From patchwork Fri Oct 25 11:21:42 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Michal Suchanek X-Patchwork-Id: 11212049 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id B0717139A for ; Fri, 25 Oct 2019 11:21:58 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 900E320679 for ; Fri, 25 Oct 2019 11:21:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2410299AbfJYLVz (ORCPT ); Fri, 25 Oct 2019 07:21:55 -0400 Received: from mx2.suse.de ([195.135.220.15]:56934 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2410165AbfJYLVz (ORCPT ); Fri, 25 Oct 2019 07:21:55 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B41ACB29B; Fri, 25 Oct 2019 11:21:52 +0000 (UTC) From: Michal Suchanek To: linux-scsi@vger.kernel.org Cc: Michal Suchanek , Christoph Hellwig , Matthew Wilcox , "Ewan D. Milne" , Jonathan Corbet , Jens Axboe , "James E.J. Bottomley" , "Martin K. Petersen" , Alexander Viro , "J. Bruce Fields" , Mauro Carvalho Chehab , Eric Biggers , Benjamin Coddington , Hannes Reinecke , Omar Sandoval , Ming Lei , Damien Le Moal , Bart Van Assche , Tejun Heo , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Subject: [PATCH v3 5/7] bdev: add open_finish. Date: Fri, 25 Oct 2019 13:21:42 +0200 Message-Id: <31f640791d9cc20cdbbb3000dfcf8370cf3c6223.1572002144.git.msuchanek@suse.de> X-Mailer: git-send-email 2.23.0 In-Reply-To: References: MIME-Version: 1.0 Sender: linux-scsi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-scsi@vger.kernel.org Opening a block device may require a long operation such as waiting for the cdrom tray to close. Performing this operation with locks held locks out other attempts to open the device. These processes waiting to open the device are not killable. To avoid this issue and still be able to perform time-consuming checks at open() time the block device driver can provide open_finish(). If it does opening the device proceeds even when an error is returned from open(), bd_mutex is released and open_finish() is called. If open_finish() succeeds the device is now open, if it fails release() is called. When -ERESTARTSYS is returned from open() blkdev_get may loop without calling open_finish(). On -ERESTARTSYS open_finish() is not called. Move a ret = 0 assignment up in the if/else branching to avoid returning -ENXIO. Previously the return value was ignored on the unhandled branch. Signed-off-by: Michal Suchanek --- Documentation/filesystems/locking.rst | 2 ++ fs/block_dev.c | 21 +++++++++++++++++---- include/linux/blkdev.h | 1 + 3 files changed, 20 insertions(+), 4 deletions(-) diff --git a/Documentation/filesystems/locking.rst b/Documentation/filesystems/locking.rst index fc3a0704553c..2471ced5a8cf 100644 --- a/Documentation/filesystems/locking.rst +++ b/Documentation/filesystems/locking.rst @@ -456,6 +456,7 @@ block_device_operations prototypes:: int (*open) (struct block_device *, fmode_t); + int (*open_finish) (struct block_device *, fmode_t, int); int (*release) (struct gendisk *, fmode_t); int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long); int (*compat_ioctl) (struct block_device *, fmode_t, unsigned, unsigned long); @@ -473,6 +474,7 @@ locking rules: ops bd_mutex ======================= =================== open: yes +open_finish: no release: yes ioctl: no compat_ioctl: no diff --git a/fs/block_dev.c b/fs/block_dev.c index 9c073dbdc1b0..009b5dedb1f7 100644 --- a/fs/block_dev.c +++ b/fs/block_dev.c @@ -1526,6 +1526,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) int partno; int perm = 0; bool first_open = false; + bool need_finish = false; if (mode & FMODE_READ) perm |= MAY_READ; @@ -1581,6 +1582,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) put_disk_and_module(disk); goto restart; } + if (bdev->bd_disk->fops->open_finish) + need_finish = true; } if (!ret) { @@ -1601,7 +1604,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) invalidate_partitions(disk, bdev); } - if (ret) + if (ret && !need_finish) goto out_clear; } else { struct block_device *whole; @@ -1627,10 +1630,14 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) if (bdev->bd_bdi == &noop_backing_dev_info) bdev->bd_bdi = bdi_get(disk->queue->backing_dev_info); } else { + ret = 0; if (bdev->bd_contains == bdev) { - ret = 0; - if (bdev->bd_disk->fops->open) + if (bdev->bd_disk->fops->open) { ret = bdev->bd_disk->fops->open(bdev, mode); + if ((ret != -ERESTARTSYS) && + bdev->bd_disk->fops->open_finish) + need_finish = true; + } /* the same as first opener case, read comment there */ if (bdev->bd_invalidated) { if (!ret) @@ -1638,7 +1645,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) else if (ret == -ENOMEDIUM) invalidate_partitions(bdev->bd_disk, bdev); } - if (ret) + if (ret && !need_finish) goto out_unlock_bdev; } } @@ -1650,6 +1657,12 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part) /* only one opener holds refs to the module and disk */ if (!first_open) put_disk_and_module(disk); + if (ret && need_finish) + ret = bdev->bd_disk->fops->open_finish(bdev, mode, ret); + if (ret) { + __blkdev_put(bdev, mode, for_part); + return ret; + } return 0; out_clear: diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index f3ea78b0c91c..b67e93c6afb7 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -1695,6 +1695,7 @@ static inline struct bio_vec *rq_integrity_vec(struct request *rq) struct block_device_operations { int (*open) (struct block_device *, fmode_t); + int (*open_finish)(struct block_device *bdev, fmode_t mode, int ret); void (*release) (struct gendisk *, fmode_t); int (*rw_page)(struct block_device *, sector_t, struct page *, unsigned int); int (*ioctl) (struct block_device *, fmode_t, unsigned, unsigned long);