to btrfs_qgroup_extent_record, we can ensure that reserved qgroup data space won't be freed half way before commit transaction, thus fix the problem. Fixes: f64d5ca ("btrfs: delayed_ref: Add new function to record reserved space into delayed ref") Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/delayed-ref.c b/fs/btrfs/delayed-ref.c
@@ -602,17 +602,14 @@ static void init_delayed_ref_head(struct btrfs_delayed_ref_head *head_ref,
 	RB_CLEAR_NODE(&head_ref->href_node);
 	head_ref->processing = 0;
 	head_ref->total_ref_mod = count_mod;
-	head_ref->qgroup_reserved = 0;
-	head_ref->qgroup_ref_root = 0;
 	spin_lock_init(&head_ref->lock);
 	mutex_init(&head_ref->mutex);
 
 	if (qrecord) {
 		if (ref_root && reserved) {
-			head_ref->qgroup_ref_root = ref_root;
-			head_ref->qgroup_reserved = reserved;
+			qrecord->data_rsv = reserved;
+			qrecord->data_rsv_refroot = ref_root;
 		}
-
 		qrecord->bytenr = bytenr;
 		qrecord->num_bytes = num_bytes;
 		qrecord->old_roots = NULL;
@@ -651,10 +648,6 @@ add_delayed_ref_head(struct btrfs_trans_handle *trans,
 	existing = htree_insert(&delayed_refs->href_root,
 				&head_ref->href_node);
 	if (existing) {
-		WARN_ON(qrecord && head_ref->qgroup_ref_root
-			&& head_ref->qgroup_reserved
-			&& existing->qgroup_ref_root
-			&& existing->qgroup_reserved);
 		update_existing_head_ref(trans, existing, head_ref,
 					 old_ref_mod);
 		/*
@@ -770,7 +763,7 @@ int btrfs_add_delayed_tree_ref(struct btrfs_trans_handle *trans,
 
 	if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) &&
 	    is_fstree(ref_root)) {
-		record = kmalloc(sizeof(*record), GFP_NOFS);
+		record = kzalloc(sizeof(*record), GFP_NOFS);
 		if (!record) {
 			kmem_cache_free(btrfs_delayed_tree_ref_cachep, ref);
 			kmem_cache_free(btrfs_delayed_ref_head_cachep, head_ref);
@@ -867,7 +860,7 @@ int btrfs_add_delayed_data_ref(struct btrfs_trans_handle *trans,
 
 	if (test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags) &&
 	    is_fstree(ref_root)) {
-		record = kmalloc(sizeof(*record), GFP_NOFS);
+		record = kzalloc(sizeof(*record), GFP_NOFS);
 		if (!record) {
 			kmem_cache_free(btrfs_delayed_data_ref_cachep, ref);
 			kmem_cache_free(btrfs_delayed_ref_head_cachep,
diff --git a/fs/btrfs/delayed-ref.h b/fs/btrfs/delayed-ref.h
@@ -102,17 +102,6 @@ struct btrfs_delayed_ref_head {
 	 */
 	int ref_mod;
 
-	/*
-	 * For qgroup reserved space freeing.
-	 *
-	 * ref_root and reserved will be recorded after
-	 * BTRFS_ADD_DELAYED_EXTENT is called.
-	 * And will be used to free reserved qgroup space at
-	 * run_delayed_refs() time.
-	 */
-	u64 qgroup_ref_root;
-	u64 qgroup_reserved;
-
 	/*
 	 * when a new extent is allocated, it is just reserved in memory
 	 * The actual extent isn't inserted into the extent allocation tree
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
@@ -2492,9 +2492,6 @@ void btrfs_cleanup_ref_head_accounting(struct btrfs_fs_info *fs_info,
 		}
 	}
 
-	/* Also free its reserved qgroup space */
-	btrfs_qgroup_free_delayed_ref(fs_info, head->qgroup_ref_root,
-				      head->qgroup_reserved);
 	btrfs_delayed_refs_rsv_release(fs_info, nr_items);
 }
 
diff --git a/fs/btrfs/qgroup.c b/fs/btrfs/qgroup.c
@@ -1546,12 +1546,18 @@ int btrfs_qgroup_trace_extent_nolock(struct btrfs_fs_info *fs_info,
 		parent_node = *p;
 		entry = rb_entry(parent_node, struct btrfs_qgroup_extent_record,
 				 node);
-		if (bytenr < entry->bytenr)
+		if (bytenr < entry->bytenr) {
 			p = &(*p)->rb_left;
-		else if (bytenr > entry->bytenr)
+		} else if (bytenr > entry->bytenr) {
 			p = &(*p)->rb_right;
-		else
+		} else {
+			if (record->data_rsv && !entry->data_rsv) {
+				entry->data_rsv = record->data_rsv;
+				entry->data_rsv_refroot =
+					record->data_rsv_refroot;
+			}
 			return 1;
+		}
 	}
 
 	rb_link_node(&record->node, parent_node, p);
@@ -1597,7 +1603,7 @@ int btrfs_qgroup_trace_extent(struct btrfs_trans_handle *trans, u64 bytenr,
 	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags)
 	    || bytenr == 0 || num_bytes == 0)
 		return 0;
-	record = kmalloc(sizeof(*record), gfp_flag);
+	record = kzalloc(sizeof(*record), gfp_flag);
 	if (!record)
 		return -ENOMEM;
 
@@ -2517,6 +2523,11 @@ int btrfs_qgroup_account_extents(struct btrfs_trans_handle *trans)
 					goto cleanup;
 			}
 
+			/* Free the reserved data space */
+			btrfs_qgroup_free_refroot(fs_info,
+					record->data_rsv_refroot,
+					record->data_rsv,
+					BTRFS_QGROUP_RSV_DATA);
 			/*
 			 * Use SEQ_LAST as time_seq to do special search, which
 			 * doesn't lock tree or delayed_refs and search current
diff --git a/fs/btrfs/qgroup.h b/fs/btrfs/qgroup.h
@@ -107,6 +107,17 @@ struct btrfs_qgroup_extent_record {
 	struct rb_node node;
 	u64 bytenr;
 	u64 num_bytes;
+
+	/*
+	 * For qgroup reserved data space freeing.
+	 *
+	 * @data_rsv_refroot and @data_rsv will be recorded after
+	 * BTRFS_ADD_DELAYED_EXTENT is called.
+	 * And will be used to free reserved qgroup space at
+	 * transaction commit time.
+	 */
+	u32 data_rsv;		/* reserved data space needs to be freed */
+	u64 data_rsv_refroot;	/* which root the reserved data belongs to */
 	struct ulist *old_roots;
 };
 
@@ -326,15 +337,6 @@ int btrfs_qgroup_inherit(struct btrfs_trans_handle *trans, u64 srcid,
 void btrfs_qgroup_free_refroot(struct btrfs_fs_info *fs_info,
 			       u64 ref_root, u64 num_bytes,
 			       enum btrfs_qgroup_rsv_type type);
-static inline void btrfs_qgroup_free_delayed_ref(struct btrfs_fs_info *fs_info,
-						 u64 ref_root, u64 num_bytes)
-{
-	if (!test_bit(BTRFS_FS_QUOTA_ENABLED, &fs_info->flags))
-		return;
-	trace_btrfs_qgroup_free_delayed_ref(fs_info, ref_root, num_bytes);
-	btrfs_qgroup_free_refroot(fs_info, ref_root, num_bytes,
-				  BTRFS_QGROUP_RSV_DATA);
-}
 
 #ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
 int btrfs_verify_qgroup_counts(struct btrfs_fs_info *fs_info, u64 qgroupid,
diff --git a/include/trace/events/btrfs.h b/include/trace/events/btrfs.h
@@ -1513,35 +1513,6 @@ DEFINE_EVENT(btrfs__qgroup_rsv_data, btrfs_qgroup_release_data,
 	TP_ARGS(inode, start, len, reserved, op)
 );
 
-DECLARE_EVENT_CLASS(btrfs__qgroup_delayed_ref,
-
-	TP_PROTO(const struct btrfs_fs_info *fs_info,
-		 u64 ref_root, u64 reserved),
-
-	TP_ARGS(fs_info, ref_root, reserved),
-
-	TP_STRUCT__entry_btrfs(
-		__field(	u64,		ref_root	)
-		__field(	u64,		reserved	)
-	),
-
-	TP_fast_assign_btrfs(fs_info,
-		__entry->ref_root	= ref_root;
-		__entry->reserved	= reserved;
-	),
-
-	TP_printk_btrfs("root=%llu reserved=%llu op=free",
-		  __entry->ref_root, __entry->reserved)
-);
-
-DEFINE_EVENT(btrfs__qgroup_delayed_ref, btrfs_qgroup_free_delayed_ref,
-
-	TP_PROTO(const struct btrfs_fs_info *fs_info,
-		 u64 ref_root, u64 reserved),
-
-	TP_ARGS(fs_info, ref_root, reserved)
-);
-
 DECLARE_EVENT_CLASS(btrfs_qgroup_extent,
 	TP_PROTO(const struct btrfs_fs_info *fs_info,
 		 const struct btrfs_qgroup_extent_record *rec),

Original file line number	Diff line number	Diff line change
`@@ -2492,9 +2492,6 @@ void btrfs_cleanup_ref_head_accounting(struct btrfs_fs_info *fs_info,`
`2492`	`2492`	`}`
`2493`	`2493`	`}`
`2494`	`2494`
`2495`		`- /* Also free its reserved qgroup space */`
`2496`		`- btrfs_qgroup_free_delayed_ref(fs_info, head->qgroup_ref_root,`
`2497`		`- head->qgroup_reserved);`
`2498`	`2495`	`btrfs_delayed_refs_rsv_release(fs_info, nr_items);`
`2499`	`2496`	`}`
`2500`	`2497`