c36258b592
Introduce a per-lockspace rwsem that's held in read mode by dlm_recv threads while working in the dlm. This allows dlm_recv activity to be suspended when the lockspace transitions to, from and between recovery cycles. The specific bug prompting this change is one where an in-progress recovery cycle is aborted by a new recovery cycle. While dlm_recv was processing a recovery message, the recovery cycle was aborted and dlm_recoverd began cleaning up. dlm_recv decremented recover_locks_count on an rsb after dlm_recoverd had reset it to zero. This is fixed by suspending dlm_recv (taking write lock on the rwsem) before aborting the current recovery. The transitions to/from normal and recovery modes are simplified by using this new ability to block dlm_recv. The switch from normal to recovery mode means dlm_recv goes from processing locking messages, to saving them for later, and vice versa. Races are avoided by blocking dlm_recv when setting the flag that switches between modes. Signed-off-by: David Teigland <teigland@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
127 lines
3.5 KiB
C
127 lines
3.5 KiB
C
/******************************************************************************
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*******************************************************************************
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**
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** Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
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** Copyright (C) 2004-2007 Red Hat, Inc. All rights reserved.
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**
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** This copyrighted material is made available to anyone wishing to use,
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** modify, copy, or redistribute it subject to the terms and conditions
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** of the GNU General Public License v.2.
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**
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*******************************************************************************
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******************************************************************************/
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/*
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* midcomms.c
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*
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* This is the appallingly named "mid-level" comms layer.
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*
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* Its purpose is to take packets from the "real" comms layer,
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* split them up into packets and pass them to the interested
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* part of the locking mechanism.
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*
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* It also takes messages from the locking layer, formats them
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* into packets and sends them to the comms layer.
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*/
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#include "dlm_internal.h"
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#include "lowcomms.h"
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#include "config.h"
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#include "lock.h"
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#include "midcomms.h"
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static void copy_from_cb(void *dst, const void *base, unsigned offset,
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unsigned len, unsigned limit)
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{
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unsigned copy = len;
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if ((copy + offset) > limit)
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copy = limit - offset;
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memcpy(dst, base + offset, copy);
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len -= copy;
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if (len)
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memcpy(dst + copy, base, len);
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}
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/*
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* Called from the low-level comms layer to process a buffer of
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* commands.
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*
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* Only complete messages are processed here, any "spare" bytes from
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* the end of a buffer are saved and tacked onto the front of the next
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* message that comes in. I doubt this will happen very often but we
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* need to be able to cope with it and I don't want the task to be waiting
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* for packets to come in when there is useful work to be done.
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*/
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int dlm_process_incoming_buffer(int nodeid, const void *base,
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unsigned offset, unsigned len, unsigned limit)
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{
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unsigned char __tmp[DLM_INBUF_LEN];
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struct dlm_header *msg = (struct dlm_header *) __tmp;
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int ret = 0;
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int err = 0;
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uint16_t msglen;
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uint32_t lockspace;
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while (len > sizeof(struct dlm_header)) {
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/* Copy just the header to check the total length. The
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message may wrap around the end of the buffer back to the
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start, so we need to use a temp buffer and copy_from_cb. */
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copy_from_cb(msg, base, offset, sizeof(struct dlm_header),
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limit);
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msglen = le16_to_cpu(msg->h_length);
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lockspace = msg->h_lockspace;
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err = -EINVAL;
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if (msglen < sizeof(struct dlm_header))
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break;
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err = -E2BIG;
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if (msglen > dlm_config.ci_buffer_size) {
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log_print("message size %d from %d too big, buf len %d",
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msglen, nodeid, len);
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break;
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}
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err = 0;
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/* If only part of the full message is contained in this
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buffer, then do nothing and wait for lowcomms to call
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us again later with more data. We return 0 meaning
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we've consumed none of the input buffer. */
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if (msglen > len)
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break;
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/* Allocate a larger temp buffer if the full message won't fit
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in the buffer on the stack (which should work for most
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ordinary messages). */
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if (msglen > sizeof(__tmp) &&
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msg == (struct dlm_header *) __tmp) {
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msg = kmalloc(dlm_config.ci_buffer_size, GFP_KERNEL);
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if (msg == NULL)
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return ret;
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}
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copy_from_cb(msg, base, offset, msglen, limit);
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BUG_ON(lockspace != msg->h_lockspace);
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ret += msglen;
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offset += msglen;
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offset &= (limit - 1);
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len -= msglen;
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dlm_receive_buffer(msg, nodeid);
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}
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if (msg != (struct dlm_header *) __tmp)
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kfree(msg);
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return err ? err : ret;
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}
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