diff options
Diffstat (limited to 'fs/xfs/libxfs/xfs_ag_resv.c')
| -rw-r--r-- | fs/xfs/libxfs/xfs_ag_resv.c | 325 |
1 files changed, 325 insertions, 0 deletions
diff --git a/fs/xfs/libxfs/xfs_ag_resv.c b/fs/xfs/libxfs/xfs_ag_resv.c new file mode 100644 index 000000000000..e3ae0f2b4294 --- /dev/null +++ b/fs/xfs/libxfs/xfs_ag_resv.c @@ -0,0 +1,325 @@ +/* + * 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" + +/* + * 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 avail < orig / 10 || avail < XFS_BTREE_MAXLEVELS; +} + +/* + * 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; +} + +/* 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; +} + +/* 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; +} + +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; + + resv = xfs_perag_resv(pag, type); + if (used > ask) + ask = used; + resv->ar_asked = ask; + resv->ar_reserved = resv->ar_orig_reserved = ask - used; + mp->m_ag_max_usable -= ask; + + trace_xfs_ag_resv_init(pag, type, ask); + + error = xfs_mod_fdblocks(mp, -(int64_t)resv->ar_reserved, true); + if (error) + trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno, + error, _RET_IP_); + + return error; +} + +/* Create a per-AG block reservation. */ +int +xfs_ag_resv_init( + struct xfs_perag *pag) +{ + 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_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_ag_resv_init(pag, XFS_AG_RESV_AGFL, ask, used); + if (error) + goto out; + } + +out: + return error; +} + +/* 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)); +} + +/* 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); +} |