On Mon, 07 May 2018, J. Bruce Fields wrote:
> On Mon, May 07, 2018 at 09:01:31AM -0400, Scott Mayhew wrote:
> > nfsd4_scsi_identify_device() performs a single IDENTIFY command for the
> > device identification VPD page using a small buffer. If the reply is
> > too large to fit in this buffer then the GETDEVICEINFO reply will not
> > contain any info for the SCSI volume aside from the registration key.
> > This can happen for example if the device has descriptors using long
> > SCSI name strings.
> >
> > When the initial reply from the device indicates a larger buffer is
> > needed, retry once using the page length from that reply.
>
> Looks good, but how did you choose 65532 as the maximum? Does the scsi
> layer give us any maximum?
So I wasn't quite sure about that. The allocation length field for an
INQUIRY command is two bytes. There are various fields that the SPC-3
doc says have to be a multiple of 4, but I couldn't find anything that
says whether that applies to the allocation length. Since the initial
value 252 is a muliple of 4, I figured it wouldn't hurt anything to have
the maximum be a multiple of 4 too.
OTOH if you look at scsi_get_vpd_buf() in drivers/scsi/scsi.c, the
initial buffer size is SCSI_VPD_PG_LEN, which is 255.
-Scott
>
> Also, I don't know why this is bothering me, but: I'd prefer "buflen" to
> "bufflen".
>
> --b.
>
> >
> > Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
> > ---
> > fs/nfsd/blocklayout.c | 18 +++++++++++++-----
> > 1 file changed, 13 insertions(+), 5 deletions(-)
> >
> > diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c
> > index 70b8bf7..0cd9249 100644
> > --- a/fs/nfsd/blocklayout.c
> > +++ b/fs/nfsd/blocklayout.c
> > @@ -216,13 +216,14 @@ static int nfsd4_scsi_identify_device(struct block_device *bdev,
> > struct request_queue *q = bdev->bd_disk->queue;
> > struct request *rq;
> > struct scsi_request *req;
> > - size_t bufflen = 252, len, id_len;
> > + size_t bufflen = 252, maxlen = 65532, len, id_len;
> > u8 *buf, *d, type, assoc;
> > - int error;
> > + int retries = 1, error;
> >
> > if (WARN_ON_ONCE(!blk_queue_scsi_passthrough(q)))
> > return -EINVAL;
> >
> > +again:
> > buf = kzalloc(bufflen, GFP_KERNEL);
> > if (!buf)
> > return -ENOMEM;
> > @@ -255,9 +256,16 @@ static int nfsd4_scsi_identify_device(struct block_device *bdev,
> >
> > len = (buf[2] << 8) + buf[3] + 4;
> > if (len > bufflen) {
> > - pr_err("pNFS: INQUIRY 0x83 response invalid (len = %zd)\n",
> > - len);
> > - goto out_put_request;
> > + if (len < maxlen && retries--) {
> > + blk_put_request(rq);
> > + kfree(buf);
> > + bufflen = len;
> > + goto again;
> > + } else {
> > + pr_err("pNFS: INQUIRY 0x83 response invalid (len = %zd)\n",
> > + len);
> > + goto out_put_request;
> > + }
> > }
> >
> > d = buf + 4;
> > --
> > 2.9.5
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