rbd: refactor rbd_header_from_disk()
This rearranges rbd_header_from_disk so that it:
- allocates the snapshot context right away
- keeps results in local variables, not changing the passed-in
header until it's known we'll succeed
- does initialization of set-once fields in a header only if
they have not already been set
The last point is moot at the moment, because rbd_read_header()
(the only caller) always supplies a zero-filled header buffer.
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Josh Durgin <josh.durgin@inktank.com>
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c
index b0fbc38..a3b6bf5 100644
--- a/drivers/block/rbd.c
+++ b/drivers/block/rbd.c
@@ -727,86 +727,109 @@
}
/*
- * Create a new header structure, translate header format from the on-disk
- * header.
+ * Fill an rbd image header with information from the given format 1
+ * on-disk header.
*/
static int rbd_header_from_disk(struct rbd_image_header *header,
struct rbd_image_header_ondisk *ondisk)
{
+ bool first_time = header->object_prefix == NULL;
+ struct ceph_snap_context *snapc;
+ char *object_prefix = NULL;
+ char *snap_names = NULL;
+ u64 *snap_sizes = NULL;
u32 snap_count;
- size_t len;
size_t size;
+ int ret = -ENOMEM;
u32 i;
+ /* Allocate this now to avoid having to handle failure below */
+
+ if (first_time) {
+ size_t len;
+
+ len = strnlen(ondisk->object_prefix,
+ sizeof (ondisk->object_prefix));
+ object_prefix = kmalloc(len + 1, GFP_KERNEL);
+ if (!object_prefix)
+ return -ENOMEM;
+ memcpy(object_prefix, ondisk->object_prefix, len);
+ object_prefix[len] = '\0';
+ }
+
+ /* Allocate the snapshot context and fill it in */
+
snap_count = le32_to_cpu(ondisk->snap_count);
-
- len = strnlen(ondisk->object_prefix, sizeof (ondisk->object_prefix));
- header->object_prefix = kmalloc(len + 1, GFP_KERNEL);
- if (!header->object_prefix)
- return -ENOMEM;
- memcpy(header->object_prefix, ondisk->object_prefix, len);
- header->object_prefix[len] = '\0';
-
+ snapc = ceph_create_snap_context(snap_count, GFP_KERNEL);
+ if (!snapc)
+ goto out_err;
+ snapc->seq = le64_to_cpu(ondisk->snap_seq);
if (snap_count) {
+ struct rbd_image_snap_ondisk *snaps;
u64 snap_names_len = le64_to_cpu(ondisk->snap_names_len);
- /* Save a copy of the snapshot names */
+ /* We'll keep a copy of the snapshot names... */
- if (snap_names_len > (u64) SIZE_MAX)
- return -EIO;
- header->snap_names = kmalloc(snap_names_len, GFP_KERNEL);
- if (!header->snap_names)
+ if (snap_names_len > (u64)SIZE_MAX)
+ goto out_2big;
+ snap_names = kmalloc(snap_names_len, GFP_KERNEL);
+ if (!snap_names)
goto out_err;
+
+ /* ...as well as the array of their sizes. */
+
+ size = snap_count * sizeof (*header->snap_sizes);
+ snap_sizes = kmalloc(size, GFP_KERNEL);
+ if (!snap_sizes)
+ goto out_err;
+
/*
- * Note that rbd_dev_v1_header_read() guarantees
- * the ondisk buffer we're working with has
+ * Copy the names, and fill in each snapshot's id
+ * and size.
+ *
+ * Note that rbd_dev_v1_header_read() guarantees the
+ * ondisk buffer we're working with has
* snap_names_len bytes beyond the end of the
* snapshot id array, this memcpy() is safe.
*/
- memcpy(header->snap_names, &ondisk->snaps[snap_count],
- snap_names_len);
-
- /* Record each snapshot's size */
-
- size = snap_count * sizeof (*header->snap_sizes);
- header->snap_sizes = kmalloc(size, GFP_KERNEL);
- if (!header->snap_sizes)
- goto out_err;
- for (i = 0; i < snap_count; i++)
- header->snap_sizes[i] =
- le64_to_cpu(ondisk->snaps[i].image_size);
- } else {
- header->snap_names = NULL;
- header->snap_sizes = NULL;
+ memcpy(snap_names, &ondisk->snaps[snap_count], snap_names_len);
+ snaps = ondisk->snaps;
+ for (i = 0; i < snap_count; i++) {
+ snapc->snaps[i] = le64_to_cpu(snaps[i].id);
+ snap_sizes[i] = le64_to_cpu(snaps[i].image_size);
+ }
}
- header->features = 0; /* No features support in v1 images */
- header->obj_order = ondisk->options.order;
- header->crypt_type = ondisk->options.crypt_type;
- header->comp_type = ondisk->options.comp_type;
+ /* We won't fail any more, fill in the header */
- /* Allocate and fill in the snapshot context */
+ if (first_time) {
+ header->object_prefix = object_prefix;
+ header->obj_order = ondisk->options.order;
+ header->crypt_type = ondisk->options.crypt_type;
+ header->comp_type = ondisk->options.comp_type;
+ /* The rest aren't used for format 1 images */
+ header->stripe_unit = 0;
+ header->stripe_count = 0;
+ header->features = 0;
+ }
+
+ /* The remaining fields always get updated (when we refresh) */
header->image_size = le64_to_cpu(ondisk->image_size);
-
- header->snapc = ceph_create_snap_context(snap_count, GFP_KERNEL);
- if (!header->snapc)
- goto out_err;
- header->snapc->seq = le64_to_cpu(ondisk->snap_seq);
- for (i = 0; i < snap_count; i++)
- header->snapc->snaps[i] = le64_to_cpu(ondisk->snaps[i].id);
+ header->snapc = snapc;
+ header->snap_names = snap_names;
+ header->snap_sizes = snap_sizes;
return 0;
-
+out_2big:
+ ret = -EIO;
out_err:
- kfree(header->snap_sizes);
- header->snap_sizes = NULL;
- kfree(header->snap_names);
- header->snap_names = NULL;
- kfree(header->object_prefix);
- header->object_prefix = NULL;
+ kfree(snap_sizes);
+ kfree(snap_names);
+ ceph_put_snap_context(snapc);
+ kfree(object_prefix);
- return -ENOMEM;
+ return ret;
}
static const char *_rbd_dev_v1_snap_name(struct rbd_device *rbd_dev, u32 which)