Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752135Ab2JNCxo (ORCPT ); Sat, 13 Oct 2012 22:53:44 -0400 Received: from order.stressinduktion.org ([87.106.68.36]:49583 "EHLO order.stressinduktion.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751922Ab2JNCxn (ORCPT ); Sat, 13 Oct 2012 22:53:43 -0400 X-Greylist: delayed 306 seconds by postgrey-1.27 at vger.kernel.org; Sat, 13 Oct 2012 22:53:43 EDT Date: Sun, 14 Oct 2012 04:48:36 +0200 From: Hannes Frederic Sowa To: npiggin@kernel.dk Cc: linux-kernel@vger.kernel.org Subject: [PATCH RFC] brd: Add miscdevice to control creation and deletion of ramdisks Message-ID: <20121014024836.GB27966@order.stressinduktion.org> Mail-Followup-To: npiggin@kernel.dk, linux-kernel@vger.kernel.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7358 Lines: 270 While toying around with a library which needs small block devices for quorum management, I came up with this small patch to dynamically create and destroy ram disks (I wanted to have non-swappable backed devices). I am not really comfortable with the the double-use of the ioctl parameter of BRD_CTL_ADD passing the size and returning the minor id. But it seemed the easiest way to go. I even don't know if going the ioctl-route is the right way. Currently new minor ids are allocated strictly sequential. Deleted ones won't get reused. If the ioctl way is the way to go, I may change the bookkeeping to idrs. Feedback appreciated! This patch is against 3.6. This patch adds the miscdevice /dev/brd-control with two ioctls: 1) BRD_CTL_ADD: Instantiates a new ram disk with a given size as parameter. This parameter is filled in with the new minor id on return. 2) BRD_CTL_DEL: Deletes a ram disk. Takes the minor id as parameter. Signed-off-by: Hannes Frederic Sowa --- Documentation/ioctl/ioctl-number.txt | 1 + drivers/block/brd.c | 115 ++++++++++++++++++++++++++++++++--- include/linux/Kbuild | 1 + include/linux/brd.h | 11 ++++ include/linux/miscdevice.h | 1 + 5 files changed, 122 insertions(+), 7 deletions(-) create mode 100644 include/linux/brd.h diff --git a/Documentation/ioctl/ioctl-number.txt b/Documentation/ioctl/ioctl-number.txt index 849b771..b8827eb 100644 --- a/Documentation/ioctl/ioctl-number.txt +++ b/Documentation/ioctl/ioctl-number.txt @@ -326,4 +326,5 @@ Code Seq#(hex) Include File Comments 0xF6 all LTTng Linux Trace Toolkit Next Generation +0xF7 00-01 drivers/block/brd.c block ram device control driver 0xFD all linux/dm-ioctl.h diff --git a/drivers/block/brd.c b/drivers/block/brd.c index 531ceb3..7401de7 100644 --- a/drivers/block/brd.c +++ b/drivers/block/brd.c @@ -19,6 +19,9 @@ #include #include #include +#include +#include +#include #include @@ -460,7 +463,7 @@ __setup("ramdisk_size=", ramdisk_size); static LIST_HEAD(brd_devices); static DEFINE_MUTEX(brd_devices_mutex); -static struct brd_device *brd_alloc(int i) +static struct brd_device *brd_alloc(int i, int size_kb) { struct brd_device *brd; struct gendisk *disk; @@ -494,7 +497,7 @@ static struct brd_device *brd_alloc(int i) disk->queue = brd->brd_queue; disk->flags |= GENHD_FL_SUPPRESS_PARTITION_INFO; sprintf(disk->disk_name, "ram%d", i); - set_capacity(disk, rd_size * 2); + set_capacity(disk, size_kb * 2); return brd; @@ -523,7 +526,7 @@ static struct brd_device *brd_init_one(int i) goto out; } - brd = brd_alloc(i); + brd = brd_alloc(i, rd_size); if (brd) { add_disk(brd->brd_disk); list_add_tail(&brd->brd_list, &brd_devices); @@ -553,9 +556,97 @@ static struct kobject *brd_probe(dev_t dev, int *part, void *data) return kobj; } +static long brd_control_ioctl(struct file *file, unsigned int cmd, + unsigned long param) +{ + int error = -ENOSYS; + int size_kb, val; + struct brd_device *brd, *brd2; + + if (rd_nr) + return -EINVAL; + + mutex_lock(&brd_devices_mutex); + switch (cmd) { + case BRD_CTL_ADD: + error = get_user(size_kb, (int __user *)param); + if (error < 0) + break; + if (size_kb < 0) { + error = -EINVAL; + break; + } + val = 0; + list_for_each_entry(brd, &brd_devices, brd_list) { + val = max(val, 1 + brd->brd_number); + } + if (val >= (MINORMASK >> part_shift)) { + error = -EINVAL; + break; + } + brd = brd_alloc(val, size_kb); + if (brd == NULL) { + error = -ENOMEM; + break; + } + list_add_tail(&brd->brd_list, &brd_devices); + add_disk(brd->brd_disk); + val <<= part_shift; + error = put_user(val, (int __user *)param); + if (error < 0) + break; + error = 0; + break; + case BRD_CTL_DEL: + error = get_user(val, (int __user *)param); + if (error < 0) + break; + if ((val & max_part) != 0) { + error = -EINVAL; + break; + } + val >>= part_shift; + brd2 = NULL; + list_for_each_entry(brd, &brd_devices, brd_list) { + if (brd->brd_number == val) { + brd2 = brd; + break; + } + } + if (brd2 == NULL) { + error = -ENODEV; + break; + } + brd_del_one(brd2); + break; + } + mutex_unlock(&brd_devices_mutex); + return error; +} + +static const struct file_operations brd_ctl_fops = { + .open = nonseekable_open, + .unlocked_ioctl = brd_control_ioctl, + .owner = THIS_MODULE, + .llseek = noop_llseek, +#ifdef CONFIG_COMPAT + .compat_ioctl = brd_control_ioctl, +#endif +}; + +static struct miscdevice brd_misc = { + .minor = BRD_CTRL_MINOR, + .name = "brd-control", + .fops = &brd_ctl_fops, +}; + +MODULE_ALIAS_MISCDEV(BRD_CTRL_MINOR); +MODULE_ALIAS("devname:brd-control"); + static int __init brd_init(void) { int i, nr; + int err = -ENOMEM; unsigned long range; struct brd_device *brd, *next; @@ -603,11 +694,18 @@ static int __init brd_init(void) range = 1UL << MINORBITS; } - if (register_blkdev(RAMDISK_MAJOR, "ramdisk")) - return -EIO; + err = misc_register(&brd_misc); + if (err < 0) + return err; + + err = register_blkdev(RAMDISK_MAJOR, "ramdisk"); + if (err < 0) { + err = -EIO; + goto out; + } for (i = 0; i < nr; i++) { - brd = brd_alloc(i); + brd = brd_alloc(i, rd_size); if (!brd) goto out_free; list_add_tail(&brd->brd_list, &brd_devices); @@ -630,8 +728,10 @@ out_free: brd_free(brd); } unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); +out: + misc_deregister(&brd_misc); - return -ENOMEM; + return err; } static void __exit brd_exit(void) @@ -646,6 +746,7 @@ static void __exit brd_exit(void) blk_unregister_region(MKDEV(RAMDISK_MAJOR, 0), range); unregister_blkdev(RAMDISK_MAJOR, "ramdisk"); + misc_deregister(&brd_misc); } module_init(brd_init); diff --git a/include/linux/Kbuild b/include/linux/Kbuild index fa21760..05b0d3f 100644 --- a/include/linux/Kbuild +++ b/include/linux/Kbuild @@ -78,6 +78,7 @@ header-y += blk_types.h header-y += blkpg.h header-y += blktrace_api.h header-y += bpqether.h +header-y += brd.h header-y += bsg.h header-y += can.h header-y += capability.h diff --git a/include/linux/brd.h b/include/linux/brd.h new file mode 100644 index 0000000..1774b2e --- /dev/null +++ b/include/linux/brd.h @@ -0,0 +1,11 @@ +#ifndef _LINUX_BRD_H__ +#define _LINUX_BRD_H__ + +#include + +#define BRD_CTL_MAGIC 0xF7 + +/* /dev/brd-control ioctl commands */ +#define BRD_CTL_ADD _IOWR(BRD_CTL_MAGIC, 0, int) +#define BRD_CTL_DEL _IOR(BRD_CTL_MAGIC, 1, int) +#endif /* __LINUX_BRD_H__ */ diff --git a/include/linux/miscdevice.h b/include/linux/miscdevice.h index e0deeb2..45df076 100644 --- a/include/linux/miscdevice.h +++ b/include/linux/miscdevice.h @@ -44,6 +44,7 @@ #define MAPPER_CTRL_MINOR 236 #define LOOP_CTRL_MINOR 237 #define VHOST_NET_MINOR 238 +#define BRD_CTRL_MINOR 239 #define MISC_DYNAMIC_MINOR 255 struct device; 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