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24972557b1
GFS2 has a transaction glock, which must be grabbed for every transaction, whose purpose is to deal with freezing the filesystem. Aside from this involving a large amount of locking, it is very easy to make the current fsfreeze code hang on unfreezing. This patch rewrites how gfs2 handles freezing the filesystem. The transaction glock is removed. In it's place is a freeze glock, which is cached (but not held) in a shared state by every node in the cluster when the filesystem is mounted. This lock only needs to be grabbed on freezing, and actions which need to be safe from freezing, like recovery. When a node wants to freeze the filesystem, it grabs this glock exclusively. When the freeze glock state changes on the nodes (either from shared to unlocked, or shared to exclusive), the filesystem does a special log flush. gfs2_log_flush() does all the work for flushing out the and shutting down the incore log, and then it tries to grab the freeze glock in a shared state again. Since the filesystem is stuck in gfs2_log_flush, no new transaction can start, and nothing can be written to disk. Unfreezing the filesytem simply involes dropping the freeze glock, allowing gfs2_log_flush() to grab and then release the shared lock, so it is cached for next time. However, in order for the unfreezing ioctl to occur, gfs2 needs to get a shared lock on the filesystem root directory inode to check permissions. If that glock has already been grabbed exclusively, fsfreeze will be unable to get the shared lock and unfreeze the filesystem. In order to allow the unfreeze, this patch makes gfs2 grab a shared lock on the filesystem root directory during the freeze, and hold it until it unfreezes the filesystem. The functions which need to grab a shared lock in order to allow the unfreeze ioctl to be issued now use the lock grabbed by the freeze code instead. The freeze and unfreeze code take care to make sure that this shared lock will not be dropped while another process is using it. Signed-off-by: Benjamin Marzinski <bmarzins@redhat.com> Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
86 lines
2.4 KiB
C
86 lines
2.4 KiB
C
/*
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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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* 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 version 2.
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*/
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#ifndef __LOG_DOT_H__
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#define __LOG_DOT_H__
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#include <linux/list.h>
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#include <linux/spinlock.h>
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#include <linux/writeback.h>
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#include "incore.h"
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/**
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* gfs2_log_lock - acquire the right to mess with the log manager
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* @sdp: the filesystem
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*
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*/
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static inline void gfs2_log_lock(struct gfs2_sbd *sdp)
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__acquires(&sdp->sd_log_lock)
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{
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spin_lock(&sdp->sd_log_lock);
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}
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/**
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* gfs2_log_unlock - release the right to mess with the log manager
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* @sdp: the filesystem
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*
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*/
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static inline void gfs2_log_unlock(struct gfs2_sbd *sdp)
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__releases(&sdp->sd_log_lock)
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{
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spin_unlock(&sdp->sd_log_lock);
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}
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static inline void gfs2_log_pointers_init(struct gfs2_sbd *sdp,
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unsigned int value)
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{
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if (++value == sdp->sd_jdesc->jd_blocks) {
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value = 0;
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}
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sdp->sd_log_head = sdp->sd_log_tail = value;
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}
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static inline void gfs2_ordered_add_inode(struct gfs2_inode *ip)
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{
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struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
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if (!test_bit(GIF_ORDERED, &ip->i_flags)) {
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spin_lock(&sdp->sd_ordered_lock);
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if (!test_and_set_bit(GIF_ORDERED, &ip->i_flags))
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list_add(&ip->i_ordered, &sdp->sd_log_le_ordered);
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spin_unlock(&sdp->sd_ordered_lock);
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}
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}
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extern void gfs2_ordered_del_inode(struct gfs2_inode *ip);
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extern unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct,
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unsigned int ssize);
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extern void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks);
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extern int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks);
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enum gfs2_flush_type {
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NORMAL_FLUSH = 0,
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SYNC_FLUSH,
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SHUTDOWN_FLUSH,
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FREEZE_FLUSH
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};
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extern void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl,
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enum gfs2_flush_type type);
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extern void gfs2_log_commit(struct gfs2_sbd *sdp, struct gfs2_trans *trans);
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extern void gfs2_remove_from_ail(struct gfs2_bufdata *bd);
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extern void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc);
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extern void gfs2_log_shutdown(struct gfs2_sbd *sdp);
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extern int gfs2_logd(void *data);
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extern void gfs2_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd);
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extern void gfs2_write_revokes(struct gfs2_sbd *sdp);
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#endif /* __LOG_DOT_H__ */
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