From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: From: Tetsuo Handa To: Jens Axboe Cc: linux-block@vger.kernel.org, Jan Kara , Tetsuo Handa , Ming Lei Subject: [PATCH 3/4] block/loop: Reorganize loop_reread_partitions() callers. Date: Wed, 26 Sep 2018 00:26:48 +0900 Message-Id: <1537889209-7208-3-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> In-Reply-To: <1537889209-7208-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> References: <1537889209-7208-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp> List-ID: We will drop loop_ctl_mutex before calling blkdev_reread_part() in order to fix circular locking dependency between bdev->bd_mutex and loop_ctl_mutex. To do that we need to make sure that we won't touch "struct loop_device" after releasing loop_ctl_mutex. As a preparation step, this patch reorganizes loop_reread_partitions() callers. According to Ming Lei, calling loop_unprepare_queue() before loop_reread_partitions() (like we did until 3.19) is fine. Therefore, this patch will not cause user visible changes. Signed-off-by: Tetsuo Handa Cc: Ming Lei --- drivers/block/loop.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 920cbb1..4b05a27 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -632,6 +632,11 @@ static void loop_reread_partitions(struct loop_device *lo, struct block_device *bdev) { int rc; + char filename[LO_NAME_SIZE]; + const int num = lo->lo_number; + const int count = atomic_read(&lo->lo_refcnt); + + memcpy(filename, lo->lo_file_name, sizeof(filename)); /* * bd_mutex has been held already in release path, so don't @@ -641,13 +646,13 @@ static void loop_reread_partitions(struct loop_device *lo, * must be at least one and it can only become zero when the * current holder is released. */ - if (!atomic_read(&lo->lo_refcnt)) + if (!count) 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); + __func__, num, filename, rc); } static inline int is_loop_device(struct file *file) @@ -730,9 +735,9 @@ static int loop_change_fd(struct loop_device *lo, struct block_device *bdev, loop_update_dio(lo); blk_mq_unfreeze_queue(lo->lo_queue); - fput(old_file); if (lo->lo_flags & LO_FLAGS_PARTSCAN) loop_reread_partitions(lo, bdev); + fput(old_file); return 0; out_putf: @@ -971,16 +976,18 @@ static int loop_set_fd(struct loop_device *lo, fmode_t mode, set_blocksize(bdev, S_ISBLK(inode->i_mode) ? block_size(inode->i_bdev) : PAGE_SIZE); + /* + * Grab the block_device to prevent its destruction after we + * put /dev/loopXX inode. Later in loop_clr_fd() we bdput(bdev). + */ + bdgrab(bdev); + lo->lo_state = Lo_bound; if (part_shift) lo->lo_flags |= LO_FLAGS_PARTSCAN; if (lo->lo_flags & LO_FLAGS_PARTSCAN) 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). - */ - bdgrab(bdev); return 0; out_putf: @@ -1033,6 +1040,7 @@ static int loop_clr_fd(struct loop_device *lo) struct file *filp = lo->lo_backing_file; gfp_t gfp = lo->old_gfp_mask; struct block_device *bdev = lo->lo_device; + bool reread; if (lo->lo_state != Lo_bound) return -ENXIO; @@ -1096,12 +1104,13 @@ 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); + reread = (lo->lo_flags & LO_FLAGS_PARTSCAN) && bdev; + loop_unprepare_queue(lo); lo->lo_flags = 0; if (!part_shift) lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN; - loop_unprepare_queue(lo); + if (reread) + loop_reread_partitions(lo, bdev); mutex_unlock(&loop_ctl_mutex); /* * Need not hold loop_ctl_mutex to fput backing file. -- 1.8.3.1