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    SubjectRe: dm core patches
    James Bottomley wrote:
    >>The mechanism is in place, but the SCSI stack still needs a few changes
    >>to pass down the correct errors. The easiest would be to pass down
    >>pseudo-sense keys (I'd rather just call them something else as not to
    >>confuse things, io error hints or something) to
    >>end_that_request_first(), changing uptodate from a bool to a hint.
    >
    >
    > Yes, I'm ready to do this in SCSI. I think the uptodate field should
    > include at least two (and possibly three) failure type indications:
    >
    > - fatal: error cannot be retried
    > - retryable: error may be retried
    >
    > and possibly
    >
    > - informational: This is dangerous, since it's giving information about
    > a transaction that actually succeeded (i.e. we'd need to fix drivers to
    > recognise it as being uptodate but with info, like sector remapped)
    >
    > Then, we also have a error origin indication:
    >
    > - device: The device is actually reporting the problem
    > - transport: the error is a transport error
    > - driver: the error comes from the device driver.
    >
    > So dm would know that fatal transport or driver errors could be
    > repathed, but fatal device errors probably couldn't.
    >

    I apologize for not starting a new thread, but I just wanted some
    feedback as to whether or not the attached patch is headed in the right
    direction or even acceptable. block-err.patch adds new errornos to
    include/linux/errno.h (it does not touch the asm values), so useful IO
    error info can passed from callers of end_that_request_first to
    bio_endio and eventually to the DM/MD endio functions.

    I have an alternative patch that defines BLK_ERR_xxx values instead of
    touching errno.h, but becuase the error values get passed through the
    request code, bio code and DM/MD code the callers of bio_endio that are
    already using -Exxx values could present a problem. It would be nice to
    change them to the BLK_ERR_xxx, so the bio layer could have a single
    error value namespace. It's a more invasive change as there are several
    callers passing at least -EIO, -EWOULDBLOCK and -EPERM, so I am not sure
    if that is going to be OK since we are already in 2.6.3?

    Thanks,

    Mike Christie
    mikenc@us.ibm.com
    diff -aurp linux-2.6.3-orig/drivers/block/ll_rw_blk.c linux-2.6.3-ec/drivers/block/ll_rw_blk.c
    --- linux-2.6.3-orig/drivers/block/ll_rw_blk.c 2004-02-17 19:57:16.000000000 -0800
    +++ linux-2.6.3-ec/drivers/block/ll_rw_blk.c 2004-02-18 12:33:50.000000000 -0800
    @@ -2456,8 +2456,13 @@ static int __end_that_request_first(stru
    if (!blk_pc_request(req))
    req->errors = 0;

    - if (!uptodate) {
    - error = -EIO;
    + /*
    + * Most drivers set uptodate to 0 for error and 1 for success.
    + * MD/DM ready drivers will set 1 for success and a -Exxx
    + * value to indicate a specific error.
    + */
    + if (uptodate < 1) {
    + error = (uptodate == 0 ? -EIO : uptodate);
    if (blk_fs_request(req) && !(req->flags & REQ_QUIET))
    printk("end_request: I/O error, dev %s, sector %llu\n",
    req->rq_disk ? req->rq_disk->disk_name : "?",
    @@ -2540,7 +2545,7 @@ static int __end_that_request_first(stru
    /**
    * end_that_request_first - end I/O on a request
    * @req: the request being processed
    - * @uptodate: 0 for I/O error
    + * @@uptodate: <= 0 to indicate an I/O error.
    * @nr_sectors: number of sectors to end I/O on
    *
    * Description:
    @@ -2561,7 +2566,7 @@ EXPORT_SYMBOL(end_that_request_first);
    /**
    * end_that_request_chunk - end I/O on a request
    * @req: the request being processed
    - * @uptodate: 0 for I/O error
    + * @uptodate: <= 0 to indicate an I/O error.
    * @nr_bytes: number of bytes to complete
    *
    * Description:
    diff -aurp linux-2.6.3-orig/include/linux/errno.h linux-2.6.3-ec/include/linux/errno.h
    --- linux-2.6.3-orig/include/linux/errno.h 2004-02-17 19:59:12.000000000 -0800
    +++ linux-2.6.3-ec/include/linux/errno.h 2004-02-18 12:45:42.000000000 -0800
    @@ -23,6 +23,14 @@
    #define EJUKEBOX 528 /* Request initiated, but will not complete before timeout */
    #define EIOCBQUEUED 529 /* iocb queued, will get completion event */

    +/* Block device error codes */
    +#define EFATALDEV 540 /* Fatal device error */
    +#define EFATALTRNSPT 541 /* Fatal transport error */
    +#define EFATALDRV 542 /* Fatal driver error */
    +#define ERETRYDEV 543 /* Device error occured, I/O may be retried */
    +#define ERETRYTRNSPT 544 /* Transport error occured, I/O may be retried */
    +#define ERETRYDRV 545 /* Driver error occured, I/O may be retried */
    +
    #endif

    #endif
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