block: RCU protect disk->conv_zones_bitmap

Ensure that a disk revalidation changing the conventional zones bitmap
of a disk does not cause invalid memory references when using the
disk_zone_is_conv() helper by RCU protecting the disk->conv_zones_bitmap
pointer.

disk_zone_is_conv() is modified to operate under the RCU read lock and
the function disk_set_conv_zones_bitmap() is added to update a disk
conv_zones_bitmap pointer using rcu_replace_pointer() with the disk
zone_wplugs_lock spinlock held.

disk_free_zone_resources() is modified to call
disk_update_zone_resources() with a NULL bitmap pointer to free the disk
conv_zones_bitmap. disk_set_conv_zones_bitmap() is also used in
disk_update_zone_resources() to set the new (revalidated) bitmap and
free the old one.

Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Link: https://lore.kernel.org/r/20241107064300.227731-2-dlemoal@kernel.org
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index f7e151f665c7e1a4c6ef03ebfccd591f6cce8f83..da710067e52756f41070fa9c567685401534c357 100644 (file)
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -350,9 +350,15 @@ fail:
 
 static inline bool disk_zone_is_conv(struct gendisk *disk, sector_t sector)
 {
-       if (!disk->conv_zones_bitmap)
-               return false;
-       return test_bit(disk_zone_no(disk, sector), disk->conv_zones_bitmap);
+       unsigned long *bitmap;
+       bool is_conv;
+
+       rcu_read_lock();
+       bitmap = rcu_dereference(disk->conv_zones_bitmap);
+       is_conv = bitmap && test_bit(disk_zone_no(disk, sector), bitmap);
+       rcu_read_unlock();
+
+       return is_conv;
 }
 
 static bool disk_zone_is_last(struct gendisk *disk, struct blk_zone *zone)
@@ -1455,6 +1461,24 @@ static void disk_destroy_zone_wplugs_hash_table(struct gendisk *disk)
        disk->zone_wplugs_hash_bits = 0;
 }
 
+static unsigned int disk_set_conv_zones_bitmap(struct gendisk *disk,
+                                              unsigned long *bitmap)
+{
+       unsigned int nr_conv_zones = 0;
+       unsigned long flags;
+
+       spin_lock_irqsave(&disk->zone_wplugs_lock, flags);
+       if (bitmap)
+               nr_conv_zones = bitmap_weight(bitmap, disk->nr_zones);
+       bitmap = rcu_replace_pointer(disk->conv_zones_bitmap, bitmap,
+                                    lockdep_is_held(&disk->zone_wplugs_lock));
+       spin_unlock_irqrestore(&disk->zone_wplugs_lock, flags);
+
+       kfree_rcu_mightsleep(bitmap);
+
+       return nr_conv_zones;
+}
+
 void disk_free_zone_resources(struct gendisk *disk)
 {
        if (!disk->zone_wplugs_pool)
@@ -1478,8 +1502,7 @@ void disk_free_zone_resources(struct gendisk *disk)
        mempool_destroy(disk->zone_wplugs_pool);
        disk->zone_wplugs_pool = NULL;
 
-       bitmap_free(disk->conv_zones_bitmap);
-       disk->conv_zones_bitmap = NULL;
+       disk_set_conv_zones_bitmap(disk, NULL);
        disk->zone_capacity = 0;
        disk->last_zone_capacity = 0;
        disk->nr_zones = 0;
@@ -1538,17 +1561,15 @@ static int disk_update_zone_resources(struct gendisk *disk,
                                      struct blk_revalidate_zone_args *args)
 {
        struct request_queue *q = disk->queue;
-       unsigned int nr_seq_zones, nr_conv_zones = 0;
+       unsigned int nr_seq_zones, nr_conv_zones;
        unsigned int pool_size;
        struct queue_limits lim;
 
        disk->nr_zones = args->nr_zones;
        disk->zone_capacity = args->zone_capacity;
        disk->last_zone_capacity = args->last_zone_capacity;
-       swap(disk->conv_zones_bitmap, args->conv_zones_bitmap);
-       if (disk->conv_zones_bitmap)
-               nr_conv_zones = bitmap_weight(disk->conv_zones_bitmap,
-                                             disk->nr_zones);
+       nr_conv_zones =
+               disk_set_conv_zones_bitmap(disk, args->conv_zones_bitmap);
        if (nr_conv_zones >= disk->nr_zones) {
                pr_warn("%s: Invalid number of conventional zones %u / %u\n",
                        disk->disk_name, nr_conv_zones, disk->nr_zones);
@@ -1817,8 +1838,6 @@ int blk_revalidate_disk_zones(struct gendisk *disk)
                disk_free_zone_resources(disk);
        blk_mq_unfreeze_queue(q);
 
-       kfree(args.conv_zones_bitmap);
-
        return ret;
 }
 EXPORT_SYMBOL_GPL(blk_revalidate_disk_zones);

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 7bfc877e159e1e81ec0d0747eaaa06d3d856cdb7..6d379803c7775b951041eeaa8a1b0e263a52407e 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -195,7 +195,7 @@ struct gendisk {
        unsigned int            nr_zones;
        unsigned int            zone_capacity;
        unsigned int            last_zone_capacity;
-       unsigned long           *conv_zones_bitmap;
+       unsigned long __rcu     *conv_zones_bitmap;
        unsigned int            zone_wplugs_hash_bits;
        spinlock_t              zone_wplugs_lock;
        struct mempool_s        *zone_wplugs_pool;