Because scsi_finish_command() subtracts the residual from the buffer length, residual overflows must not be reported. Reflect this in the SCSI documentation. See also commit 9237f04e12cc ("scsi: core: Fix scsi_get/set_resid() interface")
Cc: Damien Le Moal dlemoal@kernel.org Cc: Hannes Reinecke hare@suse.de Cc: Douglas Gilbert dgilbert@interlog.com Cc: stable@vger.kernel.org Signed-off-by: Bart Van Assche bvanassche@acm.org --- Documentation/scsi/scsi_mid_low_api.rst | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/scsi/scsi_mid_low_api.rst b/Documentation/scsi/scsi_mid_low_api.rst index 6fa3a6279501..022198c51350 100644 --- a/Documentation/scsi/scsi_mid_low_api.rst +++ b/Documentation/scsi/scsi_mid_low_api.rst @@ -1190,11 +1190,11 @@ Members of interest: - pointer to scsi_device object that this command is associated with. resid - - an LLD should set this signed integer to the requested + - an LLD should set this unsigned integer to the requested transfer length (i.e. 'request_bufflen') less the number of bytes that are actually transferred. 'resid' is preset to 0 so an LLD can ignore it if it cannot detect - underruns (overruns should be rare). If possible an LLD + underruns (overruns should not be reported). An LLD should set 'resid' prior to invoking 'done'. The most interesting case is data transfers from a SCSI target device (e.g. READs) that underrun.
Bart,
Because scsi_finish_command() subtracts the residual from the buffer length, residual overflows must not be reported. Reflect this in the SCSI documentation. See also commit 9237f04e12cc ("scsi: core: Fix scsi_get/set_resid() interface")
Applied to 6.6/scsi-staging, thanks!
On Fri, Jul 21, 2023 at 09:01:32AM -0700, Bart Van Assche wrote:
Because scsi_finish_command() subtracts the residual from the buffer length, residual overflows must not be reported. Reflect this in the SCSI documentation. See also commit 9237f04e12cc ("scsi: core: Fix scsi_get/set_resid() interface")
Cc: Damien Le Moal dlemoal@kernel.org Cc: Hannes Reinecke hare@suse.de Cc: Douglas Gilbert dgilbert@interlog.com Cc: stable@vger.kernel.org Signed-off-by: Bart Van Assche bvanassche@acm.org
Documentation/scsi/scsi_mid_low_api.rst | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/scsi/scsi_mid_low_api.rst b/Documentation/scsi/scsi_mid_low_api.rst index 6fa3a6279501..022198c51350 100644 --- a/Documentation/scsi/scsi_mid_low_api.rst +++ b/Documentation/scsi/scsi_mid_low_api.rst @@ -1190,11 +1190,11 @@ Members of interest: - pointer to scsi_device object that this command is associated with. resid
- an LLD should set this signed integer to the requested
- an LLD should set this unsigned integer to the requested transfer length (i.e. 'request_bufflen') less the number of bytes that are actually transferred. 'resid' is preset to 0 so an LLD can ignore it if it cannot detect
underruns (overruns should be rare). If possible an LLD
underruns (overruns should not be reported). An LLD
I'm very late to party, sorry. But we have certainly seen at least one overrun reported some years ago on a FC SAN. We've changed some handling in zFCP due to that ( a099b7b1fc1f ("scsi: zfcp: add handling for FCP_RESID_OVER to the fcp ingress path") ). The theory back than was, that it was cause by either a faulty ISL in the fabric, or some other "bit-errors" on the wire that caused some FC frames being dropped during transmit.
I added that we mark such commands with `DID_ERROR`, so they are retried, if that is permissible.
should set 'resid' prior to invoking 'done'. The most interesting case is data transfers from a SCSI target device (e.g. READs) that underrun.
On 8/16/23 02:58, Benjamin Block wrote:
On Fri, Jul 21, 2023 at 09:01:32AM -0700, Bart Van Assche wrote:
Because scsi_finish_command() subtracts the residual from the buffer length, residual overflows must not be reported. Reflect this in the SCSI documentation. See also commit 9237f04e12cc ("scsi: core: Fix scsi_get/set_resid() interface")
Cc: Damien Le Moal dlemoal@kernel.org Cc: Hannes Reinecke hare@suse.de Cc: Douglas Gilbert dgilbert@interlog.com Cc: stable@vger.kernel.org Signed-off-by: Bart Van Assche bvanassche@acm.org
Documentation/scsi/scsi_mid_low_api.rst | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/Documentation/scsi/scsi_mid_low_api.rst b/Documentation/scsi/scsi_mid_low_api.rst index 6fa3a6279501..022198c51350 100644 --- a/Documentation/scsi/scsi_mid_low_api.rst +++ b/Documentation/scsi/scsi_mid_low_api.rst @@ -1190,11 +1190,11 @@ Members of interest: - pointer to scsi_device object that this command is associated with. resid
- an LLD should set this signed integer to the requested
- an LLD should set this unsigned integer to the requested transfer length (i.e. 'request_bufflen') less the number of bytes that are actually transferred. 'resid' is preset to 0 so an LLD can ignore it if it cannot detect
underruns (overruns should be rare). If possible an LLD
underruns (overruns should not be reported). An LLDI'm very late to party, sorry. But we have certainly seen at least one overrun reported some years ago on a FC SAN. We've changed some handling in zFCP due to that ( a099b7b1fc1f ("scsi: zfcp: add handling for FCP_RESID_OVER to the fcp ingress path") ). The theory back than was, that it was cause by either a faulty ISL in the fabric, or some other "bit-errors" on the wire that caused some FC frames being dropped during transmit.
I added that we mark such commands with `DID_ERROR`, so they are retried, if that is permissible.
should set 'resid' prior to invoking 'done'. The most interesting case is data transfers from a SCSI target device (e.g. READs) that underrun.
Thanks, that's interesting feedback. Feel free to submit a patch that refines the scsi_set_resid() documentation further.
Bart.
linux-stable-mirror@lists.linaro.org
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