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-rw-r--r--fs/xfs/libxfs/xfs_ag_resv.c426
1 files changed, 426 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 000000000..5af123d13
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+++ b/fs/xfs/libxfs/xfs_ag_resv.c
@@ -0,0 +1,426 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ * Copyright (C) 2016 Oracle. All Rights Reserved.
+ * Author: Darrick J. Wong <darrick.wong@oracle.com>
+ */
+#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_mount.h"
+#include "xfs_alloc.h"
+#include "xfs_errortag.h"
+#include "xfs_error.h"
+#include "xfs_trace.h"
+#include "xfs_trans.h"
+#include "xfs_rmap_btree.h"
+#include "xfs_btree.h"
+#include "xfs_refcount_btree.h"
+#include "xfs_ialloc_btree.h"
+#include "xfs_ag.h"
+#include "xfs_ag_resv.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_rmapbt_resv.ar_reserved;
+ orig = pag->pag_meta_resv.ar_asked;
+ break;
+ case XFS_AG_RESV_RMAPBT:
+ avail = pag->pagf_freeblks + pag->pagf_flcount -
+ pag->pag_meta_resv.ar_reserved;
+ orig = pag->pag_rmapbt_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 < pag->pag_mount->m_agbtree_maxlevels,
+ pag->pag_mount, XFS_ERRTAG_AG_RESV_CRITICAL);
+}
+
+/*
+ * 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_rmapbt_resv.ar_reserved;
+ switch (type) {
+ case XFS_AG_RESV_METADATA:
+ case XFS_AG_RESV_RMAPBT:
+ 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);
+ if (pag->pag_agno == 0)
+ pag->pag_mount->m_ag_max_usable += resv->ar_asked;
+ /*
+ * RMAPBT blocks come from the AGFL and AGFL blocks are always
+ * considered "free", so whatever was reserved at mount time must be
+ * given back at umount.
+ */
+ if (type == XFS_AG_RESV_RMAPBT)
+ 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;
+ resv->ar_orig_reserved = 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_RMAPBT);
+ 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;
+ xfs_extlen_t hidden_space;
+
+ if (used > ask)
+ ask = used;
+
+ switch (type) {
+ case XFS_AG_RESV_RMAPBT:
+ /*
+ * Space taken by the rmapbt is not subtracted from fdblocks
+ * because the rmapbt lives in the free space. Here we must
+ * subtract the entire reservation from fdblocks so that we
+ * always have blocks available for rmapbt expansion.
+ */
+ hidden_space = ask;
+ break;
+ case XFS_AG_RESV_METADATA:
+ /*
+ * Space taken by all other metadata btrees are accounted
+ * on-disk as used space. We therefore only hide the space
+ * that is reserved but not used by the trees.
+ */
+ hidden_space = ask - used;
+ break;
+ default:
+ ASSERT(0);
+ return -EINVAL;
+ }
+
+ if (XFS_TEST_ERROR(false, mp, XFS_ERRTAG_AG_RESV_FAIL))
+ error = -ENOSPC;
+ else
+ error = xfs_mod_fdblocks(mp, -(int64_t)hidden_space, 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;
+ }
+
+ /*
+ * Reduce the maximum per-AG allocation length by however much we're
+ * trying to reserve for an AG. Since this is a filesystem-wide
+ * counter, we only make the adjustment for AG 0. This assumes that
+ * there aren't any AGs hungrier for per-AG reservation than AG 0.
+ */
+ if (pag->pag_agno == 0)
+ mp->m_ag_max_usable -= ask;
+
+ resv = xfs_perag_resv(pag, type);
+ resv->ar_asked = ask;
+ resv->ar_orig_reserved = hidden_space;
+ resv->ar_reserved = ask - used;
+
+ trace_xfs_ag_resv_init(pag, type, ask);
+ return 0;
+}
+
+/* Create a per-AG block reservation. */
+int
+xfs_ag_resv_init(
+ struct xfs_perag *pag,
+ struct xfs_trans *tp)
+{
+ struct xfs_mount *mp = pag->pag_mount;
+ xfs_extlen_t ask;
+ xfs_extlen_t used;
+ int error = 0, error2;
+ bool has_resv = false;
+
+ /* Create the metadata reservation. */
+ if (pag->pag_meta_resv.ar_asked == 0) {
+ ask = used = 0;
+
+ error = xfs_refcountbt_calc_reserves(mp, tp, pag, &ask, &used);
+ if (error)
+ goto out;
+
+ error = xfs_finobt_calc_reserves(mp, tp, pag, &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_finobt_nores = true;
+
+ error = xfs_refcountbt_calc_reserves(mp, tp, pag, &ask,
+ &used);
+ if (error)
+ goto out;
+
+ error = __xfs_ag_resv_init(pag, XFS_AG_RESV_METADATA,
+ ask, used);
+ if (error)
+ goto out;
+ }
+ if (ask)
+ has_resv = true;
+ }
+
+ /* Create the RMAPBT metadata reservation */
+ if (pag->pag_rmapbt_resv.ar_asked == 0) {
+ ask = used = 0;
+
+ error = xfs_rmapbt_calc_reserves(mp, tp, pag, &ask, &used);
+ if (error)
+ goto out;
+
+ error = __xfs_ag_resv_init(pag, XFS_AG_RESV_RMAPBT, ask, used);
+ if (error)
+ goto out;
+ if (ask)
+ has_resv = true;
+ }
+
+out:
+ /*
+ * Initialize the pagf if we have at least one active reservation on the
+ * AG. This may have occurred already via reservation calculation, but
+ * fall back to an explicit init to ensure the in-core allocbt usage
+ * counters are initialized as soon as possible. This is important
+ * because filesystems with large perag reservations are susceptible to
+ * free space reservation problems that the allocbt counter is used to
+ * address.
+ */
+ if (has_resv) {
+ error2 = xfs_alloc_read_agf(pag, tp, 0, NULL);
+ if (error2)
+ return error2;
+
+ /*
+ * If there isn't enough space in the AG to satisfy the
+ * reservation, let the caller know that there wasn't enough
+ * space. Callers are responsible for deciding what to do
+ * next, since (in theory) we can stumble along with
+ * insufficient reservation if data blocks are being freed to
+ * replenish the AG's free space.
+ */
+ if (!error &&
+ xfs_perag_resv(pag, XFS_AG_RESV_METADATA)->ar_reserved +
+ xfs_perag_resv(pag, XFS_AG_RESV_RMAPBT)->ar_reserved >
+ pag->pagf_freeblks + pag->pagf_flcount)
+ error = -ENOSPC;
+ }
+
+ 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_AGFL:
+ return;
+ case XFS_AG_RESV_METADATA:
+ case XFS_AG_RESV_RMAPBT:
+ resv = xfs_perag_resv(pag, type);
+ break;
+ default:
+ ASSERT(0);
+ fallthrough;
+ 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_RMAPBT)
+ 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_AGFL:
+ return;
+ case XFS_AG_RESV_METADATA:
+ case XFS_AG_RESV_RMAPBT:
+ resv = xfs_perag_resv(pag, type);
+ break;
+ default:
+ ASSERT(0);
+ fallthrough;
+ 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_RMAPBT)
+ 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);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-29 09:12:31 +0000