verity: change maybe_read_entries to maybe_read_entry

dm-bht.c

  /*
  * Copyright (C) 2010 The Chromium OS Authors <chromium-os-dev@chromium.org>
  *
  * Device-Mapper block hash tree interface.
  * See Documentation/device-mapper/dm-bht.txt for details.
  *
  * This file is released under the GPL.
  */
 
 #include <asm/atomic.h>
@@ skipping 287 matching lines @@
         }
 
         /* Setup callback stubs */
         bht->read_cb = &dm_bht_read_callback_stub;
         bht->write_cb = &dm_bht_write_callback_stub;
 
         status = dm_bht_initialize_entries(bht);
         if (status)
                 goto bad_entries_alloc;
 
+        /* We compute depth such that there is only be 1 block at level 0. */
+        BUG_ON(bht->levels[0].count != 1);
+
         return 0;
 
 bad_entries_alloc:
         while (bht->depth-- > 0)
                 kfree(bht->levels[bht->depth].entries);
         kfree(bht->levels);
 bad_node_count:
 bad_level_alloc:
 bad_block_count:
         kfree(bht->root_digest);
@@ skipping 136 matching lines @@
 {
         if (status) {
                 DMCRIT("an I/O error occurred while writing entry");
                 atomic_set(&entry->state, DM_BHT_ENTRY_ERROR_IO);
                 /* entry->nodes will be freed later */
                 return;
         }
 }
 EXPORT_SYMBOL(dm_bht_write_completed);
 
+/* dm_bht_maybe_read_entry
+ * Attempts to atomically acquire an entry, allocate any needed
+ * memory, and issues the I/O callback to load the hash from disk.
+ * Return value is negative on error. When positive, it is the state
+ * value.
+ */
+static int dm_bht_maybe_read_entry(struct dm_bht *bht, void *ctx,
+                                   unsigned int depth, unsigned int index)
+{
+        struct dm_bht_level *level = &bht->levels[depth];
+        struct dm_bht_entry *entry = &level->entries[index];
+        sector_t current_sector = level->sector + to_sector(index * PAGE_SIZE);
+        struct page *node_page;
+        int state;
 
-/* dm_bht_maybe_read_entries
- * Attempts to atomically acquire each entry, allocated any needed
- * memory, and issues I/O callbacks to load the hashes from disk.
- * Returns 0 if all entries are loaded and verified.  On error, the
- * return value is negative. When positive, it is the state values
- * ORd.
- */
-static int dm_bht_maybe_read_entries(struct dm_bht *bht, void *ctx,
-                                     unsigned int depth, unsigned int index,
-                                     unsigned int count, bool until_exist)
-{
-        struct dm_bht_level *level;
-        struct dm_bht_entry *entry, *last_entry;
-        sector_t current_sector;
-        int state = 0;
-        int status = 0;
-        struct page *node_page = NULL;
         BUG_ON(depth >= bht->depth);
 
-        level = &bht->levels[depth];
-        if (count > level->count - index) {
-                DMERR("dm_bht_maybe_read_entries(d=%u,ei=%u,count=%u): "
-                      "index+count exceeds available entries %u",
-                        depth, index, count, level->count);
-                return -EINVAL;
-        }
         /* XXX: hardcoding PAGE_SIZE means that a perfectly valid image
          *      on one system may not work on a different kernel.
          * TODO(wad) abstract PAGE_SIZE with a bht->entry_size or
          *           at least a define and ensure bht->entry_size is
          *           sector aligned at least.
          */
-        current_sector = level->sector + to_sector(index * PAGE_SIZE);
-        for (entry = &level->entries[index], last_entry = entry + count;
-             entry < last_entry;
-             ++entry, current_sector += to_sector(PAGE_SIZE)) {
-                /* If the entry's state is UNALLOCATED, then we'll claim it
-                 * for allocation and loading.
-                 */
-                state = atomic_cmpxchg(&entry->state,
-                                       DM_BHT_ENTRY_UNALLOCATED,
-                                       DM_BHT_ENTRY_PENDING);
-                DMDEBUG("dm_bht_maybe_read_entries(d=%u,ei=%u,count=%u): "
-                        "ei=%lu, state=%d",
-                        depth, index, count,
-                        (unsigned long)(entry - level->entries), state);
-                if (state <= DM_BHT_ENTRY_ERROR) {
-                        DMCRIT("entry %u is in an error state", index);
-                        return state;
-                }
 
-                /* Currently, the verified state is unused. */
-                if (state == DM_BHT_ENTRY_VERIFIED) {
-                        if (until_exist)
-                                return 0;
-                        /* Makes 0 == verified. Is that ideal? */
-                        continue;
-                }
+        /* If the entry's state is UNALLOCATED, then we'll claim it
+         * for allocation and loading.
+         */
+        state = atomic_cmpxchg(&entry->state,
+                               DM_BHT_ENTRY_UNALLOCATED,
+                               DM_BHT_ENTRY_PENDING);
+        DMDEBUG("dm_bht_maybe_read_entry(d=%u,ei=%u): ei=%lu, state=%d",
+                depth, index, (unsigned long)(entry - level->entries), state);
 
-                if (state != DM_BHT_ENTRY_UNALLOCATED) {
-                        /* PENDING, READY, ... */
-                        if (until_exist)
-                                return state;
-                        status |= state;
-                        continue;
-                }
-                /* Current entry is claimed for allocation and loading */
-                node_page = (struct page *) mempool_alloc(bht->entry_pool,
-                                                          GFP_NOIO);
-                if (!node_page) {
-                        DMCRIT("failed to allocate memory for "
-                               "entry->nodes from pool");
-                        return -ENOMEM;
-                }
-                /* dm-bht guarantees page-aligned memory for callbacks. */
-                entry->nodes = page_address(node_page);
-                /* Let the caller know that not all the data is yet available */
-                status |= DM_BHT_ENTRY_REQUESTED;
-                /* Issue the read callback */
-                /* TODO(wad) error check callback here too */
-                DMDEBUG("dm_bht_maybe_read_entries(d=%u,ei=%u,count=%u): "
-                        "reading %lu",
-                        depth, index, count,
-                        (unsigned long)(entry - level->entries));
-                bht->read_cb(ctx,   /* external context */
-                             current_sector,  /* starting sector */
-                             entry->nodes,  /* destination */
-                             to_sector(PAGE_SIZE),
-                             entry);  /* io context */
+        if (state != DM_BHT_ENTRY_UNALLOCATED)
+                goto out;
 
-        }
-        /* Should only be 0 if all entries were verified and not just ready */
-        return status;
+        state = DM_BHT_ENTRY_REQUESTED;
+
+        /* Current entry is claimed for allocation and loading */
+        node_page = (struct page *) mempool_alloc(bht->entry_pool, GFP_NOIO);
+        if (!node_page)
+                goto nomem;
+        /* dm-bht guarantees page-aligned memory for callbacks. */
+        entry->nodes = page_address(node_page);
+
+        /* TODO(wad) error check callback here too */
+        DMDEBUG("dm_bht_maybe_read_entry(d=%u,ei=%u): reading %lu",
+                depth, index, (unsigned long)(entry - level->entries));
+        bht->read_cb(ctx, current_sector, entry->nodes,
+                     to_sector(PAGE_SIZE), entry);
+
+out:
+        if (state <= DM_BHT_ENTRY_ERROR)
+                DMCRIT("entry %u is in an error state", index);
+
+        return state;
+
+nomem:
+        DMCRIT("failed to allocate memory for entry->nodes from pool");
+        return -ENOMEM;
+
+
 }
 
 static int dm_bht_compare_hash(struct dm_bht *bht, u8 *known, u8 *computed)
 {
         return memcmp(known, computed, bht->digest_size);
 }
 
 static int dm_bht_update_hash(struct dm_bht *bht, u8 *known, u8 *computed)
 {
 #ifdef CONFIG_DM_DEBUG
@@ skipping 249 matching lines @@
 {
         int depth, r;
 
         for (depth = bht->depth - 2; depth >= 0; depth--) {
                 struct dm_bht_level *level = dm_bht_get_level(bht, depth);
                 struct dm_bht_level *child_level = level + 1;
                 struct dm_bht_entry *entry = level->entries;
                 struct dm_bht_entry *child = child_level->entries;
                 unsigned int i, j;
 
-                r = dm_bht_maybe_read_entries(bht, read_cb_ctx, depth,
-                                              0, level->count, true);
-                if (r < 0) {
-                        DMCRIT("an error occurred while reading entry");
-                        goto out;
-                }
-
                 for (i = 0; i < level->count; i++, entry++) {
                         unsigned int count = bht->node_count;
+
+                        r = dm_bht_maybe_read_entry(bht, read_cb_ctx, depth, i);
+                        if (r < 0) {
+                                DMCRIT("an error occurred while reading entry");
+                                goto out;
+                        }
+
                         if (i == (level->count - 1))
                                 count = child_level->count % bht->node_count;
                         if (count == 0)
                                 count = bht->node_count;
                         for (j = 0; j < count; j++, child++) {
                                 struct page *pg = virt_to_page(child->nodes);
                                 u8 *digest = dm_bht_node(bht, entry, j);
 
                                 r = dm_bht_compute_hash(bht, pg, 0, digest);
                                 if (r) {
@@ skipping 115 matching lines @@
 
         /* Load in all of level 0 if the root is unverified */
         root_state = atomic_read(&bht->root_state);
         /* TODO(wad) create a separate io object for the root request which
          * can continue on and be verified and stop making every request
          * check.
          */
         if (root_state != DM_BHT_ENTRY_VERIFIED) {
                 DMDEBUG("root data is not yet loaded");
                 /* If positive, it means some are pending. */
-                populated = dm_bht_maybe_read_entries(bht, read_cb_ctx, 0, 0,
-                                                      bht->levels[0].count,
-                                                      true);
+                populated = dm_bht_maybe_read_entry(bht, read_cb_ctx, 0, 0);
                 if (populated < 0) {
                         DMCRIT("an error occurred while reading level[0]");
                         /* TODO(wad) define std error codes */
                         return populated;
                 }
         }
 
         for (depth = 1; depth < bht->depth; ++depth) {
                 level = dm_bht_get_level(bht, depth);
                 entry_index = dm_bht_index_at_level(bht, depth,
                                                     block_index);
                 DMDEBUG("populate for bi=%u on d=%d ei=%u (max=%u)",
                         block_index, depth, entry_index, level->count);
 
                 /* Except for the root node case, we should only ever need
                  * to load one entry along the path.
                  */
-                read_status = dm_bht_maybe_read_entries(bht, read_cb_ctx,
-                                                        depth, entry_index,
-                                                        1, false);
+                read_status = dm_bht_maybe_read_entry(bht, read_cb_ctx,
+                                                      depth, entry_index);
                 if (unlikely(read_status < 0)) {
                         DMCRIT("failure occurred reading entry %u depth %u",
                                entry_index, depth);
                         return read_status;
                 }
                 /* Accrue return code flags */
                 populated |= read_status;
         }
 
         /* All nodes are ready. The hash for the block_index can be verified */
@@ skipping 171 matching lines @@
         if (!bht->root_digest) {
                 DMERR("no root digest exists to export");
                 if (available > 0)
                         *hexdigest = 0;
                 return -1;
         }
         dm_bht_bin_to_hex(bht->root_digest, hexdigest, bht->digest_size);
         return 0;
 }
 EXPORT_SYMBOL(dm_bht_root_hexdigest);