When a program continually issues SG_DXFER_TO_FROM_DEV commands,
throttling via printk_ratelimit() isn't enough. If the drive is fast
and the console is slow (e.g. vesafb), it can slow down the process
quite a bit.
This patch makes sg remember last printed comm name and skip warning
message if the name matches. This can protect most use cases.
Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
---
drivers/scsi/sg.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 85d3894..913408a 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -605,8 +605,10 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
* but is is possible that the app intended SG_DXFER_TO_DEV, because there
* is a non-zero input_size, so emit a warning.
*/
- if (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV)
- if (printk_ratelimit())
+ if (hp->dxfer_direction == SG_DXFER_TO_FROM_DEV) {
+ static char last_printed[TASK_COMM_LEN];
+
+ if (strcmp(last_printed, current->comm) && printk_ratelimit()) {
printk(KERN_WARNING
"sg_write: data in/out %d/%d bytes for SCSI command 0x%x--"
"guessing data in;\n" KERN_WARNING " "
@@ -614,6 +616,10 @@ sg_write(struct file *filp, const char __user *buf, size_t count, loff_t * ppos)
old_hdr.reply_len - (int)SZ_SG_HEADER,
input_size, (unsigned int) cmnd[0],
current->comm);
+
+ memcpy(last_printed, current->comm, TASK_COMM_LEN);
+ }
+ }
k = sg_common_write(sfp, srp, cmnd, sfp->timeout, blocking);
return (k < 0) ? k : count;
}
-
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