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[PATCH] dm snapshot: allow zero chunk_size
The chunk size of snapshots cannot be changed so it is redundant to require it as a parameter when activating an existing snapshot. Allow a value of zero in this case and ignore it. For a new snapshot, use a default value if zero is specified. Signed-off-by: Mark McLoughlin <markmc@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Mark McLoughlin
Linus Torvalds
parent
92c060a692
commit
4c7e3bf44d
3 changed files with 122 additions and 101 deletions
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@ -17,6 +17,7 @@
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#include <linux/slab.h>
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#define DM_MSG_PREFIX "snapshots"
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#define DM_CHUNK_SIZE_DEFAULT_SECTORS 32 /* 16KB */
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/*-----------------------------------------------------------------
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* Persistent snapshots, by persistent we mean that the snapshot
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@ -150,6 +151,7 @@ static int alloc_area(struct pstore *ps)
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static void free_area(struct pstore *ps)
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{
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vfree(ps->area);
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ps->area = NULL;
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}
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/*
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@ -198,48 +200,79 @@ static int read_header(struct pstore *ps, int *new_snapshot)
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int r;
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struct disk_header *dh;
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chunk_t chunk_size;
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int chunk_size_supplied = 1;
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/*
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* Use default chunk size (or hardsect_size, if larger) if none supplied
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*/
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if (!ps->snap->chunk_size) {
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ps->snap->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS,
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bdev_hardsect_size(ps->snap->cow->bdev) >> 9);
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ps->snap->chunk_mask = ps->snap->chunk_size - 1;
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ps->snap->chunk_shift = ffs(ps->snap->chunk_size) - 1;
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chunk_size_supplied = 0;
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}
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r = dm_io_get(sectors_to_pages(ps->snap->chunk_size));
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if (r)
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return r;
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r = alloc_area(ps);
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if (r)
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goto bad1;
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r = chunk_io(ps, 0, READ);
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if (r)
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return r;
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goto bad2;
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dh = (struct disk_header *) ps->area;
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if (le32_to_cpu(dh->magic) == 0) {
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*new_snapshot = 1;
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} else if (le32_to_cpu(dh->magic) == SNAP_MAGIC) {
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*new_snapshot = 0;
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ps->valid = le32_to_cpu(dh->valid);
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ps->version = le32_to_cpu(dh->version);
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chunk_size = le32_to_cpu(dh->chunk_size);
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if (ps->snap->chunk_size != chunk_size) {
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DMWARN("chunk size %llu in device metadata overrides "
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"table chunk size of %llu.",
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(unsigned long long)chunk_size,
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(unsigned long long)ps->snap->chunk_size);
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/* We had a bogus chunk_size. Fix stuff up. */
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dm_io_put(sectors_to_pages(ps->snap->chunk_size));
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free_area(ps);
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ps->snap->chunk_size = chunk_size;
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ps->snap->chunk_mask = chunk_size - 1;
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ps->snap->chunk_shift = ffs(chunk_size) - 1;
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r = alloc_area(ps);
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if (r)
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return r;
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r = dm_io_get(sectors_to_pages(chunk_size));
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if (r)
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return r;
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}
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} else {
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DMWARN("Invalid/corrupt snapshot");
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r = -ENXIO;
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return 0;
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}
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if (le32_to_cpu(dh->magic) != SNAP_MAGIC) {
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DMWARN("Invalid or corrupt snapshot");
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r = -ENXIO;
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goto bad2;
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}
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*new_snapshot = 0;
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ps->valid = le32_to_cpu(dh->valid);
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ps->version = le32_to_cpu(dh->version);
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chunk_size = le32_to_cpu(dh->chunk_size);
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if (!chunk_size_supplied || ps->snap->chunk_size == chunk_size)
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return 0;
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DMWARN("chunk size %llu in device metadata overrides "
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"table chunk size of %llu.",
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(unsigned long long)chunk_size,
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(unsigned long long)ps->snap->chunk_size);
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/* We had a bogus chunk_size. Fix stuff up. */
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dm_io_put(sectors_to_pages(ps->snap->chunk_size));
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free_area(ps);
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ps->snap->chunk_size = chunk_size;
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ps->snap->chunk_mask = chunk_size - 1;
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ps->snap->chunk_shift = ffs(chunk_size) - 1;
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r = dm_io_get(sectors_to_pages(chunk_size));
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if (r)
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return r;
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r = alloc_area(ps);
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if (r)
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goto bad1;
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return 0;
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bad2:
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free_area(ps);
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bad1:
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dm_io_put(sectors_to_pages(ps->snap->chunk_size));
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return r;
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}
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@ -547,32 +580,22 @@ static void persistent_drop(struct exception_store *store)
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DMWARN("write header failed");
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}
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int dm_create_persistent(struct exception_store *store, uint32_t chunk_size)
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int dm_create_persistent(struct exception_store *store)
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{
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int r;
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struct pstore *ps;
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r = dm_io_get(sectors_to_pages(chunk_size));
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if (r)
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return r;
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/* allocate the pstore */
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ps = kmalloc(sizeof(*ps), GFP_KERNEL);
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if (!ps) {
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r = -ENOMEM;
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goto bad;
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}
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if (!ps)
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return -ENOMEM;
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ps->snap = store->snap;
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ps->valid = 1;
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ps->version = SNAPSHOT_DISK_VERSION;
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ps->area = NULL;
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ps->next_free = 2; /* skipping the header and first area */
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ps->current_committed = 0;
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r = alloc_area(ps);
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if (r)
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goto bad;
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ps->callback_count = 0;
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atomic_set(&ps->pending_count, 0);
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ps->callbacks = NULL;
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@ -586,13 +609,6 @@ int dm_create_persistent(struct exception_store *store, uint32_t chunk_size)
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store->context = ps;
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return 0;
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bad:
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dm_io_put(sectors_to_pages(chunk_size));
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if (ps && ps->area)
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free_area(ps);
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kfree(ps);
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return r;
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}
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/*-----------------------------------------------------------------
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@ -642,18 +658,16 @@ static void transient_fraction_full(struct exception_store *store,
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*denominator = get_dev_size(store->snap->cow->bdev);
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}
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int dm_create_transient(struct exception_store *store,
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struct dm_snapshot *s, int blocksize)
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int dm_create_transient(struct exception_store *store)
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{
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struct transient_c *tc;
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memset(store, 0, sizeof(*store));
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store->destroy = transient_destroy;
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store->read_metadata = transient_read_metadata;
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store->prepare_exception = transient_prepare;
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store->commit_exception = transient_commit;
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store->drop_snapshot = NULL;
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store->fraction_full = transient_fraction_full;
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store->snap = s;
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tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
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if (!tc)
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@ -398,21 +398,60 @@ static void read_snapshot_metadata(struct dm_snapshot *s)
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}
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}
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static int set_chunk_size(struct dm_snapshot *s, const char *chunk_size_arg,
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char **error)
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{
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unsigned long chunk_size;
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char *value;
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chunk_size = simple_strtoul(chunk_size_arg, &value, 10);
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if (*chunk_size_arg == '\0' || *value != '\0') {
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*error = "Invalid chunk size";
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return -EINVAL;
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}
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if (!chunk_size) {
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s->chunk_size = s->chunk_mask = s->chunk_shift = 0;
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return 0;
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}
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/*
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* Chunk size must be multiple of page size. Silently
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* round up if it's not.
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*/
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chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
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/* Check chunk_size is a power of 2 */
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if (chunk_size & (chunk_size - 1)) {
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*error = "Chunk size is not a power of 2";
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return -EINVAL;
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}
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/* Validate the chunk size against the device block size */
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if (chunk_size % (bdev_hardsect_size(s->cow->bdev) >> 9)) {
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*error = "Chunk size is not a multiple of device blocksize";
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return -EINVAL;
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}
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s->chunk_size = chunk_size;
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s->chunk_mask = chunk_size - 1;
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s->chunk_shift = ffs(chunk_size) - 1;
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return 0;
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}
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/*
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* Construct a snapshot mapping: <origin_dev> <COW-dev> <p/n> <chunk-size>
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*/
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static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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{
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struct dm_snapshot *s;
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unsigned long chunk_size;
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int r = -EINVAL;
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char persistent;
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char *origin_path;
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char *cow_path;
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char *value;
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int blocksize;
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if (argc < 4) {
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if (argc != 4) {
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ti->error = "requires exactly 4 arguments";
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r = -EINVAL;
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goto bad1;
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@ -428,13 +467,6 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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goto bad1;
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}
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chunk_size = simple_strtoul(argv[3], &value, 10);
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if (chunk_size == 0 || value == NULL) {
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ti->error = "Invalid chunk size";
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r = -EINVAL;
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goto bad1;
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}
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s = kmalloc(sizeof(*s), GFP_KERNEL);
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if (s == NULL) {
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ti->error = "Cannot allocate snapshot context private "
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@ -457,31 +489,11 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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goto bad2;
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}
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/*
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* Chunk size must be multiple of page size. Silently
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* round up if it's not.
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*/
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chunk_size = round_up(chunk_size, PAGE_SIZE >> 9);
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/* Validate the chunk size against the device block size */
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blocksize = s->cow->bdev->bd_disk->queue->hardsect_size;
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if (chunk_size % (blocksize >> 9)) {
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ti->error = "Chunk size is not a multiple of device blocksize";
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r = -EINVAL;
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r = set_chunk_size(s, argv[3], &ti->error);
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if (r)
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goto bad3;
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}
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/* Check chunk_size is a power of 2 */
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if (chunk_size & (chunk_size - 1)) {
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ti->error = "Chunk size is not a power of 2";
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r = -EINVAL;
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goto bad3;
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}
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s->chunk_size = chunk_size;
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s->chunk_mask = chunk_size - 1;
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s->type = persistent;
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s->chunk_shift = ffs(chunk_size) - 1;
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s->valid = 1;
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s->active = 0;
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@ -496,16 +508,12 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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goto bad3;
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}
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/*
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* Check the persistent flag - done here because we need the iobuf
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* to check the LV header
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*/
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s->store.snap = s;
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if (persistent == 'P')
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r = dm_create_persistent(&s->store, chunk_size);
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r = dm_create_persistent(&s->store);
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else
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r = dm_create_transient(&s->store, s, blocksize);
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r = dm_create_transient(&s->store);
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if (r) {
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ti->error = "Couldn't create exception store";
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@ -1205,7 +1213,7 @@ static int origin_status(struct dm_target *ti, status_type_t type, char *result,
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static struct target_type origin_target = {
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.name = "snapshot-origin",
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.version = {1, 4, 0},
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.version = {1, 5, 0},
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.module = THIS_MODULE,
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.ctr = origin_ctr,
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.dtr = origin_dtr,
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@ -1216,7 +1224,7 @@ static struct target_type origin_target = {
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static struct target_type snapshot_target = {
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.name = "snapshot",
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.version = {1, 4, 0},
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.version = {1, 5, 0},
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.module = THIS_MODULE,
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.ctr = snapshot_ctr,
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.dtr = snapshot_dtr,
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@ -128,10 +128,9 @@ int dm_add_exception(struct dm_snapshot *s, chunk_t old, chunk_t new);
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* Constructor and destructor for the default persistent
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* store.
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*/
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int dm_create_persistent(struct exception_store *store, uint32_t chunk_size);
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int dm_create_persistent(struct exception_store *store);
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int dm_create_transient(struct exception_store *store,
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struct dm_snapshot *s, int blocksize);
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int dm_create_transient(struct exception_store *store);
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/*
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* Return the number of sectors in the device.
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