Root/fs/ext4/mballoc.h

1/*
2 * fs/ext4/mballoc.h
3 *
4 * Written by: Alex Tomas <alex@clusterfs.com>
5 *
6 */
7#ifndef _EXT4_MBALLOC_H
8#define _EXT4_MBALLOC_H
9
10#include <linux/time.h>
11#include <linux/fs.h>
12#include <linux/namei.h>
13#include <linux/quotaops.h>
14#include <linux/buffer_head.h>
15#include <linux/module.h>
16#include <linux/swap.h>
17#include <linux/proc_fs.h>
18#include <linux/pagemap.h>
19#include <linux/seq_file.h>
20#include <linux/version.h>
21#include <linux/blkdev.h>
22#include <linux/mutex.h>
23#include "ext4_jbd2.h"
24#include "ext4.h"
25
26/*
27 * with AGGRESSIVE_CHECK allocator runs consistency checks over
28 * structures. these checks slow things down a lot
29 */
30#define AGGRESSIVE_CHECK__
31
32/*
33 * with DOUBLE_CHECK defined mballoc creates persistent in-core
34 * bitmaps, maintains and uses them to check for double allocations
35 */
36#define DOUBLE_CHECK__
37
38/*
39 */
40#define MB_DEBUG__
41#ifdef MB_DEBUG
42#define mb_debug(fmt, a...) printk(fmt, ##a)
43#else
44#define mb_debug(fmt, a...)
45#endif
46
47/*
48 * with EXT4_MB_HISTORY mballoc stores last N allocations in memory
49 * and you can monitor it in /proc/fs/ext4/<dev>/mb_history
50 */
51#define EXT4_MB_HISTORY
52#define EXT4_MB_HISTORY_ALLOC 1 /* allocation */
53#define EXT4_MB_HISTORY_PREALLOC 2 /* preallocated blocks used */
54#define EXT4_MB_HISTORY_DISCARD 4 /* preallocation discarded */
55#define EXT4_MB_HISTORY_FREE 8 /* free */
56
57#define EXT4_MB_HISTORY_DEFAULT (EXT4_MB_HISTORY_ALLOC | \
58                     EXT4_MB_HISTORY_PREALLOC)
59
60/*
61 * How long mballoc can look for a best extent (in found extents)
62 */
63#define MB_DEFAULT_MAX_TO_SCAN 200
64
65/*
66 * How long mballoc must look for a best extent
67 */
68#define MB_DEFAULT_MIN_TO_SCAN 10
69
70/*
71 * How many groups mballoc will scan looking for the best chunk
72 */
73#define MB_DEFAULT_MAX_GROUPS_TO_SCAN 5
74
75/*
76 * with 'ext4_mb_stats' allocator will collect stats that will be
77 * shown at umount. The collecting costs though!
78 */
79#define MB_DEFAULT_STATS 1
80
81/*
82 * files smaller than MB_DEFAULT_STREAM_THRESHOLD are served
83 * by the stream allocator, which purpose is to pack requests
84 * as close each to other as possible to produce smooth I/O traffic
85 * We use locality group prealloc space for stream request.
86 * We can tune the same via /proc/fs/ext4/<parition>/stream_req
87 */
88#define MB_DEFAULT_STREAM_THRESHOLD 16 /* 64K */
89
90/*
91 * for which requests use 2^N search using buddies
92 */
93#define MB_DEFAULT_ORDER2_REQS 2
94
95/*
96 * default group prealloc size 512 blocks
97 */
98#define MB_DEFAULT_GROUP_PREALLOC 512
99
100
101struct ext4_free_data {
102    /* this links the free block information from group_info */
103    struct rb_node node;
104
105    /* this links the free block information from ext4_sb_info */
106    struct list_head list;
107
108    /* group which free block extent belongs */
109    ext4_group_t group;
110
111    /* free block extent */
112    ext4_grpblk_t start_blk;
113    ext4_grpblk_t count;
114
115    /* transaction which freed this extent */
116    tid_t t_tid;
117};
118
119struct ext4_prealloc_space {
120    struct list_head pa_inode_list;
121    struct list_head pa_group_list;
122    union {
123        struct list_head pa_tmp_list;
124        struct rcu_head pa_rcu;
125    } u;
126    spinlock_t pa_lock;
127    atomic_t pa_count;
128    unsigned pa_deleted;
129    ext4_fsblk_t pa_pstart; /* phys. block */
130    ext4_lblk_t pa_lstart; /* log. block */
131    unsigned short pa_len; /* len of preallocated chunk */
132    unsigned short pa_free; /* how many blocks are free */
133    unsigned short pa_type; /* pa type. inode or group */
134    spinlock_t *pa_obj_lock;
135    struct inode *pa_inode; /* hack, for history only */
136};
137
138enum {
139    MB_INODE_PA = 0,
140    MB_GROUP_PA = 1
141};
142
143struct ext4_free_extent {
144    ext4_lblk_t fe_logical;
145    ext4_grpblk_t fe_start;
146    ext4_group_t fe_group;
147    int fe_len;
148};
149
150/*
151 * Locality group:
152 * we try to group all related changes together
153 * so that writeback can flush/allocate them together as well
154 * Size of lg_prealloc_list hash is determined by MB_DEFAULT_GROUP_PREALLOC
155 * (512). We store prealloc space into the hash based on the pa_free blocks
156 * order value.ie, fls(pa_free)-1;
157 */
158#define PREALLOC_TB_SIZE 10
159struct ext4_locality_group {
160    /* for allocator */
161    /* to serialize allocates */
162    struct mutex lg_mutex;
163    /* list of preallocations */
164    struct list_head lg_prealloc_list[PREALLOC_TB_SIZE];
165    spinlock_t lg_prealloc_lock;
166};
167
168struct ext4_allocation_context {
169    struct inode *ac_inode;
170    struct super_block *ac_sb;
171
172    /* original request */
173    struct ext4_free_extent ac_o_ex;
174
175    /* goal request (after normalization) */
176    struct ext4_free_extent ac_g_ex;
177
178    /* the best found extent */
179    struct ext4_free_extent ac_b_ex;
180
181    /* copy of the bext found extent taken before preallocation efforts */
182    struct ext4_free_extent ac_f_ex;
183
184    /* number of iterations done. we have to track to limit searching */
185    unsigned long ac_ex_scanned;
186    __u16 ac_groups_scanned;
187    __u16 ac_found;
188    __u16 ac_tail;
189    __u16 ac_buddy;
190    __u16 ac_flags; /* allocation hints */
191    __u8 ac_status;
192    __u8 ac_criteria;
193    __u8 ac_repeats;
194    __u8 ac_2order; /* if request is to allocate 2^N blocks and
195                 * N > 0, the field stores N, otherwise 0 */
196    __u8 ac_op; /* operation, for history only */
197    struct page *ac_bitmap_page;
198    struct page *ac_buddy_page;
199    /*
200     * pointer to the held semaphore upon successful
201     * block allocation
202     */
203    struct rw_semaphore *alloc_semp;
204    struct ext4_prealloc_space *ac_pa;
205    struct ext4_locality_group *ac_lg;
206};
207
208#define AC_STATUS_CONTINUE 1
209#define AC_STATUS_FOUND 2
210#define AC_STATUS_BREAK 3
211
212struct ext4_mb_history {
213    struct ext4_free_extent orig; /* orig allocation */
214    struct ext4_free_extent goal; /* goal allocation */
215    struct ext4_free_extent result; /* result allocation */
216    unsigned pid;
217    unsigned ino;
218    __u16 found; /* how many extents have been found */
219    __u16 groups; /* how many groups have been scanned */
220    __u16 tail; /* what tail broke some buddy */
221    __u16 buddy; /* buddy the tail ^^^ broke */
222    __u16 flags;
223    __u8 cr:3; /* which phase the result extent was found at */
224    __u8 op:4;
225    __u8 merged:1;
226};
227
228struct ext4_buddy {
229    struct page *bd_buddy_page;
230    void *bd_buddy;
231    struct page *bd_bitmap_page;
232    void *bd_bitmap;
233    struct ext4_group_info *bd_info;
234    struct super_block *bd_sb;
235    __u16 bd_blkbits;
236    ext4_group_t bd_group;
237    struct rw_semaphore *alloc_semp;
238};
239#define EXT4_MB_BITMAP(e4b) ((e4b)->bd_bitmap)
240#define EXT4_MB_BUDDY(e4b) ((e4b)->bd_buddy)
241
242#ifndef EXT4_MB_HISTORY
243static inline void ext4_mb_store_history(struct ext4_allocation_context *ac)
244{
245    return;
246}
247#endif
248
249#define in_range(b, first, len) ((b) >= (first) && (b) <= (first) + (len) - 1)
250
251static inline ext4_fsblk_t ext4_grp_offs_to_block(struct super_block *sb,
252                    struct ext4_free_extent *fex)
253{
254    ext4_fsblk_t block;
255
256    block = (ext4_fsblk_t) fex->fe_group * EXT4_BLOCKS_PER_GROUP(sb)
257            + fex->fe_start
258            + le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);
259    return block;
260}
261#endif
262

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