[Mesa-dev] [PATCH 7/7] util/disk_cache: also write key_blob to cache entry

[Grazvydas Ignotas]

This can be used to deal with key hash collisions from different
version (should we find that to actually happen) and to find
which mesa version produced it the entry.

Signed-off-by: Grazvydas Ignotas <notasas at gmail.com>
---
 src/util/disk_cache.c | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/src/util/disk_cache.c b/src/util/disk_cache.c
index ad591be..8ac9e48 100644
--- a/src/util/disk_cache.c
+++ b/src/util/disk_cache.c
@@ -766,6 +766,7 @@ destroy_put_job(void *job, int thread_index)
 struct cache_entry_file_data {
    uint32_t crc32;
    uint32_t uncompressed_size;
+   uint32_t key_blob_size;
 };
 
 static void
@@ -839,6 +840,7 @@ cache_put(void *job, int thread_index)
    struct cache_entry_file_data cf_data;
    cf_data.crc32 = util_hash_crc32(dc_job->data, dc_job->size);
    cf_data.uncompressed_size = dc_job->size;
+   cf_data.key_blob_size = dc_job->cache->key_blob_size;
 
    size_t cf_data_size = sizeof(cf_data);
    ret = write_all(fd, &cf_data, cf_data_size);
@@ -847,6 +849,16 @@ cache_put(void *job, int thread_index)
       goto done;
    }
 
+   /* Write the key_blob, this can be used find information about the
+    * mesa version that produced the entry or deal with hash collisions,
+    * should that ever become a real problem.
+    */
+   ret = write_all(fd, dc_job->cache->key_blob, dc_job->cache->key_blob_size);
+   if (ret == -1) {
+      unlink(filename_tmp);
+      goto done;
+   }
+
    /* Now, finally, write out the contents to the temporary file, then
     * rename them atomically to the destination filename, and also
     * perform an atomic increment of the total cache size.
@@ -859,7 +871,7 @@ cache_put(void *job, int thread_index)
    }
    rename(filename_tmp, filename);
 
-   file_size += cf_data_size;
+   file_size += cf_data_size + dc_job->cache->key_blob_size;
    p_atomic_add(dc_job->cache->size, file_size);
 
  done:
@@ -966,8 +978,16 @@ disk_cache_get(struct disk_cache *cache, const cache_key key, size_t *size)
          goto fail;
    }
 
+   if (cf_data.key_blob_size != cache->key_blob_size)
+      goto fail;
+
+   /* Right now we don't use the key_blob, just skip it */
+   ret = lseek(fd, cache->key_blob_size, SEEK_CUR);
+   if (ret == -1)
+      goto fail;
+
    /* Load the actual cache data. */
-   size_t cache_data_size = sb.st_size - cf_data_size;
+   size_t cache_data_size = sb.st_size - cf_data_size - cache->key_blob_size;
    for (len = 0; len < cache_data_size; len += ret) {
       ret = read(fd, data + len, cache_data_size - len);
       if (ret == -1)
-- 
2.7.4