dm log: avoid reinitialising io_req on every operation

rw_header function updates three members of io_req data every time
when I/O is processed. bi_rw and notify.fn are never modified once
they get initialized, and so they can be set in advance.

header_to_disk() can also be pulled out of write_header() since only one
caller needs it and write_header() can be replaced by rw_header()
directly.

Signed-off-by: Takahiro Yasui <tyasui@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

diff --git a/drivers/md/dm-log.c b/drivers/md/dm-log.c
index 13e2a1a..691cb9c 100644 (file)
--- a/drivers/md/dm-log.c
+++ b/drivers/md/dm-log.c
@@ -326,8 +326,6 @@ static void header_from_disk(struct log_header *core, struct log_header *disk)
 static int rw_header(struct log_c *lc, int rw)
 {
        lc->io_req.bi_rw = rw;
-       lc->io_req.mem.ptr.vma = lc->disk_header;
-       lc->io_req.notify.fn = NULL;
 
        return dm_io(&lc->io_req, 1, &lc->header_location, NULL);
 }
@@ -362,12 +360,6 @@ static int read_header(struct log_c *log)
        return 0;
 }
 
-static inline int write_header(struct log_c *log)
-{
-       header_to_disk(&log->header, log->disk_header);
-       return rw_header(log, WRITE);
-}
-
 /*----------------------------------------------------------------
  * core log constructor/destructor
  *
@@ -454,7 +446,9 @@ static int create_log_context(struct dm_dirty_log *log, struct dm_target *ti,
                buf_size = dm_round_up((LOG_OFFSET << SECTOR_SHIFT) +
                                       bitset_size, ti->limits.hardsect_size);
                lc->header_location.count = buf_size >> SECTOR_SHIFT;
+
                lc->io_req.mem.type = DM_IO_VMA;
+               lc->io_req.notify.fn = NULL;
                lc->io_req.client = dm_io_client_create(dm_div_up(buf_size,
                                                                   PAGE_SIZE));
                if (IS_ERR(lc->io_req.client)) {
@@ -472,6 +466,7 @@ static int create_log_context(struct dm_dirty_log *log, struct dm_target *ti,
                        return -ENOMEM;
                }
 
+               lc->io_req.mem.ptr.vma = lc->disk_header;
                lc->clean_bits = (void *)lc->disk_header +
                                 (LOG_OFFSET << SECTOR_SHIFT);
        }
@@ -636,8 +631,10 @@ static int disk_resume(struct dm_dirty_log *log)
        /* set the correct number of regions in the header */
        lc->header.nr_regions = lc->region_count;
 
+       header_to_disk(&lc->header, lc->disk_header);
+
        /* write the new header */
-       r = write_header(lc);
+       r = rw_header(lc, WRITE);
        if (r) {
                DMWARN("%s: Failed to write header on dirty region log device",
                       lc->log_dev->name);
@@ -687,7 +684,7 @@ static int disk_flush(struct dm_dirty_log *log)
        if (!lc->touched)
                return 0;
 
-       r = write_header(lc);
+       r = rw_header(lc, WRITE);
        if (r)
                fail_log_device(lc);
        else