lo_refcount counts how many openers a loop device has, but that count
is already provided by the block layer in the bd_openers field of the
whole-disk block_device. Remove lo_refcount and allow opens to
succeed even on devices beeing deleted - now that ->free_disk is
implemented we can handle that race gracefull and all I/O on it will
just fail. Similarly there is a small race window now where
loop_control_remove does not synchronize the delete vs the remove
due do bd_openers not being under lo_mutex protection, but we can
handle that just as gracefully.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Reviewed-by: Jan Kara <jack@xxxxxxx>
---
drivers/block/loop.c | 37 +++++++------------------------------
drivers/block/loop.h | 1 -
2 files changed, 7 insertions(+), 31 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ea3b0e055657f..ca7103807d34a 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1249,7 +1249,7 @@ static int loop_clr_fd(struct loop_device *lo)
* <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
* command to fail with EBUSY.
*/
- if (atomic_read(&lo->lo_refcnt) > 1) {
+ if (disk_openers(lo->lo_disk) > 1) {
lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
loop_global_unlock(lo, true);
return 0;
@@ -1729,33 +1729,15 @@ static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
}
#endif
-static int lo_open(struct block_device *bdev, fmode_t mode)
-{
- struct loop_device *lo = bdev->bd_disk->private_data;
- int err;
-
- err = mutex_lock_killable(&lo->lo_mutex);
- if (err)
- return err;
- if (lo->lo_state == Lo_deleting)
- err = -ENXIO;
- else
- atomic_inc(&lo->lo_refcnt);
- mutex_unlock(&lo->lo_mutex);
- return err;
-}
-
static void lo_release(struct gendisk *disk, fmode_t mode)
{
struct loop_device *lo = disk->private_data;
- mutex_lock(&lo->lo_mutex);
- if (atomic_dec_return(&lo->lo_refcnt))
- goto out_unlock;
+ if (disk_openers(disk) > 0)
+ return;
- if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
- if (lo->lo_state != Lo_bound)
- goto out_unlock;
+ mutex_lock(&lo->lo_mutex);
+ if (lo->lo_state == Lo_bound && (lo->lo_flags & LO_FLAGS_AUTOCLEAR)) {
lo->lo_state = Lo_rundown;
mutex_unlock(&lo->lo_mutex);
/*
@@ -1765,8 +1747,6 @@ static void lo_release(struct gendisk *disk, fmode_t mode)
__loop_clr_fd(lo, true);
return;
}
-
-out_unlock:
mutex_unlock(&lo->lo_mutex);
}
@@ -1780,7 +1760,6 @@ static void lo_free_disk(struct gendisk *disk)
static const struct block_device_operations lo_fops = {
.owner = THIS_MODULE,
- .open = lo_open,
.release = lo_release,
.ioctl = lo_ioctl,
#ifdef CONFIG_COMPAT
@@ -2034,7 +2013,6 @@ static int loop_add(int i)
*/
if (!part_shift)
disk->flags |= GENHD_FL_NO_PART;
- atomic_set(&lo->lo_refcnt, 0);
mutex_init(&lo->lo_mutex);
lo->lo_number = i;
spin_lock_init(&lo->lo_lock);
@@ -2124,13 +2102,12 @@ static int loop_control_remove(int idx)
ret = mutex_lock_killable(&lo->lo_mutex);
if (ret)
goto mark_visible;
- if (lo->lo_state != Lo_unbound ||
- atomic_read(&lo->lo_refcnt) > 0) {
+ if (lo->lo_state != Lo_unbound || disk_openers(lo->lo_disk) > 0) {
mutex_unlock(&lo->lo_mutex);
ret = -EBUSY;
goto mark_visible;
}
- /* Mark this loop device no longer open()-able. */
+ /* Mark this loop device as no more bound, but not quite unbound yet */
lo->lo_state = Lo_deleting;
mutex_unlock(&lo->lo_mutex);
diff --git a/drivers/block/loop.h b/drivers/block/loop.h
index 082d4b6bfc6a6..449d562738c52 100644
--- a/drivers/block/loop.h
+++ b/drivers/block/loop.h
@@ -28,7 +28,6 @@ struct loop_func_table;
struct loop_device {
int lo_number;
- atomic_t lo_refcnt;
loff_t lo_offset;
loff_t lo_sizelimit;
int lo_flags;
--
2.30.2
