alistair23-linux/fs/gfs2/trans.c
Benjamin Marzinski 24972557b1 GFS2: remove transaction glock
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>
2014-05-14 10:04:34 +01:00

271 lines
7 KiB
C

/*
* Copyright (C) Sistina Software, Inc. 1997-2003 All rights reserved.
* Copyright (C) 2004-2006 Red Hat, Inc. All rights reserved.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU General Public License version 2.
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/kallsyms.h>
#include <linux/gfs2_ondisk.h>
#include "gfs2.h"
#include "incore.h"
#include "glock.h"
#include "inode.h"
#include "log.h"
#include "lops.h"
#include "meta_io.h"
#include "trans.h"
#include "util.h"
#include "trace_gfs2.h"
int gfs2_trans_begin(struct gfs2_sbd *sdp, unsigned int blocks,
unsigned int revokes)
{
struct gfs2_trans *tr;
int error;
BUG_ON(current->journal_info);
BUG_ON(blocks == 0 && revokes == 0);
if (!test_bit(SDF_JOURNAL_LIVE, &sdp->sd_flags))
return -EROFS;
tr = kzalloc(sizeof(struct gfs2_trans), GFP_NOFS);
if (!tr)
return -ENOMEM;
tr->tr_ip = (unsigned long)__builtin_return_address(0);
tr->tr_blocks = blocks;
tr->tr_revokes = revokes;
tr->tr_reserved = 1;
tr->tr_alloced = 1;
if (blocks)
tr->tr_reserved += 6 + blocks;
if (revokes)
tr->tr_reserved += gfs2_struct2blk(sdp, revokes,
sizeof(u64));
INIT_LIST_HEAD(&tr->tr_databuf);
INIT_LIST_HEAD(&tr->tr_buf);
sb_start_intwrite(sdp->sd_vfs);
error = gfs2_log_reserve(sdp, tr->tr_reserved);
if (error)
goto fail;
current->journal_info = tr;
return 0;
fail:
sb_end_intwrite(sdp->sd_vfs);
kfree(tr);
return error;
}
static void gfs2_print_trans(const struct gfs2_trans *tr)
{
pr_warn("Transaction created at: %pSR\n", (void *)tr->tr_ip);
pr_warn("blocks=%u revokes=%u reserved=%u touched=%u\n",
tr->tr_blocks, tr->tr_revokes, tr->tr_reserved, tr->tr_touched);
pr_warn("Buf %u/%u Databuf %u/%u Revoke %u/%u\n",
tr->tr_num_buf_new, tr->tr_num_buf_rm,
tr->tr_num_databuf_new, tr->tr_num_databuf_rm,
tr->tr_num_revoke, tr->tr_num_revoke_rm);
}
void gfs2_trans_end(struct gfs2_sbd *sdp)
{
struct gfs2_trans *tr = current->journal_info;
s64 nbuf;
BUG_ON(!tr);
current->journal_info = NULL;
if (!tr->tr_touched) {
gfs2_log_release(sdp, tr->tr_reserved);
if (tr->tr_alloced)
kfree(tr);
sb_end_intwrite(sdp->sd_vfs);
return;
}
nbuf = tr->tr_num_buf_new + tr->tr_num_databuf_new;
nbuf -= tr->tr_num_buf_rm;
nbuf -= tr->tr_num_databuf_rm;
if (gfs2_assert_withdraw(sdp, (nbuf <= tr->tr_blocks) &&
(tr->tr_num_revoke <= tr->tr_revokes)))
gfs2_print_trans(tr);
gfs2_log_commit(sdp, tr);
if (tr->tr_alloced && !tr->tr_attached)
kfree(tr);
up_read(&sdp->sd_log_flush_lock);
if (sdp->sd_vfs->s_flags & MS_SYNCHRONOUS)
gfs2_log_flush(sdp, NULL, NORMAL_FLUSH);
sb_end_intwrite(sdp->sd_vfs);
}
static struct gfs2_bufdata *gfs2_alloc_bufdata(struct gfs2_glock *gl,
struct buffer_head *bh,
const struct gfs2_log_operations *lops)
{
struct gfs2_bufdata *bd;
bd = kmem_cache_zalloc(gfs2_bufdata_cachep, GFP_NOFS | __GFP_NOFAIL);
bd->bd_bh = bh;
bd->bd_gl = gl;
bd->bd_ops = lops;
INIT_LIST_HEAD(&bd->bd_list);
bh->b_private = bd;
return bd;
}
/**
* gfs2_trans_add_data - Add a databuf to the transaction.
* @gl: The inode glock associated with the buffer
* @bh: The buffer to add
*
* This is used in two distinct cases:
* i) In ordered write mode
* We put the data buffer on a list so that we can ensure that its
* synced to disk at the right time
* ii) In journaled data mode
* We need to journal the data block in the same way as metadata in
* the functions above. The difference is that here we have a tag
* which is two __be64's being the block number (as per meta data)
* and a flag which says whether the data block needs escaping or
* not. This means we need a new log entry for each 251 or so data
* blocks, which isn't an enormous overhead but twice as much as
* for normal metadata blocks.
*/
void gfs2_trans_add_data(struct gfs2_glock *gl, struct buffer_head *bh)
{
struct gfs2_trans *tr = current->journal_info;
struct gfs2_sbd *sdp = gl->gl_sbd;
struct address_space *mapping = bh->b_page->mapping;
struct gfs2_inode *ip = GFS2_I(mapping->host);
struct gfs2_bufdata *bd;
if (!gfs2_is_jdata(ip)) {
gfs2_ordered_add_inode(ip);
return;
}
lock_buffer(bh);
gfs2_log_lock(sdp);
bd = bh->b_private;
if (bd == NULL) {
gfs2_log_unlock(sdp);
unlock_buffer(bh);
if (bh->b_private == NULL)
bd = gfs2_alloc_bufdata(gl, bh, &gfs2_databuf_lops);
lock_buffer(bh);
gfs2_log_lock(sdp);
}
gfs2_assert(sdp, bd->bd_gl == gl);
tr->tr_touched = 1;
if (list_empty(&bd->bd_list)) {
set_bit(GLF_LFLUSH, &bd->bd_gl->gl_flags);
set_bit(GLF_DIRTY, &bd->bd_gl->gl_flags);
gfs2_pin(sdp, bd->bd_bh);
tr->tr_num_databuf_new++;
list_add_tail(&bd->bd_list, &tr->tr_databuf);
}
gfs2_log_unlock(sdp);
unlock_buffer(bh);
}
static void meta_lo_add(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
{
struct gfs2_meta_header *mh;
struct gfs2_trans *tr;
tr = current->journal_info;
tr->tr_touched = 1;
if (!list_empty(&bd->bd_list))
return;
set_bit(GLF_LFLUSH, &bd->bd_gl->gl_flags);
set_bit(GLF_DIRTY, &bd->bd_gl->gl_flags);
mh = (struct gfs2_meta_header *)bd->bd_bh->b_data;
if (unlikely(mh->mh_magic != cpu_to_be32(GFS2_MAGIC))) {
pr_err("Attempting to add uninitialised block to journal (inplace block=%lld)\n",
(unsigned long long)bd->bd_bh->b_blocknr);
BUG();
}
gfs2_pin(sdp, bd->bd_bh);
mh->__pad0 = cpu_to_be64(0);
mh->mh_jid = cpu_to_be32(sdp->sd_jdesc->jd_jid);
list_add(&bd->bd_list, &tr->tr_buf);
tr->tr_num_buf_new++;
}
void gfs2_trans_add_meta(struct gfs2_glock *gl, struct buffer_head *bh)
{
struct gfs2_sbd *sdp = gl->gl_sbd;
struct gfs2_bufdata *bd;
lock_buffer(bh);
gfs2_log_lock(sdp);
bd = bh->b_private;
if (bd == NULL) {
gfs2_log_unlock(sdp);
unlock_buffer(bh);
lock_page(bh->b_page);
if (bh->b_private == NULL)
bd = gfs2_alloc_bufdata(gl, bh, &gfs2_buf_lops);
unlock_page(bh->b_page);
lock_buffer(bh);
gfs2_log_lock(sdp);
}
gfs2_assert(sdp, bd->bd_gl == gl);
meta_lo_add(sdp, bd);
gfs2_log_unlock(sdp);
unlock_buffer(bh);
}
void gfs2_trans_add_revoke(struct gfs2_sbd *sdp, struct gfs2_bufdata *bd)
{
struct gfs2_trans *tr = current->journal_info;
BUG_ON(!list_empty(&bd->bd_list));
gfs2_add_revoke(sdp, bd);
tr->tr_touched = 1;
tr->tr_num_revoke++;
}
void gfs2_trans_add_unrevoke(struct gfs2_sbd *sdp, u64 blkno, unsigned int len)
{
struct gfs2_bufdata *bd, *tmp;
struct gfs2_trans *tr = current->journal_info;
unsigned int n = len;
gfs2_log_lock(sdp);
list_for_each_entry_safe(bd, tmp, &sdp->sd_log_le_revoke, bd_list) {
if ((bd->bd_blkno >= blkno) && (bd->bd_blkno < (blkno + len))) {
list_del_init(&bd->bd_list);
gfs2_assert_withdraw(sdp, sdp->sd_log_num_revoke);
sdp->sd_log_num_revoke--;
kmem_cache_free(gfs2_bufdata_cachep, bd);
tr->tr_num_revoke_rm++;
if (--n == 0)
break;
}
}
gfs2_log_unlock(sdp);
}