raid5-cache: new helper: r5_reserve_log_entry

Factor out code to reserve log space.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 88758285261ca840783e763e181f7ecca39544a6..ea20d740a67c1371171cdd73991d67aa1974c264 100644 (file)
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -271,6 +271,23 @@ static struct bio *r5l_bio_alloc(struct r5l_log *log, struct r5l_io_unit *io)
        return bio;
 }
 
+static void r5_reserve_log_entry(struct r5l_log *log, struct r5l_io_unit *io)
+{
+       log->log_start = r5l_ring_add(log, log->log_start, BLOCK_SECTORS);
+
+       /*
+        * If we filled up the log device start from the beginning again,
+        * which will require a new bio.
+        *
+        * Note: for this to work properly the log size needs to me a multiple
+        * of BLOCK_SECTORS.
+        */
+       if (log->log_start == 0)
+               io->current_bio = NULL;
+
+       io->log_end = log->log_start;
+}
+
 static struct r5l_io_unit *r5l_new_meta(struct r5l_log *log)
 {
        struct r5l_io_unit *io;
@@ -299,11 +316,7 @@ static struct r5l_io_unit *r5l_new_meta(struct r5l_log *log)
        bio_add_page(io->current_bio, io->meta_page, PAGE_SIZE, 0);
 
        log->seq++;
-       log->log_start = r5l_ring_add(log, log->log_start, BLOCK_SECTORS);
-       io->log_end = log->log_start;
-       /* current bio hit disk end */
-       if (log->log_start == 0)
-               io->current_bio = NULL;
+       r5_reserve_log_entry(log, io);
 
        spin_lock_irq(&log->io_list_lock);
        list_add_tail(&io->log_sibling, &log->running_ios);
@@ -357,13 +370,8 @@ alloc_bio:
                io->current_bio = NULL;
                goto alloc_bio;
        }
-       log->log_start = r5l_ring_add(log, log->log_start,
-                                     BLOCK_SECTORS);
-       /* current bio hit disk end */
-       if (log->log_start == 0)
-               io->current_bio = NULL;
 
-       io->log_end = log->log_start;
+       r5_reserve_log_entry(log, io);
 }
 
 static void r5l_log_stripe(struct r5l_log *log, struct stripe_head *sh,