Btrfs: change how we update the global block rsv

I'm writing a tool to visualize the enospc system in order to help debug enospc
bugs and I found weird data and ran it down to when we update the global block
rsv.  We add all of the remaining free space to the block rsv, do a trace event,
then remove the extra and do another trace event.  This makes my visualization
look silly and is unintuitive code as well.  Fix this stuff to only add the
amount we are missing, or free the amount we are missing.  This is less clean to
read but more explicit in what it is doing, as well as only emitting events for
values that make sense.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index e2287c7c10bebbbb6dc68f0c4aed056a97bdaafe..07f47a5d0d6f4e031f24b3711395b726d26aeedf 100644 (file)
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -5373,27 +5373,33 @@ static void update_global_block_rsv(struct btrfs_fs_info *fs_info)
 
        block_rsv->size = min_t(u64, num_bytes, SZ_512M);
 
-       num_bytes = sinfo->bytes_used + sinfo->bytes_pinned +
-                   sinfo->bytes_reserved + sinfo->bytes_readonly +
-                   sinfo->bytes_may_use;
-
-       if (sinfo->total_bytes > num_bytes) {
-               num_bytes = sinfo->total_bytes - num_bytes;
-               block_rsv->reserved += num_bytes;
-               sinfo->bytes_may_use += num_bytes;
-               trace_btrfs_space_reservation(fs_info, "space_info",
-                                     sinfo->flags, num_bytes, 1);
-       }
-
-       if (block_rsv->reserved >= block_rsv->size) {
+       if (block_rsv->reserved < block_rsv->size) {
+               num_bytes = sinfo->bytes_used + sinfo->bytes_pinned +
+                       sinfo->bytes_reserved + sinfo->bytes_readonly +
+                       sinfo->bytes_may_use;
+               if (sinfo->total_bytes > num_bytes) {
+                       num_bytes = sinfo->total_bytes - num_bytes;
+                       num_bytes = min(num_bytes,
+                                       block_rsv->size - block_rsv->reserved);
+                       block_rsv->reserved += num_bytes;
+                       sinfo->bytes_may_use += num_bytes;
+                       trace_btrfs_space_reservation(fs_info, "space_info",
+                                                     sinfo->flags, num_bytes,
+                                                     1);
+               }
+       } else if (block_rsv->reserved > block_rsv->size) {
                num_bytes = block_rsv->reserved - block_rsv->size;
                sinfo->bytes_may_use -= num_bytes;
                trace_btrfs_space_reservation(fs_info, "space_info",
                                      sinfo->flags, num_bytes, 0);
                block_rsv->reserved = block_rsv->size;
-               block_rsv->full = 1;
        }
 
+       if (block_rsv->reserved == block_rsv->size)
+               block_rsv->full = 1;
+       else
+               block_rsv->full = 0;
+
        spin_unlock(&block_rsv->lock);
        spin_unlock(&sinfo->lock);
 }