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When a node withdraws from a file system, it often leaves its journal in an incomplete state. This is especially true when the withdraw is caused by io errors writing to the journal. Before this patch, a withdraw would try to write a "shutdown" record to the journal, tell dlm it's done with the file system, and none of the other nodes know about the problem. Later, when the problem is fixed and the withdrawn node is rebooted, it would then discover that its own journal was incomplete, and replay it. However, replaying it at this point is almost guaranteed to introduce corruption because the other nodes are likely to have used affected resource groups that appeared in the journal since the time of the withdraw. Replaying the journal later will overwrite any changes made, and not through any fault of dlm, which was instructed during the withdraw to release those resources. This patch makes file system withdraws seen by the entire cluster. Withdrawing nodes dequeue their journal glock to allow recovery. The remaining nodes check all the journals to see if they are clean or in need of replay. They try to replay dirty journals, but only the journals of withdrawn nodes will be "not busy" and therefore available for replay. Until the journal replay is complete, no i/o related glocks may be given out, to ensure that the replay does not cause the aforementioned corruption: We cannot allow any journal replay to overwrite blocks associated with a glock once it is held. The "live" glock which is now used to signal when a withdraw occurs. When a withdraw occurs, the node signals its withdraw by dequeueing the "live" glock and trying to enqueue it in EX mode, thus forcing the other nodes to all see a demote request, by way of a "1CB" (one callback) try lock. The "live" glock is not granted in EX; the callback is only just used to indicate a withdraw has occurred. Note that all nodes in the cluster must wait for the recovering node to finish replaying the withdrawing node's journal before continuing. To this end, it checks that the journals are clean multiple times in a retry loop. Also note that the withdraw function may be called from a wide variety of situations, and therefore, we need to take extra precautions to make sure pointers are valid before using them in many circumstances. We also need to take care when glocks decide to withdraw, since the withdraw code now uses glocks. Also, before this patch, if a process encountered an error and decided to withdraw, if another process was already withdrawing, the second withdraw would be silently ignored, which set it free to unlock its glocks. That's correct behavior if the original withdrawer encounters further errors down the road. But if secondary waiters don't wait for the journal replay, unlocking glocks will allow other nodes to use them, despite the fact that the journal containing those blocks is being replayed. The replay needs to finish before our glocks are released to other nodes. IOW, secondary withdraws need to wait for the first withdraw to finish. For example, if an rgrp glock is unlocked by a process that didn't wait for the first withdraw, a journal replay could introduce file system corruption by replaying a rgrp block that has already been granted to a different cluster node. Signed-off-by: Bob Peterson <rpeterso@redhat.com>
55 lines
1.8 KiB
C
55 lines
1.8 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
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* Copyright (C) 2004-2006 Red Hat, Inc. All rights reserved.
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*/
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#ifndef __SUPER_DOT_H__
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#define __SUPER_DOT_H__
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#include <linux/fs.h>
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#include <linux/dcache.h>
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#include "incore.h"
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extern void gfs2_lm_unmount(struct gfs2_sbd *sdp);
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static inline unsigned int gfs2_jindex_size(struct gfs2_sbd *sdp)
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{
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unsigned int x;
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spin_lock(&sdp->sd_jindex_spin);
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x = sdp->sd_journals;
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spin_unlock(&sdp->sd_jindex_spin);
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return x;
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}
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extern void gfs2_jindex_free(struct gfs2_sbd *sdp);
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extern struct gfs2_jdesc *gfs2_jdesc_find(struct gfs2_sbd *sdp, unsigned int jid);
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extern int gfs2_jdesc_check(struct gfs2_jdesc *jd);
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extern int gfs2_lookup_in_master_dir(struct gfs2_sbd *sdp, char *filename,
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struct gfs2_inode **ipp);
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extern int gfs2_make_fs_rw(struct gfs2_sbd *sdp);
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extern int gfs2_make_fs_ro(struct gfs2_sbd *sdp);
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extern void gfs2_online_uevent(struct gfs2_sbd *sdp);
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extern int gfs2_statfs_init(struct gfs2_sbd *sdp);
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extern void gfs2_statfs_change(struct gfs2_sbd *sdp, s64 total, s64 free,
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s64 dinodes);
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extern void gfs2_statfs_change_in(struct gfs2_statfs_change_host *sc,
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const void *buf);
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extern void update_statfs(struct gfs2_sbd *sdp, struct buffer_head *m_bh,
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struct buffer_head *l_bh);
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extern int gfs2_statfs_sync(struct super_block *sb, int type);
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extern void gfs2_freeze_func(struct work_struct *work);
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extern void free_sbd(struct gfs2_sbd *sdp);
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extern struct file_system_type gfs2_fs_type;
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extern struct file_system_type gfs2meta_fs_type;
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extern const struct export_operations gfs2_export_ops;
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extern const struct super_operations gfs2_super_ops;
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extern const struct dentry_operations gfs2_dops;
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extern const struct xattr_handler *gfs2_xattr_handlers[];
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#endif /* __SUPER_DOT_H__ */
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