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Exploring inlined mutable configuration

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Currently littlefs uses a separate mutable state struct and immutable
config struct. This lets users place the config struct in ROM where
possible.

However the recent addition of LFS_STATICCFG raises the question of if
this split is still valuable.

If the config is copied into the mutable struct at runtime, this allows
a couple things:
1. Easier user interface, config can be stack allocated, no need to store
   the config struct for the lifetime of littlefs in OSs.
2. Avoids duplication when littlefs would need to change config based on
   observed superblocks, such as LFS_NAME_MAX limits
3. In theory, access to a single struct is faster/smaller as it avoids
   an additional load instruction.

Unfortunately, inlining the dynamic config runs into several issues:

1. The code size actually increases with this change! From digging into
   this it's for a couple reasons:

   - Copying the config over takes code.

   - C has notorious problems with pointer aliasing, accessing
     constants from a const struct actually allows C to assume the
     values aren't going to change in more situations.

     This suggests it may be possible to reduce the code size more by
     loading the config pointer into a variable, but I haven't explored
     this probably not-worth-it optimization.

   - Even assuming deduplication of superblock-dependent configuration,
     the config struct is significantly larger than the mutable struct,
     and it turns out combining these two exceeds the limits of
     immediate-relative-loads, discarding the possible code size
     improvement from avoiding a second dereference.

2. The implementation of dynamic configuration differs significantly from
   the static configuration. This adds mess into the compile-time #ifdefs
   needed to support both options.
This commit is contained in:
Christopher Haster
2020-11-26 10:26:51 -06:00
parent a7cdd563f6
commit f9324d1443
4 changed files with 112 additions and 89 deletions
Download Patch File Download Diff File Expand all files Collapse all files

168
lfs.c
View File

@@ -34,26 +34,26 @@
#else
// direct config towards dynamic lfs_cfg struct
#define LFS_CFG_READ(lfs, block, off, buffer, size) \
lfs->cfg->read(lfs->cfg->ctx, block, off, buffer, size)
lfs->cfg.read(lfs->cfg.ctx, block, off, buffer, size)
#define LFS_CFG_PROG(lfs, block, off, buffer, size) \
lfs->cfg->prog(lfs->cfg->ctx, block, off, buffer, size)
lfs->cfg.prog(lfs->cfg.ctx, block, off, buffer, size)
#define LFS_CFG_ERASE(lfs, block) \
lfs->cfg->erase(lfs->cfg->ctx, block)
lfs->cfg.erase(lfs->cfg.ctx, block)
#define LFS_CFG_SYNC(lfs) \
lfs->cfg->sync(lfs->cfg->ctx)
#define LFS_CFG_READ_SIZE(lfs) lfs->cfg->read_size
#define LFS_CFG_PROG_SIZE(lfs) lfs->cfg->prog_size
#define LFS_CFG_BLOCK_SIZE(lfs) lfs->cfg->block_size
#define LFS_CFG_BLOCK_COUNT(lfs) lfs->cfg->block_count
#define LFS_CFG_BLOCK_CYCLES(lfs) lfs->cfg->block_cycles
#define LFS_CFG_CACHE_SIZE(lfs) lfs->cfg->cache_size
#define LFS_CFG_LOOKAHEAD_SIZE(lfs) lfs->cfg->lookahead_size
#define LFS_CFG_READ_BUFFER(lfs) lfs->cfg->read_buffer
#define LFS_CFG_PROG_BUFFER(lfs) lfs->cfg->prog_buffer
#define LFS_CFG_LOOKAHEAD_BUFFER(lfs) lfs->cfg->lookahead_buffer
#define LFS_CFG_NAME_MAX(lfs) lfs->cfg->name_max
#define LFS_CFG_FILE_MAX(lfs) lfs->cfg->file_max
#define LFS_CFG_ATTR_MAX(lfs) lfs->cfg->attr_max
lfs->cfg.sync(lfs->cfg.ctx)
#define LFS_CFG_READ_SIZE(lfs) lfs->cfg.read_size
#define LFS_CFG_PROG_SIZE(lfs) lfs->cfg.prog_size
#define LFS_CFG_BLOCK_SIZE(lfs) lfs->cfg.block_size
#define LFS_CFG_BLOCK_COUNT(lfs) lfs->cfg.block_count
#define LFS_CFG_BLOCK_CYCLES(lfs) lfs->cfg.block_cycles
#define LFS_CFG_CACHE_SIZE(lfs) lfs->cfg.cache_size
#define LFS_CFG_LOOKAHEAD_SIZE(lfs) lfs->cfg.lookahead_size
#define LFS_CFG_READ_BUFFER(lfs) lfs->cfg.read_buffer
#define LFS_CFG_PROG_BUFFER(lfs) lfs->cfg.prog_buffer
#define LFS_CFG_LOOKAHEAD_BUFFER(lfs) lfs->cfg.lookahead_buffer
#define LFS_CFG_NAME_MAX(lfs) lfs->cfg.name_max
#define LFS_CFG_FILE_MAX(lfs) lfs->cfg.file_max
#define LFS_CFG_ATTR_MAX(lfs) lfs->cfg.attr_max
#endif
#ifdef LFS_FILE_STATICCFG
@@ -63,9 +63,9 @@
#define LFS_FILE_CFG_ATTR_COUNT(file) LFS_FILE_ATTR_COUNT
#else
// direct config towards dynamic lfs_cfg struct
#define LFS_FILE_CFG_BUFFER(file) file->cfg->buffer
#define LFS_FILE_CFG_ATTRS(file) file->cfg->attrs
#define LFS_FILE_CFG_ATTR_COUNT(file) file->cfg->attr_count
#define LFS_FILE_CFG_BUFFER(file) file->cfg.buffer
#define LFS_FILE_CFG_ATTRS(file) file->cfg.attrs
#define LFS_FILE_CFG_ATTR_COUNT(file) file->cfg.attr_count
#endif
@@ -1099,7 +1099,7 @@ static int lfs_dir_getinfo(lfs_t *lfs, lfs_mdir_t *dir,
}
lfs_stag_t tag = lfs_dir_get(lfs, dir, LFS_MKTAG(0x780, 0x3ff, 0),
LFS_MKTAG(LFS_TYPE_NAME, id, lfs->name_max+1), info->name);
LFS_MKTAG(LFS_TYPE_NAME, id, LFS_CFG_NAME_MAX(lfs)+1), info->name);
if (tag < 0) {
return (int)tag;
}
@@ -1990,7 +1990,7 @@ int lfs_mkdir(lfs_t *lfs, const char *path) {
// check that name fits
lfs_size_t nlen = strlen(path);
if (nlen > lfs->name_max) {
if (nlen > LFS_CFG_NAME_MAX(lfs)) {
LFS_TRACE("lfs_mkdir -> %d", LFS_ERR_NAMETOOLONG);
return LFS_ERR_NAMETOOLONG;
}
@@ -2445,7 +2445,11 @@ static int lfs_ctz_traverse(lfs_t *lfs,
/// Top level file operations ///
static int lfs_file_opencommon(lfs_t *lfs, lfs_file_t *file,
const char *path, int flags) {
const char *path, int flags
#ifndef LFS_FILE_STATICCFG
, const struct lfs_file_cfg *cfg
#endif
) {
// deorphan if we haven't yet, needed at most once after poweron
if ((flags & 3) != LFS_O_RDONLY) {
int err = lfs_fs_forceconsistency(lfs);
@@ -2454,6 +2458,9 @@ static int lfs_file_opencommon(lfs_t *lfs, lfs_file_t *file,
}
}
// copy over config
file->cfg = *cfg;
// setup simple file details
int err;
file->flags = flags | LFS_F_OPENED;
@@ -2481,7 +2488,7 @@ static int lfs_file_opencommon(lfs_t *lfs, lfs_file_t *file,
// check that name fits
lfs_size_t nlen = strlen(path);
if (nlen > lfs->name_max) {
if (nlen > LFS_CFG_NAME_MAX(lfs)) {
err = LFS_ERR_NAMETOOLONG;
goto cleanup;
}
@@ -2535,7 +2542,7 @@ static int lfs_file_opencommon(lfs_t *lfs, lfs_file_t *file,
}
if ((file->flags & 3) != LFS_O_RDONLY) {
if (LFS_FILE_CFG_ATTRS(file)[i].size > lfs->attr_max) {
if (LFS_FILE_CFG_ATTRS(file)[i].size > LFS_CFG_ATTR_MAX(lfs)) {
err = LFS_ERR_NOSPC;
goto cleanup;
}
@@ -2595,11 +2602,12 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
const char *path, int flags) {
LFS_TRACE("lfs_file_open(%p, %p, \"%s\", %x)",
(void*)lfs, (void*)file, path, flags);
#ifndef LFS_FILE_STATICCFG
static const struct lfs_file_cfg defaults = {0};
file->cfg = &defaults;
#endif
#ifdef LFS_FILE_STATICCFG
int err = lfs_file_opencommon(lfs, file, path, flags);
#else
int err = lfs_file_opencommon(lfs, file, path, flags,
&(struct lfs_file_cfg){0});
#endif
LFS_TRACE("lfs_file_open -> %d", err);
return err;
}
@@ -2612,8 +2620,7 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
".buffer=%p, .attrs=%p, .attr_count=%"PRIu32"})",
(void*)lfs, (void*)file, path, flags,
(void*)cfg, cfg->buffer, (void*)cfg->attrs, cfg->attr_count);
file->cfg = cfg;
int err = lfs_file_opencommon(lfs, file, path, flags);
int err = lfs_file_opencommon(lfs, file, path, flags, cfg);
LFS_TRACE("lfs_file_opencfg -> %d", err);
return err;
}
@@ -2966,7 +2973,7 @@ lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
file->pos = file->ctz.size;
}
if (file->pos + size > lfs->file_max) {
if (file->pos + size > LFS_CFG_FILE_MAX(lfs)) {
// Larger than file limit?
LFS_TRACE("lfs_file_write -> %d", LFS_ERR_FBIG);
return LFS_ERR_FBIG;
@@ -3097,7 +3104,7 @@ lfs_soff_t lfs_file_seek(lfs_t *lfs, lfs_file_t *file,
npos = file->ctz.size + off;
}
if (npos > lfs->file_max) {
if (npos > LFS_CFG_FILE_MAX(lfs)) {
// file position out of range
LFS_TRACE("lfs_file_seek -> %d", LFS_ERR_INVAL);
return LFS_ERR_INVAL;
@@ -3343,7 +3350,7 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
if (prevtag == LFS_ERR_NOENT) {
// check that name fits
lfs_size_t nlen = strlen(newpath);
if (nlen > lfs->name_max) {
if (nlen > LFS_CFG_NAME_MAX(lfs)) {
LFS_TRACE("lfs_rename -> %d", LFS_ERR_NAMETOOLONG);
return LFS_ERR_NAMETOOLONG;
}
@@ -3473,7 +3480,7 @@ lfs_ssize_t lfs_getattr(lfs_t *lfs, const char *path,
tag = lfs_dir_get(lfs, &cwd, LFS_MKTAG(0x7ff, 0x3ff, 0),
LFS_MKTAG(LFS_TYPE_USERATTR + type,
id, lfs_min(size, lfs->attr_max)),
id, lfs_min(size, LFS_CFG_ATTR_MAX(lfs))),
buffer);
if (tag < 0) {
if (tag == LFS_ERR_NOENT) {
@@ -3516,7 +3523,7 @@ int lfs_setattr(lfs_t *lfs, const char *path,
uint8_t type, const void *buffer, lfs_size_t size) {
LFS_TRACE("lfs_setattr(%p, \"%s\", %"PRIu8", %p, %"PRIu32")",
(void*)lfs, path, type, buffer, size);
if (size > lfs->attr_max) {
if (size > LFS_CFG_ATTR_MAX(lfs)) {
LFS_TRACE("lfs_setattr -> %d", LFS_ERR_NOSPC);
return LFS_ERR_NOSPC;
}
@@ -3535,9 +3542,16 @@ int lfs_removeattr(lfs_t *lfs, const char *path, uint8_t type) {
/// Filesystem operations ///
static int lfs_initcommon(lfs_t *lfs) {
static int lfs_initcommon(lfs_t *lfs
#ifndef LFS_STATICCFG
, const struct lfs_cfg *cfg
#endif
) {
int err = 0;
// copy over config
lfs->cfg = *cfg;
// validate that the lfs-cfg sizes were initiated properly before
// performing any arithmetic logics with them
LFS_ASSERT(LFS_CFG_READ_SIZE(lfs) != 0);
@@ -3605,22 +3619,28 @@ static int lfs_initcommon(lfs_t *lfs) {
// check that the size limits are sane
LFS_ASSERT(LFS_CFG_NAME_MAX(lfs) <= LFS_NAME_MAX);
lfs->name_max = LFS_CFG_NAME_MAX(lfs);
if (!lfs->name_max) {
lfs->name_max = LFS_NAME_MAX;
//lfs->name_max = LFS_CFG_NAME_MAX(lfs);
#ifndef LFS_STATICCFG
if (!lfs->cfg.name_max) {
lfs->cfg.name_max = LFS_NAME_MAX;
}
#endif
LFS_ASSERT(LFS_CFG_FILE_MAX(lfs) <= LFS_FILE_MAX);
lfs->file_max = LFS_CFG_FILE_MAX(lfs);
if (!lfs->file_max) {
lfs->file_max = LFS_FILE_MAX;
//lfs->file_max = LFS_CFG_FILE_MAX(lfs);
#ifndef LFS_STATICCFG
if (!lfs->cfg.file_max) {
lfs->cfg.file_max = LFS_FILE_MAX;
}
#endif
LFS_ASSERT(LFS_CFG_ATTR_MAX(lfs) <= LFS_ATTR_MAX);
lfs->attr_max = LFS_CFG_ATTR_MAX(lfs);
if (!lfs->attr_max) {
lfs->attr_max = LFS_ATTR_MAX;
//lfs->attr_max = LFS_CFG_ATTR_MAX(lfs);
#ifndef LFS_STATICCFG
if (!lfs->cfg.attr_max) {
lfs->cfg.attr_max = LFS_ATTR_MAX;
}
#endif
// setup default state
lfs->root[0] = LFS_BLOCK_NULL;
@@ -3658,10 +3678,18 @@ static int lfs_deinit(lfs_t *lfs) {
return 0;
}
static int lfs_formatcommon(lfs_t *lfs) {
static int lfs_formatcommon(lfs_t *lfs
#ifndef LFS_STATICCFG
, const struct lfs_cfg *cfg
#endif
) {
int err = 0;
{
#ifdef LFS_STATICCFG
err = lfs_initcommon(lfs);
#else
err = lfs_initcommon(lfs, cfg);
#endif
if (err) {
return err;
}
@@ -3686,9 +3714,9 @@ static int lfs_formatcommon(lfs_t *lfs) {
.version = LFS_DISK_VERSION,
.block_size = LFS_CFG_BLOCK_SIZE(lfs),
.block_count = LFS_CFG_BLOCK_COUNT(lfs),
.name_max = lfs->name_max,
.file_max = lfs->file_max,
.attr_max = lfs->attr_max,
.name_max = LFS_CFG_NAME_MAX(lfs),
.file_max = LFS_CFG_FILE_MAX(lfs),
.attr_max = LFS_CFG_ATTR_MAX(lfs),
};
lfs_superblock_tole32(&superblock);
@@ -3748,15 +3776,22 @@ int lfs_formatcfg(lfs_t *lfs, const struct lfs_cfg *cfg) {
cfg->block_cycles, cfg->cache_size, cfg->lookahead_size,
cfg->read_buffer, cfg->prog_buffer, cfg->lookahead_buffer,
cfg->name_max, cfg->file_max, cfg->attr_max);
lfs->cfg = cfg;
int err = lfs_formatcommon(lfs);
int err = lfs_formatcommon(lfs, cfg);
LFS_TRACE("lfs_formatcfg -> %d", err);
return err;
}
#endif
static int lfs_mountcommon(lfs_t *lfs) {
static int lfs_mountcommon(lfs_t *lfs
#ifndef LFS_STATICCFG
, const struct lfs_cfg *cfg
#endif
) {
#ifdef LFS_STATICCFG
int err = lfs_initcommon(lfs);
#else
int err = lfs_initcommon(lfs, cfg);
#endif
if (err) {
return err;
}
@@ -3814,36 +3849,36 @@ static int lfs_mountcommon(lfs_t *lfs) {
// check superblock configuration
if (superblock.name_max) {
if (superblock.name_max > lfs->name_max) {
if (superblock.name_max > LFS_CFG_NAME_MAX(lfs)) {
LFS_ERROR("Unsupported name_max (%"PRIu32" > %"PRIu32")",
superblock.name_max, lfs->name_max);
superblock.name_max, LFS_CFG_NAME_MAX(lfs));
err = LFS_ERR_INVAL;
goto cleanup;
}
lfs->name_max = superblock.name_max;
lfs->cfg.name_max = superblock.name_max;
}
if (superblock.file_max) {
if (superblock.file_max > lfs->file_max) {
if (superblock.file_max > LFS_CFG_FILE_MAX(lfs)) {
LFS_ERROR("Unsupported file_max (%"PRIu32" > %"PRIu32")",
superblock.file_max, lfs->file_max);
superblock.file_max, LFS_CFG_FILE_MAX(lfs));
err = LFS_ERR_INVAL;
goto cleanup;
}
lfs->file_max = superblock.file_max;
lfs->cfg.file_max = superblock.file_max;
}
if (superblock.attr_max) {
if (superblock.attr_max > lfs->attr_max) {
if (superblock.attr_max > LFS_CFG_ATTR_MAX(lfs)) {
LFS_ERROR("Unsupported attr_max (%"PRIu32" > %"PRIu32")",
superblock.attr_max, lfs->attr_max);
superblock.attr_max, LFS_CFG_ATTR_MAX(lfs));
err = LFS_ERR_INVAL;
goto cleanup;
}
lfs->attr_max = superblock.attr_max;
lfs->cfg.attr_max = superblock.attr_max;
}
}
@@ -3909,8 +3944,7 @@ int lfs_mountcfg(lfs_t *lfs, const struct lfs_cfg *cfg) {
cfg->block_cycles, cfg->cache_size, cfg->lookahead_size,
cfg->read_buffer, cfg->prog_buffer, cfg->lookahead_buffer,
cfg->name_max, cfg->file_max, cfg->attr_max);
lfs->cfg = cfg;
int err = lfs_mountcommon(lfs);
int err = lfs_mountcommon(lfs, cfg);
LFS_TRACE("lfs_mountcfg -> %d", err);
return err;
}
@@ -4964,9 +4998,9 @@ static int lfs_migratecommon(lfs_t *lfs) {
.version = LFS_DISK_VERSION,
.block_size = LFS_CFG_BLOCK_SIZE(lfs),
.block_count = LFS_CFG_BLOCK_COUNT(lfs),
.name_max = lfs->name_max,
.file_max = lfs->file_max,
.attr_max = lfs->attr_max,
.name_max = LFS_CFG_NAME_MAX(lfs),
.file_max = LFS_CFG_FILE_MAX(lfs),
.attr_max = LFS_CFG_ATTR_MAX(lfs),
};
lfs_superblock_tole32(&superblock);

7
lfs.h
View File

@@ -384,7 +384,7 @@ typedef struct lfs_file {
lfs_cache_t cache;
#ifndef LFS_FILE_STATICCFG
const struct lfs_file_cfg *cfg;
struct lfs_file_cfg cfg;
#endif
} lfs_file_t;
@@ -429,11 +429,8 @@ typedef struct lfs {
} free;
#ifndef LFS_STATICCFG
const struct lfs_cfg *cfg;
struct lfs_cfg cfg;
#endif
lfs_size_t name_max;
lfs_size_t file_max;
lfs_size_t attr_max;
#ifdef LFS_MIGRATE
struct lfs1 *lfs1;

24
tests/test_evil.toml
View File

@@ -12,8 +12,7 @@ code = '''
lfs_formatcfg(&lfs, &cfg) => 0;
// change tail-pointer to invalid pointers
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_initcommon(&lfs, &cfg) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
lfs_dir_commit(&lfs, &mdir, LFS_MKATTRS(
@@ -39,8 +38,7 @@ code = '''
lfs_unmount(&lfs) => 0;
// change the dir pointer to be invalid
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_initcommon(&lfs, &cfg) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
// make sure id 1 == our directory
@@ -88,8 +86,7 @@ code = '''
lfs_unmount(&lfs) => 0;
// change the file pointer to be invalid
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_initcommon(&lfs, &cfg) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
// make sure id 1 == our file
@@ -140,8 +137,7 @@ code = '''
lfs_file_close(&lfs, &file) => 0;
lfs_unmount(&lfs) => 0;
// change pointer in CTZ skip-list to be invalid
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_initcommon(&lfs, &cfg) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
// make sure id 1 == our file and get our CTZ structure
@@ -194,8 +190,7 @@ code = '''
lfs_formatcfg(&lfs, &cfg) => 0;
// create an invalid gstate
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_initcommon(&lfs, &cfg) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
lfs_fs_prepmove(&lfs, 1, (lfs_block_t [2]){
@@ -221,8 +216,7 @@ code = '''
lfs_formatcfg(&lfs, &cfg) => 0;
// change tail-pointer to point to ourself
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_initcommon(&lfs, &cfg) => 0;
lfs_mdir_t mdir;
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
lfs_dir_commit(&lfs, &mdir, LFS_MKATTRS(
@@ -244,8 +238,7 @@ code = '''
lfs_unmount(&lfs) => 0;
// find child
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_initcommon(&lfs, &cfg) => 0;
lfs_mdir_t mdir;
lfs_block_t pair[2];
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;
@@ -275,8 +268,7 @@ code = '''
lfs_unmount(&lfs) => 0;
// find child
lfs.cfg = &cfg;
lfs_initcommon(&lfs) => 0;
lfs_initcommon(&lfs, &cfg) => 0;
lfs_mdir_t mdir;
lfs_block_t pair[2];
lfs_dir_fetch(&lfs, &mdir, (lfs_block_t[2]){0, 1}) => 0;

2
tests/test_truncate.toml
View File

@@ -100,7 +100,7 @@ code = '''
lfs_file_open(&lfs, &file, "sequence",
LFS_O_RDWR | LFS_O_CREAT | LFS_O_TRUNC) => 0;
size = lfs_min(lfs.cfg->cache_size, sizeof(buffer)/2);
size = lfs_min(lfs.cfg.cache_size, sizeof(buffer)/2);
lfs_size_t qsize = size / 4;
uint8_t *wb = buffer;
uint8_t *rb = buffer + size;