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Added orphan bit to xored-globals

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Unfortunately for us, even with the new ability to store global state,
orphans can not be handled as gracefully as moves. This is due to the
fact that directory operations can create an unbounded number of
orphans. It's usually small, the fact that it's unbounded means we can't
store the orphan info in xored-globals.

However, one thing we can do to leverage the xored-global state is store
a bit indicating if _any_ orphans are present. This means in the common
case we can completely avoid the deorphan step, while only using a
single bit of the global state, which is effectively free since we can
store it in the globals tag itself.

If a littlefs drive does not want to consider the orphan bit, it's free
to use the previous behaviour of always checking for orphans on first
write.
This commit is contained in:
Christopher Haster
2018-07-31 08:07:36 -05:00
parent 1a58ba799c
commit 64df0a5e20
2 changed files with 221 additions and 173 deletions
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29
lfs.h
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@@ -110,7 +110,7 @@ enum lfs_type {
LFS_TYPE_TAIL = 0x0c0,
LFS_TYPE_SOFTTAIL = 0x0c0,
LFS_TYPE_HARDTAIL = 0x0c1,
LFS_TYPE_CRC = 0x0ff,
LFS_TYPE_CRC = 0x0ff, // TODO are trailing ones useful?
LFS_TYPE_INLINESTRUCT = 0x040,
LFS_TYPE_CTZSTRUCT = 0x041,
@@ -280,12 +280,9 @@ typedef struct lfs_mattr {
const struct lfs_mattr *next;
} lfs_mattr_t;
typedef struct lfs_globals {
struct lfs_move {
lfs_block_t pair[2];
uint16_t id;
} move;
} lfs_globals_t;
typedef union lfs_global {
uint16_t u16[5];
} lfs_global_t;
typedef struct lfs_mdir {
lfs_block_t pair[2];
@@ -296,7 +293,7 @@ typedef struct lfs_mdir {
uint16_t count;
bool erased;
bool split;
lfs_globals_t locals;
lfs_global_t locals;
} lfs_mdir_t;
typedef struct lfs_cache {
@@ -314,12 +311,13 @@ typedef struct lfs_file {
lfs_size_t size;
} ctz;
const struct lfs_file_config *cfg;
uint32_t flags;
lfs_off_t pos;
lfs_block_t block;
lfs_off_t off;
lfs_cache_t cache;
const struct lfs_file_config *cfg;
} lfs_file_t;
typedef struct lfs_dir {
@@ -353,21 +351,18 @@ typedef struct lfs_free {
// The littlefs type
typedef struct lfs {
const struct lfs_config *cfg;
lfs_cache_t rcache;
lfs_cache_t pcache;
lfs_block_t root[2];
lfs_file_t *files;
lfs_dir_t *dirs;
lfs_cache_t rcache;
lfs_cache_t pcache;
lfs_global_t globals;
lfs_global_t locals;
lfs_free_t free;
bool deorphaned;
lfs_globals_t globals2;
lfs_globals_t globals;
lfs_globals_t diff;
const struct lfs_config *cfg;
lfs_size_t inline_size;
lfs_size_t attr_size;
lfs_size_t name_size;