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Message-ID: <20120220152849.GH10342@redhat.com>
Date: Mon, 20 Feb 2012 10:28:49 -0500
From: Vivek Goyal <vgoyal@...hat.com>
To: axboe@...nel.dk
Cc: psusi@...ntu.com, psusi@....rr.com, maxim.patlasov@...il.com,
dm-devel@...hat.com, kzak@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] block: add partition resize function to blkpg ioctl
On Tue, Feb 14, 2012 at 03:39:50PM -0500, Vivek Goyal wrote:
> Add a new operation code ( BLKPG_RESIZE_PARTITION ) to the
> BLKPG ioctl that allows altering the size of an existing
> partition, even if it is currently in use.
>
> Signed-off-by: Vivek Goyal <vgoyal@...hat.com>
Hi Jens,
Can you please consider this patch for inclusion. One of our customer
does want to be able to grow partitions without having to reboot
the system.
Thanks
Vivek
> ---
> block/genhd.c | 20 ++++++++++++----
> block/ioctl.c | 57 ++++++++++++++++++++++++++++++++++++++++++--
> block/partition-generic.c | 4 ++-
> include/linux/blkpg.h | 1 +
> include/linux/genhd.h | 57 +++++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 130 insertions(+), 9 deletions(-)
>
> diff --git a/block/genhd.c b/block/genhd.c
> index 23b4f70..935e09b 100644
> --- a/block/genhd.c
> +++ b/block/genhd.c
> @@ -153,7 +153,7 @@ struct hd_struct *disk_part_iter_next(struct disk_part_iter *piter)
> part = rcu_dereference(ptbl->part[piter->idx]);
> if (!part)
> continue;
> - if (!part->nr_sects &&
> + if (!part_nr_sects_read(part) &&
> !(piter->flags & DISK_PITER_INCL_EMPTY) &&
> !(piter->flags & DISK_PITER_INCL_EMPTY_PART0 &&
> piter->idx == 0))
> @@ -190,7 +190,7 @@ EXPORT_SYMBOL_GPL(disk_part_iter_exit);
> static inline int sector_in_part(struct hd_struct *part, sector_t sector)
> {
> return part->start_sect <= sector &&
> - sector < part->start_sect + part->nr_sects;
> + sector < part->start_sect + part_nr_sects_read(part);
> }
>
> /**
> @@ -765,8 +765,8 @@ void __init printk_all_partitions(void)
>
> printk("%s%s %10llu %s %s", is_part0 ? "" : " ",
> bdevt_str(part_devt(part), devt_buf),
> - (unsigned long long)part->nr_sects >> 1,
> - disk_name(disk, part->partno, name_buf), uuid);
> + (unsigned long long)part_nr_sects_read(part) >> 1
> + , disk_name(disk, part->partno, name_buf), uuid);
> if (is_part0) {
> if (disk->driverfs_dev != NULL &&
> disk->driverfs_dev->driver != NULL)
> @@ -857,7 +857,7 @@ static int show_partition(struct seq_file *seqf, void *v)
> while ((part = disk_part_iter_next(&piter)))
> seq_printf(seqf, "%4d %7d %10llu %s\n",
> MAJOR(part_devt(part)), MINOR(part_devt(part)),
> - (unsigned long long)part->nr_sects >> 1,
> + (unsigned long long)part_nr_sects_read(part) >> 1,
> disk_name(sgp, part->partno, buf));
> disk_part_iter_exit(&piter);
>
> @@ -1263,6 +1263,16 @@ struct gendisk *alloc_disk_node(int minors, int node_id)
> }
> disk->part_tbl->part[0] = &disk->part0;
>
> + /*
> + * set_capacity() and get_capacity() currently don't use
> + * seqcounter to read/update the part0->nr_sects. Still init
> + * the counter as we can read the sectors in IO submission
> + * patch using seqence counters.
> + *
> + * TODO: Ideally set_capacity() and get_capacity() should be
> + * converted to make use of bd_mutex and sequence counters.
> + */
> + seqcount_init(&disk->part0.nr_sects_seq);
> hd_ref_init(&disk->part0);
>
> disk->minors = minors;
> diff --git a/block/ioctl.c b/block/ioctl.c
> index ba15b2d..ddbc649 100644
> --- a/block/ioctl.c
> +++ b/block/ioctl.c
> @@ -13,7 +13,7 @@ static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user
> {
> struct block_device *bdevp;
> struct gendisk *disk;
> - struct hd_struct *part;
> + struct hd_struct *part, *lpart;
> struct blkpg_ioctl_arg a;
> struct blkpg_partition p;
> struct disk_part_iter piter;
> @@ -36,8 +36,8 @@ static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user
> case BLKPG_ADD_PARTITION:
> start = p.start >> 9;
> length = p.length >> 9;
> - /* check for fit in a hd_struct */
> - if (sizeof(sector_t) == sizeof(long) &&
> + /* check for fit in a hd_struct */
> + if (sizeof(sector_t) == sizeof(long) &&
> sizeof(long long) > sizeof(long)) {
> long pstart = start, plength = length;
> if (pstart != start || plength != length
> @@ -92,6 +92,57 @@ static int blkpg_ioctl(struct block_device *bdev, struct blkpg_ioctl_arg __user
> bdput(bdevp);
>
> return 0;
> + case BLKPG_RESIZE_PARTITION:
> + start = p.start >> 9;
> + /* new length of partition in bytes */
> + length = p.length >> 9;
> + /* check for fit in a hd_struct */
> + if (sizeof(sector_t) == sizeof(long) &&
> + sizeof(long long) > sizeof(long)) {
> + long pstart = start, plength = length;
> + if (pstart != start || plength != length
> + || pstart < 0 || plength < 0)
> + return -EINVAL;
> + }
> + part = disk_get_part(disk, partno);
> + if (!part)
> + return -ENXIO;
> + bdevp = bdget(part_devt(part));
> + if (!bdevp) {
> + disk_put_part(part);
> + return -ENOMEM;
> + }
> + mutex_lock(&bdevp->bd_mutex);
> + mutex_lock_nested(&bdev->bd_mutex, 1);
> + if (start != part->start_sect) {
> + mutex_unlock(&bdevp->bd_mutex);
> + mutex_unlock(&bdev->bd_mutex);
> + disk_put_part(part);
> + return -EINVAL;
> + }
> + /* overlap? */
> + disk_part_iter_init(&piter, disk,
> + DISK_PITER_INCL_EMPTY);
> + while ((lpart = disk_part_iter_next(&piter))) {
> + if (lpart->partno != partno &&
> + !(start + length <= lpart->start_sect ||
> + start >= lpart->start_sect + lpart->nr_sects)
> + ) {
> + disk_part_iter_exit(&piter);
> + mutex_unlock(&bdevp->bd_mutex);
> + mutex_unlock(&bdev->bd_mutex);
> + disk_put_part(part);
> + return -EBUSY;
> + }
> + }
> + disk_part_iter_exit(&piter);
> + part_nr_sects_write(part, (sector_t)length);
> + i_size_write(bdevp->bd_inode, p.length);
> + mutex_unlock(&bdevp->bd_mutex);
> + mutex_unlock(&bdev->bd_mutex);
> + bdput(bdevp);
> + disk_put_part(part);
> + return 0;
> default:
> return -EINVAL;
> }
> diff --git a/block/partition-generic.c b/block/partition-generic.c
> index d06ec1c..363a6f6 100644
> --- a/block/partition-generic.c
> +++ b/block/partition-generic.c
> @@ -84,7 +84,7 @@ ssize_t part_size_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> struct hd_struct *p = dev_to_part(dev);
> - return sprintf(buf, "%llu\n",(unsigned long long)p->nr_sects);
> + return sprintf(buf, "%llu\n",(unsigned long long)part_nr_sects_read(p));
> }
>
> static ssize_t part_ro_show(struct device *dev,
> @@ -294,6 +294,8 @@ struct hd_struct *add_partition(struct gendisk *disk, int partno,
> err = -ENOMEM;
> goto out_free;
> }
> +
> + seqcount_init(&p->nr_sects_seq);
> pdev = part_to_dev(p);
>
> p->start_sect = start;
> diff --git a/include/linux/blkpg.h b/include/linux/blkpg.h
> index faf8a45..a851944 100644
> --- a/include/linux/blkpg.h
> +++ b/include/linux/blkpg.h
> @@ -40,6 +40,7 @@ struct blkpg_ioctl_arg {
> /* The subfunctions (for the op field) */
> #define BLKPG_ADD_PARTITION 1
> #define BLKPG_DEL_PARTITION 2
> +#define BLKPG_RESIZE_PARTITION 3
>
> /* Sizes of name fields. Unused at present. */
> #define BLKPG_DEVNAMELTH 64
> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
> index fe23ee7..0def3ef 100644
> --- a/include/linux/genhd.h
> +++ b/include/linux/genhd.h
> @@ -98,7 +98,13 @@ struct partition_meta_info {
>
> struct hd_struct {
> sector_t start_sect;
> + /*
> + * nr_sects is protected by sequence counter. One might extend a
> + * partition while IO is happening to it and update of nr_sects
> + * can be non-atomic on 32bit machines with 64bit sector_t.
> + */
> sector_t nr_sects;
> + seqcount_t nr_sects_seq;
> sector_t alignment_offset;
> unsigned int discard_alignment;
> struct device __dev;
> @@ -653,6 +659,57 @@ static inline void hd_struct_put(struct hd_struct *part)
> __delete_partition(part);
> }
>
> +/*
> + * Any access of part->nr_sects which is not protected by partition
> + * bd_mutex or gendisk bdev bd_mutex, should be done using this
> + * accessor function.
> + *
> + * Code written along the lines of i_size_read() and i_size_write().
> + * CONFIG_PREEMPT case optimizes the case of UP kernel with preemption
> + * on.
> + */
> +static inline sector_t part_nr_sects_read(struct hd_struct *part)
> +{
> +#if BITS_PER_LONG==32 && defined(CONFIG_LBDAF) && defined(CONFIG_SMP)
> + sector_t nr_sects;
> + unsigned seq;
> + do {
> + seq = read_seqcount_begin(&part->nr_sects_seq);
> + nr_sects = part->nr_sects;
> + } while (read_seqcount_retry(&part->nr_sects_seq, seq));
> + return nr_sects;
> +#elif BITS_PER_LONG==32 && defined(CONFIG_PREEMPT)
> + sector_t nr_sects;
> +
> + preempt_disable();
> + nr_sects = part->nr_sects;
> + preempt_enable();
> + return nr_sects;
> +#else
> + return part->nr_sects;
> +#endif
> +}
> +
> +/*
> + * Should be called with mutex lock held (typically bd_mutex) of partition
> + * to provide mutual exlusion among writers otherwise seqcount might be
> + * left in wrong state leaving the readers spinning infinitely.
> + */
> +static inline void part_nr_sects_write(struct hd_struct *part, sector_t size)
> +{
> +#if BITS_PER_LONG==32 && defined(CONFIG_LBDAF) && defined(CONFIG_SMP)
> + write_seqcount_begin(&part->nr_sects_seq);
> + part->nr_sects = size;
> + write_seqcount_end(&part->nr_sects_seq);
> +#elif BITS_PER_LONG==32 && defined(CONFIG_LBDAF) && defined(CONFIG_PREEMPT)
> + preempt_disable();
> + part->nr_sects = size;
> + preempt_enable();
> +#else
> + part->nr_sects = size;
> +#endif
> +}
> +
> #else /* CONFIG_BLOCK */
>
> static inline void printk_all_partitions(void) { }
> --
> 1.7.6.4
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