[PATCH 02/18] drbd: cleanup ondisk meta data layout calculations and defines
From: Philipp Reisner
Date: Tue Mar 19 2013 - 13:22:03 EST
From: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
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@xxxxxxxxxx>
Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
---
drivers/block/drbd/drbd_actlog.c | 28 ++++++++++---
drivers/block/drbd/drbd_bitmap.c | 13 +++++-
drivers/block/drbd/drbd_int.h | 86 ++++++++++++++++++++++----------------
drivers/block/drbd/drbd_main.c | 11 +++--
drivers/block/drbd/drbd_nl.c | 42 ++++++++++++++-----
5 files changed, 123 insertions(+), 57 deletions(-)
diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 92510f8..b230d91 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -209,7 +209,8 @@ int drbd_md_sync_page_io(struct drbd_conf *mdev, struct drbd_backing_dev *bdev,
current->comm, current->pid, __func__,
(unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
- err = _drbd_md_sync_page_io(mdev, bdev, iop, sector, rw, MD_BLOCK_SIZE);
+ /* we do all our meta data IO in aligned 4k blocks. */
+ err = _drbd_md_sync_page_io(mdev, bdev, iop, sector, rw, 4096);
if (err) {
dev_err(DEV, "drbd_md_sync_page_io(,%llus,%s) failed with error %d\n",
(unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ", err);
@@ -350,6 +351,24 @@ static unsigned int rs_extent_to_bm_page(unsigned int rs_enr)
(BM_EXT_SHIFT - BM_BLOCK_SHIFT));
}
+static sector_t al_tr_number_to_on_disk_sector(struct drbd_conf *mdev)
+{
+ const unsigned int stripes = 1;
+ const unsigned int stripe_size_4kB = MD_32kB_SECT/MD_4kB_SECT;
+
+ /* transaction number, modulo on-disk ring buffer wrap around */
+ unsigned int t = mdev->al_tr_number % (stripe_size_4kB * stripes);
+
+ /* ... to aligned 4k on disk block */
+ t = ((t % stripes) * stripe_size_4kB) + t/stripes;
+
+ /* ... to 512 byte sector in activity log */
+ t *= 8;
+
+ /* ... plus offset to the on disk position */
+ return mdev->ldev->md.md_offset + mdev->ldev->md.al_offset + t;
+}
+
static int
_al_write_transaction(struct drbd_conf *mdev)
{
@@ -432,13 +451,12 @@ _al_write_transaction(struct drbd_conf *mdev)
if (mdev->al_tr_cycle >= mdev->act_log->nr_elements)
mdev->al_tr_cycle = 0;
- sector = mdev->ldev->md.md_offset
- + mdev->ldev->md.al_offset
- + mdev->al_tr_pos * (MD_BLOCK_SIZE>>9);
+ sector = al_tr_number_to_on_disk_sector(mdev);
crc = crc32c(0, buffer, 4096);
buffer->crc32c = cpu_to_be32(crc);
+ /* normal execution path goes through all three branches */
if (drbd_bm_write_hinted(mdev))
err = -EIO;
/* drbd_chk_io_error done already */
@@ -446,8 +464,6 @@ _al_write_transaction(struct drbd_conf *mdev)
err = -EIO;
drbd_chk_io_error(mdev, 1, DRBD_META_IO_ERROR);
} else {
- /* advance ringbuffer position and transaction counter */
- mdev->al_tr_pos = (mdev->al_tr_pos + 1) % (MD_AL_SECTORS*512/MD_BLOCK_SIZE);
mdev->al_tr_number++;
}
diff --git a/drivers/block/drbd/drbd_bitmap.c b/drivers/block/drbd/drbd_bitmap.c
index 8dc2950..64fbb83 100644
--- a/drivers/block/drbd/drbd_bitmap.c
+++ b/drivers/block/drbd/drbd_bitmap.c
@@ -612,6 +612,17 @@ static void bm_memset(struct drbd_bitmap *b, size_t offset, int c, size_t len)
}
}
+/* For the layout, see comment above drbd_md_set_sector_offsets(). */
+static u64 drbd_md_on_disk_bits(struct drbd_backing_dev *ldev)
+{
+ u64 bitmap_sectors;
+ if (ldev->md.al_offset == 8)
+ bitmap_sectors = ldev->md.md_size_sect - ldev->md.bm_offset;
+ else
+ bitmap_sectors = ldev->md.al_offset - ldev->md.bm_offset;
+ return bitmap_sectors << (9 + 3);
+}
+
/*
* make sure the bitmap has enough room for the attached storage,
* if necessary, resize.
@@ -668,7 +679,7 @@ int drbd_bm_resize(struct drbd_conf *mdev, sector_t capacity, int set_new_bits)
words = ALIGN(bits, 64) >> LN2_BPL;
if (get_ldev(mdev)) {
- u64 bits_on_disk = ((u64)mdev->ldev->md.md_size_sect-MD_BM_OFFSET) << 12;
+ u64 bits_on_disk = drbd_md_on_disk_bits(mdev->ldev);
put_ldev(mdev);
if (bits > bits_on_disk) {
dev_info(DEV, "bits = %lu\n", bits);
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index db504d0..60c89e5 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -753,13 +753,8 @@ struct drbd_md {
u32 flags;
u32 md_size_sect;
- s32 al_offset; /* signed relative sector offset to al area */
+ s32 al_offset; /* signed relative sector offset to activity log */
s32 bm_offset; /* signed relative sector offset to bitmap */
-
- /* u32 al_nr_extents; important for restoring the AL
- * is stored into ldev->dc.al_extents, which in turn
- * gets applied to act_log->nr_elements
- */
};
struct drbd_backing_dev {
@@ -1009,7 +1004,6 @@ struct drbd_conf {
struct lru_cache *act_log; /* activity log */
unsigned int al_tr_number;
int al_tr_cycle;
- int al_tr_pos; /* position of the next transaction in the journal */
wait_queue_head_t seq_wait;
atomic_t packet_seq;
unsigned int peer_seq;
@@ -1151,21 +1145,41 @@ extern int drbd_bmio_clear_n_write(struct drbd_conf *mdev);
extern void drbd_ldev_destroy(struct drbd_conf *mdev);
/* Meta data layout
- We reserve a 128MB Block (4k aligned)
- * either at the end of the backing device
- * or on a separate meta data device. */
+ *
+ * We currently have two possible layouts.
+ * Offsets in (512 byte) sectors.
+ * external:
+ * |----------- md_size_sect ------------------|
+ * [ 4k superblock ][ activity log ][ Bitmap ]
+ * | al_offset == 8 |
+ * | bm_offset = al_offset + X |
+ * ==> bitmap sectors = md_size_sect - bm_offset
+ *
+ * Variants:
+ * old, indexed fixed size meta data:
+ *
+ * internal:
+ * |----------- md_size_sect ------------------|
+ * [data.....][ Bitmap ][ activity log ][ 4k superblock ][padding*]
+ * | al_offset < 0 |
+ * | bm_offset = al_offset - Y |
+ * ==> bitmap sectors = Y = al_offset - bm_offset
+ *
+ * [padding*] are zero or up to 7 unused 512 Byte sectors to the
+ * end of the device, so that the [4k superblock] will be 4k aligned.
+ *
+ * The activity log consists of 4k transaction blocks,
+ * which are written in a ring-buffer, or striped ring-buffer like fashion,
+ * which are writtensize used to be fixed 32kB,
+ * but is about to become configurable.
+ */
-/* The following numbers are sectors */
-/* Allows up to about 3.8TB, so if you want more,
+/* Our old fixed size meta data layout
+ * allows up to about 3.8TB, so if you want more,
* you need to use the "flexible" meta data format. */
-#define MD_RESERVED_SECT (128LU << 11) /* 128 MB, unit sectors */
-#define MD_AL_OFFSET 8 /* 8 Sectors after start of meta area */
-#define MD_AL_SECTORS 64 /* = 32 kB on disk activity log ring buffer */
-#define MD_BM_OFFSET (MD_AL_OFFSET + MD_AL_SECTORS)
-
-/* we do all meta data IO in 4k blocks */
-#define MD_BLOCK_SHIFT 12
-#define MD_BLOCK_SIZE (1<<MD_BLOCK_SHIFT)
+#define MD_128MB_SECT (128LLU << 11) /* 128 MB, unit sectors */
+#define MD_4kB_SECT 8
+#define MD_32kB_SECT 64
/* One activity log extent represents 4M of storage */
#define AL_EXTENT_SHIFT 22
@@ -1255,7 +1269,6 @@ struct bm_extent {
/* in one sector of the bitmap, we have this many activity_log extents. */
#define AL_EXT_PER_BM_SECT (1 << (BM_EXT_SHIFT - AL_EXTENT_SHIFT))
-#define BM_WORDS_PER_AL_EXT (1 << (AL_EXTENT_SHIFT-BM_BLOCK_SHIFT-LN2_BPL))
#define BM_BLOCKS_PER_BM_EXT_B (BM_EXT_SHIFT - BM_BLOCK_SHIFT)
#define BM_BLOCKS_PER_BM_EXT_MASK ((1<<BM_BLOCKS_PER_BM_EXT_B) - 1)
@@ -1275,16 +1288,18 @@ struct bm_extent {
*/
#define DRBD_MAX_SECTORS_32 (0xffffffffLU)
-#define DRBD_MAX_SECTORS_BM \
- ((MD_RESERVED_SECT - MD_BM_OFFSET) * (1LL<<(BM_EXT_SHIFT-9)))
-#if DRBD_MAX_SECTORS_BM < DRBD_MAX_SECTORS_32
-#define DRBD_MAX_SECTORS DRBD_MAX_SECTORS_BM
-#define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_BM
-#elif !defined(CONFIG_LBDAF) && BITS_PER_LONG == 32
+/* we have a certain meta data variant that has a fixed on-disk size of 128
+ * MiB, of which 4k are our "superblock", and 32k are the fixed size activity
+ * log, leaving this many sectors for the bitmap.
+ */
+
+#define DRBD_MAX_SECTORS_FIXED_BM \
+ ((MD_128MB_SECT - MD_32kB_SECT - MD_4kB_SECT) * (1LL<<(BM_EXT_SHIFT-9)))
+#if !defined(CONFIG_LBDAF) && BITS_PER_LONG == 32
#define DRBD_MAX_SECTORS DRBD_MAX_SECTORS_32
#define DRBD_MAX_SECTORS_FLEX DRBD_MAX_SECTORS_32
#else
-#define DRBD_MAX_SECTORS DRBD_MAX_SECTORS_BM
+#define DRBD_MAX_SECTORS DRBD_MAX_SECTORS_FIXED_BM
/* 16 TB in units of sectors */
#if BITS_PER_LONG == 32
/* adjust by one page worth of bitmap,
@@ -1792,10 +1807,10 @@ static inline sector_t drbd_md_last_sector(struct drbd_backing_dev *bdev)
switch (meta_dev_idx) {
case DRBD_MD_INDEX_INTERNAL:
case DRBD_MD_INDEX_FLEX_INT:
- return bdev->md.md_offset + MD_AL_OFFSET - 1;
+ return bdev->md.md_offset + MD_4kB_SECT -1;
case DRBD_MD_INDEX_FLEX_EXT:
default:
- return bdev->md.md_offset + bdev->md.md_size_sect;
+ return bdev->md.md_offset + bdev->md.md_size_sect -1;
}
}
@@ -1861,13 +1876,11 @@ static inline sector_t drbd_md_ss__(struct drbd_conf *mdev,
rcu_read_unlock();
switch (meta_dev_idx) {
- default: /* external, some index */
- return MD_RESERVED_SECT * meta_dev_idx;
+ default: /* external, some index; this is the old fixed size layout */
+ return MD_128MB_SECT * meta_dev_idx;
case DRBD_MD_INDEX_INTERNAL:
/* with drbd08, internal meta data is always "flexible" */
case DRBD_MD_INDEX_FLEX_INT:
- /* sizeof(struct md_on_disk_07) == 4k
- * position: last 4k aligned block of 4k size */
if (!bdev->backing_bdev) {
if (__ratelimit(&drbd_ratelimit_state)) {
dev_err(DEV, "bdev->backing_bdev==NULL\n");
@@ -1875,8 +1888,9 @@ static inline sector_t drbd_md_ss__(struct drbd_conf *mdev,
}
return 0;
}
- return (drbd_get_capacity(bdev->backing_bdev) & ~7ULL)
- - MD_AL_OFFSET;
+ /* sizeof(struct md_on_disk_07) == 4k
+ * position: last 4k aligned block of 4k size */
+ return (drbd_get_capacity(bdev->backing_bdev) & ~7ULL) - 8;
case DRBD_MD_INDEX_FLEX_EXT:
return 0;
}
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 6224963..6c4f0ff 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2837,6 +2837,7 @@ void conn_md_sync(struct drbd_tconn *tconn)
rcu_read_unlock();
}
+/* aligned 4kByte */
struct meta_data_on_disk {
u64 la_size; /* last agreed size. */
u64 uuid[UI_SIZE]; /* UUIDs. */
@@ -2846,13 +2847,13 @@ struct meta_data_on_disk {
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;
/**
@@ -2865,6 +2866,10 @@ void drbd_md_sync(struct drbd_conf *mdev)
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))
@@ -2879,7 +2884,7 @@ void drbd_md_sync(struct drbd_conf *mdev)
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++)
diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 2af26fc..581f680 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -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) {
--
1.7.9.5
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/