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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 <mike.gerdts@joyent.com>
Reviewed by: Richard Elling <Richard.Elling@RichardElling.com>
Reviewed by: Sanjay Nadkarni <sanjay.nadkarni@nexenta.com>
Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Kody Kantor <kody.kantor@joyent.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Approved by: Dan McDonald <danmcd@joyent.com>
Ported-by: Mike Gerdts <mike.gerdts@joyent.com>
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
This commit is contained in:
Mike Gerdts
+181
-8
@@ -21,7 +21,7 @@
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/*
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* Copyright (c) 2005, 2010, Oracle and/or its affiliates. All rights reserved.
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* Copyright (c) 2018, Joyent, Inc. All rights reserved.
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* Copyright 2019 Joyent, Inc.
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* Copyright (c) 2011, 2017 by Delphix. All rights reserved.
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* Copyright (c) 2012 DEY Storage Systems, Inc. All rights reserved.
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* Copyright (c) 2012 Pawel Jakub Dawidek <pawel@dawidek.net>.
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@@ -1618,6 +1618,7 @@ zfs_add_synthetic_resv(zfs_handle_t *zhp, nvlist_t *nvl)
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uint64_t new_reservation;
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zfs_prop_t resv_prop;
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nvlist_t *props;
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zpool_handle_t *zph = zpool_handle(zhp);
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/*
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* If this is an existing volume, and someone is setting the volsize,
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@@ -1632,7 +1633,7 @@ zfs_add_synthetic_resv(zfs_handle_t *zhp, nvlist_t *nvl)
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fnvlist_add_uint64(props, zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE),
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zfs_prop_get_int(zhp, ZFS_PROP_VOLBLOCKSIZE));
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if ((zvol_volsize_to_reservation(old_volsize, props) !=
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if ((zvol_volsize_to_reservation(zph, old_volsize, props) !=
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old_reservation) || nvlist_exists(nvl,
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zfs_prop_to_name(resv_prop))) {
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fnvlist_free(props);
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@@ -1643,7 +1644,7 @@ zfs_add_synthetic_resv(zfs_handle_t *zhp, nvlist_t *nvl)
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fnvlist_free(props);
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return (-1);
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}
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new_reservation = zvol_volsize_to_reservation(new_volsize, props);
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new_reservation = zvol_volsize_to_reservation(zph, new_volsize, props);
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fnvlist_free(props);
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if (nvlist_add_uint64(nvl, zfs_prop_to_name(resv_prop),
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@@ -1698,7 +1699,8 @@ zfs_fix_auto_resv(zfs_handle_t *zhp, nvlist_t *nvl)
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volsize = zfs_prop_get_int(zhp, ZFS_PROP_VOLSIZE);
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}
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resvsize = zvol_volsize_to_reservation(volsize, props);
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resvsize = zvol_volsize_to_reservation(zpool_handle(zhp), volsize,
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props);
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fnvlist_free(props);
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(void) nvlist_remove_all(nvl, zfs_prop_to_name(prop));
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@@ -5363,12 +5365,176 @@ zfs_get_holds(zfs_handle_t *zhp, nvlist_t **nvl)
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}
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/*
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* Convert the zvol's volume size to an appropriate reservation.
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* The theory of raidz space accounting
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*
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* The "referenced" property of RAIDZ vdevs is scaled such that a 128KB block
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* will "reference" 128KB, even though it allocates more than that, to store the
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* parity information (and perhaps skip sectors). This concept of the
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* "referenced" (and other DMU space accounting) being lower than the allocated
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* space by a constant factor is called "raidz deflation."
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*
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* As mentioned above, the constant factor for raidz deflation assumes a 128KB
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* block size. However, zvols typically have a much smaller block size (default
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* 8KB). These smaller blocks may require proportionally much more parity
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* information (and perhaps skip sectors). In this case, the change to the
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* "referenced" property may be much more than the logical block size.
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*
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* Suppose a raidz vdev has 5 disks with ashift=12. A 128k block may be written
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* as follows.
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*
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* +-------+-------+-------+-------+-------+
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* | disk1 | disk2 | disk3 | disk4 | disk5 |
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* +-------+-------+-------+-------+-------+
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* | P0 | D0 | D8 | D16 | D24 |
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* | P1 | D1 | D9 | D17 | D25 |
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* | P2 | D2 | D10 | D18 | D26 |
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* | P3 | D3 | D11 | D19 | D27 |
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* | P4 | D4 | D12 | D20 | D28 |
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* | P5 | D5 | D13 | D21 | D29 |
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* | P6 | D6 | D14 | D22 | D30 |
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* | P7 | D7 | D15 | D23 | D31 |
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* +-------+-------+-------+-------+-------+
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*
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* Above, notice that 160k was allocated: 8 x 4k parity sectors + 32 x 4k data
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* sectors. The dataset's referenced will increase by 128k and the pool's
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* allocated and free properties will be adjusted by 160k.
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*
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* A 4k block written to the same raidz vdev will require two 4k sectors. The
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* blank cells represent unallocated space.
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*
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* +-------+-------+-------+-------+-------+
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* | disk1 | disk2 | disk3 | disk4 | disk5 |
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* +-------+-------+-------+-------+-------+
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* | P0 | D0 | | | |
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* +-------+-------+-------+-------+-------+
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*
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* Above, notice that the 4k block required one sector for parity and another
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* for data. vdev_raidz_asize() will return 8k and as such the pool's allocated
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* and free properties will be adjusted by 8k. The dataset will not be charged
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* 8k. Rather, it will be charged a value that is scaled according to the
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* overhead of the 128k block on the same vdev. This 8k allocation will be
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* charged 8k * 128k / 160k. 128k is from SPA_OLD_MAXBLOCKSIZE and 160k is as
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* calculated in the 128k block example above.
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*
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* Every raidz allocation is sized to be a multiple of nparity+1 sectors. That
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* is, every raidz1 allocation will be a multiple of 2 sectors, raidz2
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* allocations are a multiple of 3 sectors, and raidz3 allocations are a
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* multiple of of 4 sectors. When a block does not fill the required number of
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* sectors, skip blocks (sectors) are used.
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*
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* An 8k block being written to a raidz vdev may be written as follows:
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*
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* +-------+-------+-------+-------+-------+
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* | disk1 | disk2 | disk3 | disk4 | disk5 |
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* +-------+-------+-------+-------+-------+
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* | P0 | D0 | D1 | S0 | |
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* +-------+-------+-------+-------+-------+
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*
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* In order to maintain the nparity+1 allocation size, a skip block (S0) was
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* added. For this 8k block, the pool's allocated and free properties are
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* adjusted by 16k and the dataset's referenced is increased by 16k * 128k /
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* 160k. Again, 128k is from SPA_OLD_MAXBLOCKSIZE and 160k is as calculated in
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* the 128k block example above.
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*
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* Compression may lead to a variety of block sizes being written for the same
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* volume or file. There is no clear way to reserve just the amount of space
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* that will be required, so the worst case (no compression) is assumed.
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* Note that metadata blocks will typically be compressed, so the reservation
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* size returned by zvol_volsize_to_reservation() will generally be slightly
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* larger than the maximum that the volume can reference.
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*/
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/*
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* Derived from function of same name in module/zfs/vdev_raidz.c. Returns the
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* amount of space (in bytes) that will be allocated for the specified block
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* size. Note that the "referenced" space accounted will be less than this, but
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* not necessarily equal to "blksize", due to RAIDZ deflation.
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*/
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static uint64_t
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vdev_raidz_asize(uint64_t ndisks, uint64_t nparity, uint64_t ashift,
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uint64_t blksize)
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{
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uint64_t asize, ndata;
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ASSERT3U(ndisks, >, nparity);
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ndata = ndisks - nparity;
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asize = ((blksize - 1) >> ashift) + 1;
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asize += nparity * ((asize + ndata - 1) / ndata);
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asize = roundup(asize, nparity + 1) << ashift;
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return (asize);
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}
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/*
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* Determine how much space will be allocated if it lands on the most space-
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* inefficient top-level vdev. Returns the size in bytes required to store one
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* copy of the volume data. See theory comment above.
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*/
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static uint64_t
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volsize_from_vdevs(zpool_handle_t *zhp, uint64_t nblocks, uint64_t blksize)
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{
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nvlist_t *config, *tree, **vdevs;
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uint_t nvdevs, v;
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uint64_t ret = 0;
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config = zpool_get_config(zhp, NULL);
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if (nvlist_lookup_nvlist(config, ZPOOL_CONFIG_VDEV_TREE, &tree) != 0 ||
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nvlist_lookup_nvlist_array(tree, ZPOOL_CONFIG_CHILDREN,
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&vdevs, &nvdevs) != 0) {
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return (nblocks * blksize);
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}
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for (v = 0; v < nvdevs; v++) {
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char *type;
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uint64_t nparity, ashift, asize, tsize;
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nvlist_t **disks;
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uint_t ndisks;
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uint64_t volsize;
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if (nvlist_lookup_string(vdevs[v], ZPOOL_CONFIG_TYPE,
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&type) != 0 || strcmp(type, VDEV_TYPE_RAIDZ) != 0 ||
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nvlist_lookup_uint64(vdevs[v], ZPOOL_CONFIG_NPARITY,
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&nparity) != 0 ||
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nvlist_lookup_uint64(vdevs[v], ZPOOL_CONFIG_ASHIFT,
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&ashift) != 0 ||
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nvlist_lookup_nvlist_array(vdevs[v], ZPOOL_CONFIG_CHILDREN,
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&disks, &ndisks) != 0) {
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continue;
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}
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/* allocation size for the "typical" 128k block */
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tsize = vdev_raidz_asize(ndisks, nparity, ashift,
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SPA_OLD_MAXBLOCKSIZE);
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/* allocation size for the blksize block */
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asize = vdev_raidz_asize(ndisks, nparity, ashift, blksize);
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/*
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* Scale this size down as a ratio of 128k / tsize. See theory
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* statement above.
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*/
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volsize = nblocks * asize * SPA_OLD_MAXBLOCKSIZE / tsize;
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if (volsize > ret) {
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ret = volsize;
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}
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}
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if (ret == 0) {
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ret = nblocks * blksize;
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}
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return (ret);
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}
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/*
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* Convert the zvol's volume size to an appropriate reservation. See theory
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* comment above.
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*
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* Note: If this routine is updated, it is necessary to update the ZFS test
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* suite's shell version in reservation.kshlib.
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* suite's shell version in reservation.shlib.
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*/
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uint64_t
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zvol_volsize_to_reservation(uint64_t volsize, nvlist_t *props)
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zvol_volsize_to_reservation(zpool_handle_t *zph, uint64_t volsize,
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nvlist_t *props)
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{
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uint64_t numdb;
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uint64_t nblocks, volblocksize;
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@@ -5384,7 +5550,14 @@ zvol_volsize_to_reservation(uint64_t volsize, nvlist_t *props)
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zfs_prop_to_name(ZFS_PROP_VOLBLOCKSIZE),
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&volblocksize) != 0)
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volblocksize = ZVOL_DEFAULT_BLOCKSIZE;
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nblocks = volsize/volblocksize;
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nblocks = volsize / volblocksize;
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/*
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* Metadata defaults to using 128k blocks, not volblocksize blocks. For
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* this reason, only the data blocks are scaled based on vdev config.
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*/
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volsize = volsize_from_vdevs(zph, nblocks, volblocksize);
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/* start with metadnode L0-L6 */
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numdb = 7;
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/* calculate number of indirects */
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