Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1161554AbYCSWFH (ORCPT ); Wed, 19 Mar 2008 18:05:07 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S933363AbYCSU3r (ORCPT ); Wed, 19 Mar 2008 16:29:47 -0400 Received: from ecfrec.frec.bull.fr ([129.183.4.8]:47530 "EHLO ecfrec.frec.bull.fr" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1763474AbYCSU3n (ORCPT ); Wed, 19 Mar 2008 16:29:43 -0400 Subject: Re: [PATCH][RESEND][v3] Modify loop device to be able to manage partitions of the disk image From: Laurent Vivier To: Bill Davidsen Cc: axboe@suse.de, linux-kernel@vger.kernel.org, akpm@linux-foundation.org In-Reply-To: <47E17673.4040302@tmr.com> References: <12058427603971-git-send-email-Laurent.Vivier@bull.net> <47E17673.4040302@tmr.com> Content-Type: text/plain; charset=utf-8 Organization: Bull S.A.S. Date: Wed, 19 Mar 2008 21:32:32 +0100 Message-Id: <1205958752.4758.13.camel@frecb07144> Mime-Version: 1.0 X-Mailer: Evolution 2.12.3 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7941 Lines: 213 Le mercredi 19 mars 2008 à 16:24 -0400, Bill Davidsen a écrit : > Laurent Vivier wrote: > > v3 is an updated version of v2, replacing a "%d" by a "%lu". > > > > This patch allows to use loop device with partitionned disk image. > > > How does this compare in overhead to using nbd? What do you mean ? NBD doesn't manage partitions... but I also have a patch to do that. NBD implies an NBD server and an NBD client in userspace, so loop is better when disk image is in a raw format. Laurent > > Original behavior of loop is not modified. > > > > A new parameter is introduced to define how many partition we want to be > > able to manage per loop device. This parameter is "loop_max_part". > > > > For instance, to manage 63 partitions / loop device, we will do: > > # modprobe loop loop_max_part=63 > > # ls -l /dev/loop? > > brw-rw---- 1 root disk 7, 0 2008-03-05 14:55 /dev/loop0 > > brw-rw---- 1 root disk 7, 64 2008-03-05 14:55 /dev/loop1 > > brw-rw---- 1 root disk 7, 128 2008-03-05 14:55 /dev/loop2 > > brw-rw---- 1 root disk 7, 192 2008-03-05 14:55 /dev/loop3 > > brw-rw---- 1 root disk 7, 256 2008-03-05 14:55 /dev/loop4 > > brw-rw---- 1 root disk 7, 320 2008-03-05 14:55 /dev/loop5 > > brw-rw---- 1 root disk 7, 384 2008-03-05 14:55 /dev/loop6 > > brw-rw---- 1 root disk 7, 448 2008-03-05 14:55 /dev/loop7 > > > > And to attach a raw partitionned disk image, the original losetup is used: > > > > # losetup -f etch.img > > EXT3 FS on loop0p1, internal journal > > EXT3-fs: mounted filesystem with ordered data mode. > > loop: module loaded > > loop0: p1 p2 < p5 > > > # ls -l /dev/loop?* > > brw-rw---- 1 root disk 7, 0 2008-03-05 14:55 /dev/loop0 > > brw-rw---- 1 root disk 7, 1 2008-03-05 14:57 /dev/loop0p1 > > brw-rw---- 1 root disk 7, 2 2008-03-05 14:57 /dev/loop0p2 > > brw-rw---- 1 root disk 7, 5 2008-03-05 14:57 /dev/loop0p5 > > brw-rw---- 1 root disk 7, 64 2008-03-05 14:55 /dev/loop1 > > brw-rw---- 1 root disk 7, 128 2008-03-05 14:55 /dev/loop2 > > brw-rw---- 1 root disk 7, 192 2008-03-05 14:55 /dev/loop3 > > brw-rw---- 1 root disk 7, 256 2008-03-05 14:55 /dev/loop4 > > brw-rw---- 1 root disk 7, 320 2008-03-05 14:55 /dev/loop5 > > brw-rw---- 1 root disk 7, 384 2008-03-05 14:55 /dev/loop6 > > brw-rw---- 1 root disk 7, 448 2008-03-05 14:55 /dev/loop7 > > # mount /dev/loop0p1 /mnt > > kjournald starting. Commit interval 5 seconds > > EXT3 FS on loop0p1, internal journal > > EXT3-fs: mounted filesystem with ordered data mode. > > # ls /mnt > > bench cdrom home lib mnt root srv usr > > bin dev initrd lost+found opt sbin sys var > > boot etc initrd.img media proc selinux tmp vmlinuz > > # umount /mnt > > # losetup -d /dev/loop0 > > > > Of course, the same behavior can be done using kpartx on a loop device, > > but modifying loop avoids to stack several layers of block device (loop + > > device mapper), this is a very light modification (40% of modifications > > are to manage the new parameter). > > > > Signed-off-by: Laurent Vivier > > --- > > Documentation/kernel-parameters.txt | 4 +++ > > drivers/block/loop.c | 39 ++++++++++++++++++++++++++++++---- > > 2 files changed, 38 insertions(+), 5 deletions(-) > > > > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > > index 9a5b665..7f2fd52 100644 > > --- a/Documentation/kernel-parameters.txt > > +++ b/Documentation/kernel-parameters.txt > > @@ -1075,6 +1075,10 @@ and is between 256 and 4096 characters. It is defined in the file > > be mounted > > Format: <1-256> > > > > + loop_max_part= [LOOP] Maximum number of partitions per loopback device. > > + Should be greater than 0, the maximum value depends > > + on max_loop. > > + > > maxcpus= [SMP] Maximum number of processors that an SMP kernel > > should make use of. maxcpus=n : n >= 0 limits the > > kernel to using 'n' processors. n=0 is a special case, > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > > index 91ebb00..16b2aa6 100644 > > --- a/drivers/block/loop.c > > +++ b/drivers/block/loop.c > > @@ -82,6 +82,9 @@ > > static LIST_HEAD(loop_devices); > > static DEFINE_MUTEX(loop_devices_mutex); > > > > +static int loop_max_part; > > +static int part_shift; > > + > > /* > > * Transfer functions > > */ > > @@ -692,6 +695,8 @@ static int loop_change_fd(struct loop_device *lo, struct file *lo_file, > > goto out_putf; > > > > fput(old_file); > > + if (loop_max_part > 0) > > + ioctl_by_bdev(bdev, BLKRRPART, 0); > > return 0; > > > > out_putf: > > @@ -819,6 +824,8 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file, > > } > > lo->lo_state = Lo_bound; > > wake_up_process(lo->lo_thread); > > + if (loop_max_part > 0) > > + ioctl_by_bdev(bdev, BLKRRPART, 0); > > return 0; > > > > out_clr: > > @@ -1360,6 +1367,8 @@ static struct block_device_operations lo_fops = { > > static int max_loop; > > module_param(max_loop, int, 0); > > MODULE_PARM_DESC(max_loop, "Maximum number of loop devices"); > > +module_param(loop_max_part, int, 0); > > +MODULE_PARM_DESC(loop_max_part, "Maximum number of partitions per loop device"); > > MODULE_LICENSE("GPL"); > > MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR); > > > > @@ -1412,7 +1421,7 @@ static struct loop_device *loop_alloc(int i) > > if (!lo->lo_queue) > > goto out_free_dev; > > > > - disk = lo->lo_disk = alloc_disk(1); > > + disk = lo->lo_disk = alloc_disk(1 << part_shift); > > if (!disk) > > goto out_free_queue; > > > > @@ -1422,7 +1431,7 @@ static struct loop_device *loop_alloc(int i) > > init_waitqueue_head(&lo->lo_event); > > spin_lock_init(&lo->lo_lock); > > disk->major = LOOP_MAJOR; > > - disk->first_minor = i; > > + disk->first_minor = i << part_shift; > > disk->fops = &lo_fops; > > disk->private_data = lo; > > disk->queue = lo->lo_queue; > > @@ -1502,7 +1511,12 @@ static int __init loop_init(void) > > * themselves and have kernel automatically instantiate actual > > * device on-demand. > > */ > > - if (max_loop > 1UL << MINORBITS) > > + > > + part_shift = 0; > > + if (loop_max_part > 0) > > + part_shift = fls(loop_max_part); > > + > > + if (max_loop > 1UL << (MINORBITS - part_shift)) > > return -EINVAL; > > > > if (max_loop) { > > @@ -1510,7 +1524,7 @@ static int __init loop_init(void) > > range = max_loop; > > } else { > > nr = 8; > > - range = 1UL << MINORBITS; > > + range = 1UL << (MINORBITS - part_shift); > > } > > > > if (register_blkdev(LOOP_MAJOR, "loop")) > > @@ -1549,7 +1563,7 @@ static void __exit loop_exit(void) > > unsigned long range; > > struct loop_device *lo, *next; > > > > - range = max_loop ? max_loop : 1UL << MINORBITS; > > + range = max_loop ? max_loop : 1UL << (MINORBITS - part_shift); > > > > list_for_each_entry_safe(lo, next, &loop_devices, lo_list) > > loop_del_one(lo); > > @@ -1569,4 +1583,19 @@ static int __init max_loop_setup(char *str) > > } > > > > __setup("max_loop=", max_loop_setup); > > + > > +static int __init max_part_setup(char *str) > > +{ > > + loop_max_part = simple_strtol(str, NULL, 0); > > + if (loop_max_part > (1UL << (MINORBITS - 1))) { > > + /* we must keep at least one bit for loop device number */ > > + printk(KERN_ERR > > + "loop: loop_max_part cannot be greater than %lu\n", > > + 1UL << (MINORBITS - 1)); > > + return 0; > > + } > > + return 1; > > +} > > + > > +__setup("loop_max_part=", max_part_setup); > > #endif > > -- ------- Laurent.Vivier@bull.net ------- "The best way to predict the future is to invent it." - Alan Kay -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/