ext4_extents.h

  1// SPDX-License-Identifier: GPL-2.0
  2/*
  3 * Copyright (c) 2003-2006, Cluster File Systems, Inc, info@clusterfs.com
  4 * Written by Alex Tomas <alex@clusterfs.com>
  5 */
  6
  7#ifndef _EXT4_EXTENTS
  8#define _EXT4_EXTENTS
  9
 10#include "ext4.h"
 11
 12/*
 13 * With AGGRESSIVE_TEST defined, the capacity of index/leaf blocks
 14 * becomes very small, so index split, in-depth growing and
 15 * other hard changes happen much more often.
 16 * This is for debug purposes only.
 17 */
 18#define AGGRESSIVE_TEST_
 19
 20/*
 21 * With EXTENTS_STATS defined, the number of blocks and extents
 22 * are collected in the truncate path. They'll be shown at
 23 * umount time.
 24 */
 25#define EXTENTS_STATS__
 26
 27/*
 28 * If CHECK_BINSEARCH is defined, then the results of the binary search
 29 * will also be checked by linear search.
 30 */
 31#define CHECK_BINSEARCH__
 32
 33/*
 34 * ext4_inode has i_block array (60 bytes total).
 35 * The first 12 bytes store ext4_extent_header;
 36 * the remainder stores an array of ext4_extent.
 37 * For non-inode extent blocks, ext4_extent_tail
 38 * follows the array.
 39 */
 40
 41/*
 42 * This is the extent tail on-disk structure.
 43 * All other extent structures are 12 bytes long.  It turns out that
 44 * block_size % 12 >= 4 for at least all powers of 2 greater than 512, which
 45 * covers all valid ext4 block sizes.  Therefore, this tail structure can be
 46 * crammed into the end of the block without having to rebalance the tree.
 47 */
 48struct ext4_extent_tail {
 49	__le32	et_checksum;	/* crc32c(uuid+inum+extent_block) */
 50};
 51
 52/*
 53 * This is the extent on-disk structure.
 54 * It's used at the bottom of the tree.
 55 */
 56struct ext4_extent {
 57	__le32	ee_block;	/* first logical block extent covers */
 58	__le16	ee_len;		/* number of blocks covered by extent */
 59	__le16	ee_start_hi;	/* high 16 bits of physical block */
 60	__le32	ee_start_lo;	/* low 32 bits of physical block */
 61};
 62
 63/*
 64 * This is index on-disk structure.
 65 * It's used at all the levels except the bottom.
 66 */
 67struct ext4_extent_idx {
 68	__le32	ei_block;	/* index covers logical blocks from 'block' */
 69	__le32	ei_leaf_lo;	/* pointer to the physical block of the next *
 70				 * level. leaf or next index could be there */
 71	__le16	ei_leaf_hi;	/* high 16 bits of physical block */
 72	__u16	ei_unused;
 73};
 74
 75/*
 76 * Each block (leaves and indexes), even inode-stored has header.
 77 */
 78struct ext4_extent_header {
 79	__le16	eh_magic;	/* probably will support different formats */
 80	__le16	eh_entries;	/* number of valid entries */
 81	__le16	eh_max;		/* capacity of store in entries */
 82	__le16	eh_depth;	/* has tree real underlying blocks? */
 83	__le32	eh_generation;	/* generation of the tree */
 84};
 85
 86#define EXT4_EXT_MAGIC		cpu_to_le16(0xf30a)
 87#define EXT4_MAX_EXTENT_DEPTH 5
 88
 89#define EXT4_EXTENT_TAIL_OFFSET(hdr) \
 90	(sizeof(struct ext4_extent_header) + \
 91	 (sizeof(struct ext4_extent) * le16_to_cpu((hdr)->eh_max)))
 92
 93static inline struct ext4_extent_tail *
 94find_ext4_extent_tail(struct ext4_extent_header *eh)
 95{
 96	return (struct ext4_extent_tail *)(((void *)eh) +
 97					   EXT4_EXTENT_TAIL_OFFSET(eh));
 98}
 99
100/*
101 * Array of ext4_ext_path contains path to some extent.
102 * Creation/lookup routines use it for traversal/splitting/etc.
103 * Truncate uses it to simulate recursive walking.
104 */
105struct ext4_ext_path {
106	ext4_fsblk_t			p_block;
107	__u16				p_depth;
108	__u16				p_maxdepth;
109	struct ext4_extent		*p_ext;
110	struct ext4_extent_idx		*p_idx;
111	struct ext4_extent_header	*p_hdr;
112	struct buffer_head		*p_bh;
113};
114
115/*
116 * Used to record a portion of a cluster found at the beginning or end
117 * of an extent while traversing the extent tree during space removal.
118 * A partial cluster may be removed if it does not contain blocks shared
119 * with extents that aren't being deleted (tofree state).  Otherwise,
120 * it cannot be removed (nofree state).
121 */
122struct partial_cluster {
123	ext4_fsblk_t pclu;  /* physical cluster number */
124	ext4_lblk_t lblk;   /* logical block number within logical cluster */
125	enum {initial, tofree, nofree} state;
126};
127
128/*
129 * structure for external API
130 */
131
132/*
133 * EXT_INIT_MAX_LEN is the maximum number of blocks we can have in an
134 * initialized extent. This is 2^15 and not (2^16 - 1), since we use the
135 * MSB of ee_len field in the extent datastructure to signify if this
136 * particular extent is an initialized extent or an unwritten (i.e.
137 * preallocated).
138 * EXT_UNWRITTEN_MAX_LEN is the maximum number of blocks we can have in an
139 * unwritten extent.
140 * If ee_len is <= 0x8000, it is an initialized extent. Otherwise, it is an
141 * unwritten one. In other words, if MSB of ee_len is set, it is an
142 * unwritten extent with only one special scenario when ee_len = 0x8000.
143 * In this case we can not have an unwritten extent of zero length and
144 * thus we make it as a special case of initialized extent with 0x8000 length.
145 * This way we get better extent-to-group alignment for initialized extents.
146 * Hence, the maximum number of blocks we can have in an *initialized*
147 * extent is 2^15 (32768) and in an *unwritten* extent is 2^15-1 (32767).
148 */
149#define EXT_INIT_MAX_LEN	(1UL << 15)
150#define EXT_UNWRITTEN_MAX_LEN	(EXT_INIT_MAX_LEN - 1)
151
152
153#define EXT_FIRST_EXTENT(__hdr__) \
154	((struct ext4_extent *) (((char *) (__hdr__)) +		\
155				 sizeof(struct ext4_extent_header)))
156#define EXT_FIRST_INDEX(__hdr__) \
157	((struct ext4_extent_idx *) (((char *) (__hdr__)) +	\
158				     sizeof(struct ext4_extent_header)))
159#define EXT_HAS_FREE_INDEX(__path__) \
160	(le16_to_cpu((__path__)->p_hdr->eh_entries) \
161				     < le16_to_cpu((__path__)->p_hdr->eh_max))
162#define EXT_LAST_EXTENT(__hdr__) \
163	(EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
164#define EXT_LAST_INDEX(__hdr__) \
165	(EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_entries) - 1)
166#define EXT_MAX_EXTENT(__hdr__)	\
167	((le16_to_cpu((__hdr__)->eh_max)) ? \
168	((EXT_FIRST_EXTENT((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \
169					: NULL)
170#define EXT_MAX_INDEX(__hdr__) \
171	((le16_to_cpu((__hdr__)->eh_max)) ? \
172	((EXT_FIRST_INDEX((__hdr__)) + le16_to_cpu((__hdr__)->eh_max) - 1)) \
173					: NULL)
174
175static inline struct ext4_extent_header *ext_inode_hdr(struct inode *inode)
176{
177	return (struct ext4_extent_header *) EXT4_I(inode)->i_data;
178}
179
180static inline struct ext4_extent_header *ext_block_hdr(struct buffer_head *bh)
181{
182	return (struct ext4_extent_header *) bh->b_data;
183}
184
185static inline unsigned short ext_depth(struct inode *inode)
186{
187	return le16_to_cpu(ext_inode_hdr(inode)->eh_depth);
188}
189
190static inline void ext4_ext_mark_unwritten(struct ext4_extent *ext)
191{
192	/* We can not have an unwritten extent of zero length! */
193	BUG_ON((le16_to_cpu(ext->ee_len) & ~EXT_INIT_MAX_LEN) == 0);
194	ext->ee_len |= cpu_to_le16(EXT_INIT_MAX_LEN);
195}
196
197static inline int ext4_ext_is_unwritten(struct ext4_extent *ext)
198{
199	/* Extent with ee_len of 0x8000 is treated as an initialized extent */
200	return (le16_to_cpu(ext->ee_len) > EXT_INIT_MAX_LEN);
201}
202
203static inline int ext4_ext_get_actual_len(struct ext4_extent *ext)
204{
205	return (le16_to_cpu(ext->ee_len) <= EXT_INIT_MAX_LEN ?
206		le16_to_cpu(ext->ee_len) :
207		(le16_to_cpu(ext->ee_len) - EXT_INIT_MAX_LEN));
208}
209
210static inline void ext4_ext_mark_initialized(struct ext4_extent *ext)
211{
212	ext->ee_len = cpu_to_le16(ext4_ext_get_actual_len(ext));
213}
214
215/*
216 * ext4_ext_pblock:
217 * combine low and high parts of physical block number into ext4_fsblk_t
218 */
219static inline ext4_fsblk_t ext4_ext_pblock(struct ext4_extent *ex)
220{
221	ext4_fsblk_t block;
222
223	block = le32_to_cpu(ex->ee_start_lo);
224	block |= ((ext4_fsblk_t) le16_to_cpu(ex->ee_start_hi) << 31) << 1;
225	return block;
226}
227
228/*
229 * ext4_idx_pblock:
230 * combine low and high parts of a leaf physical block number into ext4_fsblk_t
231 */
232static inline ext4_fsblk_t ext4_idx_pblock(struct ext4_extent_idx *ix)
233{
234	ext4_fsblk_t block;
235
236	block = le32_to_cpu(ix->ei_leaf_lo);
237	block |= ((ext4_fsblk_t) le16_to_cpu(ix->ei_leaf_hi) << 31) << 1;
238	return block;
239}
240
241/*
242 * ext4_ext_store_pblock:
243 * stores a large physical block number into an extent struct,
244 * breaking it into parts
245 */
246static inline void ext4_ext_store_pblock(struct ext4_extent *ex,
247					 ext4_fsblk_t pb)
248{
249	ex->ee_start_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
250	ex->ee_start_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
251				      0xffff);
252}
253
254/*
255 * ext4_idx_store_pblock:
256 * stores a large physical block number into an index struct,
257 * breaking it into parts
258 */
259static inline void ext4_idx_store_pblock(struct ext4_extent_idx *ix,
260					 ext4_fsblk_t pb)
261{
262	ix->ei_leaf_lo = cpu_to_le32((unsigned long) (pb & 0xffffffff));
263	ix->ei_leaf_hi = cpu_to_le16((unsigned long) ((pb >> 31) >> 1) &
264				     0xffff);
265}
266
267#endif /* _EXT4_EXTENTS */
268