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Commit 7c9e6c17 authored by Alasdair G Kergon's avatar Alasdair G Kergon
Browse files

dm exception store: refactor zero_area 



Use a separate buffer for writing zeroes to the on-disk snapshot
exception store, make the updating of ps->current_area explicit and
refactor the code in preparation for the fix in the next patch.

No functional change.

Signed-off-by: default avatarAlasdair G Kergon <agk@redhat.com>
Signed-off-by: default avatarMikulas Patocka <mpatocka@redhat.com>
Cc: stable@kernel.org
parent f68d4f3d

drivers/md/dm-exception-store.c

+68 −34
Original line number Diff line number Diff line
@@ -104,6 +104,11 @@ struct pstore { 
	 */

	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.
@@ -149,6 +154,13 @@ static int alloc_area(struct pstore *ps) 
	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;

}
@@ -156,6 +168,8 @@ static void free_area(struct pstore *ps) 
{

	vfree(ps->area);

	ps->area = NULL;

	vfree(ps->zero_area);

	ps->zero_area = NULL;

}



struct mdata_req {
@@ -220,25 +234,41 @@ static chunk_t area_location(struct pstore *ps, chunk_t area) 
 * Read or write a metadata area.  Remembering to skip the first

 * chunk which holds the header.

 */

static int area_io(struct pstore *ps, chunk_t area, int rw)

static int area_io(struct pstore *ps, int rw)

{

	int r;

	chunk_t chunk;



	chunk = area_location(ps, area);

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



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

	if (r)

		return r;



	ps->current_area = area;

	return 0;

}



static int zero_area(struct pstore *ps, chunk_t area)

static void zero_memory_area(struct pstore *ps)

{

	memset(ps->area, 0, ps->snap->chunk_size << SECTOR_SHIFT);

	return area_io(ps, area, WRITE);

}



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)
@@ -411,15 +441,14 @@ static int insert_exceptions(struct pstore *ps, int *full) 


static int read_exceptions(struct pstore *ps)

{

	chunk_t area;

	int r, full = 1;



	/*

	 * Keeping reading chunks and inserting exceptions until

	 * we find a partially full area.

	 */

	for (area = 0; full; area++) {

		r = area_io(ps, area, READ);

	for (ps->current_area = 0; full; ps->current_area++) {

		r = area_io(ps, READ);

		if (r)

			return r;
@@ -428,6 +457,8 @@ static int read_exceptions(struct pstore *ps) 
			return r;

	}



	ps->current_area--;



	return 0;

}
@@ -486,12 +517,13 @@ static int persistent_read_metadata(struct exception_store *store) 
			return r;

		}



		r = zero_area(ps, 0);

		ps->current_area = 0;

		zero_memory_area(ps);

		r = zero_disk_area(ps, 0);

		if (r) {

			DMWARN("zero_area(0) failed");

			DMWARN("zero_disk_area(0) failed");

			return r;

		}



	} else {

		/*

		 * Sanity checks.
@@ -551,7 +583,6 @@ static void persistent_commit(struct exception_store *store, 
			      void (*callback) (void *, int success),

			      void *callback_context)

{

	int r;

	unsigned int i;

	struct pstore *ps = get_info(store);

	struct disk_exception de;
@@ -572,34 +603,37 @@ static void persistent_commit(struct exception_store *store, 
	cb->context = callback_context;



	/*

	 * If there are no more exceptions in flight, or we have

	 * filled this metadata area we commit the exceptions to

	 * disk.

	 * 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)) {

		r = area_io(ps, ps->current_area, WRITE);

		if (r)

	if (!atomic_dec_and_test(&ps->pending_count) &&

	    (ps->current_committed != ps->exceptions_per_area))

		return;



	/*

	 * Commit exceptions to disk.

	 */

	if (area_io(ps, WRITE))

		ps->valid = 0;



	/*

		 * Have we completely filled the current area ?

	 * Advance to the next area if this one is full.

	 */

	if (ps->current_committed == ps->exceptions_per_area) {

			ps->current_committed = 0;

			r = zero_area(ps, ps->current_area + 1);

			if (r)

		if (zero_disk_area(ps, ps->current_area + 1))

			ps->valid = 0;

		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, r == 0 ? 1 : 0);

		cb->callback(cb->context, ps->valid);

	}



	ps->callback_count = 0;

}

}



static void persistent_drop(struct exception_store *store)

{