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>

1 files changed, 19 insertions, 11 deletions

diff --git a/drivers/md/raid5-cache.c b/drivers/md/raid5-cache.c
index 88758285261c..ea20d740a67c 100644
--- 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,