From 341166c8435f54936cdea366d096b1f5556292c1 Mon Sep 17 00:00:00 2001 From: Mike Gerdts Date: Sun, 30 Jun 2019 23:38:07 +0000 Subject: OpenZFS 9318 - vol_volsize_to_reservation does not account for raidz skip blocks When a volume is created in a pool with raidz vdevs and volblocksize != 128k, the volume can reference more space than is reserved with the automatically calculated refreservation. There are two deficiencies in vol_volsize_to_reservation that contribute to this: 1) Skip blocks may be added to keep each allocation a multiple of parity + 1. This is the dominating factor when volblocksize is close to 2^ashift. 2) raidz deflation for 128 KB blocks is different for most other block sizes. See "The theory of raidz space accounting" comment in libzfs_dataset.c for a full explanation. Authored by: Mike Gerdts Reviewed by: Richard Elling Reviewed by: Sanjay Nadkarni Reviewed by: Jerry Jelinek Reviewed by: Matt Ahrens Reviewed by: Kody Kantor Reviewed-by: Brian Behlendorf Approved by: Dan McDonald Ported-by: Mike Gerdts Porting Notes: * ZTS: wait for zvols to exist before writing * ZTS: use log_must_busy with {zpool|zfs} destroy OpenZFS-issue: https://www.illumos.org/issues/9318 OpenZFS-commit: https://github.com/illumos/illumos-gate/commit/b73ccab0 Closes #8973 --- lib/libzfs/libzfs_dataset.c | 189 ++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 181 insertions(+), 8 deletions(-) (limited to 'lib/libzfs') diff --git a/lib/libzfs/libzfs_dataset.c b/lib/libzfs/libzfs_dataset.c index c1aff4725..4285d1224 100644 --- a/lib/libzfs/libzfs_dataset.c +++ b/lib/libzfs/libzfs_dataset.c @@ -21,7 +21,7 @@ /* * Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved. - * Copyright (c) 2018, Joyent, Inc. All rights reserved. + * Copyright 2019 Joyent, Inc. * Copyright (c) 2011, 2018 by Delphix. All rights reserved. * Copyright (c) 2012 DEY Storage Systems, Inc. All rights reserved. * Copyright (c) 2012 Pawel Jakub Dawidek . @@ -1617,6 +1617,7 @@ zfs_add_synthetic_resv(zfs_handle_t *zhp, nvlist_t *nvl) uint64_t new_reservation; zfs_prop_t resv_prop; nvlist_t *props; + zpool_handle_t *zph = zpool_handle(zhp); /* * If this is an existing volume, and someone is setting the volsize, @@ -1631,7 +1632,7 @@ zfs_add_synthetic_resv(zfs_handle_t *zhp, nvlist_t *nvl) fnvlist_add_uint64(props, zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), zfs_prop_get_int(zhp, ZFS_PROP_VOLBLOCKSIZE)); - if ((zvol_volsize_to_reservation(old_volsize, props) != + if ((zvol_volsize_to_reservation(zph, old_volsize, props) != old_reservation) || nvlist_exists(nvl, zfs_prop_to_name(resv_prop))) { fnvlist_free(props); @@ -1642,7 +1643,7 @@ zfs_add_synthetic_resv(zfs_handle_t *zhp, nvlist_t *nvl) fnvlist_free(props); return (-1); } - new_reservation = zvol_volsize_to_reservation(new_volsize, props); + new_reservation = zvol_volsize_to_reservation(zph, new_volsize, props); fnvlist_free(props); if (nvlist_add_uint64(nvl, zfs_prop_to_name(resv_prop), @@ -1697,7 +1698,8 @@ zfs_fix_auto_resv(zfs_handle_t *zhp, nvlist_t *nvl) volsize = zfs_prop_get_int(zhp, ZFS_PROP_VOLSIZE); } - resvsize = zvol_volsize_to_reservation(volsize, props); + resvsize = zvol_volsize_to_reservation(zpool_handle(zhp), volsize, + props); fnvlist_free(props); (void) nvlist_remove_all(nvl, zfs_prop_to_name(prop)); @@ -5376,12 +5378,176 @@ zfs_get_holds(zfs_handle_t *zhp, nvlist_t **nvl) } /* - * Convert the zvol's volume size to an appropriate reservation. + * The theory of raidz space accounting + * + * The "referenced" property of RAIDZ vdevs is scaled such that a 128KB block + * will "reference" 128KB, even though it allocates more than that, to store the + * parity information (and perhaps skip sectors). This concept of the + * "referenced" (and other DMU space accounting) being lower than the allocated + * space by a constant factor is called "raidz deflation." + * + * As mentioned above, the constant factor for raidz deflation assumes a 128KB + * block size. However, zvols typically have a much smaller block size (default + * 8KB). These smaller blocks may require proportionally much more parity + * information (and perhaps skip sectors). In this case, the change to the + * "referenced" property may be much more than the logical block size. + * + * Suppose a raidz vdev has 5 disks with ashift=12. A 128k block may be written + * as follows. + * + * +-------+-------+-------+-------+-------+ + * | disk1 | disk2 | disk3 | disk4 | disk5 | + * +-------+-------+-------+-------+-------+ + * | P0 | D0 | D8 | D16 | D24 | + * | P1 | D1 | D9 | D17 | D25 | + * | P2 | D2 | D10 | D18 | D26 | + * | P3 | D3 | D11 | D19 | D27 | + * | P4 | D4 | D12 | D20 | D28 | + * | P5 | D5 | D13 | D21 | D29 | + * | P6 | D6 | D14 | D22 | D30 | + * | P7 | D7 | D15 | D23 | D31 | + * +-------+-------+-------+-------+-------+ + * + * Above, notice that 160k was allocated: 8 x 4k parity sectors + 32 x 4k data + * sectors. The dataset's referenced will increase by 128k and the pool's + * allocated and free properties will be adjusted by 160k. + * + * A 4k block written to the same raidz vdev will require two 4k sectors. The + * blank cells represent unallocated space. + * + * +-------+-------+-------+-------+-------+ + * | disk1 | disk2 | disk3 | disk4 | disk5 | + * +-------+-------+-------+-------+-------+ + * | P0 | D0 | | | | + * +-------+-------+-------+-------+-------+ + * + * Above, notice that the 4k block required one sector for parity and another + * for data. vdev_raidz_asize() will return 8k and as such the pool's allocated + * and free properties will be adjusted by 8k. The dataset will not be charged + * 8k. Rather, it will be charged a value that is scaled according to the + * overhead of the 128k block on the same vdev. This 8k allocation will be + * charged 8k * 128k / 160k. 128k is from SPA_OLD_MAXBLOCKSIZE and 160k is as + * calculated in the 128k block example above. + * + * Every raidz allocation is sized to be a multiple of nparity+1 sectors. That + * is, every raidz1 allocation will be a multiple of 2 sectors, raidz2 + * allocations are a multiple of 3 sectors, and raidz3 allocations are a + * multiple of of 4 sectors. When a block does not fill the required number of + * sectors, skip blocks (sectors) are used. + * + * An 8k block being written to a raidz vdev may be written as follows: + * + * +-------+-------+-------+-------+-------+ + * | disk1 | disk2 | disk3 | disk4 | disk5 | + * +-------+-------+-------+-------+-------+ + * | P0 | D0 | D1 | S0 | | + * +-------+-------+-------+-------+-------+ + * + * In order to maintain the nparity+1 allocation size, a skip block (S0) was + * added. For this 8k block, the pool's allocated and free properties are + * adjusted by 16k and the dataset's referenced is increased by 16k * 128k / + * 160k. Again, 128k is from SPA_OLD_MAXBLOCKSIZE and 160k is as calculated in + * the 128k block example above. + * + * Compression may lead to a variety of block sizes being written for the same + * volume or file. There is no clear way to reserve just the amount of space + * that will be required, so the worst case (no compression) is assumed. + * Note that metadata blocks will typically be compressed, so the reservation + * size returned by zvol_volsize_to_reservation() will generally be slightly + * larger than the maximum that the volume can reference. + */ + +/* + * Derived from function of same name in module/zfs/vdev_raidz.c. Returns the + * amount of space (in bytes) that will be allocated for the specified block + * size. Note that the "referenced" space accounted will be less than this, but + * not necessarily equal to "blksize", due to RAIDZ deflation. + */ +static uint64_t +vdev_raidz_asize(uint64_t ndisks, uint64_t nparity, uint64_t ashift, + uint64_t blksize) +{ + uint64_t asize, ndata; + + ASSERT3U(ndisks, >, nparity); + ndata = ndisks - nparity; + asize = ((blksize - 1) >> ashift) + 1; + asize += nparity * ((asize + ndata - 1) / ndata); + asize = roundup(asize, nparity + 1) << ashift; + + return (asize); +} + +/* + * Determine how much space will be allocated if it lands on the most space- + * inefficient top-level vdev. Returns the size in bytes required to store one + * copy of the volume data. See theory comment above. + */ +static uint64_t +volsize_from_vdevs(zpool_handle_t *zhp, uint64_t nblocks, uint64_t blksize) +{ + nvlist_t *config, *tree, **vdevs; + uint_t nvdevs, v; + uint64_t ret = 0; + + config = zpool_get_config(zhp, NULL); + if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, &tree) != 0 || + nvlist_lookup_nvlist_array(tree, ZPOOL_CONFIG_CHILDREN, + &vdevs, &nvdevs) != 0) { + return (nblocks * blksize); + } + + for (v = 0; v < nvdevs; v++) { + char *type; + uint64_t nparity, ashift, asize, tsize; + nvlist_t **disks; + uint_t ndisks; + uint64_t volsize; + + if (nvlist_lookup_string(vdevs[v], ZPOOL_CONFIG_TYPE, + &type) != 0 || strcmp(type, VDEV_TYPE_RAIDZ) != 0 || + nvlist_lookup_uint64(vdevs[v], ZPOOL_CONFIG_NPARITY, + &nparity) != 0 || + nvlist_lookup_uint64(vdevs[v], ZPOOL_CONFIG_ASHIFT, + &ashift) != 0 || + nvlist_lookup_nvlist_array(vdevs[v], ZPOOL_CONFIG_CHILDREN, + &disks, &ndisks) != 0) { + continue; + } + + /* allocation size for the "typical" 128k block */ + tsize = vdev_raidz_asize(ndisks, nparity, ashift, + SPA_OLD_MAXBLOCKSIZE); + /* allocation size for the blksize block */ + asize = vdev_raidz_asize(ndisks, nparity, ashift, blksize); + + /* + * Scale this size down as a ratio of 128k / tsize. See theory + * statement above. + */ + volsize = nblocks * asize * SPA_OLD_MAXBLOCKSIZE / tsize; + if (volsize > ret) { + ret = volsize; + } + } + + if (ret == 0) { + ret = nblocks * blksize; + } + + return (ret); +} + +/* + * Convert the zvol's volume size to an appropriate reservation. See theory + * comment above. + * * Note: If this routine is updated, it is necessary to update the ZFS test - * suite's shell version in reservation.kshlib. + * suite's shell version in reservation.shlib. */ uint64_t -zvol_volsize_to_reservation(uint64_t volsize, nvlist_t *props) +zvol_volsize_to_reservation(zpool_handle_t *zph, uint64_t volsize, + nvlist_t *props) { uint64_t numdb; uint64_t nblocks, volblocksize; @@ -5397,7 +5563,14 @@ zvol_volsize_to_reservation(uint64_t volsize, nvlist_t *props) zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE), &volblocksize) != 0) volblocksize = ZVOL_DEFAULT_BLOCKSIZE; - nblocks = volsize/volblocksize; + + nblocks = volsize / volblocksize; + /* + * Metadata defaults to using 128k blocks, not volblocksize blocks. For + * this reason, only the data blocks are scaled based on vdev config. + */ + volsize = volsize_from_vdevs(zph, nblocks, volblocksize); + /* start with metadnode L0-L6 */ numdb = 7; /* calculate number of indirects */ -- cgit v1.2.3