drbd: cleanup ondisk meta data layout calculations and defines
Add a comment about our meta data layout variants,
and rename a few defines (e.g. MD_RESERVED_SECT -> MD_128MB_SECT)
to make it clear that they are short hand for fixed constants,
and not arbitrarily to be redefined as one may see fit.
Properly pad struct meta_data_on_disk to 4kB,
and initialize to zero not only the first 512 Byte,
but all of it in drbd_md_sync().
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 731a28e..76faeab 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2834,6 +2834,7 @@
rcu_read_unlock();
}
+/* aligned 4kByte */
struct meta_data_on_disk {
u64 la_size; /* last agreed size. */
u64 uuid[UI_SIZE]; /* UUIDs. */
@@ -2843,13 +2844,13 @@
u32 magic;
u32 md_size_sect;
u32 al_offset; /* offset to this block */
- u32 al_nr_extents; /* important for restoring the AL */
+ u32 al_nr_extents; /* important for restoring the AL (userspace) */
/* `-- act_log->nr_elements <-- ldev->dc.al_extents */
u32 bm_offset; /* offset to the bitmap, from here */
u32 bm_bytes_per_bit; /* BM_BLOCK_SIZE */
u32 la_peer_max_bio_size; /* last peer max_bio_size */
- u32 reserved_u32[3];
+ u8 reserved_u8[4096 - (7*8 + 8*4)];
} __packed;
/**
@@ -2862,6 +2863,10 @@
sector_t sector;
int i;
+ /* Don't accidentally change the DRBD meta data layout. */
+ BUILD_BUG_ON(UI_SIZE != 4);
+ BUILD_BUG_ON(sizeof(struct meta_data_on_disk) != 4096);
+
del_timer(&mdev->md_sync_timer);
/* timer may be rearmed by drbd_md_mark_dirty() now. */
if (!test_and_clear_bit(MD_DIRTY, &mdev->flags))
@@ -2876,7 +2881,7 @@
if (!buffer)
goto out;
- memset(buffer, 0, 512);
+ memset(buffer, 0, sizeof(*buffer));
buffer->la_size = cpu_to_be64(drbd_get_capacity(mdev->this_bdev));
for (i = UI_CURRENT; i < UI_SIZE; i++)
