[PATCH 15/15] loop: use the atomic queue limits update API

[Christoph Hellwig]

Pass the default limits to blk_mq_alloc_disk and then use the
queue_limits_{start,commit}_update API to change the limits in an
atomic way on existing loop gendisks.

Signed-off-by: Christoph Hellwig <h...@lst.de>
---
 drivers/block/loop.c | 41 +++++++++++++++++++++++++----------------
 1 file changed, 25 insertions(+), 16 deletions(-)

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 26c8ea79086798..28a95fd366fea5 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -750,11 +750,11 @@ static void loop_sysfs_exit(struct loop_device *lo)
                                   &loop_attribute_group);
 }
 
-static void loop_config_discard(struct loop_device *lo)
+static void loop_config_discard(struct loop_device *lo,
+               struct queue_limits *lim)
 {
        struct file *file = lo->lo_backing_file;
        struct inode *inode = file->f_mapping->host;
-       struct request_queue *q = lo->lo_queue;
        u32 granularity = 0, max_discard_sectors = 0;
        struct kstatfs sbuf;
 
@@ -781,12 +781,12 @@ static void loop_config_discard(struct loop_device *lo)
                granularity = sbuf.f_bsize;
        }
 
-       blk_queue_max_discard_sectors(q, max_discard_sectors);
-       blk_queue_max_write_zeroes_sectors(q, max_discard_sectors);
+       lim->max_hw_discard_sectors = max_discard_sectors;
+       lim->max_write_zeroes_sectors = max_discard_sectors;
        if (max_discard_sectors)
-               q->limits.discard_granularity = granularity;
+               lim->discard_granularity = granularity;
        else
-               q->limits.discard_granularity = 0;
+               lim->discard_granularity = 0;
 }
 
 struct loop_worker {
@@ -975,6 +975,20 @@ loop_set_status_from_info(struct loop_device *lo,
        return 0;
 }
 
+static int loop_reconfigure_limits(struct loop_device *lo, unsigned short 
bsize,
+               bool update_discard_settings)
+{
+       struct queue_limits lim;
+
+       lim = queue_limits_start_update(lo->lo_queue);
+       lim.logical_block_size = bsize;
+       lim.physical_block_size = bsize;
+       lim.io_min = bsize;
+       if (update_discard_settings)
+               loop_config_discard(lo, &lim);
+       return queue_limits_commit_update(lo->lo_queue, &lim);
+}
+
 static int loop_configure(struct loop_device *lo, blk_mode_t mode,
                          struct block_device *bdev,
                          const struct loop_config *config)
@@ -1072,11 +1086,10 @@ static int loop_configure(struct loop_device *lo, 
blk_mode_t mode,
        else
                bsize = 512;
 
-       blk_queue_logical_block_size(lo->lo_queue, bsize);
-       blk_queue_physical_block_size(lo->lo_queue, bsize);
-       blk_queue_io_min(lo->lo_queue, bsize);
+       error = loop_reconfigure_limits(lo, bsize, true);
+       if (WARN_ON_ONCE(error))
+               goto out_unlock;
 
-       loop_config_discard(lo);
        loop_update_rotational(lo);
        loop_update_dio(lo);
        loop_sysfs_init(lo);
@@ -1143,9 +1156,7 @@ static void __loop_clr_fd(struct loop_device *lo, bool 
release)
        lo->lo_offset = 0;
        lo->lo_sizelimit = 0;
        memset(lo->lo_file_name, 0, LO_NAME_SIZE);
-       blk_queue_logical_block_size(lo->lo_queue, 512);
-       blk_queue_physical_block_size(lo->lo_queue, 512);
-       blk_queue_io_min(lo->lo_queue, 512);
+       loop_reconfigure_limits(lo, 512, false);
        invalidate_disk(lo->lo_disk);
        loop_sysfs_exit(lo);
        /* let user-space know about this change */
@@ -1477,9 +1488,7 @@ static int loop_set_block_size(struct loop_device *lo, 
unsigned long arg)
        invalidate_bdev(lo->lo_device);
 
        blk_mq_freeze_queue(lo->lo_queue);
-       blk_queue_logical_block_size(lo->lo_queue, arg);
-       blk_queue_physical_block_size(lo->lo_queue, arg);
-       blk_queue_io_min(lo->lo_queue, arg);
+       err = loop_reconfigure_limits(lo, arg, false);
        loop_update_dio(lo);
        blk_mq_unfreeze_queue(lo->lo_queue);
 
-- 
2.39.2