[PATCH 13/15] drbd: new on-disk activity log transaction format

From: Philipp Reisner
Date: Tue Aug 30 2011 - 05:06:45 EST

From: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>

Use a new on-disk transaction format for the activity log, which allows
for multiple changes to the active set per transaction.

Using 4k transaction blocks, we can now get rid of the work-around code
to deal with devices not supporting 512 byte logical block size.

Signed-off-by: Philipp Reisner <philipp.reisner@xxxxxxxxxx>
Signed-off-by: Lars Ellenberg <lars.ellenberg@xxxxxxxxxx>
---
drivers/block/drbd/drbd_actlog.c | 403 +++++++++++++++++++++++---------------
drivers/block/drbd/drbd_int.h | 44 +++--
drivers/block/drbd/drbd_main.c | 4 -
drivers/block/drbd/drbd_nl.c | 42 +---
include/linux/drbd.h | 4 +
include/linux/drbd_limits.h | 8 +-
6 files changed, 294 insertions(+), 211 deletions(-)

diff --git a/drivers/block/drbd/drbd_actlog.c b/drivers/block/drbd/drbd_actlog.c
index 44097c8..55f5a7a 100644
--- a/drivers/block/drbd/drbd_actlog.c
+++ b/drivers/block/drbd/drbd_actlog.c
@@ -24,21 +24,67 @@
*/

#include <linux/slab.h>
+#include <linux/crc32c.h>
#include <linux/drbd.h>
+#include <linux/drbd_limits.h>
+#include <linux/dynamic_debug.h>
#include "drbd_int.h"
#include "drbd_wrappers.h"

-/* We maintain a trivial checksum in our on disk activity log.
- * With that we can ensure correct operation even when the storage
- * device might do a partial (last) sector write while losing power.
- */
-struct __packed al_transaction {
- u32 magic;
- u32 tr_number;
- struct __packed {
- u32 pos;
- u32 extent; } updates[1 + AL_EXTENTS_PT];
- u32 xor_sum;
+/* all fields on disc in big endian */
+struct __packed al_transaction_on_disk {
+ /* don't we all like magic */
+ __be32 magic;
+
+ /* to identify the most recent transaction block
+ * in the on disk ring buffer */
+ __be32 tr_number;
+
+ /* checksum on the full 4k block, with this field set to 0. */
+ __be32 crc32c;
+
+ /* type of transaction, special transaction types like:
+ * purge-all, set-all-idle, set-all-active, ... to-be-defined */
+ __be16 transaction_type;
+
+ /* we currently allow only a few thousand extents,
+ * so 16bit will be enough for the slot number. */
+
+ /* how many updates in this transaction */
+ __be16 n_updates;
+
+ /* maximum slot number, "al-extents" in drbd.conf speak.
+ * Having this in each transaction should make reconfiguration
+ * of that parameter easier. */
+ __be16 context_size;
+
+ /* slot number the context starts with */
+ __be16 context_start_slot_nr;
+
+ /* Some reserved bytes. Expected usage is a 64bit counter of
+ * sectors-written since device creation, and other data generation tag
+ * supporting usage */
+ __be32 __reserved[4];
+
+ /* --- 36 byte used --- */
+
+ /* Reserve space for up to AL_UPDATES_PER_TRANSACTION changes
+ * in one transaction, then use the remaining byte in the 4k block for
+ * context information. "Flexible" number of updates per transaction
+ * does not help, as we have to account for the case when all update
+ * slots are used anyways, so it would only complicate code without
+ * additional benefit.
+ */
+ __be16 update_slot_nr[AL_UPDATES_PER_TRANSACTION];
+
+ /* but the extent number is 32bit, which at an extent size of 4 MiB
+ * allows to cover device sizes of up to 2**54 Byte (16 PiB) */
+ __be32 update_extent_nr[AL_UPDATES_PER_TRANSACTION];
+
+ /* --- 420 bytes used (36 + 64*6) --- */
+
+ /* 4096 - 420 = 3676 = 919 * 4 */
+ __be32 context[AL_CONTEXT_PER_TRANSACTION];
};

struct update_odbm_work {
@@ -48,11 +94,8 @@ struct update_odbm_work {

struct update_al_work {
struct drbd_work w;
- struct lc_element *al_ext;
struct completion event;
- unsigned int enr;
- /* if old_enr != LC_FREE, write corresponding bitmap sector, too */
- unsigned int old_enr;
+ int err;
};

struct drbd_atodb_wait {
@@ -107,67 +150,30 @@ static int _drbd_md_sync_page_io(struct drbd_conf *mdev,
int drbd_md_sync_page_io(struct drbd_conf *mdev, struct drbd_backing_dev *bdev,
sector_t sector, int rw)
{
- int logical_block_size, mask, ok;
- int offset = 0;
+ int ok;
struct page *iop = mdev->md_io_page;

D_ASSERT(mutex_is_locked(&mdev->md_io_mutex));

BUG_ON(!bdev->md_bdev);

- logical_block_size = bdev_logical_block_size(bdev->md_bdev);
- if (logical_block_size == 0)
- logical_block_size = MD_SECTOR_SIZE;
-
- /* in case logical_block_size != 512 [ s390 only? ] */
- if (logical_block_size != MD_SECTOR_SIZE) {
- mask = (logical_block_size / MD_SECTOR_SIZE) - 1;
- D_ASSERT(mask == 1 || mask == 3 || mask == 7);
- D_ASSERT(logical_block_size == (mask+1) * MD_SECTOR_SIZE);
- offset = sector & mask;
- sector = sector & ~mask;
- iop = mdev->md_io_tmpp;
-
- if (rw & WRITE) {
- /* these are GFP_KERNEL pages, pre-allocated
- * on device initialization */
- void *p = page_address(mdev->md_io_page);
- void *hp = page_address(mdev->md_io_tmpp);
-
- ok = _drbd_md_sync_page_io(mdev, bdev, iop, sector,
- READ, logical_block_size);
-
- if (unlikely(!ok)) {
- dev_err(DEV, "drbd_md_sync_page_io(,%llus,"
- "READ [logical_block_size!=512]) failed!\n",
- (unsigned long long)sector);
- return 0;
- }
-
- memcpy(hp + offset*MD_SECTOR_SIZE, p, MD_SECTOR_SIZE);
- }
- }
+ dev_dbg(DEV, "meta_data io: %s [%d]:%s(,%llus,%s)\n",
+ current->comm, current->pid, __func__,
+ (unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");

if (sector < drbd_md_first_sector(bdev) ||
- sector > drbd_md_last_sector(bdev))
+ sector + 7 > drbd_md_last_sector(bdev))
dev_alert(DEV, "%s [%d]:%s(,%llus,%s) out of range md access!\n",
current->comm, current->pid, __func__,
(unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");

- ok = _drbd_md_sync_page_io(mdev, bdev, iop, sector, rw, logical_block_size);
+ ok = _drbd_md_sync_page_io(mdev, bdev, iop, sector, rw, MD_BLOCK_SIZE);
if (unlikely(!ok)) {
dev_err(DEV, "drbd_md_sync_page_io(,%llus,%s) failed!\n",
(unsigned long long)sector, (rw & WRITE) ? "WRITE" : "READ");
return 0;
}

- if (logical_block_size != MD_SECTOR_SIZE && !(rw & WRITE)) {
- void *p = page_address(mdev->md_io_page);
- void *hp = page_address(mdev->md_io_tmpp);
-
- memcpy(p, hp + offset*MD_SECTOR_SIZE, MD_SECTOR_SIZE);
- }
-
return ok;
}

@@ -211,20 +217,34 @@ void drbd_al_begin_io(struct drbd_conf *mdev, sector_t sector)
* current->bio_tail list now.
* we have to delegate updates to the activity log
* to the worker thread. */
- init_completion(&al_work.event);
- al_work.al_ext = al_ext;
- al_work.enr = enr;
- al_work.old_enr = al_ext->lc_number;
- al_work.w.cb = w_al_write_transaction;
- al_work.w.mdev = mdev;
- drbd_queue_work_front(&mdev->tconn->data.work, &al_work.w);
- wait_for_completion(&al_work.event);

- mdev->al_writ_cnt++;
+ /* Serialize multiple transactions.
+ * This uses test_and_set_bit, memory barrier is implicit.
+ * Optimization potential:
+ * first check for transaction number > old transaction number,
+ * so not all waiters have to lock/unlock. */
+ wait_event(mdev->al_wait, lc_try_lock_for_transaction(mdev->act_log));

- spin_lock_irq(&mdev->al_lock);
- lc_committed(mdev->act_log);
- spin_unlock_irq(&mdev->al_lock);
+ /* Double check: it may have been committed by someone else,
+ * while we have been waiting for the lock. */
+ if (al_ext->lc_number != enr) {
+ init_completion(&al_work.event);
+ al_work.w.cb = w_al_write_transaction;
+ al_work.w.mdev = mdev;
+ drbd_queue_work_front(&mdev->tconn->data.work, &al_work.w);
+ wait_for_completion(&al_work.event);
+
+ mdev->al_writ_cnt++;
+
+ spin_lock_irq(&mdev->al_lock);
+ /* FIXME
+ if (al_work.err)
+ we need an "lc_cancel" here;
+ */
+ lc_committed(mdev->act_log);
+ spin_unlock_irq(&mdev->al_lock);
+ }
+ lc_unlock(mdev->act_log);
wake_up(&mdev->al_wait);
}
}
@@ -283,95 +303,108 @@ w_al_write_transaction(struct drbd_work *w, int unused)
{
struct update_al_work *aw = container_of(w, struct update_al_work, w);
struct drbd_conf *mdev = w->mdev;
- struct lc_element *updated = aw->al_ext;
- const unsigned int new_enr = aw->enr;
- const unsigned int evicted = aw->old_enr;
- struct al_transaction *buffer;
+ struct al_transaction_on_disk *buffer;
+ struct lc_element *e;
sector_t sector;
- int i, n, mx;
- unsigned int extent_nr;
- u32 xor_sum = 0;
+ int i, mx;
+ unsigned extent_nr;
+ unsigned crc = 0;

if (!get_ldev(mdev)) {
- dev_err(DEV,
- "disk is %s, cannot start al transaction (-%d +%d)\n",
- drbd_disk_str(mdev->state.disk), evicted, new_enr);
+ dev_err(DEV, "disk is %s, cannot start al transaction\n",
+ drbd_disk_str(mdev->state.disk));
+ aw->err = -EIO;
complete(&((struct update_al_work *)w)->event);
return 1;
}
- /* do we have to do a bitmap write, first?
- * TODO reduce maximum latency:
- * submit both bios, then wait for both,
- * instead of doing two synchronous sector writes.
- * For now, we must not write the transaction,
- * if we cannot write out the bitmap of the evicted extent. */
- if (mdev->state.conn < C_CONNECTED && evicted != LC_FREE)
- drbd_bm_write_page(mdev, al_extent_to_bm_page(evicted));

/* The bitmap write may have failed, causing a state change. */
if (mdev->state.disk < D_INCONSISTENT) {
dev_err(DEV,
- "disk is %s, cannot write al transaction (-%d +%d)\n",
- drbd_disk_str(mdev->state.disk), evicted, new_enr);
+ "disk is %s, cannot write al transaction\n",
+ drbd_disk_str(mdev->state.disk));
+ aw->err = -EIO;
complete(&((struct update_al_work *)w)->event);
put_ldev(mdev);
return 1;
}

mutex_lock(&mdev->md_io_mutex); /* protects md_io_buffer, al_tr_cycle, ... */
- buffer = (struct al_transaction *)page_address(mdev->md_io_page);
+ buffer = page_address(mdev->md_io_page);

- buffer->magic = __constant_cpu_to_be32(DRBD_MAGIC);
+ memset(buffer, 0, sizeof(*buffer));
+ buffer->magic = cpu_to_be32(DRBD_AL_MAGIC);
buffer->tr_number = cpu_to_be32(mdev->al_tr_number);

- n = lc_index_of(mdev->act_log, updated);
-
- buffer->updates[0].pos = cpu_to_be32(n);
- buffer->updates[0].extent = cpu_to_be32(new_enr);
+ i = 0;
+ /* no need to grab any further lock, this list cannot change
+ * while we hold the "LC_LOCKED" bit. */
+ list_for_each_entry(e, &mdev->act_log->to_be_changed, list) {
+ BUG_ON(i >= AL_UPDATES_PER_TRANSACTION);
+ buffer->update_slot_nr[i] = cpu_to_be16(e->lc_index);
+ buffer->update_extent_nr[i] = cpu_to_be32(e->lc_new_number);
+ if (e->lc_number != LC_FREE)
+ drbd_bm_mark_for_writeout(mdev,
+ al_extent_to_bm_page(e->lc_number));
+ i++;
+ }
+ buffer->n_updates = cpu_to_be16(i);
+ for ( ; i < AL_UPDATES_PER_TRANSACTION; i++) {
+ buffer->update_slot_nr[i] = cpu_to_be16(-1);
+ buffer->update_extent_nr[i] = cpu_to_be32(LC_FREE);
+ }

- xor_sum ^= new_enr;
+ buffer->context_size = cpu_to_be16(mdev->act_log->nr_elements);
+ buffer->context_start_slot_nr = cpu_to_be16(mdev->al_tr_cycle);

- mx = min_t(int, AL_EXTENTS_PT,
+ mx = min_t(int, AL_CONTEXT_PER_TRANSACTION,
mdev->act_log->nr_elements - mdev->al_tr_cycle);
for (i = 0; i < mx; i++) {
unsigned idx = mdev->al_tr_cycle + i;
extent_nr = lc_element_by_index(mdev->act_log, idx)->lc_number;
- buffer->updates[i+1].pos = cpu_to_be32(idx);
- buffer->updates[i+1].extent = cpu_to_be32(extent_nr);
- xor_sum ^= extent_nr;
- }
- for (; i < AL_EXTENTS_PT; i++) {
- buffer->updates[i+1].pos = __constant_cpu_to_be32(-1);
- buffer->updates[i+1].extent = __constant_cpu_to_be32(LC_FREE);
- xor_sum ^= LC_FREE;
+ buffer->context[i] = cpu_to_be32(extent_nr);
}
- mdev->al_tr_cycle += AL_EXTENTS_PT;
+ for (; i < AL_CONTEXT_PER_TRANSACTION; i++)
+ buffer->context[i] = cpu_to_be32(LC_FREE);
+
+ mdev->al_tr_cycle += AL_CONTEXT_PER_TRANSACTION;
if (mdev->al_tr_cycle >= mdev->act_log->nr_elements)
mdev->al_tr_cycle = 0;

- buffer->xor_sum = cpu_to_be32(xor_sum);
-
sector = mdev->ldev->md.md_offset
- + mdev->ldev->md.al_offset + mdev->al_tr_pos;
-
- if (!drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE))
- drbd_chk_io_error(mdev, 1, true);
+ + mdev->ldev->md.al_offset
+ + mdev->al_tr_pos * (MD_BLOCK_SIZE>>9);

- if (++mdev->al_tr_pos >
- div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT))
- mdev->al_tr_pos = 0;
+ crc = crc32c(0, buffer, 4096);
+ buffer->crc32c = cpu_to_be32(crc);

- D_ASSERT(mdev->al_tr_pos < MD_AL_MAX_SIZE);
- mdev->al_tr_number++;
+ if (drbd_bm_write_hinted(mdev))
+ aw->err = -EIO;
+ /* drbd_chk_io_error done already */
+ else if (!drbd_md_sync_page_io(mdev, mdev->ldev, sector, WRITE)) {
+ aw->err = -EIO;
+ drbd_chk_io_error(mdev, 1, true);
+ } 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++;
+ }

mutex_unlock(&mdev->md_io_mutex);
-
complete(&((struct update_al_work *)w)->event);
put_ldev(mdev);

return 1;
}

+/* FIXME
+ * reading of the activity log,
+ * and potentially dirtying of the affected bitmap regions,
+ * should be done from userland only.
+ * DRBD would simply always attach with an empty activity log,
+ * and refuse to attach to something that looks like a crashed primary.
+ */
+
/**
* drbd_al_read_tr() - Read a single transaction from the on disk activity log
* @mdev: DRBD device.
@@ -383,27 +416,39 @@ w_al_write_transaction(struct drbd_work *w, int unused)
*/
static int drbd_al_read_tr(struct drbd_conf *mdev,
struct drbd_backing_dev *bdev,
- struct al_transaction *b,
int index)
{
+ struct al_transaction_on_disk *b = page_address(mdev->md_io_page);
sector_t sector;
- int rv, i;
- u32 xor_sum = 0;
+ u32 crc;

- sector = bdev->md.md_offset + bdev->md.al_offset + index;
+ sector = bdev->md.md_offset
+ + bdev->md.al_offset
+ + index * (MD_BLOCK_SIZE>>9);

/* Dont process error normally,
* as this is done before disk is attached! */
if (!drbd_md_sync_page_io(mdev, bdev, sector, READ))
return -1;

- rv = (b->magic == cpu_to_be32(DRBD_MAGIC));
+ if (!expect(b->magic == cpu_to_be32(DRBD_AL_MAGIC)))
+ return 0;

- for (i = 0; i < AL_EXTENTS_PT + 1; i++)
- xor_sum ^= be32_to_cpu(b->updates[i].extent);
- rv &= (xor_sum == be32_to_cpu(b->xor_sum));
+ if (!expect(be16_to_cpu(b->n_updates) <= AL_UPDATES_PER_TRANSACTION))
+ return 0;

- return rv;
+ if (!expect(be16_to_cpu(b->context_size) <= DRBD_AL_EXTENTS_MAX))
+ return 0;
+
+ if (!expect(be16_to_cpu(b->context_start_slot_nr) < DRBD_AL_EXTENTS_MAX))
+ return 0;
+
+ crc = be32_to_cpu(b->crc32c);
+ b->crc32c = 0;
+ if (!expect(crc == crc32c(0, b, 4096)))
+ return 0;
+
+ return 1;
}

/**
@@ -415,7 +460,7 @@ static int drbd_al_read_tr(struct drbd_conf *mdev,
*/
int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
{
- struct al_transaction *buffer;
+ struct al_transaction_on_disk *b;
int i;
int rv;
int mx;
@@ -428,25 +473,36 @@ int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
u32 to_tnr = 0;
u32 cnr;

- mx = div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT);
+ /* Note that this is expected to be called with a newly created,
+ * clean and all unused activity log of the "expected size".
+ */

/* lock out all other meta data io for now,
* and make sure the page is mapped.
*/
mutex_lock(&mdev->md_io_mutex);
- buffer = page_address(mdev->md_io_page);
+ b = page_address(mdev->md_io_page);
+
+ /* Always use the full ringbuffer space for now.
+ * possible optimization: read in all of it,
+ * then scan the in-memory pages. */
+
+ mx = (MD_AL_SECTORS*512/MD_BLOCK_SIZE);

/* Find the valid transaction in the log */
- for (i = 0; i <= mx; i++) {
- rv = drbd_al_read_tr(mdev, bdev, buffer, i);
+ for (i = 0; i < mx; i++) {
+ rv = drbd_al_read_tr(mdev, bdev, i);
+ /* invalid data in that block */
if (rv == 0)
continue;
+
+ /* IO error */
if (rv == -1) {
mutex_unlock(&mdev->md_io_mutex);
return 0;
}
- cnr = be32_to_cpu(buffer->tr_number);

+ cnr = be32_to_cpu(b->tr_number);
if (++found_valid == 1) {
from = i;
to = i;
@@ -454,8 +510,11 @@ int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
to_tnr = cnr;
continue;
}
+
+ D_ASSERT(cnr != to_tnr);
+ D_ASSERT(cnr != from_tnr);
if ((int)cnr - (int)from_tnr < 0) {
- D_ASSERT(from_tnr - cnr + i - from == mx+1);
+ D_ASSERT(from_tnr - cnr + i - from == mx);
from = i;
from_tnr = cnr;
}
@@ -476,11 +535,10 @@ int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
* dev_info(DEV, "Reading from %d to %d.\n",from,to); */
i = from;
while (1) {
- int j, pos;
- unsigned int extent_nr;
- unsigned int trn;
+ struct lc_element *e;
+ unsigned j, n, slot, extent_nr;

- rv = drbd_al_read_tr(mdev, bdev, buffer, i);
+ rv = drbd_al_read_tr(mdev, bdev, i);
if (!expect(rv != 0))
goto cancel;
if (rv == -1) {
@@ -488,23 +546,55 @@ int drbd_al_read_log(struct drbd_conf *mdev, struct drbd_backing_dev *bdev)
return 0;
}

- trn = be32_to_cpu(buffer->tr_number);
+ /* deal with different transaction types.
+ * not yet implemented */
+ if (!expect(b->transaction_type == 0))
+ goto cancel;

- spin_lock_irq(&mdev->al_lock);
+ /* on the fly re-create/resize activity log?
+ * will be a special transaction type flag. */
+ if (!expect(be16_to_cpu(b->context_size) == mdev->act_log->nr_elements))
+ goto cancel;
+ if (!expect(be16_to_cpu(b->context_start_slot_nr) < mdev->act_log->nr_elements))
+ goto cancel;

- /* This loop runs backwards because in the cyclic
- elements there might be an old version of the
- updated element (in slot 0). So the element in slot 0
- can overwrite old versions. */
- for (j = AL_EXTENTS_PT; j >= 0; j--) {
- pos = be32_to_cpu(buffer->updates[j].pos);
- extent_nr = be32_to_cpu(buffer->updates[j].extent);
+ /* We are the only user of the activity log right now,
+ * don't actually need to take that lock. */
+ spin_lock_irq(&mdev->al_lock);

- if (extent_nr == LC_FREE)
- continue;
+ /* first, apply the context, ... */
+ for (j = 0, slot = be16_to_cpu(b->context_start_slot_nr);
+ j < AL_CONTEXT_PER_TRANSACTION &&
+ slot < mdev->act_log->nr_elements; j++, slot++) {
+ extent_nr = be32_to_cpu(b->context[j]);
+ e = lc_element_by_index(mdev->act_log, slot);
+ if (e->lc_number != extent_nr) {
+ if (extent_nr != LC_FREE)
+ active_extents++;
+ else
+ active_extents--;
+ }
+ lc_set(mdev->act_log, extent_nr, slot);
+ }

- lc_set(mdev->act_log, extent_nr, pos);
- active_extents++;
+ /* ... then apply the updates,
+ * which override the context information.
+ * drbd_al_read_tr already did the rangecheck
+ * on n <= AL_UPDATES_PER_TRANSACTION */
+ n = be16_to_cpu(b->n_updates);
+ for (j = 0; j < n; j++) {
+ slot = be16_to_cpu(b->update_slot_nr[j]);
+ extent_nr = be32_to_cpu(b->update_extent_nr[j]);
+ if (!expect(slot < mdev->act_log->nr_elements))
+ break;
+ e = lc_element_by_index(mdev->act_log, slot);
+ if (e->lc_number != extent_nr) {
+ if (extent_nr != LC_FREE)
+ active_extents++;
+ else
+ active_extents--;
+ }
+ lc_set(mdev->act_log, extent_nr, slot);
}
spin_unlock_irq(&mdev->al_lock);

@@ -514,15 +604,12 @@ cancel:
if (i == to)
break;
i++;
- if (i > mx)
+ if (i >= mx)
i = 0;
}

mdev->al_tr_number = to_tnr+1;
- mdev->al_tr_pos = to;
- if (++mdev->al_tr_pos >
- div_ceil(mdev->act_log->nr_elements, AL_EXTENTS_PT))
- mdev->al_tr_pos = 0;
+ mdev->al_tr_pos = (to + 1) % (MD_AL_SECTORS*512/MD_BLOCK_SIZE);

/* ok, we are done with it */
mutex_unlock(&mdev->md_io_mutex);
diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h
index f125c0e..482bd7e 100644
--- a/drivers/block/drbd/drbd_int.h
+++ b/drivers/block/drbd/drbd_int.h
@@ -1069,7 +1069,6 @@ struct drbd_conf {
atomic_t pp_in_use_by_net; /* sendpage()d, still referenced by tcp */
wait_queue_head_t ee_wait;
struct page *md_io_page; /* one page buffer for md_io */
- struct page *md_io_tmpp; /* for logical_block_size != 512 */
struct mutex md_io_mutex; /* protects the md_io_buffer */
spinlock_t al_lock;
wait_queue_head_t al_wait;
@@ -1259,22 +1258,39 @@ extern void drbd_ldev_destroy(struct drbd_conf *mdev);
* either at the end of the backing device
* or on a separate meta data device. */

-#define MD_RESERVED_SECT (128LU << 11) /* 128 MB, unit sectors */
/* The following numbers are sectors */
-#define MD_AL_OFFSET 8 /* 8 Sectors after start of meta area */
-#define MD_AL_MAX_SIZE 64 /* = 32 kb LOG ~ 3776 extents ~ 14 GB Storage */
-/* Allows up to about 3.8TB */
-#define MD_BM_OFFSET (MD_AL_OFFSET + MD_AL_MAX_SIZE)
-
-/* Since the smalles IO unit is usually 512 byte */
-#define MD_SECTOR_SHIFT 9
-#define MD_SECTOR_SIZE (1<<MD_SECTOR_SHIFT)
-
-/* activity log */
-#define AL_EXTENTS_PT ((MD_SECTOR_SIZE-12)/8-1) /* 61 ; Extents per 512B sector */
-#define AL_EXTENT_SHIFT 22 /* One extent represents 4M Storage */
+/* 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)
+
+/* One activity log extent represents 4M of storage */
+#define AL_EXTENT_SHIFT 22
#define AL_EXTENT_SIZE (1<<AL_EXTENT_SHIFT)

+/* We could make these currently hardcoded constants configurable
+ * variables at create-md time (or even re-configurable at runtime?).
+ * Which will require some more changes to the DRBD "super block"
+ * and attach code.
+ *
+ * updates per transaction:
+ * This many changes to the active set can be logged with one transaction.
+ * This number is arbitrary.
+ * context per transaction:
+ * This many context extent numbers are logged with each transaction.
+ * This number is resulting from the transaction block size (4k), the layout
+ * of the transaction header, and the number of updates per transaction.
+ * See drbd_actlog.c:struct al_transaction_on_disk
+ * */
+#define AL_UPDATES_PER_TRANSACTION 64 // arbitrary
+#define AL_CONTEXT_PER_TRANSACTION 919 // (4096 - 36 - 6*64)/4
+
#if BITS_PER_LONG == 32
#define LN2_BPL 5
#define cpu_to_lel(A) cpu_to_le32(A)
diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c
index 75b092b..47c4bae 100644
--- a/drivers/block/drbd/drbd_main.c
+++ b/drivers/block/drbd/drbd_main.c
@@ -2842,10 +2842,6 @@ void drbd_ldev_destroy(struct drbd_conf *mdev)
drbd_free_bc(mdev->ldev);
mdev->ldev = NULL;);

- if (mdev->md_io_tmpp) {
- __free_page(mdev->md_io_tmpp);
- mdev->md_io_tmpp = NULL;
- }
clear_bit(GO_DISKLESS, &mdev->flags);
}

diff --git a/drivers/block/drbd/drbd_nl.c b/drivers/block/drbd/drbd_nl.c
index 0a92f52..90d7317 100644
--- a/drivers/block/drbd/drbd_nl.c
+++ b/drivers/block/drbd/drbd_nl.c
@@ -527,7 +527,7 @@ static void drbd_md_set_sector_offsets(struct drbd_conf *mdev,
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_MAX_SIZE;
+ bdev->md.al_offset = -MD_AL_SECTORS;
/* 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);
@@ -751,8 +751,8 @@ static int drbd_check_al_size(struct drbd_conf *mdev)
unsigned int in_use;
int i;

- if (!expect(mdev->sync_conf.al_extents >= 7))
- mdev->sync_conf.al_extents = 127;
+ if (!expect(mdev->sync_conf.al_extents >= DRBD_AL_EXTENTS_MIN))
+ mdev->sync_conf.al_extents = DRBD_AL_EXTENTS_MIN;

if (mdev->act_log &&
mdev->act_log->nr_elements == mdev->sync_conf.al_extents)
@@ -760,7 +760,7 @@ static int drbd_check_al_size(struct drbd_conf *mdev)

in_use = 0;
t = mdev->act_log;
- n = lc_create("act_log", drbd_al_ext_cache, 1,
+ n = lc_create("act_log", drbd_al_ext_cache, AL_UPDATES_PER_TRANSACTION,
mdev->sync_conf.al_extents, sizeof(struct lc_element), 0);

if (n == NULL) {
@@ -932,7 +932,6 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp
union drbd_state ns, os;
enum drbd_state_rv rv;
int cp_discovered = 0;
- int logical_block_size;

drbd_reconfig_start(mdev);

@@ -1087,25 +1086,6 @@ static int drbd_nl_disk_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *nlp

drbd_md_set_sector_offsets(mdev, nbc);

- /* allocate a second IO page if logical_block_size != 512 */
- logical_block_size = bdev_logical_block_size(nbc->md_bdev);
- if (logical_block_size == 0)
- logical_block_size = MD_SECTOR_SIZE;
-
- if (logical_block_size != MD_SECTOR_SIZE) {
- if (!mdev->md_io_tmpp) {
- struct page *page = alloc_page(GFP_NOIO);
- if (!page)
- goto force_diskless_dec;
-
- dev_warn(DEV, "Meta data's bdev logical_block_size = %d != %d\n",
- logical_block_size, MD_SECTOR_SIZE);
- dev_warn(DEV, "Workaround engaged (has performance impact).\n");
-
- mdev->md_io_tmpp = page;
- }
- }
-
if (!mdev->bitmap) {
if (drbd_bm_init(mdev)) {
retcode = ERR_NOMEM;
@@ -1804,14 +1784,12 @@ static int drbd_nl_syncer_conf(struct drbd_conf *mdev, struct drbd_nl_cfg_req *n

if (!expect(sc.rate >= 1))
sc.rate = 1;
- if (!expect(sc.al_extents >= 7))
- sc.al_extents = 127; /* arbitrary minimum */
-#define AL_MAX ((MD_AL_MAX_SIZE-1) * AL_EXTENTS_PT)
- if (sc.al_extents > AL_MAX) {
- dev_err(DEV, "sc.al_extents > %d\n", AL_MAX);
- sc.al_extents = AL_MAX;
- }
-#undef AL_MAX
+
+ /* clip to allowed range */
+ if (!expect(sc.al_extents >= DRBD_AL_EXTENTS_MIN))
+ sc.al_extents = DRBD_AL_EXTENTS_MIN;
+ if (!expect(sc.al_extents <= DRBD_AL_EXTENTS_MAX))
+ sc.al_extents = DRBD_AL_EXTENTS_MAX;

/* to avoid spurious errors when configuring minors before configuring
* the minors they depend on: if necessary, first create the minor we
diff --git a/include/linux/drbd.h b/include/linux/drbd.h
index 35fc08a..70a688b 100644
--- a/include/linux/drbd.h
+++ b/include/linux/drbd.h
@@ -336,6 +336,10 @@ enum drbd_timeout_flag {
#define DRBD_MAGIC 0x83740267
#define DRBD_MAGIC_BIG 0x835a

+/* how I came up with this magic?
+ * base64 decode "actlog==" ;) */
+#define DRBD_AL_MAGIC 0x69cb65a2
+
/* these are of type "int" */
#define DRBD_MD_INDEX_INTERNAL -1
#define DRBD_MD_INDEX_FLEX_EXT -2
diff --git a/include/linux/drbd_limits.h b/include/linux/drbd_limits.h
index 447c367..75f05af 100644
--- a/include/linux/drbd_limits.h
+++ b/include/linux/drbd_limits.h
@@ -102,10 +102,12 @@
#define DRBD_RATE_DEF 250 /* kb/second */

/* less than 7 would hit performance unnecessarily.
- * 3833 is the largest prime that still does fit
- * into 64 sectors of activity log */
+ * 919 slots context information per transaction,
+ * 32k activity log, 4k transaction size,
+ * one transaction in flight:
+ * 919 * 7 = 6433 */
#define DRBD_AL_EXTENTS_MIN 7
-#define DRBD_AL_EXTENTS_MAX 3833
+#define DRBD_AL_EXTENTS_MAX 6433
#define DRBD_AL_EXTENTS_DEF 127

#define DRBD_AFTER_MIN -1
--
1.7.4.1

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