[ 09/49] sfc: Fix loop condition for efx_filter_search() when !for_insert

Greg Kroah-Hartman
2013-03-26T23:12:38Z

From: Ben Hutchings <bhutchings@solarflare.com>

[ Upstream commit 4017dbdc14af1903dc9fcba4d08b89c02325069d ]

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/sfc/filter.c | 39 +++++++++++++++++++++++----------------
1 file changed, 23 insertions(+), 16 deletions(-)

--- a/drivers/net/sfc/filter.c
+++ b/drivers/net/sfc/filter.c
@@ -335,28 +335,35 @@ static int efx_filter_search(struct efx_
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 */