dm snapshot: split out exception store implementations (4db6bfe0) · Commits · e / devices / android_kernel_xiaomi_markw

drivers/md/Makefile

+2 −1

Original line number	Diff line number	Diff line
		@@ -5,7 +5,8 @@
		dm-mod-objs := dm.o dm-table.o dm-target.o dm-linear.o dm-stripe.o \
		dm-ioctl.o dm-io.o dm-kcopyd.o dm-sysfs.o
		dm-multipath-objs := dm-path-selector.o dm-mpath.o
		dm-snapshot-objs := dm-snap.o dm-exception-store.o
		dm-snapshot-objs := dm-snap.o dm-exception-store.o dm-snap-transient.o \
		dm-snap-persistent.o
		dm-mirror-objs := dm-raid1.o
		md-mod-objs := md.o bitmap.o
		raid456-objs := raid5.o raid6algos.o raid6recov.o raid6tables.o \

drivers/md/dm-exception-store.c

+19 −730

Original line number	Diff line number	Diff line
		/*
		* dm-exception-store.c
		*
		* Copyright (C) 2001-2002 Sistina Software (UK) Limited.
		* Copyright (C) 2006 Red Hat GmbH
		* Copyright (C) 2006-2008 Red Hat GmbH
		*
		* This file is released under the GPL.
		*/

		#include "dm-exception-store.h"
		#include "dm-snap.h"

		#include <linux/mm.h>
		#include <linux/pagemap.h>
		#include <linux/vmalloc.h>
		#include <linux/slab.h>
		#include <linux/dm-io.h>
		#include <linux/dm-kcopyd.h>

		#define DM_MSG_PREFIX "snapshots"
		#define DM_CHUNK_SIZE_DEFAULT_SECTORS 32 /* 16KB */

		/*-----------------------------------------------------------------
		* 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

		struct disk_header {
		uint32_t magic;

		/*
		* Is this snapshot valid. There is no way of recovering
		* an invalid snapshot.
		*/
		uint32_t valid;

		/*
		* Simple, incrementing version. no backward
		* compatibility.
		*/
		uint32_t version;

		/* In sectors */
		uint32_t chunk_size;
		};

		struct disk_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_snapshot snap; / up pointer to my snapshot */
		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;

		/*
		* 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.
		*/
		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 unsigned sectors_to_pages(unsigned sectors)
		{
		return DIV_ROUND_UP(sectors, PAGE_SIZE >> 9);
		}

		static int alloc_area(struct pstore *ps)
		{
		int r = -ENOMEM;
		size_t len;

		len = ps->snap->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)
		return r;

		ps->zero_area = vmalloc(len);
		if (!ps->zero_area) {
		vfree(ps->area);
		return r;
		}
		memset(ps->zero_area, 0, len);

		return 0;
		}

		static void free_area(struct pstore *ps)
		{
		vfree(ps->area);
		ps->area = NULL;
		vfree(ps->zero_area);
		ps->zero_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, chunk_t chunk, int rw, int metadata)
		{
		struct dm_io_region where = {
		.bdev = ps->snap->cow->bdev,
		.sector = ps->snap->chunk_size * chunk,
		.count = ps->snap->chunk_size,
		};
		struct dm_io_request io_req = {
		.bi_rw = rw,
		.mem.type = DM_IO_VMA,
		.mem.ptr.vma = ps->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 generic_make_request recursion.
		*/
		INIT_WORK(&req.work, do_metadata);
		queue_work(ps->metadata_wq, &req.work);
		flush_workqueue(ps->metadata_wq);

		return req.result;
		}

		/*
		* Convert a metadata area index to a chunk index.
		*/
		static chunk_t area_location(struct pstore *ps, chunk_t area)
		{
		return 1 + ((ps->exceptions_per_area + 1) * area);
		}

		/*
		* Read or write a metadata area. Remembering to skip the first
		* chunk which holds the header.
		*/
		static int area_io(struct pstore *ps, int rw)
		{
		int r;
		chunk_t chunk;

		chunk = area_location(ps, ps->current_area);

		r = chunk_io(ps, chunk, rw, 0);
		if (r)
		return r;

		return 0;
		}

		static void zero_memory_area(struct pstore *ps)
		{
		memset(ps->area, 0, ps->snap->chunk_size << SECTOR_SHIFT);
		}

		static int zero_disk_area(struct pstore *ps, chunk_t area)
		{
		struct dm_io_region where = {
		.bdev = ps->snap->cow->bdev,
		.sector = ps->snap->chunk_size * area_location(ps, area),
		.count = ps->snap->chunk_size,
		};
		struct dm_io_request io_req = {
		.bi_rw = WRITE,
		.mem.type = DM_IO_VMA,
		.mem.ptr.vma = ps->zero_area,
		.client = ps->io_client,
		.notify.fn = NULL,
		};

		return dm_io(&io_req, 1, &where, NULL);
		}

		static int read_header(struct pstore ps, int new_snapshot)
		{
		int r;
		struct disk_header *dh;
		chunk_t chunk_size;
		int chunk_size_supplied = 1;

		/*
		* Use default chunk size (or hardsect_size, if larger) if none supplied
		*/
		if (!ps->snap->chunk_size) {
		ps->snap->chunk_size = max(DM_CHUNK_SIZE_DEFAULT_SECTORS,
		bdev_hardsect_size(ps->snap->cow->bdev) >> 9);
		ps->snap->chunk_mask = ps->snap->chunk_size - 1;
		ps->snap->chunk_shift = ffs(ps->snap->chunk_size) - 1;
		chunk_size_supplied = 0;
		}

		ps->io_client = dm_io_client_create(sectors_to_pages(ps->snap->
		chunk_size));
		if (IS_ERR(ps->io_client))
		return PTR_ERR(ps->io_client);

		r = alloc_area(ps);
		if (r)
		return r;

		r = chunk_io(ps, 0, READ, 1);
		if (r)
		goto bad;

		dh = (struct disk_header *) ps->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 (!chunk_size_supplied \|\| ps->snap->chunk_size == chunk_size)
		return 0;

		DMWARN("chunk size %llu in device metadata overrides "
		"table chunk size of %llu.",
		(unsigned long long)chunk_size,
		(unsigned long long)ps->snap->chunk_size);

		/* We had a bogus chunk_size. Fix stuff up. */
		free_area(ps);

		ps->snap->chunk_size = chunk_size;
		ps->snap->chunk_mask = chunk_size - 1;
		ps->snap->chunk_shift = ffs(chunk_size) - 1;

		r = dm_io_client_resize(sectors_to_pages(ps->snap->chunk_size),
		ps->io_client);
		if (r)
		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->area, 0, ps->snap->chunk_size << SECTOR_SHIFT);

		dh = (struct disk_header *) ps->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->snap->chunk_size);

		return chunk_io(ps, 0, WRITE, 1);
		}

		/*
		* Access functions for the disk exceptions, these do the endian conversions.
		*/
		static struct disk_exception get_exception(struct pstore ps, uint32_t index)
		{
		BUG_ON(index >= ps->exceptions_per_area);

		return ((struct disk_exception *) ps->area) + index;
		}

		static void read_exception(struct pstore *ps,
		uint32_t index, struct disk_exception *result)
		{
		struct disk_exception *e = get_exception(ps, index);

		/* copy it */
		result->old_chunk = le64_to_cpu(e->old_chunk);
		result->new_chunk = le64_to_cpu(e->new_chunk);
		}

		static void write_exception(struct pstore *ps,
		uint32_t index, struct disk_exception *de)
		{
		struct disk_exception *e = get_exception(ps, index);
		#include <linux/device-mapper.h>

		/* copy it */
		e->old_chunk = cpu_to_le64(de->old_chunk);
		e->new_chunk = cpu_to_le64(de->new_chunk);
		}
		#define DM_MSG_PREFIX "snapshot exception stores"

		/*
		* 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, int full)
		int dm_exception_store_init(void)
		{
		int r;
		unsigned int i;
		struct disk_exception de;

		/* presume the area is full */
		*full = 1;

		for (i = 0; i < ps->exceptions_per_area; i++) {
		read_exception(ps, i, &de);

		/*
		* 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 (de.new_chunk == 0LL) {
		ps->current_committed = i;
		*full = 0;
		break;
		}

		/*
		* Keep track of the start of the free chunks.
		*/
		if (ps->next_free <= de.new_chunk)
		ps->next_free = de.new_chunk + 1;

		/*
		* Otherwise we add the exception to the snapshot.
		*/
		r = dm_add_exception(ps->snap, de.old_chunk, de.new_chunk);
		if (r)
		return r;
		}

		return 0;
		}

		static int read_exceptions(struct pstore *ps)
		{
		int r, full = 1;

		/*
		* Keeping reading chunks and inserting exceptions until
		* we find a partially full area.
		*/
		for (ps->current_area = 0; full; ps->current_area++) {
		r = area_io(ps, READ);
		if (r)
		return r;

		r = insert_exceptions(ps, &full);
		if (r)
		return r;
		}

		ps->current_area--;

		return 0;
		}

		static struct pstore get_info(struct dm_exception_store store)
		{
		return (struct pstore *) store->context;
		}

		static void persistent_fraction_full(struct dm_exception_store *store,
		sector_t numerator, sector_t denominator)
		{
		numerator = get_info(store)->next_free store->snap->chunk_size;
		*denominator = get_dev_size(store->snap->cow->bdev);
		}

		static void persistent_destroy(struct dm_exception_store *store)
		{
		struct pstore *ps = get_info(store);

		destroy_workqueue(ps->metadata_wq);
		dm_io_client_destroy(ps->io_client);
		vfree(ps->callbacks);
		free_area(ps);
		kfree(ps);
		}

		static int persistent_read_metadata(struct dm_exception_store *store)
		{
		int r, uninitialized_var(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->snap->chunk_size << SECTOR_SHIFT) /
		sizeof(struct disk_exception);
		ps->callbacks = dm_vcalloc(ps->exceptions_per_area,
		sizeof(*ps->callbacks));
		if (!ps->callbacks)
		return -ENOMEM;

		/*
		* Do we need to setup a new snapshot ?
		*/
		if (new_snapshot) {
		r = write_header(ps);
		r = dm_transient_snapshot_init();
		if (r) {
		DMWARN("write_header failed");
		return r;
		DMERR("Unable to register transient exception store type.");
		goto transient_fail;
		}

		ps->current_area = 0;
		zero_memory_area(ps);
		r = zero_disk_area(ps, 0);
		r = dm_persistent_snapshot_init();
		if (r) {
		DMWARN("zero_disk_area(0) failed");
		return r;
		}
		} else {
		/*
		* 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);
		if (r)
		return r;
		}

		return 0;
		DMERR("Unable to register persistent exception store type");
		goto persistent_fail;
		}

		static int persistent_prepare(struct dm_exception_store *store,
		struct dm_snap_exception *e)
		{
		struct pstore *ps = get_info(store);
		uint32_t stride;
		chunk_t next_free;
		sector_t size = get_dev_size(store->snap->cow->bdev);

		/* Is there enough room ? */
		if (size < ((ps->next_free + 1) * store->snap->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.
		*/
		stride = (ps->exceptions_per_area + 1);
		next_free = ++ps->next_free;
		if (sector_div(next_free, stride) == 1)
		ps->next_free++;

		atomic_inc(&ps->pending_count);
		return 0;
		}

		static void persistent_commit(struct dm_exception_store *store,
		struct dm_snap_exception *e,
		void (callback) (void , int success),
		void *callback_context)
		{
		unsigned int i;
		struct pstore *ps = get_info(store);
		struct disk_exception de;
		struct commit_callback *cb;

		de.old_chunk = e->old_chunk;
		de.new_chunk = e->new_chunk;
		write_exception(ps, ps->current_committed++, &de);

		/*
		* 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, WRITE))
		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 void persistent_drop(struct dm_exception_store *store)
		{
		struct pstore *ps = get_info(store);

		ps->valid = 0;
		if (write_header(ps))
		DMWARN("write header failed");
		}

		int dm_create_persistent(struct dm_exception_store *store)
		{
		struct pstore *ps;

		/* allocate the pstore */
		ps = kmalloc(sizeof(*ps), GFP_KERNEL);
		if (!ps)
		return -ENOMEM;

		ps->snap = store->snap;
		ps->valid = 1;
		ps->version = SNAPSHOT_DISK_VERSION;
		ps->area = NULL;
		ps->next_free = 2; /* skipping the header and first area */
		ps->current_committed = 0;

		ps->callback_count = 0;
		atomic_set(&ps->pending_count, 0);
		ps->callbacks = NULL;

		ps->metadata_wq = create_singlethread_workqueue("ksnaphd");
		if (!ps->metadata_wq) {
		kfree(ps);
		DMERR("couldn't start header metadata update thread");
		return -ENOMEM;
		}

		store->destroy = persistent_destroy;
		store->read_metadata = persistent_read_metadata;
		store->prepare_exception = persistent_prepare;
		store->commit_exception = persistent_commit;
		store->drop_snapshot = persistent_drop;
		store->fraction_full = persistent_fraction_full;
		store->context = ps;

		return 0;
		}

		/*-----------------------------------------------------------------
		* Implementation of the store for non-persistent snapshots.
		---------------------------------------------------------------/
		struct transient_c {
		sector_t next_free;
		};

		static void transient_destroy(struct dm_exception_store *store)
		{
		kfree(store->context);
		}

		static int transient_read_metadata(struct dm_exception_store *store)
		{
		return 0;
		}

		static int transient_prepare(struct dm_exception_store *store,
		struct dm_snap_exception *e)
		{
		struct transient_c tc = (struct transient_c ) store->context;
		sector_t size = get_dev_size(store->snap->cow->bdev);

		if (size < (tc->next_free + store->snap->chunk_size))
		return -1;

		e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
		tc->next_free += store->snap->chunk_size;

		return 0;
		}

		static void transient_commit(struct dm_exception_store *store,
		struct dm_snap_exception *e,
		void (callback) (void , int success),
		void *callback_context)
		{
		/* Just succeed */
		callback(callback_context, 1);
		}

		static void transient_fraction_full(struct dm_exception_store *store,
		sector_t numerator, sector_t denominator)
		{
		numerator = ((struct transient_c ) store->context)->next_free;
		*denominator = get_dev_size(store->snap->cow->bdev);
		persistent_fail:
		dm_persistent_snapshot_exit();
		transient_fail:
		return r;
		}

		int dm_create_transient(struct dm_exception_store *store)
		void dm_exception_store_exit(void)
		{
		struct transient_c *tc;

		store->destroy = transient_destroy;
		store->read_metadata = transient_read_metadata;
		store->prepare_exception = transient_prepare;
		store->commit_exception = transient_commit;
		store->drop_snapshot = NULL;
		store->fraction_full = transient_fraction_full;

		tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
		if (!tc)
		return -ENOMEM;

		tc->next_free = 0;
		store->context = tc;

		return 0;
		dm_persistent_snapshot_exit();
		dm_transient_snapshot_exit();
		}

drivers/md/dm-exception-store.h

+9 −0

Original line number	Diff line number	Diff line
		@@ -122,9 +122,18 @@ static inline void dm_consecutive_chunk_count_inc(struct dm_snap_exception *e)

		# endif

		int dm_exception_store_init(void);
		void dm_exception_store_exit(void);

		/*
		* Two exception store implementations.
		*/
		int dm_persistent_snapshot_init(void);
		void dm_persistent_snapshot_exit(void);

		int dm_transient_snapshot_init(void);
		void dm_transient_snapshot_exit(void);

		int dm_create_persistent(struct dm_exception_store *store);

		int dm_create_transient(struct dm_exception_store *store);

drivers/md/dm-snap-persistent.c

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+694 −0

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drivers/md/dm-snap-transient.c

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Original line number	Diff line number	Diff line
		/*
		* 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 "dm-snap.h"

		#include <linux/mm.h>
		#include <linux/pagemap.h>
		#include <linux/vmalloc.h>
		#include <linux/slab.h>
		#include <linux/dm-io.h>

		#define DM_MSG_PREFIX "transient snapshot"

		/*-----------------------------------------------------------------
		* Implementation of the store for non-persistent snapshots.
		---------------------------------------------------------------/
		struct transient_c {
		sector_t next_free;
		};

		static void transient_destroy(struct dm_exception_store *store)
		{
		kfree(store->context);
		}

		static int transient_read_metadata(struct dm_exception_store *store)
		{
		return 0;
		}

		static int transient_prepare(struct dm_exception_store *store,
		struct dm_snap_exception *e)
		{
		struct transient_c tc = (struct transient_c ) store->context;
		sector_t size = get_dev_size(store->snap->cow->bdev);

		if (size < (tc->next_free + store->snap->chunk_size))
		return -1;

		e->new_chunk = sector_to_chunk(store->snap, tc->next_free);
		tc->next_free += store->snap->chunk_size;

		return 0;
		}

		static void transient_commit(struct dm_exception_store *store,
		struct dm_snap_exception *e,
		void (callback) (void , int success),
		void *callback_context)
		{
		/* Just succeed */
		callback(callback_context, 1);
		}

		static void transient_fraction_full(struct dm_exception_store *store,
		sector_t numerator, sector_t denominator)
		{
		numerator = ((struct transient_c ) store->context)->next_free;
		*denominator = get_dev_size(store->snap->cow->bdev);
		}

		int dm_create_transient(struct dm_exception_store *store)
		{
		struct transient_c *tc;

		store->destroy = transient_destroy;
		store->read_metadata = transient_read_metadata;
		store->prepare_exception = transient_prepare;
		store->commit_exception = transient_commit;
		store->drop_snapshot = NULL;
		store->fraction_full = transient_fraction_full;

		tc = kmalloc(sizeof(struct transient_c), GFP_KERNEL);
		if (!tc)
		return -ENOMEM;

		tc->next_free = 0;
		store->context = tc;

		return 0;
		}

		int dm_transient_snapshot_init(void)
		{
		return 0;
		}

		void dm_transient_snapshot_exit(void)
		{
		}