sfc: Fix loop condition for efx_filter_search() when !for_insert
Ben Hutchings [Fri, 24 Jun 2011 19:26:44 +0000 (20:26 +0100)]
efx_filter_remove_filter() fails to remove inserted filters in some cases.

For example:

  1. Two filters A and B have specifications that result in an initial
     hash collision.
  2. A is inserted first, followed by B.
  3. An attempt to remove B first succeeds, but if A is removed first
     a subsequent attempt to remove B fails.

When searching for an existing filter (!for_insert),
efx_filter_search() must always continue to the maximum search depth
for the given type rather than stopping at the first unused entry.

Signed-off-by: Ben Hutchings <bhutchings@solarflare.com>

drivers/net/sfc/filter.c

index f2fc258..054f0a3 100644 (file)
@@ -335,28 +335,35 @@ static int efx_filter_search(struct efx_filter_table *table,
                             bool for_insert, int *depth_required)
 {
        unsigned hash, incr, filter_idx, depth, depth_max;
-       struct efx_filter_spec *cmp;
 
        hash = efx_filter_hash(key);
        incr = efx_filter_increment(key);
-       depth_max = (spec->priority <= EFX_FILTER_PRI_HINT ?
-                    FILTER_CTL_SRCH_HINT_MAX : FILTER_CTL_SRCH_MAX);
-
-       for (depth = 1, filter_idx = hash & (table->size - 1);
-            depth <= depth_max && test_bit(filter_idx, table->used_bitmap);
-            ++depth) {
-               cmp = &table->spec[filter_idx];
-               if (efx_filter_equal(spec, cmp))
-                       goto found;
+
+       filter_idx = hash & (table->size - 1);
+       depth = 1;
+       depth_max = (for_insert ?
+                    (spec->priority <= EFX_FILTER_PRI_HINT ?
+                     FILTER_CTL_SRCH_HINT_MAX : FILTER_CTL_SRCH_MAX) :
+                    table->search_depth[spec->type]);
+
+       for (;;) {
+               /* Return success if entry is used and matches this spec
+                * or entry is unused and we are trying to insert.
+                */
+               if (test_bit(filter_idx, table->used_bitmap) ?
+                   efx_filter_equal(spec, &table->spec[filter_idx]) :
+                   for_insert) {
+                       *depth_required = depth;
+                       return filter_idx;
+               }
+
+               /* Return failure if we reached the maximum search depth */
+               if (depth == depth_max)
+                       return for_insert ? -EBUSY : -ENOENT;
+
                filter_idx = (filter_idx + incr) & (table->size - 1);
+               ++depth;
        }
-       if (!for_insert)
-               return -ENOENT;
-       if (depth > depth_max)
-               return -EBUSY;
-found:
-       *depth_required = depth;
-       return filter_idx;
 }
 
 /* Construct/deconstruct external filter IDs */