Hello,

On 20-12-23 16:49:04, Christoph Hellwig wrote:

set_blocksize just sets the block sise used for buffer heads and should
not be called by the driver.  blkdev_get updates the block size, so
you must already have the fd re-reading the partition table open?
I'm not entirely sure how we can work around this except by avoiding
buffer head I/O in the partition reread code.  Note that this affects
all block drivers where the block size could change at runtime.

Thank you Christoph for your comment on this.

Agreed.  BLKRRPART leads us to block_read_full_page which takes buffer
heads for I/O.

Yes, __blkdev_get() sets i_blkbits of block device inode via
set_init_blocksize.  And Yes again as nvme-cli already opened the block
device fd and requests the BLKRRPART with that fd.  Also, __bdev_get()
only updates the i_blkbits(blocksize) in case bdev->bd_openers == 0 which
is the first time to open this block device.

Then, how about having NVMe driver prevent underflow case for the
request->__data_len is smaller than the logical block size like:

diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
index ce1b61519441..030353d203bf 100644
--- a/drivers/nvme/host/core.c
+++ b/drivers/nvme/host/core.c

@@ -803,7 +803,11 @@ static inline blk_status_t nvme_setup_rw(struct nvme_ns *ns,
        cmnd->rw.opcode = op;
        cmnd->rw.nsid = cpu_to_le32(ns->head->ns_id);
        cmnd->rw.slba = cpu_to_le64(nvme_sect_to_lba(ns, blk_rq_pos(req)));
-       cmnd->rw.length = cpu_to_le16((blk_rq_bytes(req) >> ns->lba_shift) - 1);
+
+       if (unlikely(blk_rq_bytes(req) < (1 << ns->lba_shift)))
+               cmnd->rw.length = 0;
+       else
+               cmnd->rw.length = cpu_to_le16((blk_rq_bytes(req) >> ns->lba_shift) - 1);
 
        if (req_op(req) == REQ_OP_WRITE && ctrl->nr_streams)
                nvme_assign_write_stream(ctrl, req, &control, &dsmgmt);

Thanks,