[PATCH 06/19] block: add an optional probe callback to major_names

Christoph Hellwig
2020-08-26T06:40:10Z

Add a callback to the major_names array that allows a driver to override
how to probe for dev_t that doesn't currently have a gendisk registered.
This will help separating the lookup of the gendisk by dev_t vs probe
action for a not currently registered dev_t.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
block/genhd.c | 21 ++++++++++++++++++---
include/linux/genhd.h | 5 ++++-
2 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index 00164304317cfa..4cbeff3ec1ef5a 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -402,6 +402,7 @@ static struct blk_major_name {
struct blk_major_name *next;
int major;
char name[16];
+ void (*probe)(dev_t devt);
} *major_names[BLKDEV_MAJOR_HASH_SIZE];
static DEFINE_MUTEX(major_names_lock);

@@ -444,7 +445,8 @@ void blkdev_show(struct seq_file *seqf, off_t offset)
* See Documentation/admin-guide/devices.txt for the list of allocated
* major numbers.
*/
-int register_blkdev(unsigned int major, const char *name)
+int __register_blkdev(unsigned int major, const char *name,
+ void (*probe)(dev_t devt))
{
struct blk_major_name **n, *p;
int index, ret = 0;
@@ -483,6 +485,7 @@ int register_blkdev(unsigned int major, const char *name)
}

p->major = major;
+ p->probe = probe;
strlcpy(p->name, name, sizeof(p->name));
p->next = NULL;
index = major_to_index(major);
@@ -505,8 +508,7 @@ int register_blkdev(unsigned int major, const char *name)
mutex_unlock(&major_names_lock);
return ret;
}
-
-EXPORT_SYMBOL(register_blkdev);
+EXPORT_SYMBOL(__register_blkdev);

void unregister_blkdev(unsigned int major, const char *name)
{
@@ -1037,6 +1039,19 @@ static ssize_t disk_badblocks_store(struct device *dev,

static void request_gendisk_module(dev_t devt)
{
+ unsigned int major = MAJOR(devt);
+ struct blk_major_name **n;
+
+ mutex_lock(&major_names_lock);
+ for (n = &major_names[major_to_index(major)]; *n; n = &(*n)->next) {
+ if ((*n)->major == major && (*n)->probe) {
+ (*n)->probe(devt);
+ mutex_unlock(&major_names_lock);
+ return;
+ }
+ }
+ mutex_unlock(&major_names_lock);
+
if (request_module("block-major-%d-%d", MAJOR(devt), MINOR(devt)) > 0)
/* Make old-style 2.4 aliases work */
request_module("block-major-%d", MAJOR(devt));
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 4ab853461dff25..c0bde190a3dd0c 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -369,7 +369,10 @@ extern void blk_unregister_region(dev_t devt, unsigned long range);

#define alloc_disk(minors) alloc_disk_node(minors, NUMA_NO_NODE)

-int register_blkdev(unsigned int major, const char *name);
+int __register_blkdev(unsigned int major, const char *name,
+ void (*probe)(dev_t devt));
+#define register_blkdev(major, name) \
+ __register_blkdev(major, name, NULL)
void unregister_blkdev(unsigned int major, const char *name);

int revalidate_disk(struct gendisk *disk);
--
2.28.0