Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:46822 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752745AbeEKIHC (ORCPT ); Fri, 11 May 2018 04:07:02 -0400 Date: Fri, 11 May 2018 01:06:59 -0700 From: Christoph Hellwig To: Scott Mayhew Cc: bfields@fieldses.org, jlayton@kernel.org, linux-nfs@vger.kernel.org Subject: Re: [PATCH v2] nfsd: make nfsd4_scsi_identify_device retry with a larger buffer Message-ID: <20180511080659.GA6345@infradead.org> References: <20180510204929.24328-1-smayhew@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20180510204929.24328-1-smayhew@redhat.com> Sender: linux-nfs-owner@vger.kernel.org List-ID: On Thu, May 10, 2018 at 04:49:29PM -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. > > Signed-off-by: Scott Mayhew > --- > fs/nfsd/blocklayout.c | 25 ++++++++++++++++++++----- > 1 file changed, 20 insertions(+), 5 deletions(-) > > Changes since v1: > - added comment explaining the initial and max buffer lengths > - changed the len-to-maxlen comparison from "<" to "<=" > > diff --git a/fs/nfsd/blocklayout.c b/fs/nfsd/blocklayout.c > index 70b8bf7..aa1c6f9 100644 > --- a/fs/nfsd/blocklayout.c > +++ b/fs/nfsd/blocklayout.c > @@ -216,13 +216,21 @@ 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; > + /* > + * The allocation length (passed in bytes 3 and 4 of the INQUIRY > + * command descriptor block) specifies the number of bytes that have > + * been allocated for the data-in buffer. > + * 252 is the highest one-byte value that is a multiple of 4. > + * 65532 is the highest two-byte value that is a multiple of 4. > + */ > + 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 +263,16 @@ 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; No need for an else after a goto. Otherwise looks fine: Reviewed-by: Christoph Hellwig