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* Copyright (C) 2001-2003 Sistina Software (UK) Limited.
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* This file is released under the GPL.
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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/blkdev.h>
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#include <linux/bio.h>
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#include <linux/slab.h>
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#include <linux/log2.h>
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#define DM_MSG_PREFIX "striped"
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#define DM_IO_ERROR_THRESHOLD 15
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sector_t physical_start;
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sector_t stripes_mask;
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/* The size of this target / num. stripes */
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sector_t stripe_width;
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/* stripe chunk size */
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/* Needed for handling events */
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/* Work struct used for triggering events*/
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struct work_struct trigger_event;
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struct stripe stripe[0];
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* An event is triggered whenever a drive
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* drops out of a stripe volume.
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static void trigger_event(struct work_struct *work)
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struct stripe_c *sc = container_of(work, struct stripe_c,
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dm_table_event(sc->ti->table);
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static inline struct stripe_c *alloc_context(unsigned int stripes)
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if (dm_array_too_big(sizeof(struct stripe_c), sizeof(struct stripe),
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len = sizeof(struct stripe_c) + (sizeof(struct stripe) * stripes);
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return kmalloc(len, GFP_KERNEL);
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* Parse a single <dev> <sector> pair
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static int get_stripe(struct dm_target *ti, struct stripe_c *sc,
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unsigned int stripe, char **argv)
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unsigned long long start;
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if (sscanf(argv[1], "%llu", &start) != 1)
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if (dm_get_device(ti, argv[0], dm_table_get_mode(ti->table),
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&sc->stripe[stripe].dev))
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sc->stripe[stripe].physical_start = start;
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* Construct a striped mapping.
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* <number of stripes> <chunk size (2^^n)> [<dev_path> <offset>]+
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static int stripe_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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ti->error = "Not enough arguments";
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stripes = simple_strtoul(argv[0], &end, 10);
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if (!stripes || *end) {
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ti->error = "Invalid stripe count";
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chunk_size = simple_strtoul(argv[1], &end, 10);
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ti->error = "Invalid chunk_size";
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* chunk_size is a power of two
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if (!is_power_of_2(chunk_size) ||
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(chunk_size < (PAGE_SIZE >> SECTOR_SHIFT))) {
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ti->error = "Invalid chunk size";
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if (ti->len & (chunk_size - 1)) {
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ti->error = "Target length not divisible by "
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if (sector_div(width, stripes)) {
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ti->error = "Target length not divisible by "
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* Do we have enough arguments for that many stripes ?
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if (argc != (2 + 2 * stripes)) {
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ti->error = "Not enough destinations "
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sc = alloc_context(stripes);
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ti->error = "Memory allocation for striped context "
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INIT_WORK(&sc->trigger_event, trigger_event);
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/* Set pointer to dm target; used in trigger_event */
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sc->stripes = stripes;
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sc->stripe_width = width;
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if (stripes & (stripes - 1))
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sc->stripes_shift = -1;
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sc->stripes_shift = ffs(stripes) - 1;
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sc->stripes_mask = ((sector_t) stripes) - 1;
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ti->split_io = chunk_size;
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ti->num_flush_requests = stripes;
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ti->num_discard_requests = stripes;
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sc->chunk_shift = ffs(chunk_size) - 1;
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sc->chunk_mask = ((sector_t) chunk_size) - 1;
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* Get the stripe destinations.
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for (i = 0; i < stripes; i++) {
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r = get_stripe(ti, sc, i, argv);
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ti->error = "Couldn't parse stripe destination";
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dm_put_device(ti, sc->stripe[i].dev);
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atomic_set(&(sc->stripe[i].error_count), 0);
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static void stripe_dtr(struct dm_target *ti)
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struct stripe_c *sc = (struct stripe_c *) ti->private;
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for (i = 0; i < sc->stripes; i++)
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dm_put_device(ti, sc->stripe[i].dev);
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flush_work_sync(&sc->trigger_event);
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static void stripe_map_sector(struct stripe_c *sc, sector_t sector,
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uint32_t *stripe, sector_t *result)
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sector_t offset = dm_target_offset(sc->ti, sector);
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sector_t chunk = offset >> sc->chunk_shift;
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if (sc->stripes_shift < 0)
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*stripe = sector_div(chunk, sc->stripes);
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*stripe = chunk & sc->stripes_mask;
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chunk >>= sc->stripes_shift;
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*result = (chunk << sc->chunk_shift) | (offset & sc->chunk_mask);
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static void stripe_map_range_sector(struct stripe_c *sc, sector_t sector,
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uint32_t target_stripe, sector_t *result)
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stripe_map_sector(sc, sector, &stripe, result);
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if (stripe == target_stripe)
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*result &= ~sc->chunk_mask; /* round down */
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if (target_stripe < stripe)
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*result += sc->chunk_mask + 1; /* next chunk */
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static int stripe_map_discard(struct stripe_c *sc, struct bio *bio,
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uint32_t target_stripe)
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stripe_map_range_sector(sc, bio->bi_sector, target_stripe, &begin);
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stripe_map_range_sector(sc, bio->bi_sector + bio_sectors(bio),
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target_stripe, &end);
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bio->bi_bdev = sc->stripe[target_stripe].dev->bdev;
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bio->bi_sector = begin + sc->stripe[target_stripe].physical_start;
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bio->bi_size = to_bytes(end - begin);
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return DM_MAPIO_REMAPPED;
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/* The range doesn't map to the target stripe */
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return DM_MAPIO_SUBMITTED;
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static int stripe_map(struct dm_target *ti, struct bio *bio,
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union map_info *map_context)
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struct stripe_c *sc = ti->private;
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unsigned target_request_nr;
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if (bio->bi_rw & REQ_FLUSH) {
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target_request_nr = map_context->target_request_nr;
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BUG_ON(target_request_nr >= sc->stripes);
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bio->bi_bdev = sc->stripe[target_request_nr].dev->bdev;
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return DM_MAPIO_REMAPPED;
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if (unlikely(bio->bi_rw & REQ_DISCARD)) {
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target_request_nr = map_context->target_request_nr;
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BUG_ON(target_request_nr >= sc->stripes);
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return stripe_map_discard(sc, bio, target_request_nr);
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stripe_map_sector(sc, bio->bi_sector, &stripe, &bio->bi_sector);
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bio->bi_sector += sc->stripe[stripe].physical_start;
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bio->bi_bdev = sc->stripe[stripe].dev->bdev;
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return DM_MAPIO_REMAPPED;
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* #stripes [stripe_name <stripe_name>] [group word count]
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* [error count 'A|D' <error count 'A|D'>]
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* #stripes [stripe chunk size]
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* [stripe_name physical_start <stripe_name physical_start>]
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static int stripe_status(struct dm_target *ti,
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status_type_t type, char *result, unsigned int maxlen)
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struct stripe_c *sc = (struct stripe_c *) ti->private;
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char buffer[sc->stripes + 1];
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case STATUSTYPE_INFO:
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DMEMIT("%d ", sc->stripes);
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for (i = 0; i < sc->stripes; i++) {
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DMEMIT("%s ", sc->stripe[i].dev->name);
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buffer[i] = atomic_read(&(sc->stripe[i].error_count)) ?
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DMEMIT("1 %s", buffer);
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case STATUSTYPE_TABLE:
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DMEMIT("%d %llu", sc->stripes,
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(unsigned long long)sc->chunk_mask + 1);
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for (i = 0; i < sc->stripes; i++)
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DMEMIT(" %s %llu", sc->stripe[i].dev->name,
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(unsigned long long)sc->stripe[i].physical_start);
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static int stripe_end_io(struct dm_target *ti, struct bio *bio,
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int error, union map_info *map_context)
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char major_minor[16];
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struct stripe_c *sc = ti->private;
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return 0; /* I/O complete */
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if ((error == -EWOULDBLOCK) && (bio->bi_rw & REQ_RAHEAD))
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if (error == -EOPNOTSUPP)
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memset(major_minor, 0, sizeof(major_minor));
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sprintf(major_minor, "%d:%d",
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MAJOR(disk_devt(bio->bi_bdev->bd_disk)),
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MINOR(disk_devt(bio->bi_bdev->bd_disk)));
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* Test to see which stripe drive triggered the event
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* and increment error count for all stripes on that device.
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* If the error count for a given device exceeds the threshold
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* value we will no longer trigger any further events.
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for (i = 0; i < sc->stripes; i++)
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if (!strcmp(sc->stripe[i].dev->name, major_minor)) {
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atomic_inc(&(sc->stripe[i].error_count));
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if (atomic_read(&(sc->stripe[i].error_count)) <
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DM_IO_ERROR_THRESHOLD)
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schedule_work(&sc->trigger_event);
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static int stripe_iterate_devices(struct dm_target *ti,
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iterate_devices_callout_fn fn, void *data)
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struct stripe_c *sc = ti->private;
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ret = fn(ti, sc->stripe[i].dev,
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sc->stripe[i].physical_start,
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sc->stripe_width, data);
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} while (!ret && ++i < sc->stripes);
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static void stripe_io_hints(struct dm_target *ti,
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struct queue_limits *limits)
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struct stripe_c *sc = ti->private;
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unsigned chunk_size = (sc->chunk_mask + 1) << 9;
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blk_limits_io_min(limits, chunk_size);
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blk_limits_io_opt(limits, chunk_size * sc->stripes);
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static int stripe_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
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struct bio_vec *biovec, int max_size)
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struct stripe_c *sc = ti->private;
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sector_t bvm_sector = bvm->bi_sector;
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struct request_queue *q;
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stripe_map_sector(sc, bvm_sector, &stripe, &bvm_sector);
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q = bdev_get_queue(sc->stripe[stripe].dev->bdev);
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if (!q->merge_bvec_fn)
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bvm->bi_bdev = sc->stripe[stripe].dev->bdev;
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bvm->bi_sector = sc->stripe[stripe].physical_start + bvm_sector;
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return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
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static struct target_type stripe_target = {
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.version = {1, 4, 0},
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.module = THIS_MODULE,
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.end_io = stripe_end_io,
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.status = stripe_status,
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.iterate_devices = stripe_iterate_devices,
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.io_hints = stripe_io_hints,
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.merge = stripe_merge,
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int __init dm_stripe_init(void)
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r = dm_register_target(&stripe_target);
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DMWARN("target registration failed");
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void dm_stripe_exit(void)
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dm_unregister_target(&stripe_target);