3949295f36
Current implementation of dosfs in libstand reads full File Allocation Table to the RAM in the initialization code. In the extreme case of FAT32 filesystem, this structure will take up to 256-1024 Mb of loader memory, depending on the cluster size. Proposed patch reduces libstands/dosfs memory requirements to 128 Kb for all variants of dosfs filesystem. For FAT12 and FAT16 filesystems, File Allocation Table is cached in full, as before. For FAT32, File Allocation Table is broken into the equal blocks of 128 Kilobytes (32768 entries), and only current block is cached. Because per-filesystem context is now small, global FAT cache (for all instances of dosfs filesystem) is replaced by local per-instance cache. Submitted by: Mikhail.Kupchik_gmail.com Reviewed by: tsoome, allanjude Differential Revision: https://reviews.freebsd.org/D9547
124 lines
4.7 KiB
C
124 lines
4.7 KiB
C
/*
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* Copyright (c) 1996, 1998 Robert Nordier
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR(S) ``AS IS'' AND ANY EXPRESS
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* OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR(S) BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
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* GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER
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* IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
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* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
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* IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*/
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#ifndef DOSIO_H
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#define DOSIO_H
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/*
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* DOS file attributes
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*/
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#define FA_RDONLY 001 /* read-only */
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#define FA_HIDDEN 002 /* hidden file */
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#define FA_SYSTEM 004 /* system file */
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#define FA_LABEL 010 /* volume label */
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#define FA_DIR 020 /* directory */
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#define FA_ARCH 040 /* archive (file modified) */
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#define FA_XDE 017 /* extended directory entry */
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#define FA_MASK 077 /* all attributes */
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/*
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* Macros to convert DOS-format 16-bit and 32-bit quantities
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*/
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#define cv2(p) ((u_int16_t)(p)[0] | \
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((u_int16_t)(p)[1] << 010))
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#define cv4(p) ((u_int32_t)(p)[0] | \
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((u_int32_t)(p)[1] << 010) | \
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((u_int32_t)(p)[2] << 020) | \
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((u_int32_t)(p)[3] << 030))
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/*
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* Directory, filesystem, and file structures.
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*/
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typedef struct {
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u_char x_case; /* case */
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u_char c_hsec; /* created: secs/100 */
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u_char c_time[2]; /* created: time */
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u_char c_date[2]; /* created: date */
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u_char a_date[2]; /* accessed: date */
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u_char h_clus[2]; /* clus[hi] */
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} DOS_DEX;
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typedef struct {
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u_char name[8]; /* name */
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u_char ext[3]; /* extension */
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u_char attr; /* attributes */
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DOS_DEX dex; /* VFAT/FAT32 only */
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u_char time[2]; /* modified: time */
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u_char date[2]; /* modified: date */
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u_char clus[2]; /* starting cluster */
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u_char size[4]; /* size */
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} DOS_DE;
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typedef struct {
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u_char seq; /* flags */
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u_char name1[5][2]; /* 1st name area */
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u_char attr; /* (see fat_de) */
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u_char res; /* reserved */
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u_char chk; /* checksum */
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u_char name2[6][2]; /* 2nd name area */
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u_char clus[2]; /* (see fat_de) */
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u_char name3[2][2]; /* 3rd name area */
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} DOS_XDE;
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typedef union {
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DOS_DE de; /* standard directory entry */
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DOS_XDE xde; /* extended directory entry */
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} DOS_DIR;
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typedef struct {
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struct open_file *fd; /* file descriptor */
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u_char *fatbuf; /* FAT cache buffer */
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u_int fatbuf_blknum; /* number of 128K block in FAT cache buffer */
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u_int links; /* active links to structure */
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u_int spc; /* sectors per cluster */
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u_int bsize; /* cluster size in bytes */
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u_int bshift; /* cluster conversion shift */
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u_int dirents; /* root directory entries */
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u_int spf; /* sectors per fat */
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u_int rdcl; /* root directory start cluster */
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u_int lsnfat; /* start of fat */
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u_int lsndir; /* start of root dir */
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u_int lsndta; /* start of data area */
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u_int fatsz; /* FAT entry size */
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u_int xclus; /* maximum cluster number */
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DOS_DE root;
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} DOS_FS;
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typedef struct {
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DOS_FS *fs; /* associated filesystem */
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DOS_DE de; /* directory entry */
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u_int offset; /* current offset */
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u_int c; /* last cluster read */
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} DOS_FILE;
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#endif /* !DOSIO_H */
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