loop: LOOP_CONFIGURE: send uevents for partitions

[ Upstream commit bb430b69422640891b0b8db762885730579a4145 ]

LOOP_CONFIGURE is, as far as I understand it, supposed to be a way to
combine LOOP_SET_FD and LOOP_SET_STATUS64 into a single syscall.  When
using LOOP_SET_FD+LOOP_SET_STATUS64, a single uevent would be sent for
each partition found on the loop device after the second ioctl(), but
when using LOOP_CONFIGURE, no such uevent was being sent.

In the old setup, uevents are disabled for LOOP_SET_FD, but not for
LOOP_SET_STATUS64.  This makes sense, as it prevents uevents being
sent for a partially configured device during LOOP_SET_FD - they're
only sent at the end of LOOP_SET_STATUS64.  But for LOOP_CONFIGURE,
uevents were disabled for the entire operation, so that final
notification was never issued.  To fix this, reduce the critical
section to exclude the loop_reread_partitions() call, which causes
the uevents to be issued, to after uevents are re-enabled, matching
the behaviour of the LOOP_SET_FD+LOOP_SET_STATUS64 combination.

I noticed this because Busybox's losetup program recently changed from
using LOOP_SET_FD+LOOP_SET_STATUS64 to LOOP_CONFIGURE, and this broke
my setup, for which I want a notification from the kernel any time a
new partition becomes available.

Signed-off-by: Alyssa Ross <hi@alyssa.is>
[hch: reduced the critical section]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Fixes: 3448914e8cc5 ("loop: Add LOOP_CONFIGURE ioctl")
Link: https://lore.kernel.org/r/20230320125430.55367-1-hch@lst.de
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 793ae876918ceab0288d31fcba32cbd038ee36a3..426d0b42685a02c458960baaa28edec0a4637564 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -1010,9 +1010,6 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
        /* This is safe, since we have a reference from open(). */
        __module_get(THIS_MODULE);
 
-       /* suppress uevents while reconfiguring the device */
-       dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1);
-
        /*
         * If we don't hold exclusive handle for the device, upgrade to it
         * here to avoid changing device under exclusive owner.
@@ -1067,6 +1064,9 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
                }
        }
 
+       /* suppress uevents while reconfiguring the device */
+       dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 1);
+
        disk_force_media_change(lo->lo_disk, DISK_EVENT_MEDIA_CHANGE);
        set_disk_ro(lo->lo_disk, (lo->lo_flags & LO_FLAGS_READ_ONLY) != 0);
 
@@ -1109,17 +1109,17 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
        if (partscan)
                clear_bit(GD_SUPPRESS_PART_SCAN, &lo->lo_disk->state);
 
+       /* enable and uncork uevent now that we are done */
+       dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 0);
+
        loop_global_unlock(lo, is_loop);
        if (partscan)
                loop_reread_partitions(lo);
+
        if (!(mode & FMODE_EXCL))
                bd_abort_claiming(bdev, loop_configure);
 
-       error = 0;
-done:
-       /* enable and uncork uevent now that we are done */
-       dev_set_uevent_suppress(disk_to_dev(lo->lo_disk), 0);
-       return error;
+       return 0;
 
 out_unlock:
        loop_global_unlock(lo, is_loop);
@@ -1130,7 +1130,7 @@ static int loop_configure(struct loop_device *lo, fmode_t mode,
        fput(file);
        /* This is safe: open() is still holding a reference. */
        module_put(THIS_MODULE);
-       goto done;
+       return error;
 }
 
 static void __loop_clr_fd(struct loop_device *lo, bool release)