Hello,
This patch fixes I/O errors during BLKRRPART ioctl() behavior right
after format operation that changed logical block size of the block
device with a same file descriptor opened.
Testcase:
The following testcase is a case of NVMe namespace with the following
conditions:
- Current LBA format is lbaf=0 (512 bytes logical block size)
- LBA Format(lbaf=1) has 4096 bytes logical block size
# Format block device logical block size 512B to 4096B
nvme format /dev/nvme0n1 --lbaf=1 --force
This will cause I/O errors because BLKRRPART ioctl() happened right after
the format command with same file descriptor opened in application
(e.g., nvme-cli) like:
fd = open("/dev/nvme0n1", O_RDONLY);
nvme_format(fd, ...);
if (ioctl(fd, BLKRRPART) < 0)
...
Errors:
We can see the Read command with Number of LBA(NLB) 0xffff(65535) which
was under-flowed because BLKRRPART operation requested request size based
on i_blkbits of the block device which is 9 via buffer_head.
[dmesg-snip]
[ 10.771740] blk_update_request: operation not supported error, dev nvme0n1, sector 0 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0
[ 10.780262] Buffer I/O error on dev nvme0n1, logical block 0, async page read
[event-snip]
kworker/0:1H-56 [000] .... 913.456922: nvme_setup_cmd: nvme0: disk=nvme0n1, qid=1, cmdid=216, nsid=1, flags=0x0, meta=0x0, cmd=(nvme_cmd_read slba=0, len=65535, ctrl=0x0, dsmgmt=0, reftag=0)
ksoftirqd/0-9 [000] .Ns. 916.566351: nvme_complete_rq: nvme0: disk=nvme0n1, qid=1, cmdid=216, res=0x0, retries=0, flags=0x0, status=0x4002
The patch below fixes the I/O errors by rejecting I/O requests from the
block layer with setting a flag to gendisk until the file descriptor
re-opened to be updated by __blkdev_get(). This is based on the previous
discussion [1].
Since V2:
- Cover letter with testcase and error logs attached. Removed un-related
changes: empty line. (Chaitanya, [2])
- Put blkdev with blkdev_put_no_open().
Since V1:
- Updated patch to reject I/O rather than updating i_blkbits of the
block device's inode directly from driver. (Christoph, [1])
[1] https://lore.kernel.org/linux-nvme/[email protected]/T/#t
[2] https://lore.kernel.org/linux-nvme/[email protected]/T/#t
Thanks,
Minwoo Im (1):
block: reject I/O for same fd if block size changed
block/blk-settings.c | 8 ++++++++
block/partitions/core.c | 11 +++++++++++
fs/block_dev.c | 6 ++++++
include/linux/genhd.h | 1 +
4 files changed, 26 insertions(+)
--
2.17.1
This patch fixes I/O errors during BLKRRPART ioctl() behavior right
after format operation that changed logical block size of the block
device with a same file descriptor opened.
This issue can be easily reproduced with a single format command in case
of NVMe (logical block size 512B to 4096B).
nvme format /dev/nvme0n1 --lbaf=1 --force
This is because the application, nvme-cli format subcommand issues an
admin command followed by BLKRRPART ioctl to re-read partition
information without closing the file descriptor. If file descriptor
stays opened, __blkdev_get() will not be invoked at all even logical
block size has been changed.
It will cause I/O errors with invalid Read operations during the
BLKRRPART ioctl due to i_blkbits mismatch. The invalid operations in
BLKRRPART happens with under-flowed Number of LBA(NLB) values
0xffff(65535) because i_blkbits is still set to 9 even the logical block
size has been updated to 4096. The BLKRRPART will lead buffer_head to
hold 512B data which is less than the logical lock size of the block
device.
The root cause, which is because i_blkbits of inode of the block device
is not updated, can be solved easily by re-opening file descriptor
again from application. But, that's just for application's business
and kernel should reject invalid Read operations during the BLKRRPART
ioctl.
This patch rejects I/O from the path of add_partitions() to avoid
issuing invalid Read operations to device. It also sets a flag to
gendisk in blk_queue_logical_block_size to minimize caller-side updates.
Signed-off-by: Minwoo Im <[email protected]>
---
block/blk-settings.c | 8 ++++++++
block/partitions/core.c | 11 +++++++++++
fs/block_dev.c | 6 ++++++
include/linux/genhd.h | 1 +
4 files changed, 26 insertions(+)
diff --git a/block/blk-settings.c b/block/blk-settings.c
index 43990b1d148b..84136ea4e2a4 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -328,6 +328,14 @@ EXPORT_SYMBOL(blk_queue_max_segment_size);
void blk_queue_logical_block_size(struct request_queue *q, unsigned int size)
{
struct queue_limits *limits = &q->limits;
+ struct block_device *bdev;
+
+ if (q->backing_dev_info && q->backing_dev_info->owner &&
+ limits->logical_block_size != size) {
+ bdev = blkdev_get_no_open(q->backing_dev_info->owner->devt);
+ bdev->bd_disk->flags |= GENHD_FL_BLOCK_SIZE_CHANGED;
+ blkdev_put_no_open(bdev);
+ }
limits->logical_block_size = size;
diff --git a/block/partitions/core.c b/block/partitions/core.c
index e7d776db803b..5a0330c1b6f9 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -618,6 +618,17 @@ int blk_add_partitions(struct gendisk *disk, struct block_device *bdev)
if (!disk_part_scan_enabled(disk))
return 0;
+ /*
+ * Reject to check partition information if block size has been changed
+ * in the runtime. If block size of a block device has been changed,
+ * the file descriptor should be opened agian to update the blkbits.
+ */
+ if (disk->flags & GENHD_FL_BLOCK_SIZE_CHANGED) {
+ pr_warn("%s: rejecting checking partition. fd should be opened again.\n",
+ disk->disk_name);
+ return -EBADFD;
+ }
+
state = check_partition(disk, bdev);
if (!state)
return 0;
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 9293045e128c..c996de3d6084 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -131,6 +131,12 @@ EXPORT_SYMBOL(truncate_bdev_range);
static void set_init_blocksize(struct block_device *bdev)
{
bdev->bd_inode->i_blkbits = blksize_bits(bdev_logical_block_size(bdev));
+
+ /*
+ * Allow I/O commands for this block device. We can say that this
+ * block device has been set to a proper block size.
+ */
+ bdev->bd_disk->flags &= ~GENHD_FL_BLOCK_SIZE_CHANGED;
}
int set_blocksize(struct block_device *bdev, int size)
diff --git a/include/linux/genhd.h b/include/linux/genhd.h
index 809aaa32d53c..0e0e24917003 100644
--- a/include/linux/genhd.h
+++ b/include/linux/genhd.h
@@ -103,6 +103,7 @@ struct partition_meta_info {
#define GENHD_FL_BLOCK_EVENTS_ON_EXCL_WRITE 0x0100
#define GENHD_FL_NO_PART_SCAN 0x0200
#define GENHD_FL_HIDDEN 0x0400
+#define GENHD_FL_BLOCK_SIZE_CHANGED 0x0800
enum {
DISK_EVENT_MEDIA_CHANGE = 1 << 0, /* media changed */
--
2.17.1
On Mon, Jan 04, 2021 at 10:06:59PM +0900, Minwoo Im wrote:
> + if (q->backing_dev_info && q->backing_dev_info->owner &&
> + limits->logical_block_size != size) {
> + bdev = blkdev_get_no_open(q->backing_dev_info->owner->devt);
> + bdev->bd_disk->flags |= GENHD_FL_BLOCK_SIZE_CHANGED;
> + blkdev_put_no_open(bdev);
> + }
We really need the backpointer from the queue to the gendisk I've wanted
to add for a while. Can we at least restrict this to a live gendisk?
Also I think the size change flag should go into the ->state field and
use the atomic bitops helpers to avoid concurrency problems.
On Mon, Jan 04, 2021 at 06:11:08PM +0100, Christoph Hellwig wrote:
> On Mon, Jan 04, 2021 at 10:06:59PM +0900, Minwoo Im wrote:
> > + if (q->backing_dev_info && q->backing_dev_info->owner &&
> > + limits->logical_block_size != size) {
> > + bdev = blkdev_get_no_open(q->backing_dev_info->owner->devt);
> > + bdev->bd_disk->flags |= GENHD_FL_BLOCK_SIZE_CHANGED;
> > + blkdev_put_no_open(bdev);
> > + }
>
> We really need the backpointer from the queue to the gendisk I've wanted
> to add for a while. Can we at least restrict this to a live gendisk?
Alternatively we could make this request_queue QUEUE* flag for now.
Hello Christoph,
Thanks for your review.
On 21-01-04 18:11:41, Christoph Hellwig wrote:
> On Mon, Jan 04, 2021 at 06:11:08PM +0100, Christoph Hellwig wrote:
> > On Mon, Jan 04, 2021 at 10:06:59PM +0900, Minwoo Im wrote:
> > > + if (q->backing_dev_info && q->backing_dev_info->owner &&
> > > + limits->logical_block_size != size) {
> > > + bdev = blkdev_get_no_open(q->backing_dev_info->owner->devt);
> > > + bdev->bd_disk->flags |= GENHD_FL_BLOCK_SIZE_CHANGED;
> > > + blkdev_put_no_open(bdev);
> > > + }
> >
> > We really need the backpointer from the queue to the gendisk I've wanted
> > to add for a while. Can we at least restrict this to a live gendisk?
It was a point that I really would like to ask by RFC whether we can
have backpointer to the gendisk from the request_queue. And I'd like to
have it to simplify this routine and for future usages also.
I will restrict this one by checking GENHD_FL_UP flag from the gendisk
for the next patch.
>
> Alternatively we could make this request_queue QUEUE* flag for now.
As this patch rejects I/O from the block layer partition code, can we
have this flag in gendisk rather than request_queue ?
Thanks,
On Tue, Jan 05, 2021 at 10:04:56AM +0900, Minwoo Im wrote:
> It was a point that I really would like to ask by RFC whether we can
> have backpointer to the gendisk from the request_queue. And I'd like to
> have it to simplify this routine and for future usages also.
I think it is the right thing to do, at least mid-term, although I
don't want to enforce the burden on you right now.
> I will restrict this one by checking GENHD_FL_UP flag from the gendisk
> for the next patch.
>
> >
> > Alternatively we could make this request_queue QUEUE* flag for now.
>
> As this patch rejects I/O from the block layer partition code, can we
> have this flag in gendisk rather than request_queue ?
For now we can as the request_queue is required. I have some plans to
clean up this area, but just using a request_queue flag for now is
probably the simplest, even if it means more work for me later.
Hello,
On 21-01-05 08:50:09, Christoph Hellwig wrote:
> On Tue, Jan 05, 2021 at 10:04:56AM +0900, Minwoo Im wrote:
> > It was a point that I really would like to ask by RFC whether we can
> > have backpointer to the gendisk from the request_queue. And I'd like to
> > have it to simplify this routine and for future usages also.
>
> I think it is the right thing to do, at least mid-term, although I
> don't want to enforce the burden on you right now.
>
> > I will restrict this one by checking GENHD_FL_UP flag from the gendisk
> > for the next patch.
> >
> > >
> > > Alternatively we could make this request_queue QUEUE* flag for now.
> >
> > As this patch rejects I/O from the block layer partition code, can we
> > have this flag in gendisk rather than request_queue ?
>
> For now we can as the request_queue is required. I have some plans to
> clean up this area, but just using a request_queue flag for now is
> probably the simplest, even if it means more work for me later.
Please let me prepare the next quick fix for this issue with request_queue
flag.
Thanks!