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ocfs2: avoid system inode ref confusion by adding mutex lock

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The following case may lead to the same system inode ref in confusion.

A thread                            B thread
ocfs2_get_system_file_inode
->get_local_system_inode
->_ocfs2_get_system_file_inode
                                    because of *arr == NULL,
                                    ocfs2_get_system_file_inode
                                    ->get_local_system_inode
                                    ->_ocfs2_get_system_file_inode
gets first ref thru
_ocfs2_get_system_file_inode,
gets second ref thru igrab and
set *arr = inode
                                    at the moment, B thread also gets
                                    two refs, so lead to one more
                                    inode ref.

So add mutex lock to avoid multi thread set two inode ref once at the
same time.

Signed-off-by: jiangyiwen <jiangyiwen@huawei.com>
Reviewed-by: Joseph Qi <joseph.qi@huawei.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Mark Fasheh <mfasheh@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
jiangyiwen 2014-04-03 14:47:13 -07:00 committed by Linus Torvalds
parent 7dc3e83901
commit 43b10a2037
3 changed files with 7 additions and 0 deletions
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2
fs/ocfs2/ocfs2.h
View file

@ -446,6 +446,8 @@ struct ocfs2_super
/* rb tree root for refcount lock. */
struct rb_root osb_rf_lock_tree;
struct ocfs2_refcount_tree *osb_ref_tree_lru;
struct mutex system_file_mutex;
};
#define OCFS2_SB(sb) ((struct ocfs2_super *)(sb)->s_fs_info)

2
fs/ocfs2/super.c
View file

@ -2100,6 +2100,8 @@ static int ocfs2_initialize_super(struct super_block *sb,
spin_lock_init(&osb->osb_xattr_lock);
ocfs2_init_steal_slots(osb);
mutex_init(&osb->system_file_mutex);
atomic_set(&osb->alloc_stats.moves, 0);
atomic_set(&osb->alloc_stats.local_data, 0);
atomic_set(&osb->alloc_stats.bitmap_data, 0);

3
fs/ocfs2/sysfile.c
View file

@ -113,9 +113,11 @@ struct inode *ocfs2_get_system_file_inode(struct ocfs2_super *osb,
} else
arr = get_local_system_inode(osb, type, slot);
mutex_lock(&osb->system_file_mutex);
if (arr && ((inode = *arr) != NULL)) {
/* get a ref in addition to the array ref */
inode = igrab(inode);
mutex_unlock(&osb->system_file_mutex);
BUG_ON(!inode);
return inode;
@ -129,6 +131,7 @@ struct inode *ocfs2_get_system_file_inode(struct ocfs2_super *osb,
*arr = igrab(inode);
BUG_ON(!*arr);
}
mutex_unlock(&osb->system_file_mutex);
return inode;
}