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-rw-r--r--drivers/md/dm-switch.c587
1 files changed, 587 insertions, 0 deletions
diff --git a/drivers/md/dm-switch.c b/drivers/md/dm-switch.c
new file mode 100644
index 000000000..bff4c7fa1
--- /dev/null
+++ b/drivers/md/dm-switch.c
@@ -0,0 +1,587 @@
+/*
+ * Copyright (C) 2010-2012 by Dell Inc. All rights reserved.
+ * Copyright (C) 2011-2013 Red Hat, Inc.
+ *
+ * This file is released under the GPL.
+ *
+ * dm-switch is a device-mapper target that maps IO to underlying block
+ * devices efficiently when there are a large number of fixed-sized
+ * address regions but there is no simple pattern to allow for a compact
+ * mapping representation such as dm-stripe.
+ */
+
+#include <linux/device-mapper.h>
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/vmalloc.h>
+
+#define DM_MSG_PREFIX "switch"
+
+/*
+ * One region_table_slot_t holds <region_entries_per_slot> region table
+ * entries each of which is <region_table_entry_bits> in size.
+ */
+typedef unsigned long region_table_slot_t;
+
+/*
+ * A device with the offset to its start sector.
+ */
+struct switch_path {
+ struct dm_dev *dmdev;
+ sector_t start;
+};
+
+/*
+ * Context block for a dm switch device.
+ */
+struct switch_ctx {
+ struct dm_target *ti;
+
+ unsigned nr_paths; /* Number of paths in path_list. */
+
+ unsigned region_size; /* Region size in 512-byte sectors */
+ unsigned long nr_regions; /* Number of regions making up the device */
+ signed char region_size_bits; /* log2 of region_size or -1 */
+
+ unsigned char region_table_entry_bits; /* Number of bits in one region table entry */
+ unsigned char region_entries_per_slot; /* Number of entries in one region table slot */
+ signed char region_entries_per_slot_bits; /* log2 of region_entries_per_slot or -1 */
+
+ region_table_slot_t *region_table; /* Region table */
+
+ /*
+ * Array of dm devices to switch between.
+ */
+ struct switch_path path_list[];
+};
+
+static struct switch_ctx *alloc_switch_ctx(struct dm_target *ti, unsigned nr_paths,
+ unsigned region_size)
+{
+ struct switch_ctx *sctx;
+
+ sctx = kzalloc(struct_size(sctx, path_list, nr_paths), GFP_KERNEL);
+ if (!sctx)
+ return NULL;
+
+ sctx->ti = ti;
+ sctx->region_size = region_size;
+
+ ti->private = sctx;
+
+ return sctx;
+}
+
+static int alloc_region_table(struct dm_target *ti, unsigned nr_paths)
+{
+ struct switch_ctx *sctx = ti->private;
+ sector_t nr_regions = ti->len;
+ sector_t nr_slots;
+
+ if (!(sctx->region_size & (sctx->region_size - 1)))
+ sctx->region_size_bits = __ffs(sctx->region_size);
+ else
+ sctx->region_size_bits = -1;
+
+ sctx->region_table_entry_bits = 1;
+ while (sctx->region_table_entry_bits < sizeof(region_table_slot_t) * 8 &&
+ (region_table_slot_t)1 << sctx->region_table_entry_bits < nr_paths)
+ sctx->region_table_entry_bits++;
+
+ sctx->region_entries_per_slot = (sizeof(region_table_slot_t) * 8) / sctx->region_table_entry_bits;
+ if (!(sctx->region_entries_per_slot & (sctx->region_entries_per_slot - 1)))
+ sctx->region_entries_per_slot_bits = __ffs(sctx->region_entries_per_slot);
+ else
+ sctx->region_entries_per_slot_bits = -1;
+
+ if (sector_div(nr_regions, sctx->region_size))
+ nr_regions++;
+
+ if (nr_regions >= ULONG_MAX) {
+ ti->error = "Region table too large";
+ return -EINVAL;
+ }
+ sctx->nr_regions = nr_regions;
+
+ nr_slots = nr_regions;
+ if (sector_div(nr_slots, sctx->region_entries_per_slot))
+ nr_slots++;
+
+ if (nr_slots > ULONG_MAX / sizeof(region_table_slot_t)) {
+ ti->error = "Region table too large";
+ return -EINVAL;
+ }
+
+ sctx->region_table = vmalloc(array_size(nr_slots,
+ sizeof(region_table_slot_t)));
+ if (!sctx->region_table) {
+ ti->error = "Cannot allocate region table";
+ return -ENOMEM;
+ }
+
+ return 0;
+}
+
+static void switch_get_position(struct switch_ctx *sctx, unsigned long region_nr,
+ unsigned long *region_index, unsigned *bit)
+{
+ if (sctx->region_entries_per_slot_bits >= 0) {
+ *region_index = region_nr >> sctx->region_entries_per_slot_bits;
+ *bit = region_nr & (sctx->region_entries_per_slot - 1);
+ } else {
+ *region_index = region_nr / sctx->region_entries_per_slot;
+ *bit = region_nr % sctx->region_entries_per_slot;
+ }
+
+ *bit *= sctx->region_table_entry_bits;
+}
+
+static unsigned switch_region_table_read(struct switch_ctx *sctx, unsigned long region_nr)
+{
+ unsigned long region_index;
+ unsigned bit;
+
+ switch_get_position(sctx, region_nr, &region_index, &bit);
+
+ return (READ_ONCE(sctx->region_table[region_index]) >> bit) &
+ ((1 << sctx->region_table_entry_bits) - 1);
+}
+
+/*
+ * Find which path to use at given offset.
+ */
+static unsigned switch_get_path_nr(struct switch_ctx *sctx, sector_t offset)
+{
+ unsigned path_nr;
+ sector_t p;
+
+ p = offset;
+ if (sctx->region_size_bits >= 0)
+ p >>= sctx->region_size_bits;
+ else
+ sector_div(p, sctx->region_size);
+
+ path_nr = switch_region_table_read(sctx, p);
+
+ /* This can only happen if the processor uses non-atomic stores. */
+ if (unlikely(path_nr >= sctx->nr_paths))
+ path_nr = 0;
+
+ return path_nr;
+}
+
+static void switch_region_table_write(struct switch_ctx *sctx, unsigned long region_nr,
+ unsigned value)
+{
+ unsigned long region_index;
+ unsigned bit;
+ region_table_slot_t pte;
+
+ switch_get_position(sctx, region_nr, &region_index, &bit);
+
+ pte = sctx->region_table[region_index];
+ pte &= ~((((region_table_slot_t)1 << sctx->region_table_entry_bits) - 1) << bit);
+ pte |= (region_table_slot_t)value << bit;
+ sctx->region_table[region_index] = pte;
+}
+
+/*
+ * Fill the region table with an initial round robin pattern.
+ */
+static void initialise_region_table(struct switch_ctx *sctx)
+{
+ unsigned path_nr = 0;
+ unsigned long region_nr;
+
+ for (region_nr = 0; region_nr < sctx->nr_regions; region_nr++) {
+ switch_region_table_write(sctx, region_nr, path_nr);
+ if (++path_nr >= sctx->nr_paths)
+ path_nr = 0;
+ }
+}
+
+static int parse_path(struct dm_arg_set *as, struct dm_target *ti)
+{
+ struct switch_ctx *sctx = ti->private;
+ unsigned long long start;
+ int r;
+
+ r = dm_get_device(ti, dm_shift_arg(as), dm_table_get_mode(ti->table),
+ &sctx->path_list[sctx->nr_paths].dmdev);
+ if (r) {
+ ti->error = "Device lookup failed";
+ return r;
+ }
+
+ if (kstrtoull(dm_shift_arg(as), 10, &start) || start != (sector_t)start) {
+ ti->error = "Invalid device starting offset";
+ dm_put_device(ti, sctx->path_list[sctx->nr_paths].dmdev);
+ return -EINVAL;
+ }
+
+ sctx->path_list[sctx->nr_paths].start = start;
+
+ sctx->nr_paths++;
+
+ return 0;
+}
+
+/*
+ * Destructor: Don't free the dm_target, just the ti->private data (if any).
+ */
+static void switch_dtr(struct dm_target *ti)
+{
+ struct switch_ctx *sctx = ti->private;
+
+ while (sctx->nr_paths--)
+ dm_put_device(ti, sctx->path_list[sctx->nr_paths].dmdev);
+
+ vfree(sctx->region_table);
+ kfree(sctx);
+}
+
+/*
+ * Constructor arguments:
+ * <num_paths> <region_size> <num_optional_args> [<optional_args>...]
+ * [<dev_path> <offset>]+
+ *
+ * Optional args are to allow for future extension: currently this
+ * parameter must be 0.
+ */
+static int switch_ctr(struct dm_target *ti, unsigned argc, char **argv)
+{
+ static const struct dm_arg _args[] = {
+ {1, (KMALLOC_MAX_SIZE - sizeof(struct switch_ctx)) / sizeof(struct switch_path), "Invalid number of paths"},
+ {1, UINT_MAX, "Invalid region size"},
+ {0, 0, "Invalid number of optional args"},
+ };
+
+ struct switch_ctx *sctx;
+ struct dm_arg_set as;
+ unsigned nr_paths, region_size, nr_optional_args;
+ int r;
+
+ as.argc = argc;
+ as.argv = argv;
+
+ r = dm_read_arg(_args, &as, &nr_paths, &ti->error);
+ if (r)
+ return -EINVAL;
+
+ r = dm_read_arg(_args + 1, &as, &region_size, &ti->error);
+ if (r)
+ return r;
+
+ r = dm_read_arg_group(_args + 2, &as, &nr_optional_args, &ti->error);
+ if (r)
+ return r;
+ /* parse optional arguments here, if we add any */
+
+ if (as.argc != nr_paths * 2) {
+ ti->error = "Incorrect number of path arguments";
+ return -EINVAL;
+ }
+
+ sctx = alloc_switch_ctx(ti, nr_paths, region_size);
+ if (!sctx) {
+ ti->error = "Cannot allocate redirection context";
+ return -ENOMEM;
+ }
+
+ r = dm_set_target_max_io_len(ti, region_size);
+ if (r)
+ goto error;
+
+ while (as.argc) {
+ r = parse_path(&as, ti);
+ if (r)
+ goto error;
+ }
+
+ r = alloc_region_table(ti, nr_paths);
+ if (r)
+ goto error;
+
+ initialise_region_table(sctx);
+
+ /* For UNMAP, sending the request down any path is sufficient */
+ ti->num_discard_bios = 1;
+
+ return 0;
+
+error:
+ switch_dtr(ti);
+
+ return r;
+}
+
+static int switch_map(struct dm_target *ti, struct bio *bio)
+{
+ struct switch_ctx *sctx = ti->private;
+ sector_t offset = dm_target_offset(ti, bio->bi_iter.bi_sector);
+ unsigned path_nr = switch_get_path_nr(sctx, offset);
+
+ bio_set_dev(bio, sctx->path_list[path_nr].dmdev->bdev);
+ bio->bi_iter.bi_sector = sctx->path_list[path_nr].start + offset;
+
+ return DM_MAPIO_REMAPPED;
+}
+
+/*
+ * We need to parse hex numbers in the message as quickly as possible.
+ *
+ * This table-based hex parser improves performance.
+ * It improves a time to load 1000000 entries compared to the condition-based
+ * parser.
+ * table-based parser condition-based parser
+ * PA-RISC 0.29s 0.31s
+ * Opteron 0.0495s 0.0498s
+ */
+static const unsigned char hex_table[256] = {
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 255, 255, 255, 255, 255, 255,
+255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 10, 11, 12, 13, 14, 15, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255,
+255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255
+};
+
+static __always_inline unsigned long parse_hex(const char **string)
+{
+ unsigned char d;
+ unsigned long r = 0;
+
+ while ((d = hex_table[(unsigned char)**string]) < 16) {
+ r = (r << 4) | d;
+ (*string)++;
+ }
+
+ return r;
+}
+
+static int process_set_region_mappings(struct switch_ctx *sctx,
+ unsigned argc, char **argv)
+{
+ unsigned i;
+ unsigned long region_index = 0;
+
+ for (i = 1; i < argc; i++) {
+ unsigned long path_nr;
+ const char *string = argv[i];
+
+ if ((*string & 0xdf) == 'R') {
+ unsigned long cycle_length, num_write;
+
+ string++;
+ if (unlikely(*string == ',')) {
+ DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+ return -EINVAL;
+ }
+ cycle_length = parse_hex(&string);
+ if (unlikely(*string != ',')) {
+ DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+ return -EINVAL;
+ }
+ string++;
+ if (unlikely(!*string)) {
+ DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+ return -EINVAL;
+ }
+ num_write = parse_hex(&string);
+ if (unlikely(*string)) {
+ DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+ return -EINVAL;
+ }
+
+ if (unlikely(!cycle_length) || unlikely(cycle_length - 1 > region_index)) {
+ DMWARN("invalid set_region_mappings cycle length: %lu > %lu",
+ cycle_length - 1, region_index);
+ return -EINVAL;
+ }
+ if (unlikely(region_index + num_write < region_index) ||
+ unlikely(region_index + num_write >= sctx->nr_regions)) {
+ DMWARN("invalid set_region_mappings region number: %lu + %lu >= %lu",
+ region_index, num_write, sctx->nr_regions);
+ return -EINVAL;
+ }
+
+ while (num_write--) {
+ region_index++;
+ path_nr = switch_region_table_read(sctx, region_index - cycle_length);
+ switch_region_table_write(sctx, region_index, path_nr);
+ }
+
+ continue;
+ }
+
+ if (*string == ':')
+ region_index++;
+ else {
+ region_index = parse_hex(&string);
+ if (unlikely(*string != ':')) {
+ DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+ return -EINVAL;
+ }
+ }
+
+ string++;
+ if (unlikely(!*string)) {
+ DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+ return -EINVAL;
+ }
+
+ path_nr = parse_hex(&string);
+ if (unlikely(*string)) {
+ DMWARN("invalid set_region_mappings argument: '%s'", argv[i]);
+ return -EINVAL;
+ }
+ if (unlikely(region_index >= sctx->nr_regions)) {
+ DMWARN("invalid set_region_mappings region number: %lu >= %lu", region_index, sctx->nr_regions);
+ return -EINVAL;
+ }
+ if (unlikely(path_nr >= sctx->nr_paths)) {
+ DMWARN("invalid set_region_mappings device: %lu >= %u", path_nr, sctx->nr_paths);
+ return -EINVAL;
+ }
+
+ switch_region_table_write(sctx, region_index, path_nr);
+ }
+
+ return 0;
+}
+
+/*
+ * Messages are processed one-at-a-time.
+ *
+ * Only set_region_mappings is supported.
+ */
+static int switch_message(struct dm_target *ti, unsigned argc, char **argv,
+ char *result, unsigned maxlen)
+{
+ static DEFINE_MUTEX(message_mutex);
+
+ struct switch_ctx *sctx = ti->private;
+ int r = -EINVAL;
+
+ mutex_lock(&message_mutex);
+
+ if (!strcasecmp(argv[0], "set_region_mappings"))
+ r = process_set_region_mappings(sctx, argc, argv);
+ else
+ DMWARN("Unrecognised message received.");
+
+ mutex_unlock(&message_mutex);
+
+ return r;
+}
+
+static void switch_status(struct dm_target *ti, status_type_t type,
+ unsigned status_flags, char *result, unsigned maxlen)
+{
+ struct switch_ctx *sctx = ti->private;
+ unsigned sz = 0;
+ int path_nr;
+
+ switch (type) {
+ case STATUSTYPE_INFO:
+ result[0] = '\0';
+ break;
+
+ case STATUSTYPE_TABLE:
+ DMEMIT("%u %u 0", sctx->nr_paths, sctx->region_size);
+ for (path_nr = 0; path_nr < sctx->nr_paths; path_nr++)
+ DMEMIT(" %s %llu", sctx->path_list[path_nr].dmdev->name,
+ (unsigned long long)sctx->path_list[path_nr].start);
+ break;
+ }
+}
+
+/*
+ * Switch ioctl:
+ *
+ * Passthrough all ioctls to the path for sector 0
+ */
+static int switch_prepare_ioctl(struct dm_target *ti, struct block_device **bdev)
+{
+ struct switch_ctx *sctx = ti->private;
+ unsigned path_nr;
+
+ path_nr = switch_get_path_nr(sctx, 0);
+
+ *bdev = sctx->path_list[path_nr].dmdev->bdev;
+
+ /*
+ * Only pass ioctls through if the device sizes match exactly.
+ */
+ if (ti->len + sctx->path_list[path_nr].start !=
+ i_size_read((*bdev)->bd_inode) >> SECTOR_SHIFT)
+ return 1;
+ return 0;
+}
+
+static int switch_iterate_devices(struct dm_target *ti,
+ iterate_devices_callout_fn fn, void *data)
+{
+ struct switch_ctx *sctx = ti->private;
+ int path_nr;
+ int r;
+
+ for (path_nr = 0; path_nr < sctx->nr_paths; path_nr++) {
+ r = fn(ti, sctx->path_list[path_nr].dmdev,
+ sctx->path_list[path_nr].start, ti->len, data);
+ if (r)
+ return r;
+ }
+
+ return 0;
+}
+
+static struct target_type switch_target = {
+ .name = "switch",
+ .version = {1, 1, 0},
+ .module = THIS_MODULE,
+ .ctr = switch_ctr,
+ .dtr = switch_dtr,
+ .map = switch_map,
+ .message = switch_message,
+ .status = switch_status,
+ .prepare_ioctl = switch_prepare_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");
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