Messages in this thread Patch in this message | | | From | Mark Lord <> | Subject | [PATCH] drivers/scsi/sd.c: fix uninitialized variable in handling medium errors | Date | Wed, 26 Apr 2006 16:27:29 -0400 |
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From: Mark Lord <lkml@rtr.ca>
I am looking into how SCSI/SATA handle medium (disk) errors, and the observed behaviour is a little more random than expected, due to a bug in sd.c.
When scsi_get_sense_info_fld() fails (returns 0), it does NOT update the value of first_err_block. But sd_rw_intr() merrily continues to use that variable regardless, possibly making incorrect decisions about retries and the like.
This patch removes the randomness there, by using the first sector of the request (SCpnt->request->sector) in such cases, instead of first_err_block.
The patch shows more context than usual, to help see what's going on.
Signed-off-by: Mark Lord <lkml@rtr.ca> --- --- linux-2.6.17-rc2-git8/drivers/scsi/sd.c 2006-04-26 15:36:12.000000000 -0400 +++ linux/drivers/scsi/sd.c 2006-04-26 16:07:39.000000000 -0400 @@ -930,64 +930,66 @@ info_valid = scsi_get_sense_info_fld( SCpnt->sense_buffer, SCSI_SENSE_BUFFERSIZE, &first_err_block); /* * May want to warn and skip if following cast results * in actual truncation (if sector_t < 64 bits) */ error_sector = (sector_t)first_err_block; if (SCpnt->request->bio != NULL) block_sectors = bio_sectors(SCpnt->request->bio); switch (SCpnt->device->sector_size) { case 1024: error_sector <<= 1; if (block_sectors < 2) block_sectors = 2; break; case 2048: error_sector <<= 2; if (block_sectors < 4) block_sectors = 4; break; case 4096: error_sector <<=3; if (block_sectors < 8) block_sectors = 8; break; case 256: error_sector >>= 1; break; default: break; } + if (!info_valid) + error_sector = SCpnt->request->sector; error_sector &= ~(block_sectors - 1); good_bytes = (error_sector - SCpnt->request->sector) << 9; if (good_bytes < 0 || good_bytes >= this_count) good_bytes = 0; break; case RECOVERED_ERROR: /* an error occurred, but it recovered */ case NO_SENSE: /* LLDD got sense data */ /* * Inform the user, but make sure that it's not treated * as a hard error. */ scsi_print_sense("sd", SCpnt); SCpnt->result = 0; memset(SCpnt->sense_buffer, 0, SCSI_SENSE_BUFFERSIZE); good_bytes = this_count; break; case ILLEGAL_REQUEST: if (SCpnt->device->use_10_for_rw && (SCpnt->cmnd[0] == READ_10 || SCpnt->cmnd[0] == WRITE_10)) SCpnt->device->use_10_for_rw = 0; if (SCpnt->device->use_10_for_ms && (SCpnt->cmnd[0] == MODE_SENSE_10 || SCpnt->cmnd[0] == MODE_SELECT_10)) SCpnt->device->use_10_for_ms = 0; break; default: break; - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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