[PATCH 0/4] blk-lib: cleanup bdev_get_queue()

[Chaitanya Kulkarni <kch@nvidia.com>]

Hi,

Based on the comment in the include/linux/blkdev.h:bdev_get_queue()
the return value of the function will never be NULL. This patch series
removes those checks present in the blk-lib.c, also removes the not
needed local variable pointer to request_queue from the write_zeroes
helpers.

Below is the test log for  discard (__blkdev_issue_disacrd()) and
write-zeroes (__blkdev_issue_write_zeroes/__blkdev_issue_zero_pages()).

-ck

Chaitanya Kulkarni (4):
  blk-lib: don't check bdev_get_queue() NULL check
  blk-lib: don't check bdev_get_queue() NULL check
  blk-lib: don't check bdev_get_queue() NULL check
  blk-lib: don't check bdev_get_queue() NULL check

 block/blk-lib.c | 14 --------------
 1 file changed, 14 deletions(-)

1. Execute discard (__blkdev_issue_disacrd()) and write-zeroes
   (__blkdev_issue_write_zeroes, __blkdev_issue_zero_pages())

root@dev linux-block (for-next) # sh test-discard-wz.sh 
+ modprobe -r null_blk
+ modprobe null_blk
+ blkdiscard -o 0 -l 40960 /dev/nullb0
+ dmesg -c
[ 1749.411466] null_blk: module loaded
*[ 1749.425918] __blkdev_issue_discard 82 sector 0 nr_sects 80*
+ blkdiscard -z -o 0 -l 40960 /dev/nullb0
+ dmesg -c
*[ 1749.443746] __blkdev_issue_zero_pages 289 sector 0 nr_sects 80*
+ modprobe -r null_blk
+ modprobe null_blk write_zeroes=1
+ blkdiscard -z -o 0 -l 40960 /dev/nullb0
+ dmesg -c
[ 1749.532618] null_blk: module loaded
*[ 1749.542257] __blkdev_issue_write_zeroes 242 sector 0 nr_sects 80*
+ modprobe -r null_blk
+ set +x

2. Debug patch to test disacrd and write-zeroes on the
   null_blk:
root@dev linux-block (for-next) # git diff 
diff --git a/block/blk-lib.c b/block/blk-lib.c
index fc6ea52e7482..a0e7891cae60 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -79,6 +79,8 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 
                WARN_ON_ONCE((req_sects << 9) > UINT_MAX);
 
+               pr_info("%s %d sector %llu nr_sects %llu\n",
+                               __func__, __LINE__, sector, nr_sects);
                bio = blk_next_bio(bio, bdev, 0, op, gfp_mask);
                bio->bi_iter.bi_sector = sector;
                bio->bi_iter.bi_size = req_sects << 9;
@@ -237,6 +239,8 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
                return -EOPNOTSUPP;
 
        while (nr_sects) {
+               pr_info("%s %d sector %llu nr_sects %llu\n",
+                               __func__, __LINE__, sector, nr_sects);
                bio = blk_next_bio(bio, bdev, 0, REQ_OP_WRITE_ZEROES, gfp_mask);
                bio->bi_iter.bi_sector = sector;
                if (flags & BLKDEV_ZERO_NOUNMAP)
@@ -282,6 +286,8 @@ static int __blkdev_issue_zero_pages(struct block_device *bdev,
                return -EPERM;
 
        while (nr_sects != 0) {
+               pr_info("%s %d sector %llu nr_sects %llu\n",
+                               __func__, __LINE__, sector, nr_sects);
                bio = blk_next_bio(bio, bdev, __blkdev_sectors_to_bio_pages(nr_sects),
                                   REQ_OP_WRITE, gfp_mask);
                bio->bi_iter.bi_sector = sector;
diff --git a/drivers/block/null_blk/main.c b/drivers/block/null_blk/main.c
index 13004beb48ca..584ac0519c3e 100644
--- a/drivers/block/null_blk/main.c
+++ b/drivers/block/null_blk/main.c
@@ -84,6 +84,9 @@ static bool g_virt_boundary = false;
 module_param_named(virt_boundary, g_virt_boundary, bool, 0444);
 MODULE_PARM_DESC(virt_boundary, "Require a virtual boundary for the device. Default: False");
 
+static bool g_write_zeroes = false;
+module_param_named(write_zeroes, g_write_zeroes, bool, 0444);
+
 static int g_no_sched;
 module_param_named(no_sched, g_no_sched, int, 0444);
 MODULE_PARM_DESC(no_sched, "No io scheduler");
@@ -1755,25 +1758,12 @@ static void null_del_dev(struct nullb *nullb)
 
 static void null_config_discard(struct nullb *nullb)
 {
-       if (nullb->dev->discard == false)
-               return;
-
-       if (!nullb->dev->memory_backed) {
-               nullb->dev->discard = false;
-               pr_info("discard option is ignored without memory backing\n");
-               return;
-       }
-
-       if (nullb->dev->zoned) {
-               nullb->dev->discard = false;
-               pr_info("discard option is ignored in zoned mode\n");
-               return;
-       }
-
        nullb->q->limits.discard_granularity = nullb->dev->blocksize;
        nullb->q->limits.discard_alignment = nullb->dev->blocksize;
        blk_queue_max_discard_sectors(nullb->q, UINT_MAX >> 9);
        blk_queue_flag_set(QUEUE_FLAG_DISCARD, nullb->q);
+       if (g_write_zeroes)
+               blk_queue_max_write_zeroes_sectors(nullb->q, UINT_MAX >> 9);
 }
 


-- 
2.29.0