raid5-cache: use bio chaining

Simplify the bio completion handler by using bio chaining and submitting
bios as soon as they are full.

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 4e6046f1b0aa17e64e6cc0df37bb763559a5946e..d3b5441b4c1170ba2e8c636ab5294c28dd2578ce 100644 (file)
--- a/drivers/md/raid5-cache.c
+++ b/drivers/md/raid5-cache.c
@@ -100,8 +100,6 @@ struct r5l_io_unit {
        struct page *meta_page; /* store meta block */
        int meta_offset;        /* current offset in meta_page */
 
-       struct bio_list bios;
-       atomic_t pending_io;    /* pending bios not written to log yet */
        struct bio *current_bio;/* current_bio accepting new data */
 
        atomic_t pending_stripe;/* how many stripes not flushed to raid */
@@ -112,6 +110,7 @@ struct r5l_io_unit {
        struct list_head stripe_list; /* stripes added to the io_unit */
 
        int state;
+       bool need_split_bio;
 };
 
 /* r5l_io_unit state */
@@ -215,9 +214,6 @@ static void r5l_log_endio(struct bio *bio)
 
        bio_put(bio);
 
-       if (!atomic_dec_and_test(&io->pending_io))
-               return;
-
        spin_lock_irqsave(&log->io_list_lock, flags);
        __r5l_set_io_unit_state(io, IO_UNIT_IO_END);
        if (log->need_cache_flush)
@@ -235,7 +231,6 @@ static void r5l_submit_current_io(struct r5l_log *log)
 {
        struct r5l_io_unit *io = log->current_io;
        struct r5l_meta_block *block;
-       struct bio *bio;
        unsigned long flags;
        u32 crc;
 
@@ -252,22 +247,17 @@ static void r5l_submit_current_io(struct r5l_log *log)
        __r5l_set_io_unit_state(io, IO_UNIT_IO_START);
        spin_unlock_irqrestore(&log->io_list_lock, flags);
 
-       while ((bio = bio_list_pop(&io->bios)))
-               submit_bio(WRITE, bio);
+       submit_bio(WRITE, io->current_bio);
 }
 
-static struct bio *r5l_bio_alloc(struct r5l_log *log, struct r5l_io_unit *io)
+static struct bio *r5l_bio_alloc(struct r5l_log *log)
 {
        struct bio *bio = bio_kmalloc(GFP_NOIO | __GFP_NOFAIL, BIO_MAX_PAGES);
 
        bio->bi_rw = WRITE;
        bio->bi_bdev = log->rdev->bdev;
        bio->bi_iter.bi_sector = log->rdev->data_offset + log->log_start;
-       bio->bi_end_io = r5l_log_endio;
-       bio->bi_private = io;
 
-       bio_list_add(&io->bios, bio);
-       atomic_inc(&io->pending_io);
        return bio;
 }
 
@@ -283,7 +273,7 @@ static void r5_reserve_log_entry(struct r5l_log *log, struct r5l_io_unit *io)
         * of BLOCK_SECTORS.
         */
        if (log->log_start == 0)
-               io->current_bio = NULL;
+               io->need_split_bio = true;
 
        io->log_end = log->log_start;
 }
@@ -296,7 +286,6 @@ static struct r5l_io_unit *r5l_new_meta(struct r5l_log *log)
        /* We can't handle memory allocate failure so far */
        io = kmem_cache_zalloc(log->io_kc, GFP_NOIO | __GFP_NOFAIL);
        io->log = log;
-       bio_list_init(&io->bios);
        INIT_LIST_HEAD(&io->log_sibling);
        INIT_LIST_HEAD(&io->stripe_list);
        io->state = IO_UNIT_RUNNING;
@@ -312,7 +301,9 @@ static struct r5l_io_unit *r5l_new_meta(struct r5l_log *log)
        io->meta_offset = sizeof(struct r5l_meta_block);
        io->seq = log->seq++;
 
-       io->current_bio = r5l_bio_alloc(log, io);
+       io->current_bio = r5l_bio_alloc(log);
+       io->current_bio->bi_end_io = r5l_log_endio;
+       io->current_bio->bi_private = io;
        bio_add_page(io->current_bio, io->meta_page, PAGE_SIZE, 0);
 
        r5_reserve_log_entry(log, io);
@@ -361,15 +352,18 @@ static void r5l_append_payload_page(struct r5l_log *log, struct page *page)
 {
        struct r5l_io_unit *io = log->current_io;
 
-alloc_bio:
-       if (!io->current_bio)
-               io->current_bio = r5l_bio_alloc(log, io);
+       if (io->need_split_bio) {
+               struct bio *prev = io->current_bio;
 
-       if (!bio_add_page(io->current_bio, page, PAGE_SIZE, 0)) {
-               io->current_bio = NULL;
-               goto alloc_bio;
+               io->current_bio = r5l_bio_alloc(log);
+               bio_chain(io->current_bio, prev);
+
+               submit_bio(WRITE, prev);
        }
 
+       if (!bio_add_page(io->current_bio, page, PAGE_SIZE, 0))
+               BUG();
+
        r5_reserve_log_entry(log, io);
 }