Revision 35991652baa12ff3d0e420c0d0cb2ad9f7076e5b authored by Mikulas Patocka on 02 June 2012, 23:29:58 UTC, committed by Alasdair G Kergon on 02 June 2012, 23:29:58 UTC
After the failure of a group of paths, any alternative paths that need initialising do not become available until further I/O is sent to the device. Until this has happened, ioctls return -EAGAIN. With this patch, new paths are made available in response to an ioctl too. The processing of the ioctl gets delayed until this has happened. Instead of returning an error, we submit a work item to kmultipathd (that will potentially activate the new path) and retry in ten milliseconds. Note that the patch doesn't retry an ioctl if the ioctl itself fails due to a path failure. Such retries should be handled intelligently by the code that generated the ioctl in the first place, noting that some SCSI commands should not be retried because they are not idempotent (XOR write commands). For commands that could be retried, there is a danger that if the device rejected the SCSI command, the path could be errorneously marked as failed, and the request would be retried on another path which might fail too. It can be determined if the failure happens on the device or on the SCSI controller, but there is no guarantee that all SCSI drivers set these flags correctly. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
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command.c
/* SCTP kernel implementation Copyright (C) 1999-2001
* Cisco, Motorola, and IBM
* Copyright 2001 La Monte H.P. Yarroll
*
* This file is part of the SCTP kernel implementation
*
* These functions manipulate sctp command sequences.
*
* This SCTP implementation is free software;
* you can redistribute it and/or modify it under the terms of
* the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This SCTP implementation is distributed in the hope that it
* will be useful, but WITHOUT ANY WARRANTY; without even the implied
* ************************
* warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
* See the GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU CC; see the file COPYING. If not, write to
* the Free Software Foundation, 59 Temple Place - Suite 330,
* Boston, MA 02111-1307, USA.
*
* Please send any bug reports or fixes you make to the
* email address(es):
* lksctp developers <lksctp-developers@lists.sourceforge.net>
*
* Or submit a bug report through the following website:
* http://www.sf.net/projects/lksctp
*
* Written or modified by:
* La Monte H.P. Yarroll <piggy@acm.org>
* Karl Knutson <karl@athena.chicago.il.us>
*
* Any bugs reported given to us we will try to fix... any fixes shared will
* be incorporated into the next SCTP release.
*/
#include <linux/types.h>
#include <net/sctp/sctp.h>
#include <net/sctp/sm.h>
/* Initialize a block of memory as a command sequence. */
int sctp_init_cmd_seq(sctp_cmd_seq_t *seq)
{
memset(seq, 0, sizeof(sctp_cmd_seq_t));
return 1; /* We always succeed. */
}
/* Add a command to a sctp_cmd_seq_t.
* Return 0 if the command sequence is full.
*/
void sctp_add_cmd_sf(sctp_cmd_seq_t *seq, sctp_verb_t verb, sctp_arg_t obj)
{
BUG_ON(seq->next_free_slot >= SCTP_MAX_NUM_COMMANDS);
seq->cmds[seq->next_free_slot].verb = verb;
seq->cmds[seq->next_free_slot++].obj = obj;
}
/* Return the next command structure in a sctp_cmd_seq.
* Returns NULL at the end of the sequence.
*/
sctp_cmd_t *sctp_next_cmd(sctp_cmd_seq_t *seq)
{
sctp_cmd_t *retval = NULL;
if (seq->next_cmd < seq->next_free_slot)
retval = &seq->cmds[seq->next_cmd++];
return retval;
}
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