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Date: Wed, 8 Apr 2015 02:23:42 -0400 From: Jarod Wilson <jarod@...hat.com> To: linux-kernel@...r.kernel.org Cc: Jarod Wilson <jarod@...hat.com>, Christoph Hellwig <hch@...radead.org>, Jens Axboe <axboe@...nel.dk>, Tejun Heo <tj@...nel.org>, Alexander Viro <viro@...iv.linux.org.uk>, Markus Pargmann <mpa@...gutronix.de>, Stefan Weinhuber <wein@...ibm.com>, Stefan Haberland <stefan.haberland@...ibm.com>, Sebastian Ott <sebott@...ux.vnet.ibm.com>, Fabian Frederick <fabf@...net.be>, Ming Lei <ming.lei@...onical.com>, David Herrmann <dh.herrmann@...il.com>, Mike Galbraith <bitbucket@...ine.de>, Andrew Morton <akpm@...ux-foundation.org>, Peter Zijlstra <peterz@...radead.org>, nbd-general@...ts.sourceforge.net, linux-s390@...r.kernel.org Subject: [PATCH 3/7] block: loop: fix another reread part failure loop_clr_fd() can be run piggyback with lo_release(), and under this situation, reread partition may always fail because of bd_mutex which has been held in release path. This patch detects the situation by the reference count, and call blkdev_reread_part_nolock() to avoid acquiring the lock again. In the meantime, this patch switches to new kernel APIs of blkdev_reread_part() and blkdev_reread_part_nolock(). [jarod: this is a merger of my original patch, Ming's patch, and some reworking for my reworked first patch in the series.] CC: Christoph Hellwig <hch@...radead.org> CC: Jens Axboe <axboe@...nel.dk> CC: Tejun Heo <tj@...nel.org> CC: Alexander Viro <viro@...iv.linux.org.uk> CC: Markus Pargmann <mpa@...gutronix.de> CC: Stefan Weinhuber <wein@...ibm.com> CC: Stefan Haberland <stefan.haberland@...ibm.com> CC: Sebastian Ott <sebott@...ux.vnet.ibm.com> CC: Fabian Frederick <fabf@...net.be> CC: Ming Lei <ming.lei@...onical.com> CC: David Herrmann <dh.herrmann@...il.com> CC: Mike Galbraith <bitbucket@...ine.de> CC: Andrew Morton <akpm@...ux-foundation.org> CC: Peter Zijlstra <peterz@...radead.org> CC: nbd-general@...ts.sourceforge.net CC: linux-s390@...r.kernel.org Signed-off-by: Jarod Wilson <jarod@...hat.com> --- drivers/block/loop.c | 28 ++++++++++++++++++++++++---- 1 file changed, 24 insertions(+), 4 deletions(-) diff --git a/drivers/block/loop.c b/drivers/block/loop.c index 81a6bc1..ab5c678 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -528,6 +528,26 @@ 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; + bool in_release; + + mutex_lock(&lo->lo_open_mutex); + in_release = lo->lo_refcnt == 0; + mutex_unlock(&lo->lo_open_mutex); + + /* bd_mutex has been held already in release path */ + if (in_release) + 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 @@ -576,7 +596,7 @@ 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: @@ -807,7 +827,7 @@ 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). @@ -933,7 +953,7 @@ static int loop_clr_fd(struct loop_device *lo) mutex_unlock(&lo->lo_open_mutex); 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; @@ -1008,7 +1028,7 @@ 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; -- 1.8.3.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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