Patch "block: retry call probe after request_module in blk_request_module" has been added to the 5.15-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    block: retry call probe after request_module in blk_request_module

to the 5.15-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     block-retry-call-probe-after-request_module-in-blk_r.patch
and it can be found in the queue-5.15 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit de934d2a46c44fbaa8a1606f098645b837d7a468
Author: Yang Erkun <yangerkun@xxxxxxxxxx>
Date:   Mon Dec 9 19:04:35 2024 +0800

    block: retry call probe after request_module in blk_request_module
    
    [ Upstream commit 457ef47c08d2979f3e59ce66267485c3faed70c8 ]
    
    Set kernel config:
    
     CONFIG_BLK_DEV_LOOP=m
     CONFIG_BLK_DEV_LOOP_MIN_COUNT=0
    
    Do latter:
    
     mknod loop0 b 7 0
     exec 4<> loop0
    
    Before commit e418de3abcda ("block: switch gendisk lookup to a simple
    xarray"), lookup_gendisk will first use base_probe to load module loop,
    and then the retry will call loop_probe to prepare the loop disk. Finally
    open for this disk will success. However, after this commit, we lose the
    retry logic, and open will fail with ENXIO. Block device autoloading is
    deprecated and will be removed soon, but maybe we should keep open success
    until we really remove it. So, give a retry to fix it.
    
    Fixes: e418de3abcda ("block: switch gendisk lookup to a simple xarray")
    Suggested-by: Christoph Hellwig <hch@xxxxxx>
    Signed-off-by: Yang Erkun <yangerkun@xxxxxxxxxx>
    Reviewed-by: Christoph Hellwig <hch@xxxxxx>
    Link: https://lore.kernel.org/r/20241209110435.3670985-1-yangerkun@xxxxxxxxxxxxxxx
    Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/block/genhd.c b/block/genhd.c
index 2f66745de5d5a..421e02794614e 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -674,7 +674,7 @@ static ssize_t disk_badblocks_store(struct device *dev,
 }
 
 #ifdef CONFIG_BLOCK_LEGACY_AUTOLOAD
-void blk_request_module(dev_t devt)
+static bool blk_probe_dev(dev_t devt)
 {
 	unsigned int major = MAJOR(devt);
 	struct blk_major_name **n;
@@ -684,14 +684,26 @@ void blk_request_module(dev_t devt)
 		if ((*n)->major == major && (*n)->probe) {
 			(*n)->probe(devt);
 			mutex_unlock(&major_names_lock);
-			return;
+			return true;
 		}
 	}
 	mutex_unlock(&major_names_lock);
+	return false;
+}
+
+void blk_request_module(dev_t devt)
+{
+	int error;
+
+	if (blk_probe_dev(devt))
+		return;
 
-	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));
+	error = request_module("block-major-%d-%d", MAJOR(devt), MINOR(devt));
+	/* Make old-style 2.4 aliases work */
+	if (error > 0)
+		error = request_module("block-major-%d", MAJOR(devt));
+	if (!error)
+		blk_probe_dev(devt);
 }
 #endif /* CONFIG_BLOCK_LEGACY_AUTOLOAD */