[dm-devel] [PATCH 7/7] dm writecache: optimize superblock write
Mikulas Patocka
mpatocka at redhat.com
Mon Feb 24 09:20:34 UTC 2020
If we write a superblock in writecache_flush, we don't need to set bit and
scan the bitmap for it - we can just write the superblock directly. Also,
we can set the flag REQ_FUA on the write bio, so that we don't need to
submit a flush bio afterwards.
Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
---
drivers/md/dm-writecache.c | 34 ++++++++++++++++++++++++++++++++--
1 file changed, 32 insertions(+), 2 deletions(-)
Index: linux-2.6/drivers/md/dm-writecache.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-writecache.c 2020-02-24 10:19:14.000000000 +0100
+++ linux-2.6/drivers/md/dm-writecache.c 2020-02-24 10:19:14.000000000 +0100
@@ -508,6 +508,34 @@ static void ssd_commit_flushed(struct dm
memset(wc->dirty_bitmap, 0, wc->dirty_bitmap_size);
}
+static void ssd_commit_superblock(struct dm_writecache *wc)
+{
+ int r;
+ struct dm_io_region region;
+ struct dm_io_request req;
+
+ region.bdev = wc->ssd_dev->bdev;
+ region.sector = 0;
+ region.count = PAGE_SIZE;
+
+ if (unlikely(region.sector + region.count > wc->metadata_sectors))
+ region.count = wc->metadata_sectors - region.sector;
+
+ region.sector += wc->start_sector;
+
+ req.bi_op = REQ_OP_WRITE;
+ req.bi_op_flags = REQ_SYNC | REQ_FUA;
+ req.mem.type = DM_IO_VMA;
+ req.mem.ptr.vma = (char *)wc->memory_map;
+ req.client = wc->dm_io;
+ req.notify.fn = NULL;
+ req.notify.context = NULL;
+
+ r = dm_io(&req, 1, ®ion, NULL);
+ if (unlikely(r))
+ writecache_error(wc, r, "error writing superblock");
+}
+
static void writecache_commit_flushed(struct dm_writecache *wc, bool wait_for_ios)
{
if (WC_MODE_PMEM(wc))
@@ -757,8 +785,10 @@ static void writecache_flush(struct dm_w
wc->seq_count++;
pmem_assign(sb(wc)->seq_count, cpu_to_le64(wc->seq_count));
- writecache_flush_region(wc, &sb(wc)->seq_count, sizeof sb(wc)->seq_count);
- writecache_commit_flushed(wc, false);
+ if (WC_MODE_PMEM(wc))
+ writecache_commit_flushed(wc, false);
+ else
+ ssd_commit_superblock(wc);
wc->overwrote_committed = false;
More information about the dm-devel
mailing list