block: deprecate autoloading based on dev_t

Make the legacy dev_t based autoloading optional and add a deprecation
warning.  This kind of autoloading has ceased to be useful about 20 years
ago.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20220104071647.164918-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/Kconfig b/block/Kconfig
index d5d4197b7ed2d304f68d572b189bc5f0974505c4..205f8d01c69523d04d8aa0387d8039757c700101 100644 (file)
--- a/block/Kconfig
+++ b/block/Kconfig
@@ -26,6 +26,18 @@ menuconfig BLOCK
 
 if BLOCK
 
+config BLOCK_LEGACY_AUTOLOAD
+       bool "Legacy autoloading support"
+       help
+         Enable loading modules and creating block device instances based on
+         accesses through their device special file.  This is a historic Linux
+         feature and makes no sense in a udev world where device files are
+         created on demand.
+
+         Say N here unless booting or other functionality broke without it, in
+         which case you should also send a report to your distribution and
+         linux-block@vger.kernel.org.
+
 config BLK_RQ_ALLOC_TIME
        bool
 

diff --git a/block/bdev.c b/block/bdev.c
index 102837a370517c78d9d17d7793cfdf6d2ce6adc6..c687726445660851c083a7665dd7be8469d2bb37 100644 (file)
--- a/block/bdev.c
+++ b/block/bdev.c
@@ -733,12 +733,15 @@ struct block_device *blkdev_get_no_open(dev_t dev)
        struct inode *inode;
 
        inode = ilookup(blockdev_superblock, dev);
-       if (!inode) {
+       if (!inode && IS_ENABLED(CONFIG_BLOCK_LEGACY_AUTOLOAD)) {
                blk_request_module(dev);
                inode = ilookup(blockdev_superblock, dev);
-               if (!inode)
-                       return NULL;
+               if (inode)
+                       pr_warn_ratelimited(
+"block device autoloading is deprecated. It will be removed in Linux 5.19\n");
        }
+       if (!inode)
+               return NULL;
 
        /* switch from the inode reference to a device mode one: */
        bdev = &BDEV_I(inode)->bdev;

diff --git a/block/genhd.c b/block/genhd.c
index 626c8406f21a6a5b5def739ea87a8678e9732303..6ae990ff026603a7a24a71816de594081351fd01 100644 (file)
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -185,7 +185,9 @@ static struct blk_major_name {
        struct blk_major_name *next;
        int major;
        char name[16];
+#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
        void (*probe)(dev_t devt);
+#endif
 } *major_names[BLKDEV_MAJOR_HASH_SIZE];
 static DEFINE_MUTEX(major_names_lock);
 static DEFINE_SPINLOCK(major_names_spinlock);
@@ -275,7 +277,9 @@ int __register_blkdev(unsigned int major, const char *name,
        }
 
        p->major = major;
+#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
        p->probe = probe;
+#endif
        strlcpy(p->name, name, sizeof(p->name));
        p->next = NULL;
        index = major_to_index(major);
@@ -679,6 +683,7 @@ static ssize_t disk_badblocks_store(struct device *dev,
        return badblocks_store(disk->bb, page, len, 0);
 }
 
+#ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
 void blk_request_module(dev_t devt)
 {
        unsigned int major = MAJOR(devt);
@@ -698,6 +703,7 @@ void blk_request_module(dev_t devt)
                /* Make old-style 2.4 aliases work */
                request_module("block-major-%d", MAJOR(devt));
 }
+#endif /* CONFIG_BLOCK_LEGACY_AUTOLOAD */
 
 /*
  * print a full list of all partitions - intended for places where the root