Commit dc8a01ae authored by Mikuláš Patočka's avatar Mikuláš Patočka Committed by Mike Snitzer
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dm writecache: optimize superblock write

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: Mikuláš Patočka's avatarMikulas Patocka <>
Signed-off-by: Mike Snitzer's avatarMike Snitzer <>
parent 3923d485
......@@ -509,6 +509,34 @@ static void ssd_commit_flushed(struct dm_writecache *wc, bool wait_for_ios)
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, &region, 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))
......@@ -759,8 +787,10 @@ static void writecache_flush(struct dm_writecache *wc)
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);
wc->overwrote_committed = false;
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