Btrfs: Implement basic support for -ENOSPC

This is intended to prevent accidentally filling the drive.  A determined
user can still make things oops.

It includes some accounting of the current bytes under delayed allocation,
but this will change as things get optimized

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 14 insertions, 6 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index a0dff34dd437..2b92f1070274 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -1131,7 +1131,8 @@ out:
 }
 
 u64 count_range_bits(struct extent_map_tree *tree,
-                     u64 *start, u64 max_bytes, unsigned long bits)
+                     u64 *start, u64 search_end, u64 max_bytes,
+                     unsigned long bits)
 {
         struct rb_node *node;
         struct extent_state *state;
@@ -1139,9 +1140,14 @@ u64 count_range_bits(struct extent_map_tree *tree,
         u64 total_bytes = 0;
         int found = 0;
 
+        if (search_end <= cur_start) {
+                printk("search_end %Lu start %Lu\n", search_end, cur_start);
+                WARN_ON(1);
+                return 0;
+        }
+
         write_lock_irq(&tree->lock);
-        if (bits == EXTENT_DIRTY) {
-                *start = 0;
+        if (cur_start == 0 && bits == EXTENT_DIRTY) {
                 total_bytes = tree->dirty_bytes;
                 goto out;
         }
@@ -1156,8 +1162,11 @@ u64 count_range_bits(struct extent_map_tree *tree,
 
         while(1) {
                 state = rb_entry(node, struct extent_state, rb_node);
-                if ((state->state & bits)) {
-                        total_bytes += state->end - state->start + 1;
+                if (state->start > search_end)
+                        break;
+                if (state->end >= cur_start && (state->state & bits)) {
+                        total_bytes += min(search_end, state->end) + 1 -
+                                       max(cur_start, state->start);
                         if (total_bytes >= max_bytes)
                                 break;
                         if (!found) {
@@ -1173,7 +1182,6 @@ out:
         write_unlock_irq(&tree->lock);
         return total_bytes;
 }
-
 /*
  * helper function to lock both pages and extents in the tree.
  * pages must be locked first.