loop_clr_fd() can be run piggyback with lo_release(), and under this situation, reread partition may always fail because bd_mutex has been held already.
This patch detects the situation by the reference count, and call __blkdev_reread_part() to avoid acquiring the lock again. In the meantime, this patch switches to new kernel APIs of blkdev_reread_part() and __blkdev_reread_part(). Reviewed-by: Christoph Hellwig <[email protected]> Tested-by: Jarod Wilson <[email protected]> Acked-by: Jarod Wilson <[email protected]> Signed-off-by: Jarod Wilson <[email protected]> Signed-off-by: Ming Lei <[email protected]> --- drivers/block/loop.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index b3e294e..2b99e34 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -474,6 +474,28 @@ static int loop_flush(struct loop_device *lo) return loop_switch(lo, NULL); } +static void loop_reread_partitions(struct loop_device *lo, + struct block_device *bdev) +{ + 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); + if (rc) + pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n", + __func__, lo->lo_number, lo->lo_file_name, rc); +} + /* * loop_change_fd switched the backing store of a loopback device to * a new file. This is useful for operating system installers to free up @@ -522,7 +544,7 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev, fput(old_file); if (lo->lo_flags & LO_FLAGS_PARTSCAN) - ioctl_by_bdev(bdev, BLKRRPART, 0); + loop_reread_partitions(lo, bdev); return 0; out_putf: @@ -759,7 +781,7 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, if (part_shift) lo->lo_flags |= LO_FLAGS_PARTSCAN; if (lo->lo_flags & LO_FLAGS_PARTSCAN) - ioctl_by_bdev(bdev, BLKRRPART, 0); + loop_reread_partitions(lo, bdev); /* Grab the block_device to prevent its destruction after we * put /dev/loopXX inode. Later in loop_clr_fd() we bdput(bdev). @@ -877,7 +899,7 @@ static int loop_clr_fd(struct loop_device *lo) blk_mq_unfreeze_queue(lo->lo_queue); if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev) - ioctl_by_bdev(bdev, BLKRRPART, 0); + loop_reread_partitions(lo, bdev); lo->lo_flags = 0; if (!part_shift) lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN; @@ -954,7 +976,7 @@ loop_set_status(struct loop_device *lo, const struct loop_info64 *info) !(lo->lo_flags & LO_FLAGS_PARTSCAN)) { lo->lo_flags |= LO_FLAGS_PARTSCAN; lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN; - ioctl_by_bdev(lo->lo_device, BLKRRPART, 0); + loop_reread_partitions(lo, lo->lo_device); } lo->lo_encrypt_key_size = info->lo_encrypt_key_size; -- 1.9.1 ------------------------------------------------------------------------------ One dashboard for servers and applications across Physical-Virtual-Cloud Widest out-of-the-box monitoring support with 50+ applications Performance metrics, stats and reports that give you Actionable Insights Deep dive visibility with transaction tracing using APM Insight. http://ad.doubleclick.net/ddm/clk/290420510;117567292;y _______________________________________________ Nbd-general mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/nbd-general
