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block: prevent block device lookups at the beginning of del_gendisk

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As an artifact of how gendisk lookup used to work in earlier kernels,
GENHD_FL_UP is only cleared very late in del_gendisk, and a global lock
is used to prevent opens from succeeding while del_gendisk is tearing
down the gendisk.  Switch to clearing the flag early and under bd_mutex
so that callers can use bd_mutex to stabilize the flag, which removes
the need for the global mutex.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ming Lei <ming.lei@redhat.com>
Link: https://lore.kernel.org/r/20210514131842.1600568-2-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Christoph Hellwig
2021-05-14 15:18:41 +02:00
committed by Jens Axboe
parent 9a66e6bd7e
commit 6c60ff048c
3 changed files with 6 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

15
fs/block_dev.c
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@@ -1298,6 +1298,9 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode)
struct gendisk *disk = bdev->bd_disk;
int ret = 0;
if (!(disk->flags & GENHD_FL_UP))
return -ENXIO;
if (!bdev->bd_openers) {
if (!bdev_is_partition(bdev)) {
ret = 0;
@@ -1332,8 +1335,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode)
whole->bd_part_count++;
mutex_unlock(&whole->bd_mutex);
if (!(disk->flags & GENHD_FL_UP) ||
!bdev_nr_sectors(bdev)) {
if (!bdev_nr_sectors(bdev)) {
__blkdev_put(whole, mode, 1);
bdput(whole);
return -ENXIO;
@@ -1364,16 +1366,12 @@ struct block_device *blkdev_get_no_open(dev_t dev)
struct block_device *bdev;
struct gendisk *disk;
down_read(&bdev_lookup_sem);
bdev = bdget(dev);
if (!bdev) {
up_read(&bdev_lookup_sem);
blk_request_module(dev);
down_read(&bdev_lookup_sem);
bdev = bdget(dev);
if (!bdev)
goto unlock;
return NULL;
}
disk = bdev->bd_disk;
@@ -1383,14 +1381,11 @@ struct block_device *blkdev_get_no_open(dev_t dev)
goto put_disk;
if (!try_module_get(bdev->bd_disk->fops->owner))
goto put_disk;
up_read(&bdev_lookup_sem);
return bdev;
put_disk:
put_disk(disk);
bdput:
bdput(bdev);
unlock:
up_read(&bdev_lookup_sem);
return NULL;
}