target: make iblock_emulate_sync_cache asynchronous

Do not block the submitting thread when handling a SYNCHRONIZE CACHE command,
but implement it asynchronously by sending the FLUSH command ourself and
calling transport_complete_sync_cache from the completion handler.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Nicholas Bellinger <nab@linux-iscsi.org>

1 files changed, 21 insertions, 16 deletions

diff --git a/drivers/target/target_core_iblock.c b/drivers/target/target_core_iblock.c
index bf074c4b7a36..d9ad2a216eaa 100644
--- a/drivers/target/target_core_iblock.c
+++ b/drivers/target/target_core_iblock.c
@@ -313,37 +313,42 @@ static unsigned long long iblock_emulate_read_cap_with_block_size(
         return blocks_long;
 }
 
+static void iblock_end_io_flush(struct bio *bio, int err)
+{
+        struct se_cmd *cmd = bio->bi_private;
+
+        if (err)
+                pr_err("IBLOCK: cache flush failed: %d\n", err);
+
+        if (cmd)
+                transport_complete_sync_cache(cmd, err == 0);
+        bio_put(bio);
+}
+
 /*
- * Emulate SYCHRONIZE_CACHE_*
+ * Implement SYCHRONIZE CACHE.  Note that we can't handle lba ranges and must
+ * always flush the whole cache.
  */
 static void iblock_emulate_sync_cache(struct se_task *task)
 {
         struct se_cmd *cmd = task->task_se_cmd;
         struct iblock_dev *ib_dev = cmd->se_dev->dev_ptr;
         int immed = (cmd->t_task_cdb[1] & 0x2);
-        sector_t error_sector;
-        int ret;
+        struct bio *bio;
 
         /*
          * If the Immediate bit is set, queue up the GOOD response
-         * for this SYNCHRONIZE_CACHE op
+         * for this SYNCHRONIZE_CACHE op.
          */
         if (immed)
                 transport_complete_sync_cache(cmd, 1);
 
-        /*
-         * blkdev_issue_flush() does not support a specifying a range, so
-         * we have to flush the entire cache.
-         */
-        ret = blkdev_issue_flush(ib_dev->ibd_bd, GFP_KERNEL, &error_sector);
-        if (ret != 0) {
-                pr_err("IBLOCK: block_issue_flush() failed: %d "
-                        " error_sector: %llu\n", ret,
-                        (unsigned long long)error_sector);
-        }
-
+        bio = bio_alloc(GFP_KERNEL, 0);
+        bio->bi_end_io = iblock_end_io_flush;
+        bio->bi_bdev = ib_dev->ibd_bd;
         if (!immed)
-                transport_complete_sync_cache(cmd, ret == 0);
+                bio->bi_private = cmd;
+        submit_bio(WRITE_FLUSH, bio);
 }
 
 /*