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subsys/fs/littlefs: allow customization of file system configuration

There's desire to be able to customize parameters on a per-filesystem
basis, which means we need a way to override the Kconfig defaults which
are global.  This also means the littlefs data structure cannot own the
cache and lookahead buffers.

Switch to using a macro to define the littlefs data structure.  The
default version uses the Kconfig constants.  A custom one takes
arguments providing the most likely partition-specific parameters.
Finally the user is free to bypass the helper macros and set any
parameters desired, though validation is limited and only present when
CONFIG_DEBUG is enabled.

Extend the test suite with a performance module, which confirms that
these settings have an impact proportional to the log of changes to the
cache or IO sizes.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>
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pabigot authored and carlescufi committed Aug 3, 2019
1 parent a8b7a21 commit 167eb53e7491b039b95671f09e3768ed64690728
@@ -19,19 +19,86 @@ extern "C" {

/** @brief Filesystem info structure for LittleFS mount */
struct fs_littlefs {
/* Defaulted in driver, customizable before mount. */
struct lfs_config cfg;

/* Must be cfg.cache_size */
u8_t *read_buffer;

/* Must be cfg.cache_size */
u8_t *prog_buffer;

/* Mustbe cfg.lookahead_size/4 elements, and
* cfg.lookahead_size must be a multiple of 8.
*/
u32_t *lookahead_buffer[CONFIG_FS_LITTLEFS_LOOKAHEAD_SIZE / sizeof(u32_t)];

/* These structures are filled automatically at mount. */
struct lfs lfs;
struct lfs_config cfg;
const struct flash_area *area;
struct k_mutex mutex;

/* Static buffers */
u8_t read_buffer[CONFIG_FS_LITTLEFS_CACHE_SIZE];
u8_t prog_buffer[CONFIG_FS_LITTLEFS_CACHE_SIZE];
/* Multiple of 8 bytes, but 4-byte aligned (littlefs #239) */
u32_t lookahead_buffer[CONFIG_FS_LITTLEFS_LOOKAHEAD_SIZE / sizeof(u32_t)];
};

/** @brief Define a littlefs configuration with customized size
* characteristics.
*
* This defines static arrays required for caches, and initializes the
* littlefs configuration structure to use the provided values instead
* of the global Kconfig defaults. A pointer to the named object must
* be stored in the ``.fs_data`` field of a :c:type:`struct fs_mount`
* object.
*
* To define an instance for the Kconfig defaults, use
* :cpp:func:`FS_LITTLEFS_DECLARE_DEFAULT_CONFIG`.
*
* To completely control file system configuration the application can
* directly define and initialize a :c:type:`struct fs_littlefs`
* object. The application is responsible for ensuring the configured
* values are consistent with littlefs requirements.
*
* @note If you use a non-default configuration for cache size, you
* must also select :option:`CONFIG_FS_LITTLEFS_FC_MEM_POOL` to relax
* the size constraints on per-file cache allocations.
*
* @param name the name for the structure. The defined object has
* file scope.
* @param read_sz see :option:`CONFIG_FS_LITTLEFS_READ_SIZE`
* @param prog_sz see :option:`CONFIG_FS_LITTLEFS_PROG_SIZE`
* @param cache_sz see :option:`CONFIG_FS_LITTLEFS_CACHE_SIZE`
* @param lookahead_sz see :option:`CONFIG_FS_LITTLEFS_LOOKAHEAD_SIZE`
*/
#define FS_LITTLEFS_DECLARE_CUSTOM_CONFIG(name, read_sz, prog_sz, cache_sz, lookahead_sz) \
static u8_t name ## _read_buffer[cache_sz]; \
static u8_t name ## _prog_buffer[cache_sz]; \
static u32_t name ## _lookahead_buffer[(lookahead_sz) / sizeof(u32_t)]; \
static struct fs_littlefs name = { \
.cfg = { \
.read_size = (read_sz), \
.prog_size = (prog_sz), \
.cache_size = (cache_sz), \
.lookahead_size = (lookahead_sz), \
.read_buffer = name ## _read_buffer, \
.prog_buffer = name ## _prog_buffer, \
.lookahead_buffer = name ## _lookahead_buffer, \
}, \
}

/** @brief Define a littlefs configuration with default characteristics.
*
* This defines static arrays and initializes the littlefs
* configuration structure to use the default size configuration
* provided by Kconfig.
*
* @param name the name for the structure. The defined object has
* file scope.
*/
#define FS_LITTLEFS_DECLARE_DEFAULT_CONFIG(name) \
FS_LITTLEFS_DECLARE_CUSTOM_CONFIG(name, \
CONFIG_FS_LITTLEFS_READ_SIZE, \
CONFIG_FS_LITTLEFS_PROG_SIZE, \
CONFIG_FS_LITTLEFS_CACHE_SIZE, \
CONFIG_FS_LITTLEFS_LOOKAHEAD_SIZE)

#ifdef __cplusplus
}
#endif
@@ -10,8 +10,10 @@
# fs_dirent structures are big.
CONFIG_MAIN_STACK_SIZE=2048

# Let __ASSERT do its job
CONFIG_DEBUG=y

CONFIG_LOG=y
#CONFIG_FS_LOG_LEVEL_DBG=y

CONFIG_FLASH=y
CONFIG_FLASH_MAP=y
@@ -17,10 +17,10 @@
/* Matches LFS_NAME_MAX */
#define MAX_PATH_LEN 255

static struct fs_littlefs lfs_storage;
FS_LITTLEFS_DECLARE_DEFAULT_CONFIG(storage);
static struct fs_mount_t lfs_storage_mnt = {
.type = FS_LITTLEFS,
.fs_data = &lfs_storage,
.fs_data = &storage,
.storage_dev = (void *)DT_FLASH_AREA_STORAGE_ID,
.mnt_point = "/lfs",
};
@@ -128,65 +128,9 @@ config NFFS_FILESYSTEM_MAX_BLOCK_SIZE

endmenu

menu "LittleFS Settings"
visible if FILE_SYSTEM_LITTLEFS

config FS_LITTLEFS_NUM_FILES
int "Maximum number of opened files"
default 4
help
This is a global maximum across all mounted littlefs filesystems.

config FS_LITTLEFS_NUM_DIRS
int "Maximum number of opened directories"
default 4
help
This is a global maximum across all mounted littlefs filesystems.

config FS_LITTLEFS_READ_SIZE
int "Minimum size of a block read"
default 16
help
All read operations will be a multiple of this value.

config FS_LITTLEFS_PROG_SIZE
int "Minimum size of a block program"
default 16
help
All program operations will be a multiple of this value.

config FS_LITTLEFS_CACHE_SIZE
int "Size of block caches in bytes"
default 64
help
Each cache buffers a portion of a block in RAM. The littlefs
needs a read cache, a program cache, and one additional cache
per file. Larger caches can improve performance by storing
more data and reducing the number of disk accesses. Must be a
multiple of the read and program sizes of the underlying flash
device, and a factor of the block size.

config FS_LITTLEFS_LOOKAHEAD_SIZE
int "Size of lookahead buffer in bytes"
default 32
help
A larger lookahead buffer increases the number of blocks found
during an allocation pass. The lookahead buffer is stored as a
compact bitmap, so each byte of RAM can track 8 blocks. Must
be a multiple of 8.

config FS_LITTLEFS_BLOCK_CYCLES
int "Number of erase cycles before moving data to another block"
default 512
help
For dynamic wear leveling, the number of erase cycles before data
is moved to another block. Set to a non-positive value to
disable leveling.

endmenu

endif # FILE_SYSTEM

source "subsys/fs/Kconfig.littlefs"
source "subsys/fs/fcb/Kconfig"
source "subsys/fs/nvs/Kconfig"

@@ -0,0 +1,95 @@
#
# Copyright (c) 2019 Bolt Innovation Management, LLC
# Copyright (c) 2019 Peter Bigot Consulting, LLC
#
# SPDX-License-Identifier: Apache-2.0
#

menu "LittleFS Settings"
visible if FILE_SYSTEM_LITTLEFS

config FS_LITTLEFS_NUM_FILES
int "Maximum number of opened files"
default 4
help
This is a global maximum across all mounted littlefs filesystems.

config FS_LITTLEFS_NUM_DIRS
int "Maximum number of opened directories"
default 4
help
This is a global maximum across all mounted littlefs filesystems.

config FS_LITTLEFS_READ_SIZE
int "Minimum size of a block read"
default 16
help
All read operations will be a multiple of this value.

config FS_LITTLEFS_PROG_SIZE
int "Minimum size of a block program"
default 16
help
All program operations will be a multiple of this value.

config FS_LITTLEFS_CACHE_SIZE
int "Size of block caches in bytes"
default 64
help
Each cache buffers a portion of a block in RAM. The littlefs
needs a read cache, a program cache, and one additional cache
per file. Larger caches can improve performance by storing
more data and reducing the number of disk accesses. Must be a
multiple of the read and program sizes of the underlying flash
device, and a factor of the block size.

config FS_LITTLEFS_LOOKAHEAD_SIZE
int "Size of lookahead buffer in bytes"
default 32
help
A larger lookahead buffer increases the number of blocks found
during an allocation pass. The lookahead buffer is stored as a
compact bitmap, so each byte of RAM can track 8 blocks. Must
be a multiple of 8.

config FS_LITTLEFS_BLOCK_CYCLES
int "Number of erase cycles before moving data to another block"
default 512
help
For dynamic wear leveling, the number of erase cycles before data
is moved to another block. Set to a non-positive value to
disable leveling.

menuconfig FS_LITTLEFS_FC_MEM_POOL
bool "Enable flexible file cache sizes for littlefs"
help
littlefs requires a per-file buffer to cache data. For
applications that use the default configuration parameters a
memory slab is reserved to support up to
FS_LITTLE_FS_NUM_FILES blocks of FS_LITTLEFS_CACHE_SIZE bytes.

When applications customize littlefs configurations and
support different cache sizes for different partitions this
preallocation is inadequate.

Select this feature to enable a memory pool allocator for
littlefs file caches.

if FS_LITTLEFS_FC_MEM_POOL

config FS_LITTLEFS_FC_MEM_POOL_MIN_SIZE
int "Minimum block size for littlefs file cache memory pool"
default 16

config FS_LITTLEFS_FC_MEM_POOL_MAX_SIZE
int "Maximum block size for littlefs file cache memory pool"
default 1024

config FS_LITTLEFS_FC_MEM_POOL_NUM_BLOCKS
int "Number of maximum sized blocks in littlefs file cache memory pool"
default 2

endif # FS_LITTLEFS_FC_MEM_POOL

endmenu

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