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Changed block_cycles disable from 0 to -1

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As it is now, block_cycles = 0 disables wear leveling. This was a
mistake as 0 is the "default" value for several other config options.
It's even worse when migrating from v1 as it's easy to miss the addition
of block_cycles and end up with a filesystem that is not actually
wear-leveling.

Clearly, block_cycles = 0 should do anything but disable wear-leveling.

Here, I've changed block_cycles = 0 to assert. Forcing users to set a
value for block_cycles (500 is suggested). block_cycles can be set to -1
to explicitly disable wear leveling if desired.
This commit is contained in:
Christopher Haster
2019-07-17 17:05:20 -05:00
parent abd90cb84c
commit 53a6e04712
2 changed files with 11 additions and 6 deletions
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8
lfs.c
View File

@@ -1453,7 +1453,7 @@ static int lfs_dir_compact(lfs_t *lfs,
// increment revision count
dir->rev += 1;
if (lfs->cfg->block_cycles &&
if (lfs->cfg->block_cycles > 0 &&
(dir->rev % (lfs->cfg->block_cycles+1) == 0)) {
if (lfs_pair_cmp(dir->pair, (const lfs_block_t[2]){0, 1}) == 0) {
// oh no! we're writing too much to the superblock,
@@ -3192,8 +3192,10 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
LFS_ASSERT(4*lfs_npw2(0xffffffff / (lfs->cfg->block_size-2*4))
<= lfs->cfg->block_size);
// we don't support some corner cases
LFS_ASSERT(lfs->cfg->block_cycles < 0xffffffff);
// block_cycles = 0 is no longer supported, must either set a number
// of erase cycles before moving logs to another block (~500 suggested),
// or explicitly disable wear-leveling with -1.
LFS_ASSERT(lfs->cfg->block_cycles != 0);
// setup read cache
if (lfs->cfg->read_buffer) {

9
lfs.h
View File

@@ -190,9 +190,12 @@ struct lfs_config {
// Number of erasable blocks on the device.
lfs_size_t block_count;
// Number of erase cycles before we should move data to another block.
// May be zero, in which case no block-level wear-leveling is performed.
uint32_t block_cycles;
// Number of erase cycles before we should move logs to another block.
// Suggested values are in the range 100-1000, with large values having
// better performance at the cost of less consistent wear distribution.
//
// Set to -1 to disable block-level wear-leveling.
int32_t block_cycles;
// Size of block caches. Each cache buffers a portion of a block in RAM.
// The littlefs needs a read cache, a program cache, and one additional