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0ab32086d0
linux/fs/xfs/libxfs/xfs_rmap_btree.c
Brian Foster 0ab32086d0 xfs: account only rmapbt-used blocks against rmapbt perag res 
The rmapbt perag metadata reservation reserves blocks for the
reverse mapping btree (rmapbt). Since the rmapbt uses blocks from
the agfl and perag accounting is updated as blocks are allocated
from the allocation btrees, the reservation actually accounts blocks
as they are allocated to (or freed from) the agfl rather than the
rmapbt itself.

While this works for blocks that are eventually used for the rmapbt,
not all agfl blocks are destined for the rmapbt. Blocks that are
allocated to the agfl (and thus "reserved" for the rmapbt) but then
used by another structure leads to a growing inconsistency over time
between the runtime tracking of rmapbt usage vs. actual rmapbt
usage. Since the runtime tracking thinks all agfl blocks are rmapbt
blocks, it essentially believes that less future reservation is
required to satisfy the rmapbt than what is actually necessary.

The inconsistency is rectified across mount cycles because the perag
reservation is initialized based on the actual rmapbt usage at mount
time. The problem, however, is that the excessive drain of the
reservation at runtime opens a window to allocate blocks for other
purposes that might be required for the rmapbt on a subsequent
mount. This problem can be demonstrated by a simple test that runs
an allocation workload to consume agfl blocks over time and then
observe the difference in the agfl reservation requirement across an
unmount/mount cycle:

  mount ...: xfs_ag_resv_init: ... resv 3193 ask 3194 len 3194
  ...
  ...      : xfs_ag_resv_alloc_extent: ... resv 2957 ask 3194 len 1
  umount...: xfs_ag_resv_free: ... resv 2956 ask 3194 len 0
  mount ...: xfs_ag_resv_init: ... resv 3052 ask 3194 len 3194

As the above tracepoints show, the reservation requirement reduces
from 3194 blocks to 2956 blocks as the workload runs.  Without any
other changes in the filesystem, the same reservation requirement
jumps from 2956 to 3052 blocks over a umount/mount cycle.

To address this divergence, update the RMAPBT reservation to account
blocks used for the rmapbt only rather than all blocks filled into
the agfl. This patch makes several high-level changes toward that
end:

1.) Reintroduce an AGFL reservation type to serve as an accounting
    no-op for blocks allocated to (or freed from) the AGFL.
2.) Invoke RMAPBT usage accounting from the actual rmapbt block
    allocation path rather than the AGFL allocation path.

The first change is required because agfl blocks are considered free
blocks throughout their lifetime. The perag reservation subsystem is
invoked unconditionally by the allocation subsystem, so we need a
way to tell the perag subsystem (via the allocation subsystem) to
not make any accounting changes for blocks filled into the AGFL.

The second change causes the in-core RMAPBT reservation usage
accounting to remain consistent with the on-disk state at all times
and eliminates the risk of leaving the rmapbt reservation
underfilled.

Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-03-11 20:27:57 -07:00

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/*
* Copyright (c) 2014 Red Hat, Inc.
* All Rights Reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it would be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_bit.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_inode.h"
#include "xfs_trans.h"
#include "xfs_alloc.h"
#include "xfs_btree.h"
#include "xfs_rmap.h"
#include "xfs_rmap_btree.h"
#include "xfs_trace.h"
#include "xfs_cksum.h"
#include "xfs_error.h"
#include "xfs_extent_busy.h"
#include "xfs_ag_resv.h"
/*
* Reverse map btree.
*
* This is a per-ag tree used to track the owner(s) of a given extent. With
* reflink it is possible for there to be multiple owners, which is a departure
* from classic XFS. Owner records for data extents are inserted when the
* extent is mapped and removed when an extent is unmapped. Owner records for
* all other block types (i.e. metadata) are inserted when an extent is
* allocated and removed when an extent is freed. There can only be one owner
* of a metadata extent, usually an inode or some other metadata structure like
* an AG btree.
*
* The rmap btree is part of the free space management, so blocks for the tree
* are sourced from the agfl. Hence we need transaction reservation support for
* this tree so that the freelist is always large enough. This also impacts on
* the minimum space we need to leave free in the AG.
*
* The tree is ordered by [ag block, owner, offset]. This is a large key size,
* but it is the only way to enforce unique keys when a block can be owned by
* multiple files at any offset. There's no need to order/search by extent
* size for online updating/management of the tree. It is intended that most
* reverse lookups will be to find the owner(s) of a particular block, or to
* try to recover tree and file data from corrupt primary metadata.
*/
static struct xfs_btree_cur *
xfs_rmapbt_dup_cursor(
struct xfs_btree_cur *cur)
{
return xfs_rmapbt_init_cursor(cur->bc_mp, cur->bc_tp,
cur->bc_private.a.agbp, cur->bc_private.a.agno);
}
STATIC void
xfs_rmapbt_set_root(
struct xfs_btree_cur *cur,
union xfs_btree_ptr *ptr,
int inc)
{
struct xfs_buf *agbp = cur->bc_private.a.agbp;
struct xfs_agf *agf = XFS_BUF_TO_AGF(agbp);
xfs_agnumber_t seqno = be32_to_cpu(agf->agf_seqno);
int btnum = cur->bc_btnum;
struct xfs_perag *pag = xfs_perag_get(cur->bc_mp, seqno);
ASSERT(ptr->s != 0);
agf->agf_roots[btnum] = ptr->s;
be32_add_cpu(&agf->agf_levels[btnum], inc);
pag->pagf_levels[btnum] += inc;
xfs_perag_put(pag);
xfs_alloc_log_agf(cur->bc_tp, agbp, XFS_AGF_ROOTS | XFS_AGF_LEVELS);
}
STATIC int
xfs_rmapbt_alloc_block(
struct xfs_btree_cur *cur,
union xfs_btree_ptr *start,
union xfs_btree_ptr *new,
int *stat)
{
struct xfs_buf *agbp = cur->bc_private.a.agbp;
struct xfs_agf *agf = XFS_BUF_TO_AGF(agbp);
int error;
xfs_agblock_t bno;
/* Allocate the new block from the freelist. If we can't, give up. */
error = xfs_alloc_get_freelist(cur->bc_tp, cur->bc_private.a.agbp,
&bno, 1);
if (error)
return error;
trace_xfs_rmapbt_alloc_block(cur->bc_mp, cur->bc_private.a.agno,
bno, 1);
if (bno == NULLAGBLOCK) {
*stat = 0;
return 0;
}
xfs_extent_busy_reuse(cur->bc_mp, cur->bc_private.a.agno, bno, 1,
false);
xfs_trans_agbtree_delta(cur->bc_tp, 1);
new->s = cpu_to_be32(bno);
be32_add_cpu(&agf->agf_rmap_blocks, 1);
xfs_alloc_log_agf(cur->bc_tp, agbp, XFS_AGF_RMAP_BLOCKS);
xfs_ag_resv_rmapbt_alloc(cur->bc_mp, cur->bc_private.a.agno);
*stat = 1;
return 0;
}
STATIC int
xfs_rmapbt_free_block(
struct xfs_btree_cur *cur,
struct xfs_buf *bp)
{
struct xfs_buf *agbp = cur->bc_private.a.agbp;
struct xfs_agf *agf = XFS_BUF_TO_AGF(agbp);
xfs_agblock_t bno;
int error;
bno = xfs_daddr_to_agbno(cur->bc_mp, XFS_BUF_ADDR(bp));
trace_xfs_rmapbt_free_block(cur->bc_mp, cur->bc_private.a.agno,
bno, 1);
be32_add_cpu(&agf->agf_rmap_blocks, -1);
xfs_alloc_log_agf(cur->bc_tp, agbp, XFS_AGF_RMAP_BLOCKS);
error = xfs_alloc_put_freelist(cur->bc_tp, agbp, NULL, bno, 1);
if (error)
return error;
xfs_extent_busy_insert(cur->bc_tp, be32_to_cpu(agf->agf_seqno), bno, 1,
XFS_EXTENT_BUSY_SKIP_DISCARD);
xfs_trans_agbtree_delta(cur->bc_tp, -1);
xfs_ag_resv_rmapbt_free(cur->bc_mp, cur->bc_private.a.agno);
return 0;
}
STATIC int
xfs_rmapbt_get_minrecs(
struct xfs_btree_cur *cur,
int level)
{
return cur->bc_mp->m_rmap_mnr[level != 0];
}
STATIC int
xfs_rmapbt_get_maxrecs(
struct xfs_btree_cur *cur,
int level)
{
return cur->bc_mp->m_rmap_mxr[level != 0];
}
STATIC void
xfs_rmapbt_init_key_from_rec(
union xfs_btree_key *key,
union xfs_btree_rec *rec)
{
key->rmap.rm_startblock = rec->rmap.rm_startblock;
key->rmap.rm_owner = rec->rmap.rm_owner;
key->rmap.rm_offset = rec->rmap.rm_offset;
}
/*
* The high key for a reverse mapping record can be computed by shifting
* the startblock and offset to the highest value that would still map
* to that record. In practice this means that we add blockcount-1 to
* the startblock for all records, and if the record is for a data/attr
* fork mapping, we add blockcount-1 to the offset too.
*/
STATIC void
xfs_rmapbt_init_high_key_from_rec(
union xfs_btree_key *key,
union xfs_btree_rec *rec)
{
uint64_t off;
int adj;
adj = be32_to_cpu(rec->rmap.rm_blockcount) - 1;
key->rmap.rm_startblock = rec->rmap.rm_startblock;
be32_add_cpu(&key->rmap.rm_startblock, adj);
key->rmap.rm_owner = rec->rmap.rm_owner;
key->rmap.rm_offset = rec->rmap.rm_offset;
if (XFS_RMAP_NON_INODE_OWNER(be64_to_cpu(rec->rmap.rm_owner)) ||
XFS_RMAP_IS_BMBT_BLOCK(be64_to_cpu(rec->rmap.rm_offset)))
return;
off = be64_to_cpu(key->rmap.rm_offset);
off = (XFS_RMAP_OFF(off) + adj) | (off & ~XFS_RMAP_OFF_MASK);
key->rmap.rm_offset = cpu_to_be64(off);
}
STATIC void
xfs_rmapbt_init_rec_from_cur(
struct xfs_btree_cur *cur,
union xfs_btree_rec *rec)
{
rec->rmap.rm_startblock = cpu_to_be32(cur->bc_rec.r.rm_startblock);
rec->rmap.rm_blockcount = cpu_to_be32(cur->bc_rec.r.rm_blockcount);
rec->rmap.rm_owner = cpu_to_be64(cur->bc_rec.r.rm_owner);
rec->rmap.rm_offset = cpu_to_be64(
xfs_rmap_irec_offset_pack(&cur->bc_rec.r));
}
STATIC void
xfs_rmapbt_init_ptr_from_cur(
struct xfs_btree_cur *cur,
union xfs_btree_ptr *ptr)
{
struct xfs_agf *agf = XFS_BUF_TO_AGF(cur->bc_private.a.agbp);
ASSERT(cur->bc_private.a.agno == be32_to_cpu(agf->agf_seqno));
ASSERT(agf->agf_roots[cur->bc_btnum] != 0);
ptr->s = agf->agf_roots[cur->bc_btnum];
}
STATIC int64_t
xfs_rmapbt_key_diff(
struct xfs_btree_cur *cur,
union xfs_btree_key *key)
{
struct xfs_rmap_irec *rec = &cur->bc_rec.r;
struct xfs_rmap_key *kp = &key->rmap;
__u64 x, y;
int64_t d;
d = (int64_t)be32_to_cpu(kp->rm_startblock) - rec->rm_startblock;
if (d)
return d;
x = be64_to_cpu(kp->rm_owner);
y = rec->rm_owner;
if (x > y)
return 1;
else if (y > x)
return -1;
x = XFS_RMAP_OFF(be64_to_cpu(kp->rm_offset));
y = rec->rm_offset;
if (x > y)
return 1;
else if (y > x)
return -1;
return 0;
}
STATIC int64_t
xfs_rmapbt_diff_two_keys(
struct xfs_btree_cur *cur,
union xfs_btree_key *k1,
union xfs_btree_key *k2)
{
struct xfs_rmap_key *kp1 = &k1->rmap;
struct xfs_rmap_key *kp2 = &k2->rmap;
int64_t d;
__u64 x, y;
d = (int64_t)be32_to_cpu(kp1->rm_startblock) -
be32_to_cpu(kp2->rm_startblock);
if (d)
return d;
x = be64_to_cpu(kp1->rm_owner);
y = be64_to_cpu(kp2->rm_owner);
if (x > y)
return 1;
else if (y > x)
return -1;
x = XFS_RMAP_OFF(be64_to_cpu(kp1->rm_offset));
y = XFS_RMAP_OFF(be64_to_cpu(kp2->rm_offset));
if (x > y)
return 1;
else if (y > x)
return -1;
return 0;
}
static xfs_failaddr_t
xfs_rmapbt_verify(
struct xfs_buf *bp)
{
struct xfs_mount *mp = bp->b_target->bt_mount;
struct xfs_btree_block *block = XFS_BUF_TO_BLOCK(bp);
struct xfs_perag *pag = bp->b_pag;
xfs_failaddr_t fa;
unsigned int level;
/*
* magic number and level verification
*
* During growfs operations, we can't verify the exact level or owner as
* the perag is not fully initialised and hence not attached to the
* buffer. In this case, check against the maximum tree depth.
*
* Similarly, during log recovery we will have a perag structure
* attached, but the agf information will not yet have been initialised
* from the on disk AGF. Again, we can only check against maximum limits
* in this case.
*/
if (block->bb_magic != cpu_to_be32(XFS_RMAP_CRC_MAGIC))
return __this_address;
if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
return __this_address;
fa = xfs_btree_sblock_v5hdr_verify(bp);
if (fa)
return fa;
level = be16_to_cpu(block->bb_level);
if (pag && pag->pagf_init) {
if (level >= pag->pagf_levels[XFS_BTNUM_RMAPi])
return __this_address;
} else if (level >= mp->m_rmap_maxlevels)
return __this_address;
return xfs_btree_sblock_verify(bp, mp->m_rmap_mxr[level != 0]);
}
static void
xfs_rmapbt_read_verify(
struct xfs_buf *bp)
{
xfs_failaddr_t fa;
if (!xfs_btree_sblock_verify_crc(bp))
xfs_verifier_error(bp, -EFSBADCRC, __this_address);
else {
fa = xfs_rmapbt_verify(bp);
if (fa)
xfs_verifier_error(bp, -EFSCORRUPTED, fa);
}
if (bp->b_error)
trace_xfs_btree_corrupt(bp, _RET_IP_);
}
static void
xfs_rmapbt_write_verify(
struct xfs_buf *bp)
{
xfs_failaddr_t fa;
fa = xfs_rmapbt_verify(bp);
if (fa) {
trace_xfs_btree_corrupt(bp, _RET_IP_);
xfs_verifier_error(bp, -EFSCORRUPTED, fa);
return;
}
xfs_btree_sblock_calc_crc(bp);
}
const struct xfs_buf_ops xfs_rmapbt_buf_ops = {
.name = "xfs_rmapbt",
.verify_read = xfs_rmapbt_read_verify,
.verify_write = xfs_rmapbt_write_verify,
.verify_struct = xfs_rmapbt_verify,
};
STATIC int
xfs_rmapbt_keys_inorder(
struct xfs_btree_cur *cur,
union xfs_btree_key *k1,
union xfs_btree_key *k2)
{
uint32_t x;
uint32_t y;
uint64_t a;
uint64_t b;
x = be32_to_cpu(k1->rmap.rm_startblock);
y = be32_to_cpu(k2->rmap.rm_startblock);
if (x < y)
return 1;
else if (x > y)
return 0;
a = be64_to_cpu(k1->rmap.rm_owner);
b = be64_to_cpu(k2->rmap.rm_owner);
if (a < b)
return 1;
else if (a > b)
return 0;
a = XFS_RMAP_OFF(be64_to_cpu(k1->rmap.rm_offset));
b = XFS_RMAP_OFF(be64_to_cpu(k2->rmap.rm_offset));
if (a <= b)
return 1;
return 0;
}
STATIC int
xfs_rmapbt_recs_inorder(
struct xfs_btree_cur *cur,
union xfs_btree_rec *r1,
union xfs_btree_rec *r2)
{
uint32_t x;
uint32_t y;
uint64_t a;
uint64_t b;
x = be32_to_cpu(r1->rmap.rm_startblock);
y = be32_to_cpu(r2->rmap.rm_startblock);
if (x < y)
return 1;
else if (x > y)
return 0;
a = be64_to_cpu(r1->rmap.rm_owner);
b = be64_to_cpu(r2->rmap.rm_owner);
if (a < b)
return 1;
else if (a > b)
return 0;
a = XFS_RMAP_OFF(be64_to_cpu(r1->rmap.rm_offset));
b = XFS_RMAP_OFF(be64_to_cpu(r2->rmap.rm_offset));
if (a <= b)
return 1;
return 0;
}
static const struct xfs_btree_ops xfs_rmapbt_ops = {
.rec_len = sizeof(struct xfs_rmap_rec),
.key_len = 2 * sizeof(struct xfs_rmap_key),
.dup_cursor = xfs_rmapbt_dup_cursor,
.set_root = xfs_rmapbt_set_root,
.alloc_block = xfs_rmapbt_alloc_block,
.free_block = xfs_rmapbt_free_block,
.get_minrecs = xfs_rmapbt_get_minrecs,
.get_maxrecs = xfs_rmapbt_get_maxrecs,
.init_key_from_rec = xfs_rmapbt_init_key_from_rec,
.init_high_key_from_rec = xfs_rmapbt_init_high_key_from_rec,
.init_rec_from_cur = xfs_rmapbt_init_rec_from_cur,
.init_ptr_from_cur = xfs_rmapbt_init_ptr_from_cur,
.key_diff = xfs_rmapbt_key_diff,
.buf_ops = &xfs_rmapbt_buf_ops,
.diff_two_keys = xfs_rmapbt_diff_two_keys,
.keys_inorder = xfs_rmapbt_keys_inorder,
.recs_inorder = xfs_rmapbt_recs_inorder,
};
/*
* Allocate a new allocation btree cursor.
*/
struct xfs_btree_cur *
xfs_rmapbt_init_cursor(
struct xfs_mount *mp,
struct xfs_trans *tp,
struct xfs_buf *agbp,
xfs_agnumber_t agno)
{
struct xfs_agf *agf = XFS_BUF_TO_AGF(agbp);
struct xfs_btree_cur *cur;
cur = kmem_zone_zalloc(xfs_btree_cur_zone, KM_NOFS);
cur->bc_tp = tp;
cur->bc_mp = mp;
/* Overlapping btree; 2 keys per pointer. */
cur->bc_btnum = XFS_BTNUM_RMAP;
cur->bc_flags = XFS_BTREE_CRC_BLOCKS | XFS_BTREE_OVERLAPPING;
cur->bc_blocklog = mp->m_sb.sb_blocklog;
cur->bc_ops = &xfs_rmapbt_ops;
cur->bc_nlevels = be32_to_cpu(agf->agf_levels[XFS_BTNUM_RMAP]);
cur->bc_statoff = XFS_STATS_CALC_INDEX(xs_rmap_2);
cur->bc_private.a.agbp = agbp;
cur->bc_private.a.agno = agno;
return cur;
}
/*
* Calculate number of records in an rmap btree block.
*/
int
xfs_rmapbt_maxrecs(
struct xfs_mount *mp,
int blocklen,
int leaf)
{
blocklen -= XFS_RMAP_BLOCK_LEN;
if (leaf)
return blocklen / sizeof(struct xfs_rmap_rec);
return blocklen /
(2 * sizeof(struct xfs_rmap_key) + sizeof(xfs_rmap_ptr_t));
}
/* Compute the maximum height of an rmap btree. */
void
xfs_rmapbt_compute_maxlevels(
struct xfs_mount *mp)
{
/*
* On a non-reflink filesystem, the maximum number of rmap
* records is the number of blocks in the AG, hence the max
* rmapbt height is log_$maxrecs($agblocks). However, with
* reflink each AG block can have up to 2^32 (per the refcount
* record format) owners, which means that theoretically we
* could face up to 2^64 rmap records.
*
* That effectively means that the max rmapbt height must be
* XFS_BTREE_MAXLEVELS. "Fortunately" we'll run out of AG
* blocks to feed the rmapbt long before the rmapbt reaches
* maximum height. The reflink code uses ag_resv_critical to
* disallow reflinking when less than 10% of the per-AG metadata
* block reservation since the fallback is a regular file copy.
*/
if (xfs_sb_version_hasreflink(&mp->m_sb))
mp->m_rmap_maxlevels = XFS_BTREE_MAXLEVELS;
else
mp->m_rmap_maxlevels = xfs_btree_compute_maxlevels(mp,
mp->m_rmap_mnr, mp->m_sb.sb_agblocks);
}
/* Calculate the refcount btree size for some records. */
xfs_extlen_t
xfs_rmapbt_calc_size(
struct xfs_mount *mp,
unsigned long long len)
{
return xfs_btree_calc_size(mp, mp->m_rmap_mnr, len);
}
/*
* Calculate the maximum refcount btree size.
*/
xfs_extlen_t
xfs_rmapbt_max_size(
struct xfs_mount *mp,
xfs_agblock_t agblocks)
{
/* Bail out if we're uninitialized, which can happen in mkfs. */
if (mp->m_rmap_mxr[0] == 0)
return 0;
return xfs_rmapbt_calc_size(mp, agblocks);
}
/*
* Figure out how many blocks to reserve and how many are used by this btree.
*/
int
xfs_rmapbt_calc_reserves(
struct xfs_mount *mp,
xfs_agnumber_t agno,
xfs_extlen_t *ask,
xfs_extlen_t *used)
{
struct xfs_buf *agbp;
struct xfs_agf *agf;
xfs_agblock_t agblocks;
xfs_extlen_t tree_len;
int error;
if (!xfs_sb_version_hasrmapbt(&mp->m_sb))
return 0;
error = xfs_alloc_read_agf(mp, NULL, agno, 0, &agbp);
if (error)
return error;
agf = XFS_BUF_TO_AGF(agbp);
agblocks = be32_to_cpu(agf->agf_length);
tree_len = be32_to_cpu(agf->agf_rmap_blocks);
xfs_buf_relse(agbp);
/* Reserve 1% of the AG or enough for 1 block per record. */
*ask += max(agblocks / 100, xfs_rmapbt_max_size(mp, agblocks));
*used += tree_len;
return error;
}
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