nfsd: make nfsd4_scsi_identify_device retry with a larger buffer

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 <[email protected]>

---
 fs/nfsd/blocklayout.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

fs/nfsd/blocklayout.c +13 -5

index 70b8bf7..0cd9249 100644
@@ -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;

Signature · 1 line

2.9.5

Quoted 7 lines · Scott Mayhew

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.

Quoted 2 lines

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?

Also, I don't know why this is bothering me, but: I'd prefer "buflen" to "bufflen".

--b.

Quoted 49 lines

Signed-off-by Scott Mayhew <[email protected]>

---
 fs/nfsd/blocklayout.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

fs/nfsd/blocklayout.c +13 -5

index 70b8bf7..0cd9249 100644
@@ -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;

Signature · 1 line

2.9.5

Quoted 8 lines · J. Bruce Fields

Quoted 7 lines · Scott Mayhew

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.

Quoted 5 lines

Quoted 2 lines

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

Quoted 55 lines

Also, I don't know why this is bothering me, but: I'd prefer "buflen" to "bufflen".

--b.

Quoted 49 lines

Signed-off-by Scott Mayhew <[email protected]>

---
 fs/nfsd/blocklayout.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

fs/nfsd/blocklayout.c +13 -5

index 70b8bf7..0cd9249 100644
@@ -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;

Signature · 1 line

2.9.5