Albert Lee wrote:
Tejun Heo wrote:
Albert Lee wrote:
This patch makes qc->tf well preserved, except we still have
qc->tf got overwritten by ata_pio_bytes().
Maybe we also need the attached follow-up patch?
--
albert
--- 02_atapi_pio_bytes/drivers/scsi/libata-core.c 2006-05-18
14:20:32.000000000 +0800
+++ 03_atapi_pio_bytes/drivers/scsi/libata-core.c 2006-05-18
14:25:41.000000000 +0800
@@ -3861,10 +3861,10 @@ static void atapi_pio_bytes(struct ata_q
unsigned int ireason, bc_lo, bc_hi, bytes;
int i_write, do_write = (qc->tf.flags & ATA_TFLAG_WRITE) ? 1 : 0;
- ap->ops->tf_read(ap, &qc->tf);
- ireason = qc->tf.nsect;
- bc_lo = qc->tf.lbam;
- bc_hi = qc->tf.lbah;
+ ap->ops->tf_read(ap, &qc->result_tf);
+ ireason = qc->result_tf.nsect;
+ bc_lo = qc->result_tf.lbam;
+ bc_hi = qc->result_tf.lbah;
bytes = (bc_hi << 8) | bc_lo;
/* shall be cleared to zero, indicating xfer of data */
I actually think above should be done with local variable. It's not
comannd TF nor result TF.
You're right. But local variable adds 18+ extra bytes to the kernel stack.
And
- For normal completion, qc->result_tf is not relevant.
- For error, qc->result_tf is later overwritten by ata_qc_complete().
Maybe we can use qc->result_tf for temp storage of intermediate TF here
and save some stack usage?
Yeah, maybe. But, please note in the code that the use is not to record
result.
--
tejun
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