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Date:   Sun, 30 Aug 2020 08:24:30 +0200
From:   Christoph Hellwig <hch@....de>
To:     Jens Axboe <axboe@...nel.dk>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Denis Efremov <efremov@...ux.com>,
        "David S. Miller" <davem@...emloft.net>,
        Song Liu <song@...nel.org>, Al Viro <viro@...iv.linux.org.uk>,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-ide@...r.kernel.org, linux-raid@...r.kernel.org,
        linux-scsi@...r.kernel.org, linux-m68k@...ts.linux-m68k.org
Subject: [PATCH 04/19] block: split block_class_lock

Split the block_class_lock mutex into one each to protect bdev_map
and major_names.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 block/genhd.c | 29 +++++++++++++++--------------
 1 file changed, 15 insertions(+), 14 deletions(-)

diff --git a/block/genhd.c b/block/genhd.c
index df6485223a2c3d..0ae6210e141ee5 100644
--- a/block/genhd.c
+++ b/block/genhd.c
@@ -25,7 +25,6 @@
 
 #include "blk.h"
 
-static DEFINE_MUTEX(block_class_lock);
 static struct kobject *block_depr;
 
 struct bdev_map {
@@ -37,6 +36,7 @@ struct bdev_map {
 	int (*lock)(dev_t, void *);
 	void *data;
 } *bdev_map[255];
+static DEFINE_MUTEX(bdev_map_lock);
 
 /* for extended dynamic devt allocation, currently only one major is used */
 #define NR_EXT_DEVT		(1 << MINORBITS)
@@ -403,6 +403,7 @@ static struct blk_major_name {
 	int major;
 	char name[16];
 } *major_names[BLKDEV_MAJOR_HASH_SIZE];
+static DEFINE_MUTEX(major_names_lock);
 
 /* index in the above - for now: assume no multimajor ranges */
 static inline int major_to_index(unsigned major)
@@ -415,11 +416,11 @@ void blkdev_show(struct seq_file *seqf, off_t offset)
 {
 	struct blk_major_name *dp;
 
-	mutex_lock(&block_class_lock);
+	mutex_lock(&major_names_lock);
 	for (dp = major_names[major_to_index(offset)]; dp; dp = dp->next)
 		if (dp->major == offset)
 			seq_printf(seqf, "%3d %s\n", dp->major, dp->name);
-	mutex_unlock(&block_class_lock);
+	mutex_unlock(&major_names_lock);
 }
 #endif /* CONFIG_PROC_FS */
 
@@ -448,7 +449,7 @@ int register_blkdev(unsigned int major, const char *name)
 	struct blk_major_name **n, *p;
 	int index, ret = 0;
 
-	mutex_lock(&block_class_lock);
+	mutex_lock(&major_names_lock);
 
 	/* temporary */
 	if (major == 0) {
@@ -501,7 +502,7 @@ int register_blkdev(unsigned int major, const char *name)
 		kfree(p);
 	}
 out:
-	mutex_unlock(&block_class_lock);
+	mutex_unlock(&major_names_lock);
 	return ret;
 }
 
@@ -513,7 +514,7 @@ void unregister_blkdev(unsigned int major, const char *name)
 	struct blk_major_name *p = NULL;
 	int index = major_to_index(major);
 
-	mutex_lock(&block_class_lock);
+	mutex_lock(&major_names_lock);
 	for (n = &major_names[index]; *n; n = &(*n)->next)
 		if ((*n)->major == major)
 			break;
@@ -523,7 +524,7 @@ void unregister_blkdev(unsigned int major, const char *name)
 		p = *n;
 		*n = p->next;
 	}
-	mutex_unlock(&block_class_lock);
+	mutex_unlock(&major_names_lock);
 	kfree(p);
 }
 
@@ -674,7 +675,7 @@ void blk_register_region(dev_t devt, unsigned long range, struct module *module,
 		p->data = data;
 	}
 
-	mutex_lock(&block_class_lock);
+	mutex_lock(&bdev_map_lock);
 	for (i = 0, p -= n; i < n; i++, p++, index++) {
 		struct bdev_map **s = &bdev_map[index % 255];
 		while (*s && (*s)->range < range)
@@ -682,7 +683,7 @@ void blk_register_region(dev_t devt, unsigned long range, struct module *module,
 		p->next = *s;
 		*s = p;
 	}
-	mutex_unlock(&block_class_lock);
+	mutex_unlock(&bdev_map_lock);
 }
 EXPORT_SYMBOL(blk_register_region);
 
@@ -693,7 +694,7 @@ void blk_unregister_region(dev_t devt, unsigned long range)
 	unsigned i;
 	struct bdev_map *found = NULL;
 
-	mutex_lock(&block_class_lock);
+	mutex_lock(&bdev_map_lock);
 	for (i = 0; i < min(n, 255u); i++, index++) {
 		struct bdev_map **s;
 		for (s = &bdev_map[index % 255]; *s; s = &(*s)->next) {
@@ -706,7 +707,7 @@ void blk_unregister_region(dev_t devt, unsigned long range)
 			}
 		}
 	}
-	mutex_unlock(&block_class_lock);
+	mutex_unlock(&bdev_map_lock);
 	kfree(found);
 }
 EXPORT_SYMBOL(blk_unregister_region);
@@ -1041,7 +1042,7 @@ static struct gendisk *lookup_gendisk(dev_t dev, int *partno)
 	unsigned long best = ~0UL;
 
 retry:
-	mutex_lock(&block_class_lock);
+	mutex_lock(&bdev_map_lock);
 	for (p = bdev_map[MAJOR(dev) % 255]; p; p = p->next) {
 		struct kobject *(*probe)(dev_t, int *, void *);
 		struct module *owner;
@@ -1062,7 +1063,7 @@ static struct gendisk *lookup_gendisk(dev_t dev, int *partno)
 			module_put(owner);
 			continue;
 		}
-		mutex_unlock(&block_class_lock);
+		mutex_unlock(&bdev_map_lock);
 		kobj = probe(dev, partno, data);
 		/* Currently ->owner protects _only_ ->probe() itself. */
 		module_put(owner);
@@ -1070,7 +1071,7 @@ static struct gendisk *lookup_gendisk(dev_t dev, int *partno)
 			return dev_to_disk(kobj_to_dev(kobj));
 		goto retry;
 	}
-	mutex_unlock(&block_class_lock);
+	mutex_unlock(&bdev_map_lock);
 	return NULL;
 }
 
-- 
2.28.0

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