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linux-next/fs/ocfs2/dlmglue.h
Larry Chen 133b81f28e ocfs2: ocfs2_inode_lock_tracker does not distinguish lock level 
ocfs2_inode_lock_tracker as a variant of ocfs2_inode_lock, is used to
prevent deadlock due to recursive lock acquisition.

But this function does not distinguish whether the requested level is EX
or PR.

If a RP lock has been attained, this function will immediately return
success afterwards even an EX lock is requested.

But actually the return value does not mean that the process got a EX
lock, because ocfs2_inode_lock has not been called.

When taking lock levels into account, we face some different situations:

1. no lock is held
   In this case, just lock the inode and return 0

2. We are holding a lock
   For this situation, things diverges into several cases

   wanted     holding	     what to do
   ex		ex	    see 2.1 below
   ex		pr	    see 2.2 below
   pr		ex	    see 2.1 below
   pr		pr	    see 2.1 below

   2.1 lock level that is been held is compatible
   with the wanted level, so no lock action will be tacken.

   2.2 Otherwise, an upgrade is needed, but it is forbidden.

Reason why upgrade within a process is forbidden is that lock upgrade
may cause dead lock.  The following illustrate how it happens.

        process 1                             process 2
ocfs2_inode_lock_tracker(ex=0)
                               <======   ocfs2_inode_lock_tracker(ex=1)

ocfs2_inode_lock_tracker(ex=1)

For the status quo of ocfs2, without this patch, neither a bug nor
end-user impact will be caused because the wrong logic is avoided.

But I'm afraid this generic interface, may be called by other developers
in future and used in this situation.

  a process
ocfs2_inode_lock_tracker(ex=0)
ocfs2_inode_lock_tracker(ex=1)

Link: http://lkml.kernel.org/r/20180510053230.17217-1-lchen@suse.com
Signed-off-by: Larry Chen <lchen@suse.com>
Reviewed-by: Gang He <ghe@suse.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Cc: Changwei Ge <ge.changwei@h3c.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2018-06-07 17:34:33 -07:00

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/* -*- mode: c; c-basic-offset: 8; -*-
* vim: noexpandtab sw=8 ts=8 sts=0:
*
* dlmglue.h
*
* description here
*
* Copyright (C) 2002, 2004 Oracle. All rights reserved.
*
* This program 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 of the License, or (at your option) any later version.
*
* This program 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 this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#ifndef DLMGLUE_H
#define DLMGLUE_H
#include "dcache.h"
#define OCFS2_LVB_VERSION 5
struct ocfs2_meta_lvb {
__u8 lvb_version;
__u8 lvb_reserved0;
__be16 lvb_idynfeatures;
__be32 lvb_iclusters;
__be32 lvb_iuid;
__be32 lvb_igid;
__be64 lvb_iatime_packed;
__be64 lvb_ictime_packed;
__be64 lvb_imtime_packed;
__be64 lvb_isize;
__be16 lvb_imode;
__be16 lvb_inlink;
__be32 lvb_iattr;
__be32 lvb_igeneration;
__be32 lvb_reserved2;
};
#define OCFS2_QINFO_LVB_VERSION 1
struct ocfs2_qinfo_lvb {
__u8 lvb_version;
__u8 lvb_reserved[3];
__be32 lvb_bgrace;
__be32 lvb_igrace;
__be32 lvb_syncms;
__be32 lvb_blocks;
__be32 lvb_free_blk;
__be32 lvb_free_entry;
};
#define OCFS2_ORPHAN_LVB_VERSION 1
struct ocfs2_orphan_scan_lvb {
__u8 lvb_version;
__u8 lvb_reserved[3];
__be32 lvb_os_seqno;
};
#define OCFS2_TRIMFS_LVB_VERSION 1
struct ocfs2_trim_fs_lvb {
__u8 lvb_version;
__u8 lvb_success;
__u8 lvb_reserved[2];
__be32 lvb_nodenum;
__be64 lvb_start;
__be64 lvb_len;
__be64 lvb_minlen;
__be64 lvb_trimlen;
};
struct ocfs2_trim_fs_info {
u8 tf_valid; /* lvb is valid, or not */
u8 tf_success; /* trim is successful, or not */
u32 tf_nodenum; /* osb node number */
u64 tf_start; /* trim start offset in clusters */
u64 tf_len; /* trim end offset in clusters */
u64 tf_minlen; /* trim minimum contiguous free clusters */
u64 tf_trimlen; /* trimmed length in bytes */
};
struct ocfs2_lock_holder {
struct list_head oh_list;
struct pid *oh_owner_pid;
int oh_ex;
};
/* ocfs2_inode_lock_full() 'arg_flags' flags */
/* don't wait on recovery. */
#define OCFS2_META_LOCK_RECOVERY (0x01)
/* Instruct the dlm not to queue ourselves on the other node. */
#define OCFS2_META_LOCK_NOQUEUE (0x02)
/* don't block waiting for the downconvert thread, instead return -EAGAIN */
#define OCFS2_LOCK_NONBLOCK (0x04)
/* just get back disk inode bh if we've got cluster lock. */
#define OCFS2_META_LOCK_GETBH (0x08)
/* Locking subclasses of inode cluster lock */
enum {
OI_LS_NORMAL = 0,
OI_LS_PARENT,
OI_LS_RENAME1,
OI_LS_RENAME2,
OI_LS_REFLINK_TARGET,
};
int ocfs2_dlm_init(struct ocfs2_super *osb);
void ocfs2_dlm_shutdown(struct ocfs2_super *osb, int hangup_pending);
void ocfs2_lock_res_init_once(struct ocfs2_lock_res *res);
void ocfs2_inode_lock_res_init(struct ocfs2_lock_res *res,
enum ocfs2_lock_type type,
unsigned int generation,
struct inode *inode);
void ocfs2_dentry_lock_res_init(struct ocfs2_dentry_lock *dl,
u64 parent, struct inode *inode);
struct ocfs2_file_private;
void ocfs2_file_lock_res_init(struct ocfs2_lock_res *lockres,
struct ocfs2_file_private *fp);
struct ocfs2_mem_dqinfo;
void ocfs2_qinfo_lock_res_init(struct ocfs2_lock_res *lockres,
struct ocfs2_mem_dqinfo *info);
void ocfs2_refcount_lock_res_init(struct ocfs2_lock_res *lockres,
struct ocfs2_super *osb, u64 ref_blkno,
unsigned int generation);
void ocfs2_lock_res_free(struct ocfs2_lock_res *res);
int ocfs2_create_new_inode_locks(struct inode *inode);
int ocfs2_drop_inode_locks(struct inode *inode);
int ocfs2_rw_lock(struct inode *inode, int write);
int ocfs2_try_rw_lock(struct inode *inode, int write);
void ocfs2_rw_unlock(struct inode *inode, int write);
int ocfs2_open_lock(struct inode *inode);
int ocfs2_try_open_lock(struct inode *inode, int write);
void ocfs2_open_unlock(struct inode *inode);
int ocfs2_inode_lock_atime(struct inode *inode,
struct vfsmount *vfsmnt,
int *level, int wait);
int ocfs2_inode_lock_full_nested(struct inode *inode,
struct buffer_head **ret_bh,
int ex,
int arg_flags,
int subclass);
int ocfs2_inode_lock_with_page(struct inode *inode,
struct buffer_head **ret_bh,
int ex,
struct page *page);
/* Variants without special locking class or flags */
#define ocfs2_inode_lock_full(i, r, e, f)\
ocfs2_inode_lock_full_nested(i, r, e, f, OI_LS_NORMAL)
#define ocfs2_inode_lock_nested(i, b, e, s)\
ocfs2_inode_lock_full_nested(i, b, e, 0, s)
/* 99% of the time we don't want to supply any additional flags --
* those are for very specific cases only. */
#define ocfs2_inode_lock(i, b, e) ocfs2_inode_lock_full_nested(i, b, e, 0, OI_LS_NORMAL)
#define ocfs2_try_inode_lock(i, b, e)\
ocfs2_inode_lock_full_nested(i, b, e, OCFS2_META_LOCK_NOQUEUE,\
OI_LS_NORMAL)
void ocfs2_inode_unlock(struct inode *inode,
int ex);
int ocfs2_super_lock(struct ocfs2_super *osb,
int ex);
void ocfs2_super_unlock(struct ocfs2_super *osb,
int ex);
int ocfs2_orphan_scan_lock(struct ocfs2_super *osb, u32 *seqno);
void ocfs2_orphan_scan_unlock(struct ocfs2_super *osb, u32 seqno);
int ocfs2_rename_lock(struct ocfs2_super *osb);
void ocfs2_rename_unlock(struct ocfs2_super *osb);
int ocfs2_nfs_sync_lock(struct ocfs2_super *osb, int ex);
void ocfs2_nfs_sync_unlock(struct ocfs2_super *osb, int ex);
void ocfs2_trim_fs_lock_res_init(struct ocfs2_super *osb);
void ocfs2_trim_fs_lock_res_uninit(struct ocfs2_super *osb);
int ocfs2_trim_fs_lock(struct ocfs2_super *osb,
struct ocfs2_trim_fs_info *info, int trylock);
void ocfs2_trim_fs_unlock(struct ocfs2_super *osb,
struct ocfs2_trim_fs_info *info);
int ocfs2_dentry_lock(struct dentry *dentry, int ex);
void ocfs2_dentry_unlock(struct dentry *dentry, int ex);
int ocfs2_file_lock(struct file *file, int ex, int trylock);
void ocfs2_file_unlock(struct file *file);
int ocfs2_qinfo_lock(struct ocfs2_mem_dqinfo *oinfo, int ex);
void ocfs2_qinfo_unlock(struct ocfs2_mem_dqinfo *oinfo, int ex);
struct ocfs2_refcount_tree;
int ocfs2_refcount_lock(struct ocfs2_refcount_tree *ref_tree, int ex);
void ocfs2_refcount_unlock(struct ocfs2_refcount_tree *ref_tree, int ex);
void ocfs2_mark_lockres_freeing(struct ocfs2_super *osb,
struct ocfs2_lock_res *lockres);
void ocfs2_simple_drop_lockres(struct ocfs2_super *osb,
struct ocfs2_lock_res *lockres);
/* for the downconvert thread */
void ocfs2_wake_downconvert_thread(struct ocfs2_super *osb);
struct ocfs2_dlm_debug *ocfs2_new_dlm_debug(void);
void ocfs2_put_dlm_debug(struct ocfs2_dlm_debug *dlm_debug);
/* To set the locking protocol on module initialization */
void ocfs2_set_locking_protocol(void);
/* The _tracker pair is used to avoid cluster recursive locking */
int ocfs2_inode_lock_tracker(struct inode *inode,
struct buffer_head **ret_bh,
int ex,
struct ocfs2_lock_holder *oh);
void ocfs2_inode_unlock_tracker(struct inode *inode,
int ex,
struct ocfs2_lock_holder *oh,
int had_lock);
#endif /* DLMGLUE_H */
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