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block: add a disk_openers helper

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Add a helper that returns the openers for a given gendisk to avoid having
drivers poke into disk->part0 to get at this information in a somewhat
cumbersome way.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20220330052917.2566582-5-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig 2022-03-30 07:29:06 +02:00 committed by Jens Axboe
parent 7a86d6dc14
commit dbdc1be325
3 changed files with 19 additions and 4 deletions
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4
drivers/block/nbd.c
View File

@ -1219,7 +1219,7 @@ static int nbd_reconnect_socket(struct nbd_device *nbd, unsigned long arg)
static void nbd_bdev_reset(struct nbd_device *nbd)
{
if (nbd->disk->part0->bd_openers > 1)
if (disk_openers(nbd->disk) > 1)
return;
set_capacity(nbd->disk, 0);
}
@ -1576,7 +1576,7 @@ static void nbd_release(struct gendisk *disk, fmode_t mode)
struct nbd_device *nbd = disk->private_data;
if (test_bit(NBD_RT_DISCONNECT_ON_CLOSE, &nbd->config->runtime_flags) &&
disk->part0->bd_openers == 0)
disk_openers(disk) == 0)
nbd_disconnect_and_put(nbd);
nbd_config_put(nbd);

4
drivers/block/zram/zram_drv.c
View File

@ -1800,7 +1800,7 @@ static ssize_t reset_store(struct device *dev,
mutex_lock(&disk->open_mutex);
/* Do not reset an active device or claimed device */
if (disk->part0->bd_openers || zram->claim) {
if (disk_openers(disk) || zram->claim) {
mutex_unlock(&disk->open_mutex);
return -EBUSY;
}
@ -1989,7 +1989,7 @@ static int zram_remove(struct zram *zram)
bool claimed;
mutex_lock(&zram->disk->open_mutex);
if (zram->disk->part0->bd_openers) {
if (disk_openers(zram->disk)) {
mutex_unlock(&zram->disk->open_mutex);
return -EBUSY;
}

15
include/linux/blkdev.h
View File

@ -176,6 +176,21 @@ static inline bool disk_live(struct gendisk *disk)
return !inode_unhashed(disk->part0->bd_inode);
}
/**
* disk_openers - returns how many openers are there for a disk
* @disk: disk to check
*
* This returns the number of openers for a disk. Note that this value is only
* stable if disk->open_mutex is held.
*
* Note: Due to a quirk in the block layer open code, each open partition is
* only counted once even if there are multiple openers.
*/
static inline unsigned int disk_openers(struct gendisk *disk)
{
return disk->part0->bd_openers;
}
/*
* The gendisk is refcounted by the part0 block_device, and the bd_device
* therein is also used for device model presentation in sysfs.