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authorAlasdair G Kergon <agk@redhat.com>2008-10-21 17:44:55 +0100
committerAlasdair G Kergon <agk@redhat.com>2008-10-21 17:44:55 +0100
commit7c9e6c17325fab380fbe9c9787680ff7d4a51abd (patch)
tree3d92b66810b90bcef66a0e021e3944f335ebf9fa /drivers/md
parentf68d4f3d394da5b1f69d855b8513f4256ccc803e (diff)
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: Alasdair G Kergon <agk@redhat.com> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Cc: stable@kernel.org
Diffstat (limited to 'drivers/md')
-rw-r--r--drivers/md/dm-exception-store.c102
1 files changed, 68 insertions, 34 deletions
diff --git a/drivers/md/dm-exception-store.c b/drivers/md/dm-exception-store.c
index 769ab677f8e..fe6cef8df20 100644
--- a/drivers/md/dm-exception-store.c
+++ b/drivers/md/dm-exception-store.c
@@ -105,6 +105,11 @@ 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;
@@ -572,33 +603,36 @@ 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)
- ps->valid = 0;
+ if (!atomic_dec_and_test(&ps->pending_count) &&
+ (ps->current_committed != ps->exceptions_per_area))
+ return;
- /*
- * Have we completely filled the current area ?
- */
- if (ps->current_committed == ps->exceptions_per_area) {
- ps->current_committed = 0;
- r = zero_area(ps, ps->current_area + 1);
- if (r)
- ps->valid = 0;
- }
+ /*
+ * Commit exceptions to disk.
+ */
+ if (area_io(ps, WRITE))
+ ps->valid = 0;
- for (i = 0; i < ps->callback_count; i++) {
- cb = ps->callbacks + i;
- cb->callback(cb->context, r == 0 ? 1 : 0);
- }
+ /*
+ * Advance to the next area if this one is full.
+ */
+ if (ps->current_committed == ps->exceptions_per_area) {
+ if (zero_disk_area(ps, ps->current_area + 1))
+ ps->valid = 0;
+ ps->current_committed = 0;
+ ps->current_area++;
+ zero_memory_area(ps);
+ }
- ps->callback_count = 0;
+ 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 exception_store *store)