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drbd: cleanup ondisk meta data layout calculations and defines

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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>
This commit is contained in:
Lars Ellenberg
2013-03-19 18:16:43 +01:00
committed by Jens Axboe
parent 9114d79569
commit ae8bf312e9
5 changed files with 123 additions and 57 deletions
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drivers/block/drbd/drbd_nl.c
+31 -11
View File
@@ -696,12 +696,32 @@ out:
return 0;
}
/* initializes the md.*_offset members, so we are able to find
* the on disk meta data */
/* Initializes the md.*_offset members, so we are able to find
* the on disk meta data.
*
* We currently have two possible layouts:
* external:
* |----------- md_size_sect ------------------|
* [ 4k superblock ][ activity log ][ Bitmap ]
* | al_offset == 8 |
* | bm_offset = al_offset + X |
* ==> bitmap sectors = md_size_sect - bm_offset
*
* internal:
* |----------- md_size_sect ------------------|
* [data.....][ Bitmap ][ activity log ][ 4k superblock ]
* | al_offset < 0 |
* | bm_offset = al_offset - Y |
* ==> bitmap sectors = Y = al_offset - bm_offset
*
* Activity log size used to be fixed 32kB,
* but is about to become configurable.
*/
static void drbd_md_set_sector_offsets(struct drbd_conf *mdev,
struct drbd_backing_dev *bdev)
{
sector_t md_size_sect = 0;
unsigned int al_size_sect = MD_32kB_SECT;
int meta_dev_idx;
rcu_read_lock();
@@ -710,23 +730,23 @@ static void drbd_md_set_sector_offsets(struct drbd_conf *mdev,
switch (meta_dev_idx) {
default:
/* v07 style fixed size indexed meta data */
bdev->md.md_size_sect = MD_RESERVED_SECT;
bdev->md.md_size_sect = MD_128MB_SECT;
bdev->md.md_offset = drbd_md_ss__(mdev, bdev);
bdev->md.al_offset = MD_AL_OFFSET;
bdev->md.bm_offset = MD_BM_OFFSET;
bdev->md.al_offset = MD_4kB_SECT;
bdev->md.bm_offset = MD_4kB_SECT + al_size_sect;
break;
case DRBD_MD_INDEX_FLEX_EXT:
/* just occupy the full device; unit: sectors */
bdev->md.md_size_sect = drbd_get_capacity(bdev->md_bdev);
bdev->md.md_offset = 0;
bdev->md.al_offset = MD_AL_OFFSET;
bdev->md.bm_offset = MD_BM_OFFSET;
bdev->md.al_offset = MD_4kB_SECT;
bdev->md.bm_offset = MD_4kB_SECT + al_size_sect;
break;
case DRBD_MD_INDEX_INTERNAL:
case DRBD_MD_INDEX_FLEX_INT:
bdev->md.md_offset = drbd_md_ss__(mdev, bdev);
/* al size is still fixed */
bdev->md.al_offset = -MD_AL_SECTORS;
bdev->md.al_offset = -al_size_sect;
/* we need (slightly less than) ~ this much bitmap sectors: */
md_size_sect = drbd_get_capacity(bdev->backing_bdev);
md_size_sect = ALIGN(md_size_sect, BM_SECT_PER_EXT);
@@ -735,11 +755,11 @@ static void drbd_md_set_sector_offsets(struct drbd_conf *mdev,
/* plus the "drbd meta data super block",
* and the activity log; */
md_size_sect += MD_BM_OFFSET;
md_size_sect += MD_4kB_SECT + al_size_sect;
bdev->md.md_size_sect = md_size_sect;
/* bitmap offset is adjusted by 'super' block size */
bdev->md.bm_offset = -md_size_sect + MD_AL_OFFSET;
bdev->md.bm_offset = -md_size_sect + MD_4kB_SECT;
break;
}
rcu_read_unlock();
@@ -1416,7 +1436,7 @@ int drbd_adm_attach(struct sk_buff *skb, struct genl_info *info)
min_md_device_sectors = (2<<10);
} else {
max_possible_sectors = DRBD_MAX_SECTORS;
min_md_device_sectors = MD_RESERVED_SECT * (new_disk_conf->meta_dev_idx + 1);
min_md_device_sectors = MD_128MB_SECT * (new_disk_conf->meta_dev_idx + 1);
}
if (drbd_get_capacity(nbc->md_bdev) < min_md_device_sectors) {