Btrfs: fix BUG_ON() caused by ENOSPC when relocating space
When we balanced the chunks across the devices, BUG_ON() in
__finish_chunk_alloc() was triggered.
------------[ cut here ]------------
kernel BUG at fs/btrfs/volumes.c:2568!
[SNIP]
Call Trace:
[<ffffffffa049525e>] btrfs_alloc_chunk+0x8e/0xa0 [btrfs]
[<ffffffffa04546b0>] do_chunk_alloc+0x330/0x3a0 [btrfs]
[<ffffffffa045c654>] btrfs_reserve_extent+0xb4/0x1f0 [btrfs]
[<ffffffffa045c86b>] btrfs_alloc_free_block+0xdb/0x350 [btrfs]
[<ffffffffa048a8d8>] ? read_extent_buffer+0xd8/0x1d0 [btrfs]
[<ffffffffa04476fd>] __btrfs_cow_block+0x14d/0x5e0 [btrfs]
[<ffffffffa044660d>] ? read_block_for_search+0x14d/0x4d0 [btrfs]
[<ffffffffa0447c9b>] btrfs_cow_block+0x10b/0x240 [btrfs]
[<ffffffffa044dd5e>] btrfs_search_slot+0x49e/0x7a0 [btrfs]
[<ffffffffa044f07d>] btrfs_insert_empty_items+0x8d/0xf0 [btrfs]
[<ffffffffa045e973>] insert_with_overflow+0x43/0x110 [btrfs]
[<ffffffffa045eb0d>] btrfs_insert_dir_item+0xcd/0x1f0 [btrfs]
[<ffffffffa0489bd0>] ? map_extent_buffer+0xb0/0xc0 [btrfs]
[<ffffffff812276ad>] ? rb_insert_color+0x9d/0x160
[<ffffffffa046cc40>] ? inode_tree_add+0xf0/0x150 [btrfs]
[<ffffffffa0474801>] btrfs_add_link+0xc1/0x1c0 [btrfs]
[<ffffffff811dacac>] ? security_inode_init_security+0x1c/0x30
[<ffffffffa04a28aa>] ? btrfs_init_acl+0x4a/0x180 [btrfs]
[<ffffffffa047492f>] btrfs_add_nondir+0x2f/0x70 [btrfs]
[<ffffffffa046af16>] ? btrfs_init_inode_security+0x46/0x60 [btrfs]
[<ffffffffa0474ac0>] btrfs_create+0x150/0x1d0 [btrfs]
[<ffffffff81159c63>] ? generic_permission+0x23/0xb0
[<ffffffff8115b415>] vfs_create+0xa5/0xc0
[<ffffffff8115ce6e>] do_last+0x5fe/0x880
[<ffffffff8115dc0d>] path_openat+0xcd/0x3d0
[<ffffffff8115e029>] do_filp_open+0x49/0xa0
[<ffffffff8116a965>] ? alloc_fd+0x95/0x160
[<ffffffff8114f0c7>] do_sys_open+0x107/0x1e0
[<ffffffff810bcc3f>] ? audit_syscall_entry+0x1bf/0x1f0
[<ffffffff8114f1e0>] sys_open+0x20/0x30
[<ffffffff81484ec2>] system_call_fastpath+0x16/0x1b
[SNIP]
RIP [<ffffffffa049444a>] __finish_chunk_alloc+0x20a/0x220 [btrfs]
The reason is:
Task1 Space balance task
do_chunk_alloc()
__finish_chunk_alloc()
update device info
in the chunk tree
alloc system metadata block
relocate system metadata block group
set system metadata block group
readonly, This block group is the
only one that can allocate space. So
there is no free space that can be
allocated now.
find no space and don't try
to alloc new chunk, and then
return ENOSPC
BUG_ON() in __finish_chunk_alloc()
was triggered.
Fix this bug by allocating a new system metadata chunk before relocating the
old one if we find there is no free space which can be allocated after setting
the old block group to be read-only.
Reported-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Tested-by: Tsutomu Itoh <t-itoh@jp.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index d7031e7..7021dde 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -6526,15 +6526,28 @@
return flags;
}
-static int set_block_group_ro(struct btrfs_block_group_cache *cache)
+static int set_block_group_ro(struct btrfs_block_group_cache *cache, int force)
{
struct btrfs_space_info *sinfo = cache->space_info;
u64 num_bytes;
+ u64 min_allocable_bytes;
int ret = -ENOSPC;
if (cache->ro)
return 0;
+ /*
+ * We need some metadata space and system metadata space for
+ * allocating chunks in some corner cases until we force to set
+ * it to be readonly.
+ */
+ if ((sinfo->flags &
+ (BTRFS_BLOCK_GROUP_SYSTEM | BTRFS_BLOCK_GROUP_METADATA)) &&
+ !force)
+ min_allocable_bytes = 1 * 1024 * 1024;
+ else
+ min_allocable_bytes = 0;
+
spin_lock(&sinfo->lock);
spin_lock(&cache->lock);
num_bytes = cache->key.offset - cache->reserved - cache->pinned -
@@ -6542,7 +6555,8 @@
if (sinfo->bytes_used + sinfo->bytes_reserved + sinfo->bytes_pinned +
sinfo->bytes_may_use + sinfo->bytes_readonly +
- cache->reserved_pinned + num_bytes <= sinfo->total_bytes) {
+ cache->reserved_pinned + num_bytes + min_allocable_bytes <=
+ sinfo->total_bytes) {
sinfo->bytes_readonly += num_bytes;
sinfo->bytes_reserved += cache->reserved_pinned;
cache->reserved_pinned = 0;
@@ -6573,7 +6587,7 @@
do_chunk_alloc(trans, root, 2 * 1024 * 1024, alloc_flags,
CHUNK_ALLOC_FORCE);
- ret = set_block_group_ro(cache);
+ ret = set_block_group_ro(cache, 0);
if (!ret)
goto out;
alloc_flags = get_alloc_profile(root, cache->space_info->flags);
@@ -6581,7 +6595,7 @@
CHUNK_ALLOC_FORCE);
if (ret < 0)
goto out;
- ret = set_block_group_ro(cache);
+ ret = set_block_group_ro(cache, 0);
out:
btrfs_end_transaction(trans, root);
return ret;
@@ -7018,7 +7032,7 @@
set_avail_alloc_bits(root->fs_info, cache->flags);
if (btrfs_chunk_readonly(root, cache->key.objectid))
- set_block_group_ro(cache);
+ set_block_group_ro(cache, 1);
}
list_for_each_entry_rcu(space_info, &root->fs_info->space_info, list) {
@@ -7032,9 +7046,9 @@
* mirrored block groups.
*/
list_for_each_entry(cache, &space_info->block_groups[3], list)
- set_block_group_ro(cache);
+ set_block_group_ro(cache, 1);
list_for_each_entry(cache, &space_info->block_groups[4], list)
- set_block_group_ro(cache);
+ set_block_group_ro(cache, 1);
}
init_global_block_rsv(info);