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Date: Fri, 18 Dec 2020 10:11:54 +0800
From: Ruan Shiyang <ruansy.fnst@...fujitsu.com>
To: "Darrick J. Wong" <darrick.wong@...cle.com>
CC: <linux-kernel@...r.kernel.org>, <linux-xfs@...r.kernel.org>,
<linux-nvdimm@...ts.01.org>, <linux-mm@...ck.org>,
<linux-fsdevel@...r.kernel.org>, <linux-raid@...r.kernel.org>,
<dan.j.williams@...el.com>, <david@...morbit.com>, <hch@....de>,
<song@...nel.org>, <rgoldwyn@...e.de>, <qi.fuli@...itsu.com>,
<y-goto@...itsu.com>, Theodore Ts'o <tytso@....edu>
Subject: Re: [RFC PATCH v3 8/9] md: Implement ->corrupted_range()
On 2020/12/16 上午4:51, Darrick J. Wong wrote:
> On Tue, Dec 15, 2020 at 08:14:13PM +0800, Shiyang Ruan wrote:
>> With the support of ->rmap(), it is possible to obtain the superblock on
>> a mapped device.
>>
>> If a pmem device is used as one target of mapped device, we cannot
>> obtain its superblock directly. With the help of SYSFS, the mapped
>> device can be found on the target devices. So, we iterate the
>> bdev->bd_holder_disks to obtain its mapped device.
>>
>> Signed-off-by: Shiyang Ruan <ruansy.fnst@...fujitsu.com>
>> ---
>> drivers/md/dm.c | 66 +++++++++++++++++++++++++++++++++++++++++++
>> drivers/nvdimm/pmem.c | 9 ++++--
>> fs/block_dev.c | 21 ++++++++++++++
>> include/linux/genhd.h | 7 +++++
>> 4 files changed, 100 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/md/dm.c b/drivers/md/dm.c
>> index 4e0cbfe3f14d..9da1f9322735 100644
>> --- a/drivers/md/dm.c
>> +++ b/drivers/md/dm.c
>> @@ -507,6 +507,71 @@ static int dm_blk_report_zones(struct gendisk *disk, sector_t sector,
>> #define dm_blk_report_zones NULL
>> #endif /* CONFIG_BLK_DEV_ZONED */
>>
>> +struct dm_blk_corrupt {
>> + struct block_device *bdev;
>> + sector_t offset;
>> +};
>> +
>> +static int dm_blk_corrupt_fn(struct dm_target *ti, struct dm_dev *dev,
>> + sector_t start, sector_t len, void *data)
>> +{
>> + struct dm_blk_corrupt *bc = data;
>> +
>> + return bc->bdev == (void *)dev->bdev &&
>> + (start <= bc->offset && bc->offset < start + len);
>> +}
>> +
>> +static int dm_blk_corrupted_range(struct gendisk *disk,
>> + struct block_device *target_bdev,
>> + loff_t target_offset, size_t len, void *data)
>> +{
>> + struct mapped_device *md = disk->private_data;
>> + struct block_device *md_bdev = md->bdev;
>> + struct dm_table *map;
>> + struct dm_target *ti;
>> + struct super_block *sb;
>> + int srcu_idx, i, rc = 0;
>> + bool found = false;
>> + sector_t disk_sec, target_sec = to_sector(target_offset);
>> +
>> + map = dm_get_live_table(md, &srcu_idx);
>> + if (!map)
>> + return -ENODEV;
>> +
>> + for (i = 0; i < dm_table_get_num_targets(map); i++) {
>> + ti = dm_table_get_target(map, i);
>> + if (ti->type->iterate_devices && ti->type->rmap) {
>> + struct dm_blk_corrupt bc = {target_bdev, target_sec};
>> +
>> + found = ti->type->iterate_devices(ti, dm_blk_corrupt_fn, &bc);
>> + if (!found)
>> + continue;
>> + disk_sec = ti->type->rmap(ti, target_sec);
>
> What happens if the dm device has multiple reverse mappings because the
> physical storage is being shared at multiple LBAs? (e.g. a
> deduplication target)
I thought that the dm device knows the mapping relationship, and it can
be done by implementation of ->rmap() in each target. Did I understand
it wrong?
>
>> + break;
>> + }
>> + }
>> +
>> + if (!found) {
>> + rc = -ENODEV;
>> + goto out;
>> + }
>> +
>> + sb = get_super(md_bdev);
>> + if (!sb) {
>> + rc = bd_disk_holder_corrupted_range(md_bdev, to_bytes(disk_sec), len, data);
>> + goto out;
>> + } else if (sb->s_op->corrupted_range) {
>> + loff_t off = to_bytes(disk_sec - get_start_sect(md_bdev));
>> +
>> + rc = sb->s_op->corrupted_range(sb, md_bdev, off, len, data);
>
> This "call bd_disk_holder_corrupted_range or sb->s_op->corrupted_range"
> logic appears twice; should it be refactored into a common helper?
>
> Or, should the superblock dispatch part move to
> bd_disk_holder_corrupted_range?
bd_disk_holder_corrupted_range() requires SYSFS configuration. I
introduce it to handle those block devices that can not obtain
superblock by `get_super()`.
Usually, if we create filesystem directly on a pmem device, or make some
partitions at first, we can use `get_super()` to get the superblock. In
other case, such as creating a LVM on pmem device, `get_super()` does
not work.
So, I think refactoring it into a common helper looks better.
--
Thanks,
Ruan Shiyang.
>
>> + }
>> + drop_super(sb);
>> +
>> +out:
>> + dm_put_live_table(md, srcu_idx);
>> + return rc;
>> +}
>> +
>> static int dm_prepare_ioctl(struct mapped_device *md, int *srcu_idx,
>> struct block_device **bdev)
>> {
>> @@ -3084,6 +3149,7 @@ static const struct block_device_operations dm_blk_dops = {
>> .getgeo = dm_blk_getgeo,
>> .report_zones = dm_blk_report_zones,
>> .pr_ops = &dm_pr_ops,
>> + .corrupted_range = dm_blk_corrupted_range,
>> .owner = THIS_MODULE
>> };
>>
>> diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
>> index 4688bff19c20..e8cfaf860149 100644
>> --- a/drivers/nvdimm/pmem.c
>> +++ b/drivers/nvdimm/pmem.c
>> @@ -267,11 +267,14 @@ static int pmem_corrupted_range(struct gendisk *disk, struct block_device *bdev,
>>
>> bdev_offset = (disk_sector - get_start_sect(bdev)) << SECTOR_SHIFT;
>> sb = get_super(bdev);
>> - if (sb && sb->s_op->corrupted_range) {
>> + if (!sb) {
>> + rc = bd_disk_holder_corrupted_range(bdev, bdev_offset, len, data);
>> + goto out;
>> + } else if (sb->s_op->corrupted_range)
>> rc = sb->s_op->corrupted_range(sb, bdev, bdev_offset, len, data);
>> - drop_super(sb);
>
> This is out of scope for this patch(set) but do you think that the scsi
> disk driver should intercept media errors from sense data and call
> ->corrupted_range too? ISTR Ted muttering that one of his employers had
> a patchset to do more with sense data than the upstream kernel currently
> does...
>
>> - }
>> + drop_super(sb);
>>
>> +out:
>> bdput(bdev);
>> return rc;
>> }
>> diff --git a/fs/block_dev.c b/fs/block_dev.c
>> index 9e84b1928b94..d3e6bddb8041 100644
>> --- a/fs/block_dev.c
>> +++ b/fs/block_dev.c
>> @@ -1171,6 +1171,27 @@ struct bd_holder_disk {
>> int refcnt;
>> };
>>
>> +int bd_disk_holder_corrupted_range(struct block_device *bdev, loff_t off, size_t len, void *data)
>> +{
>> + struct bd_holder_disk *holder;
>> + struct gendisk *disk;
>> + int rc = 0;
>> +
>> + if (list_empty(&(bdev->bd_holder_disks)))
>> + return -ENODEV;
>> +
>> + list_for_each_entry(holder, &bdev->bd_holder_disks, list) {
>> + disk = holder->disk;
>> + if (disk->fops->corrupted_range) {
>> + rc = disk->fops->corrupted_range(disk, bdev, off, len, data);
>> + if (rc != -ENODEV)
>> + break;
>> + }
>> + }
>> + return rc;
>> +}
>> +EXPORT_SYMBOL_GPL(bd_disk_holder_corrupted_range);
>> +
>> static struct bd_holder_disk *bd_find_holder_disk(struct block_device *bdev,
>> struct gendisk *disk)
>> {
>> diff --git a/include/linux/genhd.h b/include/linux/genhd.h
>> index ed06209008b8..fba247b852fa 100644
>> --- a/include/linux/genhd.h
>> +++ b/include/linux/genhd.h
>> @@ -382,9 +382,16 @@ int blkdev_ioctl(struct block_device *, fmode_t, unsigned, unsigned long);
>> long compat_blkdev_ioctl(struct file *, unsigned, unsigned long);
>>
>> #ifdef CONFIG_SYSFS
>> +int bd_disk_holder_corrupted_range(struct block_device *bdev, loff_t off,
>> + size_t len, void *data);
>> int bd_link_disk_holder(struct block_device *bdev, struct gendisk *disk);
>> void bd_unlink_disk_holder(struct block_device *bdev, struct gendisk *disk);
>> #else
>> +int bd_disk_holder_corrupted_range(struct block_device *bdev, loff_t off,
>> + size_t len, void *data)
>> +{
>> + return 0;
>> +}
>> static inline int bd_link_disk_holder(struct block_device *bdev,
>> struct gendisk *disk)
>> {
>> --
>> 2.29.2
>>
>>
>>
>
>
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