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rockbox/firmware/include/dircache.h
Michael Sevakis 7d1a47cf13 Rewrite filesystem code (WIP) 
This patch redoes the filesystem code from the FAT driver up to the
clipboard code in onplay.c.

Not every aspect of this is finished therefore it is still "WIP". I
don't wish to do too much at once (haha!). What is left to do is get
dircache back in the sim and find an implementation for the dircache
indicies in the tagcache and playlist code or do something else that
has the same benefit. Leaving these out for now does not make anything
unusable. All the basics are done.

Phone app code should probably get vetted (and app path handling
just plain rewritten as environment expansions); the SDL app and
Android run well.

Main things addressed:
1) Thread safety: There is none right now in the trunk code. Most of
what currently works is luck when multiple threads are involved or
multiple descriptors to the same file are open.

2) POSIX compliance: Many of the functions behave nothing like their
counterparts on a host system. This leads to inconsistent code or very
different behavior from native to hosted. One huge offender was
rename(). Going point by point would fill a book.

3) Actual running RAM usage: Many targets will use less RAM and less
stack space (some more RAM because I upped the number of cache buffers
for large memory). There's very little memory lying fallow in rarely-used
areas (see 'Key core changes' below). Also, all targets may open the same
number of directory streams whereas before those with less than 8MB RAM
were limited to 8, not 12 implying those targets will save slightly
less.

4) Performance: The test_disk plugin shows markedly improved performance,
particularly in the area of (uncached) directory scanning, due partly to
more optimal directory reading and to a better sector cache algorithm.
Uncached times tend to be better while there is a bit of a slowdown in
dircache due to it being a bit heavier of an implementation. It's not
noticeable by a human as far as I can say.

Key core changes:
1) Files and directories share core code and data structures.

2) The filesystem code knows which descriptors refer to same file.
This ensures that changes from one stream are appropriately reflected
in every open descriptor for that file (fileobj_mgr.c).

3) File and directory cache buffers are borrowed from the main sector
cache. This means that when they are not in use by a file, they are not
wasted, but used for the cache. Most of the time, only a few of them
are needed. It also means that adding more file and directory handles
is less expensive. All one must do in ensure a large enough cache to
borrow from.

4) Relative path components are supported and the namespace is unified.
It does not support full relative paths to an implied current directory;
what is does support is use of "." and "..". Adding the former would
not be very difficult. The namespace is unified in the sense that
volumes may be specified several times along with relative parts, e.g.:
"/<0>/foo/../../<1>/bar" :<=> "/<1>/bar".

5) Stack usage is down due to sharing of data, static allocation and
less duplication of strings on the stack. This requires more
serialization than I would like but since the number of threads is
limited to a low number, the tradoff in favor of the stack seems
reasonable.

6) Separates and heirarchicalizes (sic) the SIM and APP filesystem
code. SIM path and volume handling is just like the target. Some
aspects of the APP file code get more straightforward (e.g. no path
hashing is needed).

Dircache:
Deserves its own section. Dircache is new but pays homage to the old.
The old one was not compatible and so it, since it got redone, does
all the stuff it always should have done such as:

1) It may be update and used at any time during the build process.
No longer has one to wait for it to finish building to do basic file
management (create, remove, rename, etc.).

2) It does not need to be either fully scanned or completely disabled;
it can be incomplete (i.e. overfilled, missing paths), still be
of benefit and be correct.

3) Handles mounting and dismounting of individual volumes which means
a full rebuild is not needed just because you pop a new SD card in the
slot. Now, because it reuses its freed entry data, may rebuild only
that volume.

4) Much more fundamental to the file code. When it is built, it is
the keeper of the master file list whether enabled or not ("disabled"
is just a state of the cache). Its must always to ready to be started
and bind all streams opened prior to being enabled.

5) Maintains any short filenames in OEM format which means that it does
not need to be rebuilt when changing the default codepage.

Miscellaneous Compatibility:
1) Update any other code that would otherwise not work such as the
hotswap mounting code in various card drivers.

2) File management: Clipboard needed updating because of the behavioral
changes. Still needs a little more work on some finer points.

3) Remove now-obsolete functionality such as the mutex's "no preempt"
flag (which was only for the prior FAT driver).

4) struct dirinfo uses time_t rather than raw FAT directory entry
time fields. I plan to follow up on genericizing everything there
(i.e. no FAT attributes).

5) unicode.c needed some redoing so that the file code does not try
try to load codepages during a scan, which is actually a problem with
the current code. The default codepage, if any is required, is now
kept in RAM separarately (bufalloced) from codepages specified to
iso_decode() (which must not be bufalloced because the conversion
may be done by playback threads).

Brings with it some additional reusable core code:
1) Revised file functions: Reusable code that does things such as
safe path concatenation and parsing without buffer limitations or
data duplication. Variants that copy or alter the input path may be
based off these.

To do:
1) Put dircache functionality back in the sim. Treating it internally
as a different kind of file system seems the best approach at this
time.

2) Restore use of dircache indexes in the playlist and database or
something effectively the same. Since the cache doesn't have to be
complete in order to be used, not getting a hit on the cache doesn't
unambiguously say if the path exists or not.

Change-Id: Ia30f3082a136253e3a0eae0784e3091d138915c8
Reviewed-on: http://gerrit.rockbox.org/566
Reviewed-by: Michael Sevakis <jethead71@rockbox.org>
Tested: Michael Sevakis <jethead71@rockbox.org>
2014-08-30 03:48:23 +02:00

175 lines
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/***************************************************************************
* __________ __ ___.
* Open \______ \ ____ ____ | | _\_ |__ _______ ___
* Source | _// _ \_/ ___\| |/ /| __ \ / _ \ \/ /
* Jukebox | | ( <_> ) \___| < | \_\ ( <_> > < <
* Firmware |____|_ /\____/ \___ >__|_ \|___ /\____/__/\_ \
* \/ \/ \/ \/ \/
* $Id$
*
* Copyright (C) 2005 by Miika Pekkarinen
* Copyright (C) 2014 by Michael Sevakis
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version 2
* of the License, or (at your option) any later version.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
****************************************************************************/
#ifndef _DIRCACHE_H
#define _DIRCACHE_H
#include "mv.h"
#include <string.h> /* size_t */
#include <sys/types.h> /* ssize_t */
#ifdef HAVE_DIRCACHE
/****************************************************************************
** Configurable values
**/
#if 0
/* enable dumping code */
#define DIRCACHE_DUMPSTER
#define DIRCACHE_DUMPSTER_BIN "/dircache_dump.bin"
#define DIRCACHE_DUMPSTER_CSV "/dircache_dump.csv"
#endif
/* dircache builds won't search below this but will work down to this point
while below it the cache will just pass requests through to the storage;
the limiting factor is the scanning thread stack size, not the
implementation -- tune the two together */
#define DIRCACHE_MAX_DEPTH 15
#define DIRCACHE_STACK_SIZE (DEFAULT_STACK_SIZE + 0x100)
/* memory buffer constants that control allocation */
#define DIRCACHE_RESERVE (1024*64) /* 64 KB - new entry slack */
#define DIRCACHE_MIN (1024*1024*1) /* 1 MB - provision min size */
#define DIRCACHE_LIMIT (1024*1024*6) /* 6 MB - provision max size */
/* make it easy to change serialnumber size without modifying anything else;
32 bits allows 21845 builds before wrapping in a 6MB cache that is filled
exclusively with entries and nothing else (32 byte entries), making that
figure pessimistic */
typedef uint32_t dc_serial_t;
/**
****************************************************************************/
#if CONFIG_PLATFORM & PLATFORM_NATIVE
/* native dircache is lower-level than on a hosted target */
#define DIRCACHE_NATIVE
#endif
struct dircache_file
{
int idx; /* this file's cache index */
dc_serial_t serialnum; /* this file's serial number */
};
enum dircache_status
{
DIRCACHE_IDLE = 0, /* no volume is initialized */
DIRCACHE_SCANNING = 1, /* dircache is scanning a volume */
DIRCACHE_READY = 2, /* dircache is ready to be used */
};
/** Dircache control **/
void dircache_wait(void);
void dircache_suspend(void);
int dircache_resume(void);
int dircache_enable(void);
void dircache_disable(void);
void dircache_free_buffer(void);
/** Volume mounting **/
void dircache_mount(void); /* always tries building everything it can */
void dircache_unmount(IF_MV_NONVOID(int volume));
/** File API service functions **/
/* avoid forcing #include of file_internal.h, fat.h and dir.h */
struct filestr_base;
struct file_base_info;
struct file_base_binding;
struct dirent;
struct dirscan_info;
struct dirinfo_native;
int dircache_readdir_dirent(struct filestr_base *stream,
struct dirscan_info *scanp,
struct dirent *entry);
void dircache_rewinddir_dirent(struct dirscan_info *scanp);
#ifdef DIRCACHE_NATIVE
struct fat_direntry;
int dircache_readdir_internal(struct filestr_base *stream,
struct file_base_info *infop,
struct fat_direntry *fatent);
void dircache_rewinddir_internal(struct file_base_info *info);
#endif /* DIRCACHE_NATIVE */
/** Dircache live updating **/
void dircache_get_rootinfo(struct file_base_info *infop);
void dircache_bind_file(struct file_base_binding *bindp);
void dircache_unbind_file(struct file_base_binding *bindp);
void dircache_fileop_create(struct file_base_info *dirinfop,
struct file_base_binding *bindp,
const char *basename,
const struct dirinfo_native *dinp);
void dircache_fileop_rename(struct file_base_info *dirinfop,
struct file_base_binding *bindp,
const char *basename);
void dircache_fileop_remove(struct file_base_binding *bindp);
void dircache_fileop_sync(struct file_base_binding *infop,
const struct dirinfo_native *dinp);
/** Dircache paths and files **/
ssize_t dircache_get_path(const struct dircache_file *dcfilep, char *buf,
size_t size);
int dircache_get_file(const char *path, struct dircache_file *dcfilep);
/** Debug screen/info stuff **/
struct dircache_info
{
enum dircache_status status; /* current composite status value */
const char *statusdesc; /* pointer to string describing 'status' */
size_t last_size; /* cache size after last build */
size_t size; /* total size of entries (with holes) */
size_t sizeused; /* bytes of 'size' actually utilized */
size_t size_limit; /* maximum possible size */
size_t reserve; /* size of reserve area */
size_t reserve_used; /* amount of reserve used */
unsigned int entry_count; /* number of cache entries */
long build_ticks; /* total time used to build cache */
};
void dircache_get_info(struct dircache_info *info);
#ifdef DIRCACHE_DUMPSTER
void dircache_dump(void);
#endif /* DIRCACHE_DUMPSTER */
/** Misc. stuff **/
void dircache_dcfile_init(struct dircache_file *dcfilep);
#ifdef HAVE_EEPROM_SETTINGS
int dircache_load(void);
int dircache_save(void);
#endif /* HAVE_EEPROM_SETTINGS */
void dircache_init(size_t last_size) INIT_ATTR;
#endif /* HAVE_DIRCACHE */
#endif /* _DIRCACHE_H */
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