openharmony/third_party_littlefs
1
0
Fork 0
mirror of https://gitee.com/openharmony/third_party_littlefs synced 2024-11-27 09:01:27 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity

Fix incorrect lookahead population before ack

Browse Source 
Rather than tracking all in-flight blocks blocks during a lookahead,
littlefs uses an ack scheme to mark the first allocated block that
hasn't reached the disk yet. littlefs assumes all blocks since the
last ack are bad or in-flight, and uses this to know when it's out
of storage.

However, these unacked allocations were still being populated in the
lookahead buffer. If the whole block device fits in the lookahead
buffer, _and_ littlefs managed to scan around the whole storage while
an unacked block was still in-flight, it would assume the block was
free and misallocate it.

The fix is to only fill the lookahead buffer up to the last ack.
The internal free structure was restructured to simplify the runtime
calculation of lookahead size.
This commit is contained in:
Christopher Haster 2018-02-08 01:30:21 -06:00
parent a25743a82a
commit e611cf5050
3 changed files with 54 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

38
lfs.c
View File

@ -278,7 +278,7 @@ static int lfs_alloc_lookahead(void *p, lfs_block_t block) {
% (lfs_soff_t)(lfs->cfg->block_count))
+ lfs->cfg->block_count) % lfs->cfg->block_count;
if (off < lfs->cfg->lookahead) {
if (off < lfs->free.size) {
lfs->free.buffer[off / 32] |= 1U << (off % 32);
}
@ -287,18 +287,7 @@ static int lfs_alloc_lookahead(void *p, lfs_block_t block) {
static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
while (true) {
while (true) {
// check if we have looked at all blocks since last ack
if (lfs->free.begin + lfs->free.off == lfs->free.end) {
LFS_WARN("No more free space %d", lfs->free.end);
return LFS_ERR_NOSPC;
}
if (lfs->free.off >= lfs_min(
lfs->cfg->lookahead, lfs->cfg->block_count)) {
break;
}
while (lfs->free.off != lfs->free.size) {
lfs_block_t off = lfs->free.off;
lfs->free.off += 1;
@ -309,7 +298,15 @@ static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
}
}
lfs->free.begin += lfs_min(lfs->cfg->lookahead, lfs->cfg->block_count);
// check if we have looked at all blocks since last ack
if (lfs->free.off == lfs->free.ack - lfs->free.begin) {
LFS_WARN("No more free space %d", lfs->free.off + lfs->free.begin);
return LFS_ERR_NOSPC;
}
lfs->free.begin += lfs->free.size;
lfs->free.size = lfs_min(lfs->cfg->lookahead,
lfs->free.ack - lfs->free.begin);
lfs->free.off = 0;
// find mask of free blocks from tree
@ -322,7 +319,7 @@ static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
}
static void lfs_alloc_ack(lfs_t *lfs) {
lfs->free.end = lfs->free.begin + lfs->free.off + lfs->cfg->block_count;
lfs->free.ack = lfs->free.off-1 + lfs->free.begin + lfs->cfg->block_count;
}
@ -2035,11 +2032,11 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
// create free lookahead
memset(lfs->free.buffer, 0, lfs->cfg->lookahead/8);
lfs->free.begin = 0;
lfs->free.size = lfs_min(lfs->cfg->lookahead, lfs->cfg->block_count);
lfs->free.off = 0;
lfs->free.end = lfs->free.begin + lfs->free.off + lfs->cfg->block_count;
lfs_alloc_ack(lfs);
// create superblock dir
lfs_alloc_ack(lfs);
lfs_dir_t superdir;
err = lfs_dir_alloc(lfs, &superdir);
if (err) {
@ -2112,9 +2109,10 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
}
// setup free lookahead
lfs->free.begin = -lfs_min(lfs->cfg->lookahead, lfs->cfg->block_count);
lfs->free.off = -lfs->free.begin;
lfs->free.end = lfs->free.begin + lfs->free.off + lfs->cfg->block_count;
lfs->free.begin = 0;
lfs->free.size = 0;
lfs->free.off = 0;
lfs_alloc_ack(lfs);
// load superblock
lfs_dir_t dir;

3
lfs.h
View File

@ -260,8 +260,9 @@ typedef struct lfs_superblock {
typedef struct lfs_free {
lfs_block_t begin;
lfs_block_t end;
lfs_block_t size;
lfs_block_t off;
lfs_block_t ack;
uint32_t *buffer;
} lfs_free_t;

34
tests/test_alloc.sh
View File

@ -266,6 +266,40 @@ tests/test.py << TEST
lfs_mkdir(&lfs, "exhaustiondir2") => LFS_ERR_NOSPC;
TEST
echo "--- Split dir test ---"
rm -rf blocks
tests/test.py << TEST
lfs_format(&lfs, &cfg) => 0;
TEST
tests/test.py << TEST
lfs_mount(&lfs, &cfg) => 0;
// create one block whole for half a directory
lfs_file_open(&lfs, &file[0], "bump", LFS_O_WRONLY | LFS_O_CREAT) => 0;
lfs_file_write(&lfs, &file[0], (void*)"hi", 2) => 2;
lfs_file_close(&lfs, &file[0]) => 0;
lfs_file_open(&lfs, &file[0], "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
size = strlen("blahblahblahblah");
memcpy(buffer, "blahblahblahblah", size);
for (lfs_size_t i = 0;
i < (cfg.block_count-6)*(cfg.block_size-8);
i += size) {
lfs_file_write(&lfs, &file[0], buffer, size) => size;
}
lfs_file_close(&lfs, &file[0]) => 0;
// open whole
lfs_remove(&lfs, "bump") => 0;
lfs_mkdir(&lfs, "splitdir") => 0;
lfs_file_open(&lfs, &file[0], "splitdir/bump",
LFS_O_WRONLY | LFS_O_CREAT) => 0;
lfs_file_write(&lfs, &file[0], buffer, size) => LFS_ERR_NOSPC;
lfs_file_close(&lfs, &file[0]) => 0;
lfs_unmount(&lfs) => 0;
TEST
echo "--- Results ---"
tests/stats.py