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Merge pull request #487 from littlefs-project/fix-alloc-reset-modulus

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Fix several wear-leveling issues found in lfs_alloc_reset
This commit is contained in:
Christopher Haster
2020-12-03 22:33:47 -06:00
committed by GitHub
parent 1dc6ae94b9 0aba71d0d6
commit e273a82679
2 changed files with 27 additions and 14 deletions
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39
lfs.c
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@@ -452,14 +452,16 @@ static int lfs_alloc_lookahead(void *p, lfs_block_t block) {
return 0; return 0;
} }
// indicate allocated blocks have been committed into the filesystem, this
// is to prevent blocks from being garbage collected in the middle of a
// commit operation
static void lfs_alloc_ack(lfs_t *lfs) { static void lfs_alloc_ack(lfs_t *lfs) {
lfs->free.ack = lfs->cfg->block_count; lfs->free.ack = lfs->cfg->block_count;
} }
// Invalidate the lookahead buffer. This is done during mounting and // drop the lookahead buffer, this is done during mounting and failed
// failed traversals // traversals in order to avoid invalid lookahead state
static void lfs_alloc_reset(lfs_t *lfs) { static void lfs_alloc_drop(lfs_t *lfs) {
lfs->free.off = lfs->seed % lfs->cfg->block_size;
lfs->free.size = 0; lfs->free.size = 0;
lfs->free.i = 0; lfs->free.i = 0;
lfs_alloc_ack(lfs); lfs_alloc_ack(lfs);
@@ -505,7 +507,7 @@ static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
memset(lfs->free.buffer, 0, lfs->cfg->lookahead_size); memset(lfs->free.buffer, 0, lfs->cfg->lookahead_size);
int err = lfs_fs_traverseraw(lfs, lfs_alloc_lookahead, lfs, true); int err = lfs_fs_traverseraw(lfs, lfs_alloc_lookahead, lfs, true);
if (err) { if (err) {
lfs_alloc_reset(lfs); lfs_alloc_drop(lfs);
return err; return err;
} }
} }
@@ -870,8 +872,10 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
ptag ^= (lfs_tag_t)(lfs_tag_chunk(tag) & 1U) << 31; ptag ^= (lfs_tag_t)(lfs_tag_chunk(tag) & 1U) << 31;
// toss our crc into the filesystem seed for // toss our crc into the filesystem seed for
// pseudorandom numbers // pseudorandom numbers, note we use another crc here
lfs->seed ^= crc; // as a collection function because it is sufficiently
// random and convenient
lfs->seed = lfs_crc(lfs->seed, &crc, sizeof(crc));
// update with what's found so far // update with what's found so far
besttag = tempbesttag; besttag = tempbesttag;
@@ -1261,12 +1265,13 @@ static int lfs_dir_commitattr(lfs_t *lfs, struct lfs_commit *commit,
} }
static int lfs_dir_commitcrc(lfs_t *lfs, struct lfs_commit *commit) { static int lfs_dir_commitcrc(lfs_t *lfs, struct lfs_commit *commit) {
const lfs_off_t off1 = commit->off;
const uint32_t crc1 = commit->crc;
// align to program units // align to program units
const lfs_off_t end = lfs_alignup(off1 + 2*sizeof(uint32_t), const lfs_off_t end = lfs_alignup(commit->off + 2*sizeof(uint32_t),
lfs->cfg->prog_size); lfs->cfg->prog_size);
lfs_off_t off1 = 0;
uint32_t crc1 = 0;
// create crc tags to fill up remainder of commit, note that // create crc tags to fill up remainder of commit, note that
// padding is not crced, which lets fetches skip padding but // padding is not crced, which lets fetches skip padding but
// makes committing a bit more complicated // makes committing a bit more complicated
@@ -1302,6 +1307,12 @@ static int lfs_dir_commitcrc(lfs_t *lfs, struct lfs_commit *commit) {
return err; return err;
} }
// keep track of non-padding checksum to verify
if (off1 == 0) {
off1 = commit->off + sizeof(uint32_t);
crc1 = commit->crc;
}
commit->off += sizeof(tag)+lfs_tag_size(tag); commit->off += sizeof(tag)+lfs_tag_size(tag);
commit->ptag = tag ^ ((lfs_tag_t)reset << 31); commit->ptag = tag ^ ((lfs_tag_t)reset << 31);
commit->crc = 0xffffffff; // reset crc for next "commit" commit->crc = 0xffffffff; // reset crc for next "commit"
@@ -1315,7 +1326,7 @@ static int lfs_dir_commitcrc(lfs_t *lfs, struct lfs_commit *commit) {
// successful commit, check checksums to make sure // successful commit, check checksums to make sure
lfs_off_t off = commit->begin; lfs_off_t off = commit->begin;
lfs_off_t noff = off1 + sizeof(uint32_t); lfs_off_t noff = off1;
while (off < end) { while (off < end) {
uint32_t crc = 0xffffffff; uint32_t crc = 0xffffffff;
for (lfs_off_t i = off; i < noff+sizeof(uint32_t); i++) { for (lfs_off_t i = off; i < noff+sizeof(uint32_t); i++) {
@@ -3797,8 +3808,10 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
lfs->gstate.tag += !lfs_tag_isvalid(lfs->gstate.tag); lfs->gstate.tag += !lfs_tag_isvalid(lfs->gstate.tag);
lfs->gdisk = lfs->gstate; lfs->gdisk = lfs->gstate;
// setup free lookahead // setup free lookahead, to distribute allocations uniformly across
lfs_alloc_reset(lfs); // boots, we start the allocator at a random location
lfs->free.off = lfs->seed % lfs->cfg->block_count;
lfs_alloc_drop(lfs);
LFS_TRACE("lfs_mount -> %d", 0); LFS_TRACE("lfs_mount -> %d", 0);
return 0; return 0;

2
scripts/readtree.py
View File

@@ -106,7 +106,7 @@ def main(args):
struct.unpack('<HH', superblock[1].data[0:4].ljust(4, b'\xff')))) struct.unpack('<HH', superblock[1].data[0:4].ljust(4, b'\xff'))))
print("%-47s%s" % ("littlefs v%s.%s" % version, print("%-47s%s" % ("littlefs v%s.%s" % version,
"data (truncated, if it fits)" "data (truncated, if it fits)"
if not any([args.no_truncate, args.tags, args.log, args.all]) else "")) if not any([args.no_truncate, args.log, args.all]) else ""))
# print gstate # print gstate
print("gstate 0x%s" % ''.join('%02x' % c for c in gstate)) print("gstate 0x%s" % ''.join('%02x' % c for c in gstate))