From ae8bf312e97d554b6aa32e7b2ceb993812ad0835 Mon Sep 17 00:00:00 2001 From: Lars Ellenberg Date: Tue, 19 Mar 2013 18:16:43 +0100 Subject: 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 Signed-off-by: Lars Ellenberg Signed-off-by: Jens Axboe 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.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 731a28e..76faeab 100644 --- a/drivers/block/drbd/drbd_main.c +++ b/drivers/block/drbd/drbd_main.c @@ -2834,6 +2834,7 @@ 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. */ @@ -2843,13 +2844,13 @@ 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; /** @@ -2862,6 +2863,10 @@ 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)) @@ -2876,7 +2881,7 @@ 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) { -- cgit v0.10.2