Re: [PATCH v2] scsi_debug: fix sleep in invalid context
> "Doug" == Douglas Gilbert writes: Doug> In this post: Doug> http://www.spinics.net/lists/linux-scsi/msg97124.html the author Doug> shows some kernel infrastructure complaining about a sleep in an Doug> invalid context. Remove offending call to vmalloc(). Instead of Doug> using kzalloc() which reviewers didn't like, use a bucket system Doug> (64 bytes on the stack) and potentially multiple calls to Doug> sg_pcopy_from_buffer() to construct the 'data-in' buffer for the Doug> SCSI REPORT LUNS command. Applied to 4.8/scsi-queue. -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v2] scsi_debug: fix sleep in invalid context
On 05/31/2016 02:15 PM, Douglas Gilbert wrote: In this post: http://www.spinics.net/lists/linux-scsi/msg97124.html the author shows some kernel infrastructure complaining about a sleep in an invalid context. Remove offending call to vmalloc(). Instead of using kzalloc() which reviewers didn't like, use a bucket system (64 bytes on the stack) and potentially multiple calls to sg_pcopy_from_buffer() to construct the 'data-in' buffer for the SCSI REPORT LUNS command. Reviewed-by: Bart Van Assche -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v2] scsi_debug: fix sleep in invalid context
Oh well, not a fan og the casting, but as this is an important fix let's get it in for now: Acked-by: Christoph Hellwig -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH v2] scsi_debug: fix sleep in invalid context
On 2016-06-08 04:57 PM, Douglas Gilbert wrote:
On 2016-06-07 09:55 PM, Christoph Hellwig wrote:
+static int p_fill_from_dev_buffer(struct scsi_cmnd *scp, const void *arr,
+ int arr_len, unsigned int off_dst)
+{
+int act_len, n;
+struct scsi_data_buffer *sdb = scsi_in(scp);
+off_t skip = off_dst;
Why off_t which is a signed value instead of the unsigned in passed in?
Because off_t is the type of the last argument to sg_pcopy_from_buffer()
which is where the off_dst value goes. So there is potentially a size
of integer change plus signedness, IMO best expressed by defining a
new auto variable. I notice some projects have a uoff_t typedef for
offsets that make no sense when negative (like this case), but not the
Linux kernel.
+#define RL_BUCKET_ELEMS 8
+
/* Even though each pseudo target has a REPORT LUNS "well known logical unit"
* (W-LUN), the normal Linux scanning logic does not associate it with a
* device (e.g. /dev/sg7). The following magic will make that association:
@@ -3285,12 +3315,14 @@ static int resp_report_luns(struct scsi_cmnd *scp,
unsigned char select_report;
u64 lun;
struct scsi_lun *lun_p;
-u8 *arr;
+u8 arr[RL_BUCKET_ELEMS * sizeof(struct scsi_lun)];
just use an on-stack array of type struct scsi_lun here, e.g.:
struct scsi_lun arr[RL_BUCKET_ELEMS];
Which you can then use directly instead of lun_p later, but which can
also be passed p_fill_from_dev_buffer as that takes a void pointer.
Can do.
When I looked at doing this, it's not that simple. The first 8 byte
"slot" is not a LUN, it's the response header, which just happens
to be 8 bytes long. That is the reason for the comment above that loop:
/* loops rely on sizeof response header same as sizeof lun (both 8) */
So IMO: 'struct scsi_lun arr[RL_BUCKET_ELEMS];' will work but
is deceptive. IMO the v2 patch should stand, unless someone has an
alternate patch. The original patch is also fine. This is a bug
fix, not a new feature.
Doug Gilbert
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Re: [PATCH v2] scsi_debug: fix sleep in invalid context
On 2016-06-07 09:55 PM, Christoph Hellwig wrote:
+static int p_fill_from_dev_buffer(struct scsi_cmnd *scp, const void *arr,
+ int arr_len, unsigned int off_dst)
+{
+ int act_len, n;
+ struct scsi_data_buffer *sdb = scsi_in(scp);
+ off_t skip = off_dst;
Why off_t which is a signed value instead of the unsigned in passed in?
Because off_t is the type of the last argument to sg_pcopy_from_buffer()
which is where the off_dst value goes. So there is potentially a size
of integer change plus signedness, IMO best expressed by defining a
new auto variable. I notice some projects have a uoff_t typedef for
offsets that make no sense when negative (like this case), but not the
Linux kernel.
+#define RL_BUCKET_ELEMS 8
+
/* Even though each pseudo target has a REPORT LUNS "well known logical unit"
* (W-LUN), the normal Linux scanning logic does not associate it with a
* device (e.g. /dev/sg7). The following magic will make that association:
@@ -3285,12 +3315,14 @@ static int resp_report_luns(struct scsi_cmnd *scp,
unsigned char select_report;
u64 lun;
struct scsi_lun *lun_p;
- u8 *arr;
+ u8 arr[RL_BUCKET_ELEMS * sizeof(struct scsi_lun)];
just use an on-stack array of type struct scsi_lun here, e.g.:
struct scsi_lun arr[RL_BUCKET_ELEMS];
Which you can then use directly instead of lun_p later, but which can
also be passed p_fill_from_dev_buffer as that takes a void pointer.
Can do.
Doug Gilbert
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Re: [PATCH v2] scsi_debug: fix sleep in invalid context
> +static int p_fill_from_dev_buffer(struct scsi_cmnd *scp, const void *arr,
> + int arr_len, unsigned int off_dst)
> +{
> + int act_len, n;
> + struct scsi_data_buffer *sdb = scsi_in(scp);
> + off_t skip = off_dst;
Why off_t which is a signed value instead of the unsigned in passed in?
> +#define RL_BUCKET_ELEMS 8
> +
> /* Even though each pseudo target has a REPORT LUNS "well known logical unit"
> * (W-LUN), the normal Linux scanning logic does not associate it with a
> * device (e.g. /dev/sg7). The following magic will make that association:
> @@ -3285,12 +3315,14 @@ static int resp_report_luns(struct scsi_cmnd *scp,
> unsigned char select_report;
> u64 lun;
> struct scsi_lun *lun_p;
> - u8 *arr;
> + u8 arr[RL_BUCKET_ELEMS * sizeof(struct scsi_lun)];
just use an on-stack array of type struct scsi_lun here, e.g.:
struct scsi_lun arr[RL_BUCKET_ELEMS];
Which you can then use directly instead of lun_p later, but which can
also be passed p_fill_from_dev_buffer as that takes a void pointer.
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Re: [PATCH v2] scsi_debug: fix sleep in invalid context
> "Doug" == Douglas Gilbert writes: Doug> In this post: Doug> http://www.spinics.net/lists/linux-scsi/msg97124.html the author Doug> shows some kernel infrastructure complaining about a sleep in an Doug> invalid context. Remove offending call to vmalloc(). Instead of Doug> using kzalloc() which reviewers didn't like, use a bucket system Doug> (64 bytes on the stack) and potentially multiple calls to Doug> sg_pcopy_from_buffer() to construct the 'data-in' buffer for the Doug> SCSI REPORT LUNS command. It would be great to get this reviewed... -- Martin K. Petersen Oracle Linux Engineering -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH v2] scsi_debug: fix sleep in invalid context
In this post: http://www.spinics.net/lists/linux-scsi/msg97124.html
the author shows some kernel infrastructure complaining about a
sleep in an invalid context. Remove offending call to vmalloc().
Instead of using kzalloc() which reviewers didn't like, use a
bucket system (64 bytes on the stack) and potentially multiple
calls to sg_pcopy_from_buffer() to construct the 'data-in' buffer
for the SCSI REPORT LUNS command.
Signed-off-by: Douglas Gilbert
---
drivers/scsi/scsi_debug.c | 93 +--
1 file changed, 66 insertions(+), 27 deletions(-)
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 0f9ba41..6a219a0 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -890,7 +890,7 @@ static int make_ua(struct scsi_cmnd *scp, struct
sdebug_dev_info *devip)
return 0;
}
-/* Returns 0 if ok else (DID_ERROR << 16). Sets scp->resid . */
+/* Build SCSI "data-in" buffer. Returns 0 if ok else (DID_ERROR << 16). */
static int fill_from_dev_buffer(struct scsi_cmnd *scp, unsigned char *arr,
int arr_len)
{
@@ -909,7 +909,35 @@ static int fill_from_dev_buffer(struct scsi_cmnd *scp,
unsigned char *arr,
return 0;
}
-/* Returns number of bytes fetched into 'arr' or -1 if error. */
+/* Partial build of SCSI "data-in" buffer. Returns 0 if ok else
+ * (DID_ERROR << 16). Can write to offset in data-in buffer. If multiple
+ * calls, not required to write in ascending offset order. Assumes resid
+ * set to scsi_bufflen() prior to any calls.
+ */
+static int p_fill_from_dev_buffer(struct scsi_cmnd *scp, const void *arr,
+ int arr_len, unsigned int off_dst)
+{
+ int act_len, n;
+ struct scsi_data_buffer *sdb = scsi_in(scp);
+ off_t skip = off_dst;
+
+ if (sdb->length <= off_dst)
+ return 0;
+ if (!(scsi_bidi_cmnd(scp) || scp->sc_data_direction == DMA_FROM_DEVICE))
+ return DID_ERROR << 16;
+
+ act_len = sg_pcopy_from_buffer(sdb->table.sgl, sdb->table.nents,
+ arr, arr_len, skip);
+ pr_debug("%s: off_dst=%u, scsi_bufflen=%u, act_len=%u, resid=%d\n",
+__func__, off_dst, scsi_bufflen(scp), act_len, sdb->resid);
+ n = (int)scsi_bufflen(scp) - ((int)off_dst + act_len);
+ sdb->resid = min(sdb->resid, n);
+ return 0;
+}
+
+/* Fetches from SCSI "data-out" buffer. Returns number of bytes fetched into
+ * 'arr' or -1 if error.
+ */
static int fetch_to_dev_buffer(struct scsi_cmnd *scp, unsigned char *arr,
int arr_len)
{
@@ -3269,6 +3297,8 @@ static int resp_get_lba_status(struct scsi_cmnd *scp,
return fill_from_dev_buffer(scp, arr, SDEBUG_GET_LBA_STATUS_LEN);
}
+#define RL_BUCKET_ELEMS 8
+
/* Even though each pseudo target has a REPORT LUNS "well known logical unit"
* (W-LUN), the normal Linux scanning logic does not associate it with a
* device (e.g. /dev/sg7). The following magic will make that association:
@@ -3285,12 +3315,14 @@ static int resp_report_luns(struct scsi_cmnd *scp,
unsigned char select_report;
u64 lun;
struct scsi_lun *lun_p;
- u8 *arr;
+ u8 arr[RL_BUCKET_ELEMS * sizeof(struct scsi_lun)];
unsigned int lun_cnt; /* normal LUN count (max: 256) */
unsigned int wlun_cnt; /* report luns W-LUN count */
unsigned int tlun_cnt; /* total LUN count */
unsigned int rlen; /* response length (in bytes) */
- int i, res;
+ int k, j, n, res;
+ unsigned int off_rsp = 0;
+ const int sz_lun = sizeof(struct scsi_lun);
clear_luns_changed_on_target(devip);
@@ -3329,33 +3361,40 @@ static int resp_report_luns(struct scsi_cmnd *scp,
--lun_cnt;
tlun_cnt = lun_cnt + wlun_cnt;
-
- rlen = (tlun_cnt * sizeof(struct scsi_lun)) + 8;
- arr = vmalloc(rlen);
- if (!arr) {
- mk_sense_buffer(scp, ILLEGAL_REQUEST, INSUFF_RES_ASC,
- INSUFF_RES_ASCQ);
- return check_condition_result;
- }
- memset(arr, 0, rlen);
+ rlen = tlun_cnt * sz_lun; /* excluding 8 byte header */
+ scsi_set_resid(scp, scsi_bufflen(scp));
pr_debug("select_report %d luns = %d wluns = %d no_lun0 %d\n",
select_report, lun_cnt, wlun_cnt, sdebug_no_lun_0);
- /* luns start at byte 8 in response following the header */
- lun_p = (struct scsi_lun *)&arr[8];
-
- /* LUNs use single level peripheral device addressing method */
+ /* loops rely on sizeof response header same as sizeof lun (both 8) */
lun = sdebug_no_lun_0 ? 1 : 0;
- for (i = 0; i < lun_cnt; i++)
- int_to_scsilun(lun++, lun_p++);
-
- if (wlun_cnt)
- int_to_scsilun(SCSI_W_LUN_REPORT_LUNS, lun_p++);
-
- put_unaligned_be32(rlen - 8, &arr[0]);
-
-
