Release 4.11 fs/xfs/libxfs/xfs_ag_resv.c
/*
* Copyright (C) 2016 Oracle. All Rights Reserved.
*
* Author: Darrick J. Wong <darrick.wong@oracle.com>
*
* 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; either version 2
* of the License, or (at your option) any later version.
*
* 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_sb.h"
#include "xfs_mount.h"
#include "xfs_defer.h"
#include "xfs_alloc.h"
#include "xfs_error.h"
#include "xfs_trace.h"
#include "xfs_cksum.h"
#include "xfs_trans.h"
#include "xfs_bit.h"
#include "xfs_bmap.h"
#include "xfs_bmap_btree.h"
#include "xfs_ag_resv.h"
#include "xfs_trans_space.h"
#include "xfs_rmap_btree.h"
#include "xfs_btree.h"
#include "xfs_refcount_btree.h"
#include "xfs_ialloc_btree.h"
/*
* Per-AG Block Reservations
*
* For some kinds of allocation group metadata structures, it is advantageous
* to reserve a small number of blocks in each AG so that future expansions of
* that data structure do not encounter ENOSPC because errors during a btree
* split cause the filesystem to go offline.
*
* Prior to the introduction of reflink, this wasn't an issue because the free
* space btrees maintain a reserve of space (the AGFL) to handle any expansion
* that may be necessary; and allocations of other metadata (inodes, BMBT,
* dir/attr) aren't restricted to a single AG. However, with reflink it is
* possible to allocate all the space in an AG, have subsequent reflink/CoW
* activity expand the refcount btree, and discover that there's no space left
* to handle that expansion. Since we can calculate the maximum size of the
* refcount btree, we can reserve space for it and avoid ENOSPC.
*
* Handling per-AG reservations consists of three changes to the allocator's
* behavior: First, because these reservations are always needed, we decrease
* the ag_max_usable counter to reflect the size of the AG after the reserved
* blocks are taken. Second, the reservations must be reflected in the
* fdblocks count to maintain proper accounting. Third, each AG must maintain
* its own reserved block counter so that we can calculate the amount of space
* that must remain free to maintain the reservations. Fourth, the "remaining
* reserved blocks" count must be used when calculating the length of the
* longest free extent in an AG and to clamp maxlen in the per-AG allocation
* functions. In other words, we maintain a virtual allocation via in-core
* accounting tricks so that we don't have to clean up after a crash. :)
*
* Reserved blocks can be managed by passing one of the enum xfs_ag_resv_type
* values via struct xfs_alloc_arg or directly to the xfs_free_extent
* function. It might seem a little funny to maintain a reservoir of blocks
* to feed another reservoir, but the AGFL only holds enough blocks to get
* through the next transaction. The per-AG reservation is to ensure (we
* hope) that each AG never runs out of blocks. Each data structure wanting
* to use the reservation system should update ask/used in xfs_ag_resv_init.
*/
/*
* Are we critically low on blocks? For now we'll define that as the number
* of blocks we can get our hands on being less than 10% of what we reserved
* or less than some arbitrary number (maximum btree height).
*/
bool
xfs_ag_resv_critical(
struct xfs_perag *pag,
enum xfs_ag_resv_type type)
{
xfs_extlen_t avail;
xfs_extlen_t orig;
switch (type) {
case XFS_AG_RESV_METADATA:
avail = pag->pagf_freeblks - pag->pag_agfl_resv.ar_reserved;
orig = pag->pag_meta_resv.ar_asked;
break;
case XFS_AG_RESV_AGFL:
avail = pag->pagf_freeblks + pag->pagf_flcount -
pag->pag_meta_resv.ar_reserved;
orig = pag->pag_agfl_resv.ar_asked;
break;
default:
ASSERT(0);
return false;
}
trace_xfs_ag_resv_critical(pag, type, avail);
/* Critically low if less than 10% or max btree height remains. */
return XFS_TEST_ERROR(avail < orig / 10 || avail < XFS_BTREE_MAXLEVELS,
pag->pag_mount, XFS_ERRTAG_AG_RESV_CRITICAL,
XFS_RANDOM_AG_RESV_CRITICAL);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darrick J. Wong | 119 | 100.00% | 2 | 100.00% |
| Total | 119 | 100.00% | 2 | 100.00% |
/*
* How many blocks are reserved but not used, and therefore must not be
* allocated away?
*/
xfs_extlen_t
xfs_ag_resv_needed(
struct xfs_perag *pag,
enum xfs_ag_resv_type type)
{
xfs_extlen_t len;
len = pag->pag_meta_resv.ar_reserved + pag->pag_agfl_resv.ar_reserved;
switch (type) {
case XFS_AG_RESV_METADATA:
case XFS_AG_RESV_AGFL:
len -= xfs_perag_resv(pag, type)->ar_reserved;
break;
case XFS_AG_RESV_NONE:
/* empty */
break;
default:
ASSERT(0);
}
trace_xfs_ag_resv_needed(pag, type, len);
return len;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darrick J. Wong | 78 | 100.00% | 1 | 100.00% |
| Total | 78 | 100.00% | 1 | 100.00% |
/* Clean out a reservation */
static int
__xfs_ag_resv_free(
struct xfs_perag *pag,
enum xfs_ag_resv_type type)
{
struct xfs_ag_resv *resv;
xfs_extlen_t oldresv;
int error;
trace_xfs_ag_resv_free(pag, type, 0);
resv = xfs_perag_resv(pag, type);
pag->pag_mount->m_ag_max_usable += resv->ar_asked;
/*
* AGFL blocks are always considered "free", so whatever
* was reserved at mount time must be given back at umount.
*/
if (type == XFS_AG_RESV_AGFL)
oldresv = resv->ar_orig_reserved;
else
oldresv = resv->ar_reserved;
error = xfs_mod_fdblocks(pag->pag_mount, oldresv, true);
resv->ar_reserved = 0;
resv->ar_asked = 0;
if (error)
trace_xfs_ag_resv_free_error(pag->pag_mount, pag->pag_agno,
error, _RET_IP_);
return error;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darrick J. Wong | 121 | 100.00% | 1 | 100.00% |
| Total | 121 | 100.00% | 1 | 100.00% |
/* Free a per-AG reservation. */
int
xfs_ag_resv_free(
struct xfs_perag *pag)
{
int error;
int err2;
error = __xfs_ag_resv_free(pag, XFS_AG_RESV_AGFL);
err2 = __xfs_ag_resv_free(pag, XFS_AG_RESV_METADATA);
if (err2 && !error)
error = err2;
return error;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darrick J. Wong | 48 | 100.00% | 1 | 100.00% |
| Total | 48 | 100.00% | 1 | 100.00% |
static int
__xfs_ag_resv_init(
struct xfs_perag *pag,
enum xfs_ag_resv_type type,
xfs_extlen_t ask,
xfs_extlen_t used)
{
struct xfs_mount *mp = pag->pag_mount;
struct xfs_ag_resv *resv;
int error;
xfs_extlen_t reserved;
if (used > ask)
ask = used;
reserved = ask - used;
error = xfs_mod_fdblocks(mp, -(int64_t)reserved, true);
if (error) {
trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
error, _RET_IP_);
xfs_warn(mp,
"Per-AG reservation for AG %u failed. Filesystem may run out of space.",
pag->pag_agno);
return error;
}
mp->m_ag_max_usable -= ask;
resv = xfs_perag_resv(pag, type);
resv->ar_asked = ask;
resv->ar_reserved = resv->ar_orig_reserved = reserved;
trace_xfs_ag_resv_init(pag, type, ask);
return 0;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darrick J. Wong | 89 | 59.33% | 1 | 33.33% |
| Christoph Hellwig | 61 | 40.67% | 2 | 66.67% |
| Total | 150 | 100.00% | 3 | 100.00% |
/* Create a per-AG block reservation. */
int
xfs_ag_resv_init(
struct xfs_perag *pag)
{
struct xfs_mount *mp = pag->pag_mount;
xfs_agnumber_t agno = pag->pag_agno;
xfs_extlen_t ask;
xfs_extlen_t used;
int error = 0;
/* Create the metadata reservation. */
if (pag->pag_meta_resv.ar_asked == 0) {
ask = used = 0;
error = xfs_refcountbt_calc_reserves(mp, agno, &ask, &used);
if (error)
goto out;
error = xfs_finobt_calc_reserves(mp, agno, &ask, &used);
if (error)
goto out;
error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
ask, used);
if (error) {
/*
* Because we didn't have per-AG reservations when the
* finobt feature was added we might not be able to
* reserve all needed blocks. Warn and fall back to the
* old and potentially buggy code in that case, but
* ensure we do have the reservation for the refcountbt.
*/
ask = used = 0;
mp->m_inotbt_nores = true;
error = xfs_refcountbt_calc_reserves(mp, agno, &ask,
&used);
if (error)
goto out;
error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
ask, used);
if (error)
goto out;
}
}
/* Create the AGFL metadata reservation */
if (pag->pag_agfl_resv.ar_asked == 0) {
ask = used = 0;
error = xfs_rmapbt_calc_reserves(mp, agno, &ask, &used);
if (error)
goto out;
error = __xfs_ag_resv_init(pag, XFS_AG_RESV_AGFL, ask, used);
if (error)
goto out;
}
#ifdef DEBUG
/* need to read in the AGF for the ASSERT below to work */
error = xfs_alloc_pagf_init(pag->pag_mount, NULL, pag->pag_agno, 0);
if (error)
return error;
ASSERT(xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved +
xfs_perag_resv(pag, XFS_AG_RESV_AGFL)->ar_reserved <=
pag->pagf_freeblks + pag->pagf_flcount);
#endif
out:
return error;
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darrick J. Wong | 175 | 58.53% | 3 | 75.00% |
| Christoph Hellwig | 124 | 41.47% | 1 | 25.00% |
| Total | 299 | 100.00% | 4 | 100.00% |
/* Allocate a block from the reservation. */
void
xfs_ag_resv_alloc_extent(
struct xfs_perag *pag,
enum xfs_ag_resv_type type,
struct xfs_alloc_arg *args)
{
struct xfs_ag_resv *resv;
xfs_extlen_t len;
uint field;
trace_xfs_ag_resv_alloc_extent(pag, type, args->len);
switch (type) {
case XFS_AG_RESV_METADATA:
case XFS_AG_RESV_AGFL:
resv = xfs_perag_resv(pag, type);
break;
default:
ASSERT(0);
/* fall through */
case XFS_AG_RESV_NONE:
field = args->wasdel ? XFS_TRANS_SB_RES_FDBLOCKS :
XFS_TRANS_SB_FDBLOCKS;
xfs_trans_mod_sb(args->tp, field, -(int64_t)args->len);
return;
}
len = min_t(xfs_extlen_t, args->len, resv->ar_reserved);
resv->ar_reserved -= len;
if (type == XFS_AG_RESV_AGFL)
return;
/* Allocations of reserved blocks only need on-disk sb updates... */
xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_RES_FDBLOCKS, -(int64_t)len);
/* ...but non-reserved blocks need in-core and on-disk updates. */
if (args->len > len)
xfs_trans_mod_sb(args->tp, XFS_TRANS_SB_FDBLOCKS,
-((int64_t)args->len - len));
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darrick J. Wong | 175 | 100.00% | 1 | 100.00% |
| Total | 175 | 100.00% | 1 | 100.00% |
/* Free a block to the reservation. */
void
xfs_ag_resv_free_extent(
struct xfs_perag *pag,
enum xfs_ag_resv_type type,
struct xfs_trans *tp,
xfs_extlen_t len)
{
xfs_extlen_t leftover;
struct xfs_ag_resv *resv;
trace_xfs_ag_resv_free_extent(pag, type, len);
switch (type) {
case XFS_AG_RESV_METADATA:
case XFS_AG_RESV_AGFL:
resv = xfs_perag_resv(pag, type);
break;
default:
ASSERT(0);
/* fall through */
case XFS_AG_RESV_NONE:
xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, (int64_t)len);
return;
}
leftover = min_t(xfs_extlen_t, len, resv->ar_asked - resv->ar_reserved);
resv->ar_reserved += leftover;
if (type == XFS_AG_RESV_AGFL)
return;
/* Freeing into the reserved pool only requires on-disk update... */
xfs_trans_mod_sb(tp, XFS_TRANS_SB_RES_FDBLOCKS, len);
/* ...but freeing beyond that requires in-core and on-disk update. */
if (len > leftover)
xfs_trans_mod_sb(tp, XFS_TRANS_SB_FDBLOCKS, len - leftover);
}
Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darrick J. Wong | 142 | 100.00% | 1 | 100.00% |
| Total | 142 | 100.00% | 1 | 100.00% |
Overall Contributors
| Person | Tokens | Prop | Commits | CommitProp |
| Darrick J. Wong | 1022 | 84.46% | 4 | 66.67% |
| Christoph Hellwig | 188 | 15.54% | 2 | 33.33% |
| Total | 1210 | 100.00% | 6 | 100.00% |
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