[PATCH 28/51] xfs_repair: create a slab API for allocating arrays in large chunks

Darrick J. Wong
2015-10-07T05:08:24Z

Create a slab-based array and a bag-of-pointers data structure to
facilitate rapid linear scans of reverse-mapping data for later
reconstruction of the refcount and rmap btrees.

Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
---
repair/Makefile | 4
repair/slab.c | 473 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
repair/slab.h | 58 +++++++
3 files changed, 533 insertions(+), 2 deletions(-)
create mode 100644 repair/slab.c
create mode 100644 repair/slab.h

diff --git a/repair/Makefile b/repair/Makefile
index 6d84ade..82cba8e 100644
--- a/repair/Makefile
+++ b/repair/Makefile
@@ -11,14 +11,14 @@ LTCOMMAND = xfs_repair

HFILES = agheader.h attr_repair.h avl.h avl64.h bmap.h btree.h \
dinode.h dir2.h err_protos.h globals.h incore.h protos.h rt.h \
- progress.h scan.h versions.h prefetch.h threads.h
+ progress.h scan.h versions.h prefetch.h threads.h slab.h

CFILES = agheader.c attr_repair.c avl.c avl64.c bmap.c btree.c \
dino_chunks.c dinode.c dir2.c globals.c incore.c \
incore_bmc.c init.c incore_ext.c incore_ino.c phase1.c \
phase2.c phase3.c phase4.c phase5.c phase6.c phase7.c \
progress.c prefetch.c rt.c sb.c scan.c threads.c \
- versions.c xfs_repair.c
+ versions.c xfs_repair.c slab.c

LLDLIBS = $(LIBXFS) $(LIBXLOG) $(LIBUUID) $(LIBRT) $(LIBPTHREAD)
LTDEPENDENCIES = $(LIBXFS) $(LIBXLOG)
diff --git a/repair/slab.c b/repair/slab.c
new file mode 100644
index 0000000..bb7019a
--- /dev/null
+++ b/repair/slab.c
@@ -0,0 +1,473 @@
+/*
+ * Copyright (c) 2015 Oracle.
+ * 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 <libxfs.h>
+#include "slab.h"
+
+#undef SLAB_DEBUG
+
+#ifdef SLAB_DEBUG
+# define dbg_printf(f, a...) do {printf(f, ## a); fflush(stdout); } while (0)
+#else
+# define dbg_printf(f, a...)
+#endif
+
+/*
+ * Slab Arrays and Bags
+ *
+ * The slab array is a dynamically growable linear array. Internally it
+ * maintains a list of slabs of increasing size; when a slab fills up, another
+ * is allocated. Each slab is sorted individually, which means that one must
+ * use an iterator to walk the entire logical array, sorted order or otherwise.
+ * Array items can neither be removed nor accessed randomly, since (at the
+ * moment) the only user of them (storing reverse mappings) doesn't need either
+ * piece. Pointers are not stable across sort operations.
+ *
+ * A bag is a collection of pointers. The bag can be added to or removed from
+ * arbitrarily, and the bag items can be iterated. Bags are used to process
+ * rmaps into refcount btree entries.
+ */
+
+/*
+ * Slabs -- each slab_hdr holds an array of items; when a slab_hdr fills up, we
+ * allocate a new one and add to that one. The slab object coordinates the
+ * slab_hdrs.
+ */
+
+/* Each slab holds at least 4096 items */
+#define MIN_SLAB_NR 4096
+/* and cannot be larger than 128M */
+#define MAX_SLAB_SIZE (128 * 1048576)
+struct xfs_slab_hdr {
+ size_t sh_nr;
+ size_t sh_inuse; /* items in use */
+ struct xfs_slab_hdr *sh_next; /* next slab hdr */
+ /* objects follow */
+};
+
+struct xfs_slab {
+ size_t s_item_sz; /* item size */
+ size_t s_nr_slabs; /* # of slabs */
+ size_t s_nr_items; /* # of items */
+ struct xfs_slab_hdr *s_first; /* first slab header */
+ struct xfs_slab_hdr *s_last; /* last sh_next pointer */
+};
+
+/*
+ * Slab cursors -- each slab_hdr_cursor tracks a slab_hdr; the slab_cursor
+ * tracks the slab_hdr_cursors. If a compare_fn is specified, the cursor
+ * returns objects in increasing order (if you've previously sorted the
+ * slabs with qsort_slab()). If compare_fn == NULL, it returns slab items
+ * in order.
+ */
+struct xfs_slab_hdr_cursor {
+ struct xfs_slab_hdr *hdr; /* a slab header */
+ size_t loc; /* where we are in the slab */
+};
+
+struct xfs_slab_cursor {
+ size_t nr; /* # of per-slab cursors */
+ struct xfs_slab *slab; /* pointer to the slab */
+ struct xfs_slab_hdr_cursor *last_hcur; /* last header we took from */
+ int (*compare_fn)(const void *, const void *); /* compare function */
+ struct xfs_slab_hdr_cursor hcur[0]; /* per-slab curosr */
+};
+
+/*
+ * Bags -- each bag is an array of pointers items; when a bag fills up, we
+ * resize it.
+ */
+#define MIN_BAG_SIZE 4096
+struct xfs_bag {
+ size_t bg_nr; /* number of pointers */
+ size_t bg_inuse; /* number of slots in use */
+ void **bg_ptrs; /* pointers */
+};
+#define BAG_SIZE(nr) (sizeof(struct xfs_bag) + ((nr) * sizeof(void *)))
+#define BAG_END(bag) (&(bag)->bg_ptrs[(bag)->bg_nr])
+
+/**
+ * init_slab() -- Create a slab to hold some objects.
+ *
+ * @slab: The slab.
+ * @item_size: Create items of this size.
+ */
+int
+init_slab(
+ struct xfs_slab **slab,
+ size_t item_size)
+{
+ struct xfs_slab *ptr;
+
+ ptr = calloc(1, sizeof(struct xfs_slab));
+ if (!ptr)
+ return -ENOMEM;
+ ptr->s_item_sz = item_size;
+ ptr->s_last = NULL;
+ *slab = ptr;
+
+ return 0;
+}
+
+/**
+ * free_slab() -- Frees a slab.
+ */
+void
+free_slab(
+ struct xfs_slab **slab)
+{
+ struct xfs_slab *ptr;
+ struct xfs_slab_hdr *hdr;
+ struct xfs_slab_hdr *nhdr;
+
+ ptr = *slab;
+ if (!ptr)
+ return;
+ hdr = ptr->s_first;
+ while (hdr) {
+ nhdr = hdr->sh_next;
+ free(hdr);
+ hdr = nhdr;
+ }
+ free(ptr);
+ *slab = NULL;
+}
+
+static void *
+slab_ptr(
+ struct xfs_slab *slab,
+ struct xfs_slab_hdr *hdr,
+ size_t idx)
+{
+ char *p;
+
+ ASSERT(idx < hdr->sh_inuse);
+ p = (char *)(hdr + 1);
+ p += slab->s_item_sz * idx;
+ return p;
+}
+
+/**
+ * slab_add() -- Add an item to the slab.
+ */
+int
+slab_add(
+ struct xfs_slab *slab,
+ void *item)
+{
+ struct xfs_slab_hdr *hdr;
+ void *p;
+
+ hdr = slab->s_last;
+ if (!hdr || hdr->sh_inuse == hdr->sh_nr) {
+ size_t n;
+
+ n = (hdr ? hdr->sh_nr * 2 : MIN_SLAB_NR);
+ if (n * slab->s_item_sz > MAX_SLAB_SIZE)
+ n = MAX_SLAB_SIZE / slab->s_item_sz;
+ hdr = malloc(sizeof(struct xfs_slab_hdr) + (n * slab->s_item_sz));
+ if (!hdr)
+ return -ENOMEM;
+ hdr->sh_nr = n;
+ hdr->sh_inuse = 0;
+ hdr->sh_next = NULL;
+ if (slab->s_last)
+ slab->s_last->sh_next = hdr;
+ if (!slab->s_first)
+ slab->s_first = hdr;
+ slab->s_last = hdr;
+ slab->s_nr_slabs++;
+ }
+ hdr->sh_inuse++;
+ p = slab_ptr(slab, hdr, hdr->sh_inuse - 1);
+ memcpy(p, item, slab->s_item_sz);
+ slab->s_nr_items++;
+
+ return 0;
+}
+
+/**
+ * qsort_slab() -- Sort the items in the slab. Do not run this method
+ * if there are any cursors holding on to the slab.
+ */
+void
+qsort_slab(
+ struct xfs_slab *slab,
+ int (*compare_fn)(const void *, const void *))
+{
+ struct xfs_slab_hdr *hdr;
+
+ hdr = slab->s_first;
+ while (hdr) {
+ qsort(slab_ptr(slab, hdr, 0), hdr->sh_inuse, slab->s_item_sz,
+ compare_fn);
+ hdr = hdr->sh_next;
+ }
+}
+
+/*
+ * init_slab_cursor() -- Create a slab cursor to iterate the slab items.
+ *
+ * @slab: The slab.
+ * @compare_fn: If specified, use this function to return items in ascending order.
+ * @cur: The new cursor.
+ */
+int
+init_slab_cursor(
+ struct xfs_slab *slab,
+ int (*compare_fn)(const void *, const void *),
+ struct xfs_slab_cursor **cur)
+{
+ struct xfs_slab_cursor *c;
+ struct xfs_slab_hdr_cursor *hcur;
+ struct xfs_slab_hdr *hdr;
+
+ c = malloc(sizeof(struct xfs_slab_cursor) +
+ (sizeof(struct xfs_slab_hdr_cursor) * slab->s_nr_slabs));
+ if (!c)
+ return -ENOMEM;
+ c->nr = slab->s_nr_slabs;
+ c->slab = slab;
+ c->compare_fn = compare_fn;
+ c->last_hcur = NULL;
+ hcur = (struct xfs_slab_hdr_cursor *)(c + 1);
+ hdr = slab->s_first;
+ while (hdr) {
+ hcur->hdr = hdr;
+ hcur->loc = 0;
+ hcur++;
+ hdr = hdr->sh_next;
+ }
+ *cur = c;
+ return 0;
+}
+
+/**
+ * free_slab_cursor() -- Free the slab cursor.
+ */
+void
+free_slab_cursor(
+ struct xfs_slab_cursor **cur)
+{
+ if (!*cur)
+ return;
+ free(*cur);
+ *cur = NULL;
+}
+
+/**
+ * peek_slab_cursor() -- Return the smallest item in the slab, without
+ * advancing the iterator. The slabs must be sorted prior to the creation
+ * of the cursor.
+ */
+void *
+peek_slab_cursor(
+ struct xfs_slab_cursor *cur)
+{
+ struct xfs_slab_hdr_cursor *hcur;
+ void *p = NULL;
+ void *q;
+ size_t i;
+
+ cur->last_hcur = NULL;
+
+ /* no compare function; inorder traversal */
+ if (!cur->compare_fn) {
+ if (!cur->last_hcur)
+ cur->last_hcur = &cur->hcur[0];
+ hcur = cur->last_hcur;
+ while (hcur < &cur->hcur[cur->nr] &&
+ hcur->loc >= hcur->hdr->sh_inuse)
+ hcur++;
+ if (hcur == &cur->hcur[cur->nr])
+ return NULL;
+ p = slab_ptr(cur->slab, hcur->hdr, hcur->loc);
+ cur->last_hcur = hcur;
+ return p;
+ }
+
+ /* otherwise return things in increasing order */
+ for (i = 0, hcur = &cur->hcur[i]; i < cur->nr; i++, hcur++) {
+ if (hcur->loc >= hcur->hdr->sh_inuse)
+ continue;
+ q = slab_ptr(cur->slab, hcur->hdr, hcur->loc);
+ if (!p || cur->compare_fn(p, q) > 0) {
+ p = q;
+ cur->last_hcur = hcur;
+ }
+ }
+
+ return p;
+}
+
+/**
+ * advance_slab_cursor() -- After a peek operation, advance the cursor.
+ */
+void
+advance_slab_cursor(
+ struct xfs_slab_cursor *cur)
+{
+ ASSERT(cur->last_hcur);
+ cur->last_hcur->loc++;
+}
+
+/**
+ * pop_slab_cursor() -- Retrieve the next item in the slab and advance the
+ * cursor.
+ */
+void *
+pop_slab_cursor(
+ struct xfs_slab_cursor *cur)
+{
+ void *p;
+
+ p = peek_slab_cursor(cur);
+ if (p)
+ advance_slab_cursor(cur);
+ return p;
+}
+
+/**
+ * slab_count() -- Return the number of items in the slab.
+ */
+size_t
+slab_count(
+ struct xfs_slab *slab)
+{
+ return slab->s_nr_items;
+}
+
+/**
+ * init_bag() -- Create a bag to point to some objects.
+ *
+ * @bag: The bag.
+ */
+int
+init_bag(
+ struct xfs_bag **bag)
+{
+ struct xfs_bag *ptr;
+
+ ptr = calloc(1, sizeof(struct xfs_bag));
+ if (!ptr)
+ return -ENOMEM;
+ ptr->bg_ptrs = calloc(MIN_BAG_SIZE, sizeof(void *));
+ if (!ptr->bg_ptrs) {
+ free(ptr);
+ return -ENOMEM;
+ }
+ ptr->bg_nr = MIN_BAG_SIZE;
+ *bag = ptr;
+ return 0;
+}
+
+/**
+ * free_bag() - Free a bag of pointers.
+ *
+ * @bag: The bag to free.
+ */
+void
+free_bag(
+ struct xfs_bag **bag)
+{
+ struct xfs_bag *ptr;
+
+ ptr = *bag;
+ if (!ptr)
+ return;
+ free(ptr->bg_ptrs);
+ free(ptr);
+ *bag = NULL;
+}
+
+/**
+ * bag_add() - Add an object to the pointer bag.
+ *
+ * @bag: The bag.
+ * @ptr: The pointer to add to the bag.
+ */
+int
+bag_add(
+ struct xfs_bag *bag,
+ void *ptr)
+{
+ void **p, **x;
+
+ p = &bag->bg_ptrs[bag->bg_inuse];
+ if (p == BAG_END(bag)) {
+ /* No free space, alloc more pointers */
+ size_t nr;
+
+ nr = bag->bg_nr * 2;
+ x = realloc(bag->bg_ptrs, nr * sizeof(void *));
+ if (!x)
+ return -ENOMEM;
+ bag->bg_ptrs = x;
+ memset(BAG_END(bag), 0, bag->bg_nr * sizeof(void *));
+ bag->bg_nr = nr;
+ }
+ bag->bg_ptrs[bag->bg_inuse] = ptr;
+ bag->bg_inuse++;
+ return 0;
+}
+
+/**
+ * bag_remove() - Remove a pointer from a bag.
+ *
+ * @bag: The bag.
+ * @idx: The number of the pointer to remove.
+ */
+int
+bag_remove(
+ struct xfs_bag *bag,
+ size_t nr)
+{
+ ASSERT(nr < bag->bg_inuse);
+ memmove(&bag->bg_ptrs[nr], &bag->bg_ptrs[nr + 1],
+ (bag->bg_inuse - nr) * sizeof(void *));
+ bag->bg_inuse--;
+ return 0;
+}
+
+/**
+ * bag_count() - Return the number of items in a bag.
+ *
+ * @bag: The bag.
+ */
+size_t
+bag_count(
+ struct xfs_bag *bag)
+{
+ return bag->bg_inuse;
+}
+
+/**
+ * bag_item() - Return the nth item in a bag.
+ *
+ * @bag: The bag.
+ * @nr: The item number.
+ */
+void *
+bag_item(
+ struct xfs_bag *bag,
+ size_t nr)
+{
+ if (nr >= bag->bg_inuse)
+ return NULL;
+ return bag->bg_ptrs[nr];
+}
diff --git a/repair/slab.h b/repair/slab.h
new file mode 100644
index 0000000..8142914
--- /dev/null
+++ b/repair/slab.h
@@ -0,0 +1,58 @@
+/*
+ * Copyright (c) 2015 Oracle.
+ * 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
+ */
+#ifndef SLAB_H_
+#define SLAB_H_
+
+struct xfs_slab;
+struct xfs_slab_cursor;
+
+extern int init_slab(struct xfs_slab **, size_t);
+extern void free_slab(struct xfs_slab **);
+
+extern int slab_add(struct xfs_slab *, void *);
+extern void qsort_slab(struct xfs_slab *, int (*)(const void *, const void *));
+extern size_t slab_count(struct xfs_slab *);
+
+extern int init_slab_cursor(struct xfs_slab *,
+ int (*)(const void *, const void *), struct xfs_slab_cursor **);
+extern void free_slab_cursor(struct xfs_slab_cursor **);
+
+extern void *peek_slab_cursor(struct xfs_slab_cursor *);
+extern void advance_slab_cursor(struct xfs_slab_cursor *);
+extern void *pop_slab_cursor(struct xfs_slab_cursor *);
+
+struct xfs_bag;
+
+extern int init_bag(struct xfs_bag **);
+extern void free_bag(struct xfs_bag **);
+extern int bag_add(struct xfs_bag *, void *);
+extern int bag_remove(struct xfs_bag *, size_t);
+extern size_t bag_count(struct xfs_bag *);
+extern void *bag_item(struct xfs_bag *, size_t);
+
+#define foreach_bag_ptr(bag, idx, ptr) \
+ for ((idx) = 0, (ptr) = bag_item((bag), (idx)); \
+ (idx) < bag_count(bag); \
+ (idx)++, (ptr) = bag_item((bag), (idx)))
+
+#define foreach_bag_ptr_reverse(bag, idx, ptr) \
+ for ((idx) = bag_count(bag) - 1, (ptr) = bag_item((bag), (idx)); \
+ (idx) >= 0 && (ptr) != NULL; \
+ (idx)--, (ptr) = bag_item((bag), (idx)))
+
+#endif /* SLAB_H_ */