| Message ID | 20181128031148.357-7-suy.fnst@cn.fujitsu.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: implementation of priority aware allocator | expand |
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index d63078930a1e..5bae757786dc 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -31,6 +31,15 @@ #undef SCRAMBLE_DELAYED_REFS +/* The block group is used by find_free_extent() */ +#define PRIORITY_BG_BUSY -1 + +/* The block group is in remove or removed */ +#define PRIORITY_BG_DELETED -2 + +/* The block group' priority needs to be updated */ +#define PRIORITY_BG_UPDATING -3 + /* * control flags for do_chunk_alloc's force field * CHUNK_ALLOC_NO_FORCE means to only allocate a chunk
In origin design, the order of space_info::block_groups is changed only when add/remove block group(s). In design of priority aware allocator, block groups may be moved from one priority tree to another one. What the operation is usually that 1) lock block_group down_write first_tree down_write second_tree do unlink .... do link up_write second_tree up_write first_tree unlock blcok_group However, the expected order in find_free_extent() is 2) down_read tree lock block_group ... unlock block_group up_read tree Obviously, orders of operation 1 and operation 2 are on the contrary and will cause dead lock. The ugly method is to introduce special status to mark block group status. Then: 1) After priority changed: lock block_group mark block_group to be updated unlock blcok_group down_write first_tree down_write second_tree lock block_group check block group should be moved do unlink .... do link unlock blcok_group up_write second_tree up_write first_tree 2) find_free_extent(): down_read tree lock block_group check the block group is not in special status ... unlock block_group up_read tree This patch introduce three macros to represents block group is removing /need to updated / busy. Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com> --- fs/btrfs/extent-tree.c | 9 +++++++++ 1 file changed, 9 insertions(+)