OSCL-LXR linux-6.0.1/​drivers/​md/​dm-snap-persistent.c	Source navigation Diff markup Identifier search General search
	Version: linux-6.0.1 spark-3.0.0 hadoop-3.2.0-src hadoop-3.3.0-src spark-2.4.7 linux-4.15.13 hadoop-2.7.4-src Revert   Change

 /*
  * Copyright (C) 2001-2002 Sistina Software (UK) Limited.
  * Copyright (C) 2006-2008 Red Hat GmbH
  *
  * This file is released under the GPL.
  */
 
 #include "dm-exception-store.h"
 
 #include <linux/ctype.h>
 #include <linux/mm.h>
 #include <linux/pagemap.h>
 #include <linux/vmalloc.h>
 #include <linux/export.h>
 #include <linux/slab.h>
 #include <linux/dm-io.h>
 #include <linux/dm-bufio.h>
 
 #define DM_MSG_PREFIX "persistent snapshot"
 #define DM_CHUNK_SIZE_DEFAULT_SECTORS 32U   /* 16KB */
 
 #define DM_PREFETCH_CHUNKS      12
 
 /*-----------------------------------------------------------------
  * Persistent snapshots, by persistent we mean that the snapshot
  * will survive a reboot.
  *---------------------------------------------------------------*/
 
 /*
  * We need to store a record of which parts of the origin have
  * been copied to the snapshot device.  The snapshot code
  * requires that we copy exception chunks to chunk aligned areas
  * of the COW store.  It makes sense therefore, to store the
  * metadata in chunk size blocks.
  *
  * There is no backward or forward compatibility implemented,
  * snapshots with different disk versions than the kernel will
  * not be usable.  It is expected that "lvcreate" will blank out
  * the start of a fresh COW device before calling the snapshot
  * constructor.
  *
  * The first chunk of the COW device just contains the header.
  * After this there is a chunk filled with exception metadata,
  * followed by as many exception chunks as can fit in the
  * metadata areas.
  *
  * All on disk structures are in little-endian format.  The end
  * of the exceptions info is indicated by an exception with a
  * new_chunk of 0, which is invalid since it would point to the
  * header chunk.
  */
 
 /*
  * Magic for persistent snapshots: "SnAp" - Feeble isn't it.
  */
 #define SNAP_MAGIC 0x70416e53
 
 /*
  * The on-disk version of the metadata.
  */
 #define SNAPSHOT_DISK_VERSION 1
 
 #define NUM_SNAPSHOT_HDR_CHUNKS 1
 
 struct disk_header {
     __le32 magic;
 
     /*
      * Is this snapshot valid.  There is no way of recovering
      * an invalid snapshot.
      */
     __le32 valid;
 
     /*
      * Simple, incrementing version. no backward
      * compatibility.
      */
     __le32 version;
 
     /* In sectors */
     __le32 chunk_size;
 } __packed;
 
 struct disk_exception {
     __le64 old_chunk;
     __le64 new_chunk;
 } __packed;
 
 struct core_exception {
     uint64_t old_chunk;
     uint64_t new_chunk;
 };
 
 struct commit_callback {
     void (*callback)(void *, int success);
     void *context;
 };
 
 /*
  * The top level structure for a persistent exception store.
  */
 struct pstore {
     struct dm_exception_store *store;
     int version;
     int valid;
     uint32_t exceptions_per_area;
 
     /*
      * Now that we have an asynchronous kcopyd there is no
      * need for large chunk sizes, so it wont hurt to have a
      * whole chunks worth of metadata in memory at once.
      */
     void *area;
 
     /*
      * An area of zeros used to clear the next area.
      */
     void *zero_area;
 
     /*
      * An area used for header. The header can be written
      * concurrently with metadata (when invalidating the snapshot),
      * so it needs a separate buffer.
      */
     void *header_area;
 
     /*
      * Used to keep track of which metadata area the data in
      * 'chunk' refers to.
      */
     chunk_t current_area;
 
     /*
      * The next free chunk for an exception.
      *
      * When creating exceptions, all the chunks here and above are
      * free.  It holds the next chunk to be allocated.  On rare
      * occasions (e.g. after a system crash) holes can be left in
      * the exception store because chunks can be committed out of
      * order.
      *
      * When merging exceptions, it does not necessarily mean all the
      * chunks here and above are free.  It holds the value it would
      * have held if all chunks had been committed in order of
      * allocation.  Consequently the value may occasionally be
      * slightly too low, but since it's only used for 'status' and
      * it can never reach its minimum value too early this doesn't
      * matter.
      */
 
     chunk_t next_free;
 
     /*
      * The index of next free exception in the current
      * metadata area.
      */
     uint32_t current_committed;
 
     atomic_t pending_count;
     uint32_t callback_count;
     struct commit_callback *callbacks;
     struct dm_io_client *io_client;
 
     struct workqueue_struct *metadata_wq;
 };
 
 static int alloc_area(struct pstore *ps)
 {
     int r = -ENOMEM;
     size_t len;
 
     len = ps->store->chunk_size << SECTOR_SHIFT;
 
     /*
      * Allocate the chunk_size block of memory that will hold
      * a single metadata area.
      */
     ps->area = vmalloc(len);
     if (!ps->area)
         goto err_area;
 
     ps->zero_area = vzalloc(len);
     if (!ps->zero_area)
         goto err_zero_area;
 
     ps->header_area = vmalloc(len);
     if (!ps->header_area)
         goto err_header_area;
 
     return 0;
 
 err_header_area:
     vfree(ps->zero_area);
 
 err_zero_area:
     vfree(ps->area);
 
 err_area:
     return r;
 }
 
 static void free_area(struct pstore *ps)
 {
     vfree(ps->area);
     ps->area = NULL;
     vfree(ps->zero_area);
     ps->zero_area = NULL;
     vfree(ps->header_area);
     ps->header_area = NULL;
 }
 
 struct mdata_req {
     struct dm_io_region *where;
     struct dm_io_request *io_req;
     struct work_struct work;
     int result;
 };
 
 static void do_metadata(struct work_struct *work)
 {
     struct mdata_req *req = container_of(work, struct mdata_req, work);
 
     req->result = dm_io(req->io_req, 1, req->where, NULL);
 }
 
 /*
  * Read or write a chunk aligned and sized block of data from a device.
  */
 static int chunk_io(struct pstore *ps, void *area, chunk_t chunk, blk_opf_t opf,
             int metadata)
 {
     struct dm_io_region where = {
         .bdev = dm_snap_cow(ps->store->snap)->bdev,
         .sector = ps->store->chunk_size * chunk,
         .count = ps->store->chunk_size,
     };
     struct dm_io_request io_req = {
         .bi_opf = opf,
         .mem.type = DM_IO_VMA,
         .mem.ptr.vma = area,
         .client = ps->io_client,
         .notify.fn = NULL,
     };
     struct mdata_req req;
 
     if (!metadata)
         return dm_io(&io_req, 1, &where, NULL);
 
     req.where = &where;
     req.io_req = &io_req;
 
     /*
      * Issue the synchronous I/O from a different thread
      * to avoid submit_bio_noacct recursion.
      */
     INIT_WORK_ONSTACK(&req.work, do_metadata);
     queue_work(ps->metadata_wq, &req.work);
     flush_workqueue(ps->metadata_wq);
     destroy_work_on_stack(&req.work);
 
     return req.result;
 }
 
 /*
  * Convert a metadata area index to a chunk index.
  */
 static chunk_t area_location(struct pstore *ps, chunk_t area)
 {
     return NUM_SNAPSHOT_HDR_CHUNKS + ((ps->exceptions_per_area + 1) * area);
 }
 
 static void skip_metadata(struct pstore *ps)
 {
     uint32_t stride = ps->exceptions_per_area + 1;
     chunk_t next_free = ps->next_free;
     if (sector_div(next_free, stride) == NUM_SNAPSHOT_HDR_CHUNKS)
         ps->next_free++;
 }
 
 /*
  * Read or write a metadata area.  Remembering to skip the first
  * chunk which holds the header.
  */
 static int area_io(struct pstore *ps, blk_opf_t opf)
 {
     chunk_t chunk = area_location(ps, ps->current_area);
 
     return chunk_io(ps, ps->area, chunk, opf, 0);
 }
 
 static void zero_memory_area(struct pstore *ps)
 {
     memset(ps->area, 0, ps->store->chunk_size << SECTOR_SHIFT);
 }
 
 static int zero_disk_area(struct pstore *ps, chunk_t area)
 {
     return chunk_io(ps, ps->zero_area, area_location(ps, area),
             REQ_OP_WRITE, 0);
 }
 
 static int read_header(struct pstore *ps, int *new_snapshot)
 {
     int r;
     struct disk_header *dh;
     unsigned chunk_size;
     int chunk_size_supplied = 1;
     char *chunk_err;
 
     /*
      * Use default chunk size (or logical_block_size, if larger)
      * if none supplied
      */
     if (!ps->store->chunk_size) {
         ps->store->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS,
             bdev_logical_block_size(dm_snap_cow(ps->store->snap)->
                         bdev) >> 9);
         ps->store->chunk_mask = ps->store->chunk_size - 1;
         ps->store->chunk_shift = __ffs(ps->store->chunk_size);
         chunk_size_supplied = 0;
     }
 
     ps->io_client = dm_io_client_create();
     if (IS_ERR(ps->io_client))
         return PTR_ERR(ps->io_client);
 
     r = alloc_area(ps);
     if (r)
         return r;
 
     r = chunk_io(ps, ps->header_area, 0, REQ_OP_READ, 1);
     if (r)
         goto bad;
 
     dh = ps->header_area;
 
     if (le32_to_cpu(dh->magic) == 0) {
         *new_snapshot = 1;
         return 0;
     }
 
     if (le32_to_cpu(dh->magic) != SNAP_MAGIC) {
         DMWARN("Invalid or corrupt snapshot");
         r = -ENXIO;
         goto bad;
     }
 
     *new_snapshot = 0;
     ps->valid = le32_to_cpu(dh->valid);
     ps->version = le32_to_cpu(dh->version);
     chunk_size = le32_to_cpu(dh->chunk_size);
 
     if (ps->store->chunk_size == chunk_size)
         return 0;
 
     if (chunk_size_supplied)
         DMWARN("chunk size %u in device metadata overrides "
                "table chunk size of %u.",
                chunk_size, ps->store->chunk_size);
 
     /* We had a bogus chunk_size. Fix stuff up. */
     free_area(ps);
 
     r = dm_exception_store_set_chunk_size(ps->store, chunk_size,
                           &chunk_err);
     if (r) {
         DMERR("invalid on-disk chunk size %u: %s.",
               chunk_size, chunk_err);
         return r;
     }
 
     r = alloc_area(ps);
     return r;
 
 bad:
     free_area(ps);
     return r;
 }
 
 static int write_header(struct pstore *ps)
 {
     struct disk_header *dh;
 
     memset(ps->header_area, 0, ps->store->chunk_size << SECTOR_SHIFT);
 
     dh = ps->header_area;
     dh->magic = cpu_to_le32(SNAP_MAGIC);
     dh->valid = cpu_to_le32(ps->valid);
     dh->version = cpu_to_le32(ps->version);
     dh->chunk_size = cpu_to_le32(ps->store->chunk_size);
 
     return chunk_io(ps, ps->header_area, 0, REQ_OP_WRITE, 1);
 }
 
 /*
  * Access functions for the disk exceptions, these do the endian conversions.
  */
 static struct disk_exception *get_exception(struct pstore *ps, void *ps_area,
                         uint32_t index)
 {
     BUG_ON(index >= ps->exceptions_per_area);
 
     return ((struct disk_exception *) ps_area) + index;
 }
 
 static void read_exception(struct pstore *ps, void *ps_area,
                uint32_t index, struct core_exception *result)
 {
     struct disk_exception *de = get_exception(ps, ps_area, index);
 
     /* copy it */
     result->old_chunk = le64_to_cpu(de->old_chunk);
     result->new_chunk = le64_to_cpu(de->new_chunk);
 }
 
 static void write_exception(struct pstore *ps,
                 uint32_t index, struct core_exception *e)
 {
     struct disk_exception *de = get_exception(ps, ps->area, index);
 
     /* copy it */
     de->old_chunk = cpu_to_le64(e->old_chunk);
     de->new_chunk = cpu_to_le64(e->new_chunk);
 }
 
 static void clear_exception(struct pstore *ps, uint32_t index)
 {
     struct disk_exception *de = get_exception(ps, ps->area, index);
 
     /* clear it */
     de->old_chunk = 0;
     de->new_chunk = 0;
 }
 
 /*
  * Registers the exceptions that are present in the current area.
  * 'full' is filled in to indicate if the area has been
  * filled.
  */
 static int insert_exceptions(struct pstore *ps, void *ps_area,
                  int (*callback)(void *callback_context,
                          chunk_t old, chunk_t new),
                  void *callback_context,
                  int *full)
 {
     int r;
     unsigned int i;
     struct core_exception e;
 
     /* presume the area is full */
     *full = 1;
 
     for (i = 0; i < ps->exceptions_per_area; i++) {
         read_exception(ps, ps_area, i, &e);
 
         /*
          * If the new_chunk is pointing at the start of
          * the COW device, where the first metadata area
          * is we know that we've hit the end of the
          * exceptions.  Therefore the area is not full.
          */
         if (e.new_chunk == 0LL) {
             ps->current_committed = i;
             *full = 0;
             break;
         }
 
         /*
          * Keep track of the start of the free chunks.
          */
         if (ps->next_free <= e.new_chunk)
             ps->next_free = e.new_chunk + 1;
 
         /*
          * Otherwise we add the exception to the snapshot.
          */
         r = callback(callback_context, e.old_chunk, e.new_chunk);
         if (r)
             return r;
     }
 
     return 0;
 }
 
 static int read_exceptions(struct pstore *ps,
                int (*callback)(void *callback_context, chunk_t old,
                        chunk_t new),
                void *callback_context)
 {
     int r, full = 1;
     struct dm_bufio_client *client;
     chunk_t prefetch_area = 0;
 
     client = dm_bufio_client_create(dm_snap_cow(ps->store->snap)->bdev,
                     ps->store->chunk_size << SECTOR_SHIFT,
                     1, 0, NULL, NULL, 0);
 
     if (IS_ERR(client))
         return PTR_ERR(client);
 
     /*
      * Setup for one current buffer + desired readahead buffers.
      */
     dm_bufio_set_minimum_buffers(client, 1 + DM_PREFETCH_CHUNKS);
 
     /*
      * Keeping reading chunks and inserting exceptions until
      * we find a partially full area.
      */
     for (ps->current_area = 0; full; ps->current_area++) {
         struct dm_buffer *bp;
         void *area;
         chunk_t chunk;
 
         if (unlikely(prefetch_area < ps->current_area))
             prefetch_area = ps->current_area;
 
         if (DM_PREFETCH_CHUNKS) do {
             chunk_t pf_chunk = area_location(ps, prefetch_area);
             if (unlikely(pf_chunk >= dm_bufio_get_device_size(client)))
                 break;
             dm_bufio_prefetch(client, pf_chunk, 1);
             prefetch_area++;
             if (unlikely(!prefetch_area))
                 break;
         } while (prefetch_area <= ps->current_area + DM_PREFETCH_CHUNKS);
 
         chunk = area_location(ps, ps->current_area);
 
         area = dm_bufio_read(client, chunk, &bp);
         if (IS_ERR(area)) {
             r = PTR_ERR(area);
             goto ret_destroy_bufio;
         }
 
         r = insert_exceptions(ps, area, callback, callback_context,
                       &full);
 
         if (!full)
             memcpy(ps->area, area, ps->store->chunk_size << SECTOR_SHIFT);
 
         dm_bufio_release(bp);
 
         dm_bufio_forget(client, chunk);
 
         if (unlikely(r))
             goto ret_destroy_bufio;
     }
 
     ps->current_area--;
 
     skip_metadata(ps);
 
     r = 0;
 
 ret_destroy_bufio:
     dm_bufio_client_destroy(client);
 
     return r;
 }
 
 static struct pstore *get_info(struct dm_exception_store *store)
 {
     return (struct pstore *) store->context;
 }
 
 static void persistent_usage(struct dm_exception_store *store,
                  sector_t *total_sectors,
                  sector_t *sectors_allocated,
                  sector_t *metadata_sectors)
 {
     struct pstore *ps = get_info(store);
 
     *sectors_allocated = ps->next_free * store->chunk_size;
     *total_sectors = get_dev_size(dm_snap_cow(store->snap)->bdev);
 
     /*
      * First chunk is the fixed header.
      * Then there are (ps->current_area + 1) metadata chunks, each one
      * separated from the next by ps->exceptions_per_area data chunks.
      */
     *metadata_sectors = (ps->current_area + 1 + NUM_SNAPSHOT_HDR_CHUNKS) *
                 store->chunk_size;
 }
 
 static void persistent_dtr(struct dm_exception_store *store)
 {
     struct pstore *ps = get_info(store);
 
     destroy_workqueue(ps->metadata_wq);
 
     /* Created in read_header */
     if (ps->io_client)
         dm_io_client_destroy(ps->io_client);
     free_area(ps);
 
     /* Allocated in persistent_read_metadata */
     kvfree(ps->callbacks);
 
     kfree(ps);
 }
 
 static int persistent_read_metadata(struct dm_exception_store *store,
                     int (*callback)(void *callback_context,
                             chunk_t old, chunk_t new),
                     void *callback_context)
 {
     int r, new_snapshot;
     struct pstore *ps = get_info(store);
 
     /*
      * Read the snapshot header.
      */
     r = read_header(ps, &new_snapshot);
     if (r)
         return r;
 
     /*
      * Now we know correct chunk_size, complete the initialisation.
      */
     ps->exceptions_per_area = (ps->store->chunk_size << SECTOR_SHIFT) /
                   sizeof(struct disk_exception);
     ps->callbacks = kvcalloc(ps->exceptions_per_area,
                  sizeof(*ps->callbacks), GFP_KERNEL);
     if (!ps->callbacks)
         return -ENOMEM;
 
     /*
      * Do we need to setup a new snapshot ?
      */
     if (new_snapshot) {
         r = write_header(ps);
         if (r) {
             DMWARN("write_header failed");
             return r;
         }
 
         ps->current_area = 0;
         zero_memory_area(ps);
         r = zero_disk_area(ps, 0);
         if (r)
             DMWARN("zero_disk_area(0) failed");
         return r;
     }
     /*
      * Sanity checks.
      */
     if (ps->version != SNAPSHOT_DISK_VERSION) {
         DMWARN("unable to handle snapshot disk version %d",
                ps->version);
         return -EINVAL;
     }
 
     /*
      * Metadata are valid, but snapshot is invalidated
      */
     if (!ps->valid)
         return 1;
 
     /*
      * Read the metadata.
      */
     r = read_exceptions(ps, callback, callback_context);
 
     return r;
 }
 
 static int persistent_prepare_exception(struct dm_exception_store *store,
                     struct dm_exception *e)
 {
     struct pstore *ps = get_info(store);
     sector_t size = get_dev_size(dm_snap_cow(store->snap)->bdev);
 
     /* Is there enough room ? */
     if (size < ((ps->next_free + 1) * store->chunk_size))
         return -ENOSPC;
 
     e->new_chunk = ps->next_free;
 
     /*
      * Move onto the next free pending, making sure to take
      * into account the location of the metadata chunks.
      */
     ps->next_free++;
     skip_metadata(ps);
 
     atomic_inc(&ps->pending_count);
     return 0;
 }
 
 static void persistent_commit_exception(struct dm_exception_store *store,
                     struct dm_exception *e, int valid,
                     void (*callback) (void *, int success),
                     void *callback_context)
 {
     unsigned int i;
     struct pstore *ps = get_info(store);
     struct core_exception ce;
     struct commit_callback *cb;
 
     if (!valid)
         ps->valid = 0;
 
     ce.old_chunk = e->old_chunk;
     ce.new_chunk = e->new_chunk;
     write_exception(ps, ps->current_committed++, &ce);
 
     /*
      * Add the callback to the back of the array.  This code
      * is the only place where the callback array is
      * manipulated, and we know that it will never be called
      * multiple times concurrently.
      */
     cb = ps->callbacks + ps->callback_count++;
     cb->callback = callback;
     cb->context = callback_context;
 
     /*
      * If there are exceptions in flight and we have not yet
      * filled this metadata area there's nothing more to do.
      */
     if (!atomic_dec_and_test(&ps->pending_count) &&
         (ps->current_committed != ps->exceptions_per_area))
         return;
 
     /*
      * If we completely filled the current area, then wipe the next one.
      */
     if ((ps->current_committed == ps->exceptions_per_area) &&
         zero_disk_area(ps, ps->current_area + 1))
         ps->valid = 0;
 
     /*
      * Commit exceptions to disk.
      */
     if (ps->valid && area_io(ps, REQ_OP_WRITE | REQ_PREFLUSH | REQ_FUA |
                  REQ_SYNC))
         ps->valid = 0;
 
     /*
      * Advance to the next area if this one is full.
      */
     if (ps->current_committed == ps->exceptions_per_area) {
         ps->current_committed = 0;
         ps->current_area++;
         zero_memory_area(ps);
     }
 
     for (i = 0; i < ps->callback_count; i++) {
         cb = ps->callbacks + i;
         cb->callback(cb->context, ps->valid);
     }
 
     ps->callback_count = 0;
 }
 
 static int persistent_prepare_merge(struct dm_exception_store *store,
                     chunk_t *last_old_chunk,
                     chunk_t *last_new_chunk)
 {
     struct pstore *ps = get_info(store);
     struct core_exception ce;
     int nr_consecutive;
     int r;
 
     /*
      * When current area is empty, move back to preceding area.
      */
     if (!ps->current_committed) {
         /*
          * Have we finished?
          */
         if (!ps->current_area)
             return 0;
 
         ps->current_area--;
         r = area_io(ps, REQ_OP_READ);
         if (r < 0)
             return r;
         ps->current_committed = ps->exceptions_per_area;
     }
 
     read_exception(ps, ps->area, ps->current_committed - 1, &ce);
     *last_old_chunk = ce.old_chunk;
     *last_new_chunk = ce.new_chunk;
 
     /*
      * Find number of consecutive chunks within the current area,
      * working backwards.
      */
     for (nr_consecutive = 1; nr_consecutive < ps->current_committed;
          nr_consecutive++) {
         read_exception(ps, ps->area,
                    ps->current_committed - 1 - nr_consecutive, &ce);
         if (ce.old_chunk != *last_old_chunk - nr_consecutive ||
             ce.new_chunk != *last_new_chunk - nr_consecutive)
             break;
     }
 
     return nr_consecutive;
 }
 
 static int persistent_commit_merge(struct dm_exception_store *store,
                    int nr_merged)
 {
     int r, i;
     struct pstore *ps = get_info(store);
 
     BUG_ON(nr_merged > ps->current_committed);
 
     for (i = 0; i < nr_merged; i++)
         clear_exception(ps, ps->current_committed - 1 - i);
 
     r = area_io(ps, REQ_OP_WRITE | REQ_PREFLUSH | REQ_FUA);
     if (r < 0)
         return r;
 
     ps->current_committed -= nr_merged;
 
     /*
      * At this stage, only persistent_usage() uses ps->next_free, so
      * we make no attempt to keep ps->next_free strictly accurate
      * as exceptions may have been committed out-of-order originally.
      * Once a snapshot has become merging, we set it to the value it
      * would have held had all the exceptions been committed in order.
      *
      * ps->current_area does not get reduced by prepare_merge() until
      * after commit_merge() has removed the nr_merged previous exceptions.
      */
     ps->next_free = area_location(ps, ps->current_area) +
             ps->current_committed + 1;
 
     return 0;
 }
 
 static void persistent_drop_snapshot(struct dm_exception_store *store)
 {
     struct pstore *ps = get_info(store);
 
     ps->valid = 0;
     if (write_header(ps))
         DMWARN("write header failed");
 }
 
 static int persistent_ctr(struct dm_exception_store *store, char *options)
 {
     struct pstore *ps;
     int r;
 
     /* allocate the pstore */
     ps = kzalloc(sizeof(*ps), GFP_KERNEL);
     if (!ps)
         return -ENOMEM;
 
     ps->store = store;
     ps->valid = 1;
     ps->version = SNAPSHOT_DISK_VERSION;
     ps->area = NULL;
     ps->zero_area = NULL;
     ps->header_area = NULL;
     ps->next_free = NUM_SNAPSHOT_HDR_CHUNKS + 1; /* header and 1st area */
     ps->current_committed = 0;
 
     ps->callback_count = 0;
     atomic_set(&ps->pending_count, 0);
     ps->callbacks = NULL;
 
     ps->metadata_wq = alloc_workqueue("ksnaphd", WQ_MEM_RECLAIM, 0);
     if (!ps->metadata_wq) {
         DMERR("couldn't start header metadata update thread");
         r = -ENOMEM;
         goto err_workqueue;
     }
 
     if (options) {
         char overflow = toupper(options[0]);
         if (overflow == 'O')
             store->userspace_supports_overflow = true;
         else {
             DMERR("Unsupported persistent store option: %s", options);
             r = -EINVAL;
             goto err_options;
         }
     }
 
     store->context = ps;
 
     return 0;
 
 err_options:
     destroy_workqueue(ps->metadata_wq);
 err_workqueue:
     kfree(ps);
 
     return r;
 }
 
 static unsigned persistent_status(struct dm_exception_store *store,
                   status_type_t status, char *result,
                   unsigned maxlen)
 {
     unsigned sz = 0;
 
     switch (status) {
     case STATUSTYPE_INFO:
         break;
     case STATUSTYPE_TABLE:
         DMEMIT(" %s %llu", store->userspace_supports_overflow ? "PO" : "P",
                (unsigned long long)store->chunk_size);
         break;
     case STATUSTYPE_IMA:
         *result = '\0';
         break;
     }
 
     return sz;
 }
 
 static struct dm_exception_store_type _persistent_type = {
     .name = "persistent",
     .module = THIS_MODULE,
     .ctr = persistent_ctr,
     .dtr = persistent_dtr,
     .read_metadata = persistent_read_metadata,
     .prepare_exception = persistent_prepare_exception,
     .commit_exception = persistent_commit_exception,
     .prepare_merge = persistent_prepare_merge,
     .commit_merge = persistent_commit_merge,
     .drop_snapshot = persistent_drop_snapshot,
     .usage = persistent_usage,
     .status = persistent_status,
 };
 
 static struct dm_exception_store_type _persistent_compat_type = {
     .name = "P",
     .module = THIS_MODULE,
     .ctr = persistent_ctr,
     .dtr = persistent_dtr,
     .read_metadata = persistent_read_metadata,
     .prepare_exception = persistent_prepare_exception,
     .commit_exception = persistent_commit_exception,
     .prepare_merge = persistent_prepare_merge,
     .commit_merge = persistent_commit_merge,
     .drop_snapshot = persistent_drop_snapshot,
     .usage = persistent_usage,
     .status = persistent_status,
 };
 
 int dm_persistent_snapshot_init(void)
 {
     int r;
 
     r = dm_exception_store_type_register(&_persistent_type);
     if (r) {
         DMERR("Unable to register persistent exception store type");
         return r;
     }
 
     r = dm_exception_store_type_register(&_persistent_compat_type);
     if (r) {
         DMERR("Unable to register old-style persistent exception "
               "store type");
         dm_exception_store_type_unregister(&_persistent_type);
         return r;
     }
 
     return r;
 }
 
 void dm_persistent_snapshot_exit(void)
 {
     dm_exception_store_type_unregister(&_persistent_type);
     dm_exception_store_type_unregister(&_persistent_compat_type);
 }

This page was automatically generated by the 2.1.0 LXR engine. The LXR team