539 lines
14 KiB
C
539 lines
14 KiB
C
/*
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* Copyright (C) 2010-2012 by Dell Inc. All rights reserved.
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* Copyright (C) 2011-2013 Red Hat, Inc.
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*
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* This file is released under the GPL.
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*
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* dm-switch is a device-mapper target that maps IO to underlying block
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* devices efficiently when there are a large number of fixed-sized
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* address regions but there is no simple pattern to allow for a compact
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* mapping representation such as dm-stripe.
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*/
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#include <linux/device-mapper.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/vmalloc.h>
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#define DM_MSG_PREFIX "switch"
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/*
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* One region_table_slot_t holds <region_entries_per_slot> region table
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* entries each of which is <region_table_entry_bits> in size.
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*/
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typedef unsigned long region_table_slot_t;
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/*
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* A device with the offset to its start sector.
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*/
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struct switch_path {
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struct dm_dev *dmdev;
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sector_t start;
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};
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/*
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* Context block for a dm switch device.
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*/
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struct switch_ctx {
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struct dm_target *ti;
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unsigned nr_paths; /* Number of paths in path_list. */
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unsigned region_size; /* Region size in 512-byte sectors */
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unsigned long nr_regions; /* Number of regions making up the device */
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signed char region_size_bits; /* log2 of region_size or -1 */
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unsigned char region_table_entry_bits; /* Number of bits in one region table entry */
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unsigned char region_entries_per_slot; /* Number of entries in one region table slot */
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signed char region_entries_per_slot_bits; /* log2 of region_entries_per_slot or -1 */
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region_table_slot_t *region_table; /* Region table */
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/*
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* Array of dm devices to switch between.
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*/
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struct switch_path path_list[0];
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};
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static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned nr_paths,
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unsigned region_size)
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{
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struct switch_ctx *sctx;
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sctx = kzalloc(sizeof(struct switch_ctx) + nr_paths * sizeof(struct switch_path),
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GFP_KERNEL);
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if (!sctx)
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return NULL;
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sctx->ti = ti;
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sctx->region_size = region_size;
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ti->private = sctx;
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return sctx;
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}
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static int alloc_region_table(struct dm_target *ti, unsigned nr_paths)
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{
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struct switch_ctx *sctx = ti->private;
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sector_t nr_regions = ti->len;
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sector_t nr_slots;
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if (!(sctx->region_size & (sctx->region_size - 1)))
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sctx->region_size_bits = __ffs(sctx->region_size);
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else
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sctx->region_size_bits = -1;
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sctx->region_table_entry_bits = 1;
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while (sctx->region_table_entry_bits < sizeof(region_table_slot_t) * 8 &&
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(region_table_slot_t)1 << sctx->region_table_entry_bits < nr_paths)
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sctx->region_table_entry_bits++;
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sctx->region_entries_per_slot = (sizeof(region_table_slot_t) * 8) / sctx->region_table_entry_bits;
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if (!(sctx->region_entries_per_slot & (sctx->region_entries_per_slot - 1)))
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sctx->region_entries_per_slot_bits = __ffs(sctx->region_entries_per_slot);
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else
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sctx->region_entries_per_slot_bits = -1;
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if (sector_div(nr_regions, sctx->region_size))
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nr_regions++;
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sctx->nr_regions = nr_regions;
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if (sctx->nr_regions != nr_regions || sctx->nr_regions >= ULONG_MAX) {
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ti->error = "Region table too large";
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return -EINVAL;
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}
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nr_slots = nr_regions;
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if (sector_div(nr_slots, sctx->region_entries_per_slot))
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nr_slots++;
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if (nr_slots > ULONG_MAX / sizeof(region_table_slot_t)) {
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ti->error = "Region table too large";
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return -EINVAL;
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}
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sctx->region_table = vmalloc(nr_slots * sizeof(region_table_slot_t));
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if (!sctx->region_table) {
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ti->error = "Cannot allocate region table";
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return -ENOMEM;
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}
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return 0;
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}
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static void switch_get_position(struct switch_ctx *sctx, unsigned long region_nr,
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unsigned long *region_index, unsigned *bit)
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{
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if (sctx->region_entries_per_slot_bits >= 0) {
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*region_index = region_nr >> sctx->region_entries_per_slot_bits;
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*bit = region_nr & (sctx->region_entries_per_slot - 1);
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} else {
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*region_index = region_nr / sctx->region_entries_per_slot;
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*bit = region_nr % sctx->region_entries_per_slot;
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}
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*bit *= sctx->region_table_entry_bits;
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}
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/*
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* Find which path to use at given offset.
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*/
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static unsigned switch_get_path_nr(struct switch_ctx *sctx, sector_t offset)
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{
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unsigned long region_index;
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unsigned bit, path_nr;
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sector_t p;
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p = offset;
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if (sctx->region_size_bits >= 0)
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p >>= sctx->region_size_bits;
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else
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sector_div(p, sctx->region_size);
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switch_get_position(sctx, p, ®ion_index, &bit);
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path_nr = (ACCESS_ONCE(sctx->region_table[region_index]) >> bit) &
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((1 << sctx->region_table_entry_bits) - 1);
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/* This can only happen if the processor uses non-atomic stores. */
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if (unlikely(path_nr >= sctx->nr_paths))
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path_nr = 0;
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return path_nr;
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}
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static void switch_region_table_write(struct switch_ctx *sctx, unsigned long region_nr,
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unsigned value)
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{
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unsigned long region_index;
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unsigned bit;
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region_table_slot_t pte;
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switch_get_position(sctx, region_nr, ®ion_index, &bit);
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pte = sctx->region_table[region_index];
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pte &= ~((((region_table_slot_t)1 << sctx->region_table_entry_bits) - 1) << bit);
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pte |= (region_table_slot_t)value << bit;
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sctx->region_table[region_index] = pte;
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}
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/*
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* Fill the region table with an initial round robin pattern.
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*/
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static void initialise_region_table(struct switch_ctx *sctx)
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{
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unsigned path_nr = 0;
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unsigned long region_nr;
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for (region_nr = 0; region_nr < sctx->nr_regions; region_nr++) {
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switch_region_table_write(sctx, region_nr, path_nr);
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if (++path_nr >= sctx->nr_paths)
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path_nr = 0;
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}
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}
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static int parse_path(struct dm_arg_set *as, struct dm_target *ti)
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{
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struct switch_ctx *sctx = ti->private;
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unsigned long long start;
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int r;
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r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
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&sctx->path_list[sctx->nr_paths].dmdev);
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if (r) {
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ti->error = "Device lookup failed";
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return r;
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}
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if (kstrtoull(dm_shift_arg(as), 10, &start) || start != (sector_t)start) {
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ti->error = "Invalid device starting offset";
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dm_put_device(ti, sctx->path_list[sctx->nr_paths].dmdev);
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return -EINVAL;
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}
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sctx->path_list[sctx->nr_paths].start = start;
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sctx->nr_paths++;
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return 0;
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}
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/*
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* Destructor: Don't free the dm_target, just the ti->private data (if any).
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*/
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static void switch_dtr(struct dm_target *ti)
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{
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struct switch_ctx *sctx = ti->private;
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while (sctx->nr_paths--)
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dm_put_device(ti, sctx->path_list[sctx->nr_paths].dmdev);
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vfree(sctx->region_table);
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kfree(sctx);
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}
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/*
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* Constructor arguments:
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* <num_paths> <region_size> <num_optional_args> [<optional_args>...]
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* [<dev_path> <offset>]+
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*
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* Optional args are to allow for future extension: currently this
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* parameter must be 0.
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*/
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static int switch_ctr(struct dm_target *ti, unsigned argc, char **argv)
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{
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static struct dm_arg _args[] = {
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{1, (KMALLOC_MAX_SIZE - sizeof(struct switch_ctx)) / sizeof(struct switch_path), "Invalid number of paths"},
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{1, UINT_MAX, "Invalid region size"},
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{0, 0, "Invalid number of optional args"},
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};
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struct switch_ctx *sctx;
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struct dm_arg_set as;
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unsigned nr_paths, region_size, nr_optional_args;
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int r;
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as.argc = argc;
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as.argv = argv;
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r = dm_read_arg(_args, &as, &nr_paths, &ti->error);
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if (r)
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return -EINVAL;
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r = dm_read_arg(_args + 1, &as, ®ion_size, &ti->error);
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if (r)
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return r;
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r = dm_read_arg_group(_args + 2, &as, &nr_optional_args, &ti->error);
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if (r)
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return r;
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/* parse optional arguments here, if we add any */
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if (as.argc != nr_paths * 2) {
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ti->error = "Incorrect number of path arguments";
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return -EINVAL;
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}
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sctx = alloc_switch_ctx(ti, nr_paths, region_size);
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if (!sctx) {
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ti->error = "Cannot allocate redirection context";
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return -ENOMEM;
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}
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r = dm_set_target_max_io_len(ti, region_size);
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if (r)
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goto error;
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while (as.argc) {
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r = parse_path(&as, ti);
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if (r)
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goto error;
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}
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r = alloc_region_table(ti, nr_paths);
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if (r)
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goto error;
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initialise_region_table(sctx);
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/* For UNMAP, sending the request down any path is sufficient */
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ti->num_discard_bios = 1;
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return 0;
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error:
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switch_dtr(ti);
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return r;
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}
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static int switch_map(struct dm_target *ti, struct bio *bio)
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{
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struct switch_ctx *sctx = ti->private;
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sector_t offset = dm_target_offset(ti, bio->bi_sector);
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unsigned path_nr = switch_get_path_nr(sctx, offset);
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bio->bi_bdev = sctx->path_list[path_nr].dmdev->bdev;
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bio->bi_sector = sctx->path_list[path_nr].start + offset;
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return DM_MAPIO_REMAPPED;
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}
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/*
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* We need to parse hex numbers in the message as quickly as possible.
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*
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* This table-based hex parser improves performance.
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* It improves a time to load 1000000 entries compared to the condition-based
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* parser.
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* table-based parser condition-based parser
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* PA-RISC 0.29s 0.31s
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* Opteron 0.0495s 0.0498s
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*/
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static const unsigned char hex_table[256] = {
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255, 255,
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255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
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255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255
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};
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static __always_inline unsigned long parse_hex(const char **string)
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{
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unsigned char d;
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unsigned long r = 0;
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while ((d = hex_table[(unsigned char)**string]) < 16) {
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r = (r << 4) | d;
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(*string)++;
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}
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return r;
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}
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static int process_set_region_mappings(struct switch_ctx *sctx,
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unsigned argc, char **argv)
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{
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unsigned i;
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unsigned long region_index = 0;
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for (i = 1; i < argc; i++) {
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unsigned long path_nr;
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const char *string = argv[i];
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if (*string == ':')
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region_index++;
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else {
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region_index = parse_hex(&string);
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if (unlikely(*string != ':')) {
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DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
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return -EINVAL;
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}
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}
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string++;
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if (unlikely(!*string)) {
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DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
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return -EINVAL;
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}
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path_nr = parse_hex(&string);
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if (unlikely(*string)) {
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DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
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return -EINVAL;
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}
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if (unlikely(region_index >= sctx->nr_regions)) {
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DMWARN("invalid set_region_mappings region number: %lu >= %lu", region_index, sctx->nr_regions);
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return -EINVAL;
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}
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if (unlikely(path_nr >= sctx->nr_paths)) {
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DMWARN("invalid set_region_mappings device: %lu >= %u", path_nr, sctx->nr_paths);
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return -EINVAL;
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}
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switch_region_table_write(sctx, region_index, path_nr);
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}
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return 0;
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}
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/*
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* Messages are processed one-at-a-time.
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*
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* Only set_region_mappings is supported.
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*/
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static int switch_message(struct dm_target *ti, unsigned argc, char **argv)
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{
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static DEFINE_MUTEX(message_mutex);
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struct switch_ctx *sctx = ti->private;
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int r = -EINVAL;
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mutex_lock(&message_mutex);
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if (!strcasecmp(argv[0], "set_region_mappings"))
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r = process_set_region_mappings(sctx, argc, argv);
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else
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DMWARN("Unrecognised message received.");
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mutex_unlock(&message_mutex);
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return r;
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}
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static void switch_status(struct dm_target *ti, status_type_t type,
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unsigned status_flags, char *result, unsigned maxlen)
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{
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struct switch_ctx *sctx = ti->private;
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unsigned sz = 0;
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int path_nr;
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switch (type) {
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case STATUSTYPE_INFO:
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result[0] = '\0';
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break;
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case STATUSTYPE_TABLE:
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DMEMIT("%u %u 0", sctx->nr_paths, sctx->region_size);
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for (path_nr = 0; path_nr < sctx->nr_paths; path_nr++)
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DMEMIT(" %s %llu", sctx->path_list[path_nr].dmdev->name,
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(unsigned long long)sctx->path_list[path_nr].start);
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break;
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}
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}
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/*
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* Switch ioctl:
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*
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* Passthrough all ioctls to the path for sector 0
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*/
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static int switch_ioctl(struct dm_target *ti, unsigned cmd,
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unsigned long arg)
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{
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struct switch_ctx *sctx = ti->private;
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struct block_device *bdev;
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fmode_t mode;
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unsigned path_nr;
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int r = 0;
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path_nr = switch_get_path_nr(sctx, 0);
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bdev = sctx->path_list[path_nr].dmdev->bdev;
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mode = sctx->path_list[path_nr].dmdev->mode;
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/*
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* Only pass ioctls through if the device sizes match exactly.
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*/
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if (ti->len + sctx->path_list[path_nr].start != i_size_read(bdev->bd_inode) >> SECTOR_SHIFT)
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r = scsi_verify_blk_ioctl(NULL, cmd);
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return r ? : __blkdev_driver_ioctl(bdev, mode, cmd, arg);
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}
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static int switch_iterate_devices(struct dm_target *ti,
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iterate_devices_callout_fn fn, void *data)
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{
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struct switch_ctx *sctx = ti->private;
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int path_nr;
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int r;
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for (path_nr = 0; path_nr < sctx->nr_paths; path_nr++) {
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r = fn(ti, sctx->path_list[path_nr].dmdev,
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sctx->path_list[path_nr].start, ti->len, data);
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if (r)
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return r;
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}
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return 0;
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}
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static struct target_type switch_target = {
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.name = "switch",
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.version = {1, 0, 0},
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.module = THIS_MODULE,
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.ctr = switch_ctr,
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.dtr = switch_dtr,
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.map = switch_map,
|
|
.message = switch_message,
|
|
.status = switch_status,
|
|
.ioctl = switch_ioctl,
|
|
.iterate_devices = switch_iterate_devices,
|
|
};
|
|
|
|
static int __init dm_switch_init(void)
|
|
{
|
|
int r;
|
|
|
|
r = dm_register_target(&switch_target);
|
|
if (r < 0)
|
|
DMERR("dm_register_target() failed %d", r);
|
|
|
|
return r;
|
|
}
|
|
|
|
static void __exit dm_switch_exit(void)
|
|
{
|
|
dm_unregister_target(&switch_target);
|
|
}
|
|
|
|
module_init(dm_switch_init);
|
|
module_exit(dm_switch_exit);
|
|
|
|
MODULE_DESCRIPTION(DM_NAME " dynamic path switching target");
|
|
MODULE_AUTHOR("Kevin D. O'Kelley <Kevin_OKelley@dell.com>");
|
|
MODULE_AUTHOR("Narendran Ganapathy <Narendran_Ganapathy@dell.com>");
|
|
MODULE_AUTHOR("Jim Ramsay <Jim_Ramsay@dell.com>");
|
|
MODULE_AUTHOR("Mikulas Patocka <mpatocka@redhat.com>");
|
|
MODULE_LICENSE("GPL");
|