loop: Move special partition reread handling in loop_clr_fd()

The call of __blkdev_reread_part() from loop_reread_partition() happens
only when we need to invalidate partitions from loop_release(). Thus
move a detection for this into loop_clr_fd() and simplify
loop_reread_partition().

This makes loop_reread_partition() safe to use without loop_ctl_mutex
because we use only lo->lo_number and lo->lo_file_name in case of error
for reporting purposes (thus possibly reporting outdate information is
not a big deal) and we are safe from 'lo' going away under us by
elevated lo->lo_refcnt.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index ea5e313908b1462b6807a3a28314851bf2746f44..f1d7a4fe30fcd1721eeccc0b86f0d30c12077dd6 100644 (file)
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -630,18 +630,7 @@ static void loop_reread_partitions(struct loop_device *lo,
 {
        int rc;
 
-       /*
-        * bd_mutex has been held already in release path, so don't
-        * acquire it if this function is called in such case.
-        *
-        * If the reread partition isn't from release path, lo_refcnt
-        * must be at least one and it can only become zero when the
-        * current holder is released.
-        */
-       if (!atomic_read(&lo->lo_refcnt))
-               rc = __blkdev_reread_part(bdev);
-       else
-               rc = blkdev_reread_part(bdev);
+       rc = blkdev_reread_part(bdev);
        if (rc)
                pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
                        __func__, lo->lo_number, lo->lo_file_name, rc);
@@ -1095,8 +1084,24 @@ static int __loop_clr_fd(struct loop_device *lo)
        module_put(THIS_MODULE);
        blk_mq_unfreeze_queue(lo->lo_queue);
 
-       if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)
-               loop_reread_partitions(lo, bdev);
+       if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev) {
+               /*
+                * bd_mutex has been held already in release path, so don't
+                * acquire it if this function is called in such case.
+                *
+                * If the reread partition isn't from release path, lo_refcnt
+                * must be at least one and it can only become zero when the
+                * current holder is released.
+                */
+               if (!atomic_read(&lo->lo_refcnt))
+                       err = __blkdev_reread_part(bdev);
+               else
+                       err = blkdev_reread_part(bdev);
+               pr_warn("%s: partition scan of loop%d failed (rc=%d)\n",
+                       __func__, lo->lo_number, err);
+               /* Device is gone, no point in returning error */
+               err = 0;
+       }
        lo->lo_flags = 0;
        if (!part_shift)
                lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;