xref: /openbmc/linux/fs/xfs/xfs_refcount_item.h (revision 182696fb)
1 // SPDX-License-Identifier: GPL-2.0+
2 /*
3  * Copyright (C) 2016 Oracle.  All Rights Reserved.
4  * Author: Darrick J. Wong <darrick.wong@oracle.com>
5  */
6 #ifndef	__XFS_REFCOUNT_ITEM_H__
7 #define	__XFS_REFCOUNT_ITEM_H__
8 
9 /*
10  * There are (currently) two pairs of refcount btree redo item types:
11  * increase and decrease.  The log items for these are CUI (refcount
12  * update intent) and CUD (refcount update done).  The redo item type
13  * is encoded in the flags field of each xfs_map_extent.
14  *
15  * *I items should be recorded in the *first* of a series of rolled
16  * transactions, and the *D items should be recorded in the same
17  * transaction that records the associated refcountbt updates.
18  *
19  * Should the system crash after the commit of the first transaction
20  * but before the commit of the final transaction in a series, log
21  * recovery will use the redo information recorded by the intent items
22  * to replay the refcountbt metadata updates.
23  */
24 
25 /* kernel only CUI/CUD definitions */
26 
27 struct xfs_mount;
28 struct kmem_cache;
29 
30 /*
31  * Max number of extents in fast allocation path.
32  */
33 #define	XFS_CUI_MAX_FAST_EXTENTS	16
34 
35 /*
36  * This is the "refcount update intent" log item.  It is used to log
37  * the fact that some reverse mappings need to change.  It is used in
38  * conjunction with the "refcount update done" log item described
39  * below.
40  *
41  * These log items follow the same rules as struct xfs_efi_log_item;
42  * see the comments about that structure (in xfs_extfree_item.h) for
43  * more details.
44  */
45 struct xfs_cui_log_item {
46 	struct xfs_log_item		cui_item;
47 	atomic_t			cui_refcount;
48 	atomic_t			cui_next_extent;
49 	struct xfs_cui_log_format	cui_format;
50 };
51 
52 static inline size_t
xfs_cui_log_item_sizeof(unsigned int nr)53 xfs_cui_log_item_sizeof(
54 	unsigned int		nr)
55 {
56 	return offsetof(struct xfs_cui_log_item, cui_format) +
57 			xfs_cui_log_format_sizeof(nr);
58 }
59 
60 /*
61  * This is the "refcount update done" log item.  It is used to log the
62  * fact that some refcountbt updates mentioned in an earlier cui item
63  * have been performed.
64  */
65 struct xfs_cud_log_item {
66 	struct xfs_log_item		cud_item;
67 	struct xfs_cui_log_item		*cud_cuip;
68 	struct xfs_cud_log_format	cud_format;
69 };
70 
71 extern struct kmem_cache	*xfs_cui_cache;
72 extern struct kmem_cache	*xfs_cud_cache;
73 
74 #endif	/* __XFS_REFCOUNT_ITEM_H__ */
75