OpenCores
URL https://opencores.org/ocsvn/or1k/or1k/trunk

Subversion Repositories or1k

[/] [or1k/] [trunk/] [rc203soc/] [sw/] [uClinux/] [fs/] [fat/] [buffer.c] - Blame information for rev 1765

Details | Compare with Previous | View Log

Line No. Rev Author Line
1 1628 jcastillo 
/*
2 
 * linux/fs/fat/buffer.c
3 
 *
4 
 *
5 
 */
6 
 
7 
#include <linux/mm.h>
8 
#include <linux/malloc.h>
9 
#include <linux/string.h>
10 
#include <linux/fs.h>
11 
#include <linux/msdos_fs.h>
12 
 
13 
#if 0
14 
#  define PRINTK(x) printk x
15 
#else
16 
#  define PRINTK(x)
17 
#endif
18 
 
19 
struct buffer_head *fat_bread (
20 
        struct super_block *sb,
21 
        int block)
22 
{
23 
        struct buffer_head *ret = NULL;
24 
 
25 
        PRINTK(("fat_bread: block=0x%x\n", block));
26 
        /* Note that the blocksize is 512 or 1024, but the first read
27 
           is always of size 1024. Doing readahead may be counterproductive
28 
           or just plain wrong. */
29 
        if (sb->s_blocksize == 512) {
30 
                ret = bread (sb->s_dev,block,512);
31 
        } else {
32 
                struct buffer_head *real = bread (sb->s_dev,block>>1,1024);
33 
 
34 
                if (real != NULL){
35 
                        ret = (struct buffer_head *)
36 
                          kmalloc (sizeof(struct buffer_head), GFP_KERNEL);
37 
                        if (ret != NULL) {
38 
                                /* #Specification: msdos / strategy / special device / dummy blocks
39 
                                        Many special device (Scsi optical disk for one) use
40 
                                        larger hardware sector size. This allows for higher
41 
                                        capacity.
42 
 
43 
                                        Most of the time, the MsDOS file system that sit
44 
                                        on this device is totally unaligned. It use logically
45 
                                        512 bytes sector size, with logical sector starting
46 
                                        in the middle of a hardware block. The bad news is
47 
                                        that a hardware sector may hold data own by two
48 
                                        different files. This means that the hardware sector
49 
                                        must be read, patch and written almost all the time.
50 
 
51 
                                        Needless to say that it kills write performance
52 
                                        on all OS.
53 
 
54 
                                        Internally the linux msdos fs is using 512 bytes
55 
                                        logical sector. When accessing such a device, we
56 
                                        allocate dummy buffer cache blocks, that we stuff
57 
                                        with the information of a real one (1k large).
58 
 
59 
                                        This strategy is used to hide this difference to
60 
                                        the core of the msdos fs. The slowdown is not
61 
                                        hidden though!
62 
                                */
63 
                                /*
64 
                                        The memset is there only to catch errors. The msdos
65 
                                        fs is only using b_data
66 
                                */
67 
                                memset (ret,0,sizeof(*ret));
68 
                                ret->b_data = real->b_data;
69 
                                if (block & 1) ret->b_data += 512;
70 
                                ret->b_next = real;
71 
                        }else{
72 
                                brelse (real);
73 
                        }
74 
                }
75 
        }
76 
        return ret;
77 
}
78 
struct buffer_head *fat_getblk (
79 
        struct super_block *sb,
80 
        int block)
81 
{
82 
        struct buffer_head *ret = NULL;
83 
        PRINTK(("fat_getblk: block=0x%x\n", block));
84 
        if (sb->s_blocksize == 512){
85 
                ret = getblk (sb->s_dev,block,512);
86 
        }else{
87 
                /* #Specification: msdos / special device / writing
88 
                        A write is always preceded by a read of the complete block
89 
                        (large hardware sector size). This defeat write performance.
90 
                        There is a possibility to optimize this when writing large
91 
                        chunk by making sure we are filling large block. Volunteer ?
92 
                */
93 
                ret = fat_bread (sb,block);
94 
        }
95 
        return ret;
96 
}
97 
 
98 
void fat_brelse (
99 
        struct super_block *sb,
100 
        struct buffer_head *bh)
101 
{
102 
        if (bh != NULL){
103 
                if (sb->s_blocksize == 512){
104 
                        brelse (bh);
105 
                }else{
106 
                        brelse (bh->b_next);
107 
                        /* We can free the dummy because a new one is allocated at
108 
                                each fat_getblk() and fat_bread().
109 
                        */
110 
                        kfree (bh);
111 
                }
112 
        }
113 
}
114 
 
115 
void fat_mark_buffer_dirty (
116 
        struct super_block *sb,
117 
        struct buffer_head *bh,
118 
        int dirty_val)
119 
{
120 
        if (sb->s_blocksize != 512){
121 
                bh = bh->b_next;
122 
        }
123 
        mark_buffer_dirty (bh,dirty_val);
124 
}
125 
 
126 
void fat_set_uptodate (
127 
        struct super_block *sb,
128 
        struct buffer_head *bh,
129 
        int val)
130 
{
131 
        if (sb->s_blocksize != 512){
132 
                bh = bh->b_next;
133 
        }
134 
        mark_buffer_uptodate(bh, val);
135 
}
136 
int fat_is_uptodate (
137 
        struct super_block *sb,
138 
        struct buffer_head *bh)
139 
{
140 
        if (sb->s_blocksize != 512){
141 
                bh = bh->b_next;
142 
        }
143 
        return buffer_uptodate(bh);
144 
}
145 
 
146 
void fat_ll_rw_block (
147 
        struct super_block *sb,
148 
        int opr,
149 
        int nbreq,
150 
        struct buffer_head *bh[32])
151 
{
152 
        if (sb->s_blocksize == 512){
153 
                ll_rw_block(opr,nbreq,bh);
154 
        }else{
155 
                struct buffer_head *tmp[32];
156 
                int i;
157 
                for (i=0; i<nbreq; i++){
158 
                        tmp[i] = bh[i]->b_next;
159 
                }
160 
                ll_rw_block(opr,nbreq,tmp);
161 
        }
162 
}
163 
 

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.