* [PATCH (resend)] brd: remove brd_devices_mutex mutex
@ 2021-12-17 11:03 Tetsuo Handa
2021-12-19 21:35 ` Luis Chamberlain
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: Tetsuo Handa @ 2021-12-17 11:03 UTC (permalink / raw)
To: Christoph Hellwig, Luis Chamberlain; +Cc: linux-block
If brd_alloc() from brd_probe() is called before brd_alloc() from
brd_init() is called, module loading will fail with -EEXIST error.
To close this race, call __register_blkdev() just before leaving
brd_init().
Then, we can remove brd_devices_mutex mutex, for brd_device list
will no longer be accessed concurrently.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
---
drivers/block/brd.c | 73 +++++++++++++++++++--------------------------
1 file changed, 30 insertions(+), 43 deletions(-)
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index a896ee175d86..4aab5ed21ae8 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -362,7 +362,6 @@ __setup("ramdisk_size=", ramdisk_size);
* (should share code eventually).
*/
static LIST_HEAD(brd_devices);
-static DEFINE_MUTEX(brd_devices_mutex);
static struct dentry *brd_debugfs_dir;
static int brd_alloc(int i)
@@ -372,21 +371,14 @@ static int brd_alloc(int i)
char buf[DISK_NAME_LEN];
int err = -ENOMEM;
- mutex_lock(&brd_devices_mutex);
- list_for_each_entry(brd, &brd_devices, brd_list) {
- if (brd->brd_number == i) {
- mutex_unlock(&brd_devices_mutex);
+ list_for_each_entry(brd, &brd_devices, brd_list)
+ if (brd->brd_number == i)
return -EEXIST;
- }
- }
brd = kzalloc(sizeof(*brd), GFP_KERNEL);
- if (!brd) {
- mutex_unlock(&brd_devices_mutex);
+ if (!brd)
return -ENOMEM;
- }
brd->brd_number = i;
list_add_tail(&brd->brd_list, &brd_devices);
- mutex_unlock(&brd_devices_mutex);
spin_lock_init(&brd->brd_lock);
INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
@@ -430,9 +422,7 @@ static int brd_alloc(int i)
out_cleanup_disk:
blk_cleanup_disk(disk);
out_free_dev:
- mutex_lock(&brd_devices_mutex);
list_del(&brd->brd_list);
- mutex_unlock(&brd_devices_mutex);
kfree(brd);
return err;
}
@@ -442,15 +432,19 @@ static void brd_probe(dev_t dev)
brd_alloc(MINOR(dev) / max_part);
}
-static void brd_del_one(struct brd_device *brd)
+static void brd_cleanup(void)
{
- del_gendisk(brd->brd_disk);
- blk_cleanup_disk(brd->brd_disk);
- brd_free_pages(brd);
- mutex_lock(&brd_devices_mutex);
- list_del(&brd->brd_list);
- mutex_unlock(&brd_devices_mutex);
- kfree(brd);
+ struct brd_device *brd, *next;
+
+ debugfs_remove_recursive(brd_debugfs_dir);
+
+ list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
+ del_gendisk(brd->brd_disk);
+ blk_cleanup_disk(brd->brd_disk);
+ brd_free_pages(brd);
+ list_del(&brd->brd_list);
+ kfree(brd);
+ }
}
static inline void brd_check_and_reset_par(void)
@@ -474,9 +468,18 @@ static inline void brd_check_and_reset_par(void)
static int __init brd_init(void)
{
- struct brd_device *brd, *next;
int err, i;
+ brd_check_and_reset_par();
+
+ brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);
+
+ for (i = 0; i < rd_nr; i++) {
+ err = brd_alloc(i);
+ if (err)
+ goto out_free;
+ }
+
/*
* brd module now has a feature to instantiate underlying device
* structure on-demand, provided that there is an access dev node.
@@ -492,28 +495,16 @@ static int __init brd_init(void)
* dynamically.
*/
- if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe))
- return -EIO;
-
- brd_check_and_reset_par();
-
- brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);
-
- for (i = 0; i < rd_nr; i++) {
- err = brd_alloc(i);
- if (err)
- goto out_free;
+ if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe)) {
+ err = -EIO;
+ goto out_free;
}
pr_info("brd: module loaded\n");
return 0;
out_free:
- unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
- debugfs_remove_recursive(brd_debugfs_dir);
-
- list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
- brd_del_one(brd);
+ brd_cleanup();
pr_info("brd: module NOT loaded !!!\n");
return err;
@@ -521,13 +512,9 @@ static int __init brd_init(void)
static void __exit brd_exit(void)
{
- struct brd_device *brd, *next;
unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
- debugfs_remove_recursive(brd_debugfs_dir);
-
- list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
- brd_del_one(brd);
+ brd_cleanup();
pr_info("brd: module unloaded\n");
}
--
2.32.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH (resend)] brd: remove brd_devices_mutex mutex
2021-12-17 11:03 [PATCH (resend)] brd: remove brd_devices_mutex mutex Tetsuo Handa
@ 2021-12-19 21:35 ` Luis Chamberlain
2021-12-21 9:34 ` Christoph Hellwig
2021-12-23 14:50 ` Tetsuo Handa
2 siblings, 0 replies; 4+ messages in thread
From: Luis Chamberlain @ 2021-12-19 21:35 UTC (permalink / raw)
To: Tetsuo Handa; +Cc: Christoph Hellwig, linux-block
On Fri, Dec 17, 2021 at 08:03:48PM +0900, Tetsuo Handa wrote:
> If brd_alloc() from brd_probe() is called before brd_alloc() from
> brd_init() is called, module loading will fail with -EEXIST error.
> To close this race, call __register_blkdev() just before leaving
> brd_init().
>
> Then, we can remove brd_devices_mutex mutex, for brd_device list
> will no longer be accessed concurrently.
>
> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Luis
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH (resend)] brd: remove brd_devices_mutex mutex
2021-12-17 11:03 [PATCH (resend)] brd: remove brd_devices_mutex mutex Tetsuo Handa
2021-12-19 21:35 ` Luis Chamberlain
@ 2021-12-21 9:34 ` Christoph Hellwig
2021-12-23 14:50 ` Tetsuo Handa
2 siblings, 0 replies; 4+ messages in thread
From: Christoph Hellwig @ 2021-12-21 9:34 UTC (permalink / raw)
To: Tetsuo Handa; +Cc: Christoph Hellwig, Luis Chamberlain, linux-block
Looks good,
Reviewed-by: Christoph Hellwig <hch@lst.de>
^ permalink raw reply [flat|nested] 4+ messages in thread
* [PATCH (resend)] brd: remove brd_devices_mutex mutex
2021-12-17 11:03 [PATCH (resend)] brd: remove brd_devices_mutex mutex Tetsuo Handa
2021-12-19 21:35 ` Luis Chamberlain
2021-12-21 9:34 ` Christoph Hellwig
@ 2021-12-23 14:50 ` Tetsuo Handa
2 siblings, 0 replies; 4+ messages in thread
From: Tetsuo Handa @ 2021-12-23 14:50 UTC (permalink / raw)
To: Jens Axboe; +Cc: linux-block
If brd_alloc() from brd_probe() is called before brd_alloc() from
brd_init() is called, module loading will fail with -EEXIST error.
To close this race, call __register_blkdev() just before leaving
brd_init().
Then, we can remove brd_devices_mutex mutex, for brd_device list
will no longer be accessed concurrently.
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Reviewed-by: Luis Chamberlain <mcgrof@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
---
drivers/block/brd.c | 73 +++++++++++++++++++--------------------------
1 file changed, 30 insertions(+), 43 deletions(-)
diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index a896ee175d86..4aab5ed21ae8 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -362,7 +362,6 @@ __setup("ramdisk_size=", ramdisk_size);
* (should share code eventually).
*/
static LIST_HEAD(brd_devices);
-static DEFINE_MUTEX(brd_devices_mutex);
static struct dentry *brd_debugfs_dir;
static int brd_alloc(int i)
@@ -372,21 +371,14 @@ static int brd_alloc(int i)
char buf[DISK_NAME_LEN];
int err = -ENOMEM;
- mutex_lock(&brd_devices_mutex);
- list_for_each_entry(brd, &brd_devices, brd_list) {
- if (brd->brd_number == i) {
- mutex_unlock(&brd_devices_mutex);
+ list_for_each_entry(brd, &brd_devices, brd_list)
+ if (brd->brd_number == i)
return -EEXIST;
- }
- }
brd = kzalloc(sizeof(*brd), GFP_KERNEL);
- if (!brd) {
- mutex_unlock(&brd_devices_mutex);
+ if (!brd)
return -ENOMEM;
- }
brd->brd_number = i;
list_add_tail(&brd->brd_list, &brd_devices);
- mutex_unlock(&brd_devices_mutex);
spin_lock_init(&brd->brd_lock);
INIT_RADIX_TREE(&brd->brd_pages, GFP_ATOMIC);
@@ -430,9 +422,7 @@ static int brd_alloc(int i)
out_cleanup_disk:
blk_cleanup_disk(disk);
out_free_dev:
- mutex_lock(&brd_devices_mutex);
list_del(&brd->brd_list);
- mutex_unlock(&brd_devices_mutex);
kfree(brd);
return err;
}
@@ -442,15 +432,19 @@ static void brd_probe(dev_t dev)
brd_alloc(MINOR(dev) / max_part);
}
-static void brd_del_one(struct brd_device *brd)
+static void brd_cleanup(void)
{
- del_gendisk(brd->brd_disk);
- blk_cleanup_disk(brd->brd_disk);
- brd_free_pages(brd);
- mutex_lock(&brd_devices_mutex);
- list_del(&brd->brd_list);
- mutex_unlock(&brd_devices_mutex);
- kfree(brd);
+ struct brd_device *brd, *next;
+
+ debugfs_remove_recursive(brd_debugfs_dir);
+
+ list_for_each_entry_safe(brd, next, &brd_devices, brd_list) {
+ del_gendisk(brd->brd_disk);
+ blk_cleanup_disk(brd->brd_disk);
+ brd_free_pages(brd);
+ list_del(&brd->brd_list);
+ kfree(brd);
+ }
}
static inline void brd_check_and_reset_par(void)
@@ -474,9 +468,18 @@ static inline void brd_check_and_reset_par(void)
static int __init brd_init(void)
{
- struct brd_device *brd, *next;
int err, i;
+ brd_check_and_reset_par();
+
+ brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);
+
+ for (i = 0; i < rd_nr; i++) {
+ err = brd_alloc(i);
+ if (err)
+ goto out_free;
+ }
+
/*
* brd module now has a feature to instantiate underlying device
* structure on-demand, provided that there is an access dev node.
@@ -492,28 +495,16 @@ static int __init brd_init(void)
* dynamically.
*/
- if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe))
- return -EIO;
-
- brd_check_and_reset_par();
-
- brd_debugfs_dir = debugfs_create_dir("ramdisk_pages", NULL);
-
- for (i = 0; i < rd_nr; i++) {
- err = brd_alloc(i);
- if (err)
- goto out_free;
+ if (__register_blkdev(RAMDISK_MAJOR, "ramdisk", brd_probe)) {
+ err = -EIO;
+ goto out_free;
}
pr_info("brd: module loaded\n");
return 0;
out_free:
- unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
- debugfs_remove_recursive(brd_debugfs_dir);
-
- list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
- brd_del_one(brd);
+ brd_cleanup();
pr_info("brd: module NOT loaded !!!\n");
return err;
@@ -521,13 +512,9 @@ static int __init brd_init(void)
static void __exit brd_exit(void)
{
- struct brd_device *brd, *next;
unregister_blkdev(RAMDISK_MAJOR, "ramdisk");
- debugfs_remove_recursive(brd_debugfs_dir);
-
- list_for_each_entry_safe(brd, next, &brd_devices, brd_list)
- brd_del_one(brd);
+ brd_cleanup();
pr_info("brd: module unloaded\n");
}
--
2.32.0
^ permalink raw reply related [flat|nested] 4+ messages in thread
end of thread, other threads:[~2021-12-23 14:50 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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2021-12-17 11:03 [PATCH (resend)] brd: remove brd_devices_mutex mutex Tetsuo Handa
2021-12-19 21:35 ` Luis Chamberlain
2021-12-21 9:34 ` Christoph Hellwig
2021-12-23 14:50 ` Tetsuo Handa
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