Merge branch 'brent-cycle-detection' into rbyd-master

This of course should never happen normally, two half-orphans requires
two parents, which is disallowed in littlefs for this reason. But it can
happen if there is an outdated half-orphan later in the metadata
linked-list. The two half-orphans can cause the deorphan step to get
stuck, constantly "fixing" the first half-orphan before it has a chance
to remove the problematic, outdated half-orphan later in the list.

The solution here is to do a full check for half-orphans before
restarting the half-orphan loop. This strategy has the potential to
visit more metadata blocks unnecessarily, but avoids situations where
removing a later half-orphan will eventually cause an earlier
half-orphan to resolve itself.

Found with heuristic powerloss testing with test_relocations_reentrant_renames
after 192 nested powerlosses.

bd/lfs_emubd.c

@@ -584,13 +584,14 @@ lfs_emubd_swear_t lfs_emubd_wear(const struct lfs_config *cfg,
         wear = 0;
     }
 
-    LFS_EMUBD_TRACE("lfs_emubd_wear -> %"PRIu32, wear);
+    LFS_EMUBD_TRACE("lfs_emubd_wear -> %"PRIi32, wear);
     return wear;
 }
 
 int lfs_emubd_setwear(const struct lfs_config *cfg,
         lfs_block_t block, lfs_emubd_wear_t wear) {
-    LFS_EMUBD_TRACE("lfs_emubd_setwear(%p, %"PRIu32")", (void*)cfg, block);
+    LFS_EMUBD_TRACE("lfs_emubd_setwear(%p, %"PRIu32", %"PRIi32")",
+            (void*)cfg, block, wear);
     lfs_emubd_t *bd = cfg->context;
 
     // check if block is valid
@@ -599,12 +600,12 @@ int lfs_emubd_setwear(const struct lfs_config *cfg,
     // set the wear
     lfs_emubd_block_t *b = lfs_emubd_mutblock(cfg, &bd->blocks[block]);
     if (!b) {
-        LFS_EMUBD_TRACE("lfs_emubd_setwear -> %"PRIu32, LFS_ERR_NOMEM);
+        LFS_EMUBD_TRACE("lfs_emubd_setwear -> %d", LFS_ERR_NOMEM);
         return LFS_ERR_NOMEM;
     }
     b->wear = wear;
 
-    LFS_EMUBD_TRACE("lfs_emubd_setwear -> %"PRIu32, 0);
+    LFS_EMUBD_TRACE("lfs_emubd_setwear -> %d", 0);
     return 0;
 }
 

lfs.c

@@ -135,14 +135,14 @@ static int lfs_bd_cmp(lfs_t *lfs,
         uint8_t dat[8];
 
         diff = lfs_min(size-i, sizeof(dat));
-        int res = lfs_bd_read(lfs,
+        int err = lfs_bd_read(lfs,
                 pcache, rcache, hint-i,
                 block, off+i, &dat, diff);
-        if (res) {
-            return res;
+        if (err) {
+            return err;
         }
 
-        res = memcmp(dat, data + i, diff);
+        int res = memcmp(dat, data + i, diff);
         if (res) {
             return res < 0 ? LFS_CMP_LT : LFS_CMP_GT;
         }
@@ -151,6 +151,27 @@ static int lfs_bd_cmp(lfs_t *lfs,
     return LFS_CMP_EQ;
 }
 
+static int lfs_bd_crc(lfs_t *lfs,
+        const lfs_cache_t *pcache, lfs_cache_t *rcache, lfs_size_t hint,
+        lfs_block_t block, lfs_off_t off, lfs_size_t size, uint32_t *crc) {
+    lfs_size_t diff = 0;
+
+    for (lfs_off_t i = 0; i < size; i += diff) {
+        uint8_t dat[8];
+        diff = lfs_min(size-i, sizeof(dat));
+        int err = lfs_bd_read(lfs,
+                pcache, rcache, hint-i,
+                block, off+i, &dat, diff);
+        if (err) {
+            return err;
+        }
+
+        *crc = lfs_crc(*crc, &dat, diff);
+    }
+
+    return 0;
+}
+
 #ifndef LFS_READONLY
 static int lfs_bd_flush(lfs_t *lfs,
         lfs_cache_t *pcache, lfs_cache_t *rcache, bool validate) {
@@ -323,6 +344,10 @@ static inline uint16_t lfs_tag_type1(lfs_tag_t tag) {
     return (tag & 0x70000000) >> 20;
 }
 
+static inline uint16_t lfs_tag_type2(lfs_tag_t tag) {
+    return (tag & 0x78000000) >> 20;
+}
+
 static inline uint16_t lfs_tag_type3(lfs_tag_t tag) {
     return (tag & 0x7ff00000) >> 20;
 }
@@ -411,6 +436,24 @@ static inline void lfs_gstate_tole32(lfs_gstate_t *a) {
 }
 #endif
 
+// operations on forward-CRCs used to track erased state
+struct lfs_fcrc {
+    lfs_size_t size;
+    uint32_t crc;
+};
+
+static void lfs_fcrc_fromle32(struct lfs_fcrc *fcrc) {
+    fcrc->size = lfs_fromle32(fcrc->size);
+    fcrc->crc = lfs_fromle32(fcrc->crc);
+}
+
+#ifndef LFS_READONLY
+static void lfs_fcrc_tole32(struct lfs_fcrc *fcrc) {
+    fcrc->size = lfs_tole32(fcrc->size);
+    fcrc->crc = lfs_tole32(fcrc->crc);
+}
+#endif
+
 // other endianness operations
 static void lfs_ctz_fromle32(struct lfs_ctz *ctz) {
     ctz->head = lfs_fromle32(ctz->head);
@@ -1033,6 +1076,11 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
         bool tempsplit = false;
         lfs_stag_t tempbesttag = besttag;
 
+        // assume not erased until proven otherwise
+        bool maybeerased = false;
+        bool hasfcrc = false;
+        struct lfs_fcrc fcrc;
+
         dir->rev = lfs_tole32(dir->rev);
         uint32_t crc = lfs_crc(0xffffffff, &dir->rev, sizeof(dir->rev));
         dir->rev = lfs_fromle32(dir->rev);
@@ -1047,7 +1095,6 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
             if (err) {
                 if (err == LFS_ERR_CORRUPT) {
                     // can't continue?
-                    dir->erased = false;
                     break;
                 }
                 return err;
@@ -1056,19 +1103,18 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
             crc = lfs_crc(crc, &tag, sizeof(tag));
             tag = lfs_frombe32(tag) ^ ptag;
 
-            // next commit not yet programmed or we're not in valid range
+            // next commit not yet programmed?
             if (!lfs_tag_isvalid(tag)) {
-                dir->erased = (lfs_tag_type1(ptag) == LFS_TYPE_CRC &&
-                        dir->off % lfs->cfg->prog_size == 0);
+                maybeerased = true;
                 break;
+            // out of range?
             } else if (off + lfs_tag_dsize(tag) > lfs->cfg->block_size) {
-                dir->erased = false;
                 break;
             }
 
             ptag = tag;
 
-            if (lfs_tag_type1(tag) == LFS_TYPE_CRC) {
+            if (lfs_tag_type2(tag) == LFS_TYPE_CCRC) {
                 // check the crc attr
                 uint32_t dcrc;
                 err = lfs_bd_read(lfs,
@@ -1076,7 +1122,6 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
                         dir->pair[0], off+sizeof(tag), &dcrc, sizeof(dcrc));
                 if (err) {
                     if (err == LFS_ERR_CORRUPT) {
-                        dir->erased = false;
                         break;
                     }
                     return err;
@@ -1084,7 +1129,6 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
                 dcrc = lfs_fromle32(dcrc);
 
                 if (crc != dcrc) {
-                    dir->erased = false;
                     break;
                 }
 
@@ -1111,21 +1155,19 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
                 continue;
             }
 
-            // crc the entry first, hopefully leaving it in the cache
-            for (lfs_off_t j = sizeof(tag); j < lfs_tag_dsize(tag); j++) {
-                uint8_t dat;
-                err = lfs_bd_read(lfs,
-                        NULL, &lfs->rcache, lfs->cfg->block_size,
-                        dir->pair[0], off+j, &dat, 1);
-                if (err) {
-                    if (err == LFS_ERR_CORRUPT) {
-                        dir->erased = false;
-                        break;
-                    }
-                    return err;
-                }
+            // fcrc is only valid when last tag was a crc
+            hasfcrc = false;
 
-                crc = lfs_crc(crc, &dat, 1);
+            // crc the entry first, hopefully leaving it in the cache
+            err = lfs_bd_crc(lfs,
+                    NULL, &lfs->rcache, lfs->cfg->block_size,
+                    dir->pair[0], off+sizeof(tag),
+                    lfs_tag_dsize(tag)-sizeof(tag), &crc);
+            if (err) {
+                if (err == LFS_ERR_CORRUPT) {
+                    break;
+                }
+                return err;
             }
 
             // directory modification tags?
@@ -1152,12 +1194,24 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
                         dir->pair[0], off+sizeof(tag), &temptail, 8);
                 if (err) {
                     if (err == LFS_ERR_CORRUPT) {
-                        dir->erased = false;
                         break;
                     }
                     return err;
                 }
                 lfs_pair_fromle32(temptail);
+            } else if (lfs_tag_type3(tag) == LFS_TYPE_FCRC) {
+                err = lfs_bd_read(lfs,
+                        NULL, &lfs->rcache, lfs->cfg->block_size,
+                        dir->pair[0], off+sizeof(tag),
+                        &fcrc, sizeof(fcrc));
+                if (err) {
+                    if (err == LFS_ERR_CORRUPT) {
+                        break;
+                    }
+                }
+
+                lfs_fcrc_fromle32(&fcrc);
+                hasfcrc = true;
             }
 
             // found a match for our fetcher?
@@ -1166,7 +1220,6 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
                         dir->pair[0], off+sizeof(tag)});
                 if (res < 0) {
                     if (res == LFS_ERR_CORRUPT) {
-                        dir->erased = false;
                         break;
                     }
                     return res;
@@ -1188,35 +1241,54 @@ static lfs_stag_t lfs_dir_fetchmatch(lfs_t *lfs,
             }
         }
 
-        // consider what we have good enough
-        if (dir->off > 0) {
-            // synthetic move
-            if (lfs_gstate_hasmovehere(&lfs->gdisk, dir->pair)) {
-                if (lfs_tag_id(lfs->gdisk.tag) == lfs_tag_id(besttag)) {
-                    besttag |= 0x80000000;
-                } else if (besttag != -1 &&
-                        lfs_tag_id(lfs->gdisk.tag) < lfs_tag_id(besttag)) {
-                    besttag -= LFS_MKTAG(0, 1, 0);
-                }
+        // found no valid commits?
+        if (dir->off == 0) {
+            // try the other block?
+            lfs_pair_swap(dir->pair);
+            dir->rev = revs[(r+1)%2];
+            continue;
+        }
+
+        // did we end on a valid commit? we may have an erased block
+        dir->erased = false;
+        if (maybeerased && hasfcrc && dir->off % lfs->cfg->prog_size == 0) {
+            // check for an fcrc matching the next prog's erased state, if
+            // this failed most likely a previous prog was interrupted, we
+            // need a new erase
+            uint32_t fcrc_ = 0xffffffff;
+            int err = lfs_bd_crc(lfs,
+                    NULL, &lfs->rcache, lfs->cfg->block_size,
+                    dir->pair[0], dir->off, fcrc.size, &fcrc_);
+            if (err && err != LFS_ERR_CORRUPT) {
+                return err;
             }
 
-            // found tag? or found best id?
-            if (id) {
-                *id = lfs_min(lfs_tag_id(besttag), dir->count);
-            }
+            // found beginning of erased part?
+            dir->erased = (fcrc_ == fcrc.crc);
+        }
 
-            if (lfs_tag_isvalid(besttag)) {
-                return besttag;
-            } else if (lfs_tag_id(besttag) < dir->count) {
-                return LFS_ERR_NOENT;
-            } else {
-                return 0;
+        // synthetic move
+        if (lfs_gstate_hasmovehere(&lfs->gdisk, dir->pair)) {
+            if (lfs_tag_id(lfs->gdisk.tag) == lfs_tag_id(besttag)) {
+                besttag |= 0x80000000;
+            } else if (besttag != -1 &&
+                    lfs_tag_id(lfs->gdisk.tag) < lfs_tag_id(besttag)) {
+                besttag -= LFS_MKTAG(0, 1, 0);
             }
         }
 
-        // failed, try the other block?
-        lfs_pair_swap(dir->pair);
-        dir->rev = revs[(r+1)%2];
+        // found tag? or found best id?
+        if (id) {
+            *id = lfs_min(lfs_tag_id(besttag), dir->count);
+        }
+
+        if (lfs_tag_isvalid(besttag)) {
+            return besttag;
+        } else if (lfs_tag_id(besttag) < dir->count) {
+            return LFS_ERR_NOENT;
+        } else {
+            return 0;
+        }
     }
 
     LFS_ERROR("Corrupted dir pair at {0x%"PRIx32", 0x%"PRIx32"}",
@@ -1490,9 +1562,15 @@ static int lfs_dir_commitattr(lfs_t *lfs, struct lfs_commit *commit,
 #endif
 
 #ifndef LFS_READONLY
+
 static int lfs_dir_commitcrc(lfs_t *lfs, struct lfs_commit *commit) {
     // align to program units
-    const lfs_off_t end = lfs_alignup(commit->off + 2*sizeof(uint32_t),
+    //
+    // this gets a bit complex as we have two types of crcs:
+    // - 5-word crc with fcrc to check following prog (middle of block)
+    // - 2-word crc with no following prog (end of block)
+    const lfs_off_t end = lfs_alignup(
+            lfs_min(commit->off + 5*sizeof(uint32_t), lfs->cfg->block_size),
             lfs->cfg->prog_size);
 
     lfs_off_t off1 = 0;
@@ -1502,89 +1580,116 @@ static int lfs_dir_commitcrc(lfs_t *lfs, struct lfs_commit *commit) {
     // padding is not crced, which lets fetches skip padding but
     // makes committing a bit more complicated
     while (commit->off < end) {
-        lfs_off_t off = commit->off + sizeof(lfs_tag_t);
-        lfs_off_t noff = lfs_min(end - off, 0x3fe) + off;
+        lfs_off_t noff = (
+                lfs_min(end - (commit->off+sizeof(lfs_tag_t)), 0x3fe)
+                + (commit->off+sizeof(lfs_tag_t)));
+        // too large for crc tag? need padding commits
         if (noff < end) {
-            noff = lfs_min(noff, end - 2*sizeof(uint32_t));
+            noff = lfs_min(noff, end - 5*sizeof(uint32_t));
         }
 
-        // read erased state from next program unit
-        lfs_tag_t tag = 0xffffffff;
-        int err = lfs_bd_read(lfs,
-                NULL, &lfs->rcache, sizeof(tag),
-                commit->block, noff, &tag, sizeof(tag));
-        if (err && err != LFS_ERR_CORRUPT) {
-            return err;
+        // space for fcrc?
+        uint8_t eperturb = -1;
+        if (noff >= end && noff <= lfs->cfg->block_size - lfs->cfg->prog_size) {
+            // first read the leading byte, this always contains a bit
+            // we can perturb to avoid writes that don't change the fcrc
+            int err = lfs_bd_read(lfs,
+                    NULL, &lfs->rcache, lfs->cfg->prog_size,
+                    commit->block, noff, &eperturb, 1);
+            if (err && err != LFS_ERR_CORRUPT) {
+                return err;
+            }
+
+            // find the expected fcrc, don't bother avoiding a reread
+            // of the eperturb, it should still be in our cache
+            struct lfs_fcrc fcrc = {.size=lfs->cfg->prog_size, .crc=0xffffffff};
+            err = lfs_bd_crc(lfs,
+                    NULL, &lfs->rcache, lfs->cfg->prog_size,
+                    commit->block, noff, fcrc.size, &fcrc.crc);
+            if (err && err != LFS_ERR_CORRUPT) {
+                return err;
+            }
+
+            lfs_fcrc_tole32(&fcrc);
+            err = lfs_dir_commitattr(lfs, commit,
+                    LFS_MKTAG(LFS_TYPE_FCRC, 0x3ff, sizeof(struct lfs_fcrc)),
+                    &fcrc);
+            if (err) {
+                return err;
+            }
         }
 
-        // build crc tag
-        bool reset = ~lfs_frombe32(tag) >> 31;
-        tag = LFS_MKTAG(LFS_TYPE_CRC + reset, 0x3ff, noff - off);
+        // build commit crc
+        struct {
+            lfs_tag_t tag;
+            uint32_t crc;
+        } ccrc;
+        lfs_tag_t ntag = LFS_MKTAG(
+                LFS_TYPE_CCRC + (((uint8_t)~eperturb) >> 7), 0x3ff,
+                noff - (commit->off+sizeof(lfs_tag_t)));
+        ccrc.tag = lfs_tobe32(ntag ^ commit->ptag);
+        commit->crc = lfs_crc(commit->crc, &ccrc.tag, sizeof(lfs_tag_t));
+        ccrc.crc = lfs_tole32(commit->crc);
 
-        // write out crc
-        uint32_t footer[2];
-        footer[0] = lfs_tobe32(tag ^ commit->ptag);
-        commit->crc = lfs_crc(commit->crc, &footer[0], sizeof(footer[0]));
-        footer[1] = lfs_tole32(commit->crc);
-        err = lfs_bd_prog(lfs,
+        int err = lfs_bd_prog(lfs,
                 &lfs->pcache, &lfs->rcache, false,
-                commit->block, commit->off, &footer, sizeof(footer));
+                commit->block, commit->off, &ccrc, sizeof(ccrc));
         if (err) {
             return err;
         }
 
         // keep track of non-padding checksum to verify
         if (off1 == 0) {
-            off1 = commit->off + sizeof(uint32_t);
+            off1 = commit->off + sizeof(lfs_tag_t);
             crc1 = commit->crc;
         }
 
-        commit->off += sizeof(tag)+lfs_tag_size(tag);
-        commit->ptag = tag ^ ((lfs_tag_t)reset << 31);
-        commit->crc = 0xffffffff; // reset crc for next "commit"
+        commit->off = noff;
+        // perturb valid bit?
+        commit->ptag = ntag ^ ((0x80 & ~eperturb) << 24);
+        // reset crc for next commit
+        commit->crc = 0xffffffff;
+
+        // manually flush here since we don't prog the padding, this confuses
+        // the caching layer
+        if (noff >= end || noff >= lfs->pcache.off + lfs->cfg->cache_size) {
+            // flush buffers
+            int err = lfs_bd_sync(lfs, &lfs->pcache, &lfs->rcache, false);
+            if (err) {
+                return err;
+            }
+        }
     }
 
-    // flush buffers
-    int err = lfs_bd_sync(lfs, &lfs->pcache, &lfs->rcache, false);
+    // successful commit, check checksums to make sure
+    //
+    // note that we don't need to check padding commits, worst
+    // case if they are corrupted we would have had to compact anyways
+    lfs_off_t off = commit->begin;
+    uint32_t crc = 0xffffffff;
+    int err = lfs_bd_crc(lfs,
+            NULL, &lfs->rcache, off1+sizeof(uint32_t),
+            commit->block, off, off1-off, &crc);
     if (err) {
         return err;
     }
 
-    // successful commit, check checksums to make sure
-    lfs_off_t off = commit->begin;
-    lfs_off_t noff = off1;
-    while (off < end) {
-        uint32_t crc = 0xffffffff;
-        for (lfs_off_t i = off; i < noff+sizeof(uint32_t); i++) {
-            // check against written crc, may catch blocks that
-            // become readonly and match our commit size exactly
-            if (i == off1 && crc != crc1) {
-                return LFS_ERR_CORRUPT;
-            }
+    // check non-padding commits against known crc
+    if (crc != crc1) {
+        return LFS_ERR_CORRUPT;
+    }
 
-            // leave it up to caching to make this efficient
-            uint8_t dat;
-            err = lfs_bd_read(lfs,
-                    NULL, &lfs->rcache, noff+sizeof(uint32_t)-i,
-                    commit->block, i, &dat, 1);
-            if (err) {
-                return err;
-            }
+    // make sure to check crc in case we happen to pick
+    // up an unrelated crc (frozen block?)
+    err = lfs_bd_crc(lfs,
+            NULL, &lfs->rcache, sizeof(uint32_t),
+            commit->block, off1, sizeof(uint32_t), &crc);
+    if (err) {
+        return err;
+    }
 
-            crc = lfs_crc(crc, &dat, 1);
-        }
-
-        // detected write error?
-        if (crc != 0) {
-            return LFS_ERR_CORRUPT;
-        }
-
-        // skip padding
-        off = lfs_min(end - noff, 0x3fe) + noff;
-        if (off < end) {
-            off = lfs_min(off, end - 2*sizeof(uint32_t));
-        }
-        noff = off + sizeof(uint32_t);
+    if (crc != 0) {
+        return LFS_ERR_CORRUPT;
     }
 
     return 0;
@@ -4468,7 +4573,8 @@ static lfs_stag_t lfs_fs_parent(lfs_t *lfs, const lfs_block_t pair[2],
 
 #ifndef LFS_READONLY
 static int lfs_fs_preporphans(lfs_t *lfs, int8_t orphans) {
-    LFS_ASSERT(lfs_tag_size(lfs->gstate.tag) > 0 || orphans >= 0);
+    LFS_ASSERT(lfs_tag_size(lfs->gstate.tag) > 0x000 || orphans >= 0);
+    LFS_ASSERT(lfs_tag_size(lfs->gstate.tag) < 0x3ff || orphans <= 0);
     lfs->gstate.tag += orphans;
     lfs->gstate.tag = ((lfs->gstate.tag & ~LFS_MKTAG(0x800, 0, 0)) |
             ((uint32_t)lfs_gstate_hasorphans(&lfs->gstate) << 31));
@@ -4499,6 +4605,10 @@ static int lfs_fs_demove(lfs_t *lfs) {
             lfs->gdisk.pair[1],
             lfs_tag_id(lfs->gdisk.tag));
 
+    // no other gstate is supported at this time, so if we found something else
+    // something most likely went wrong in gstate calculation
+    LFS_ASSERT(lfs_tag_type3(lfs->gdisk.tag) == LFS_TYPE_DELETE);
+
     // fetch and delete the moved entry
     lfs_mdir_t movedir;
     int err = lfs_dir_fetch(lfs, &movedir, lfs->gdisk.pair);
@@ -4527,7 +4637,6 @@ static int lfs_fs_deorphan(lfs_t *lfs, bool powerloss) {
 
     int8_t found = 0;
 
-restart:
     // Check for orphans in two separate passes:
     // - 1 for half-orphans (relocations)
     // - 2 for full-orphans (removes/renames)
@@ -4536,10 +4645,12 @@ restart:
     // references to full-orphans, effectively hiding them from the deorphan
     // search.
     //
-    for (int pass = 0; pass < 2; pass++) {
+    int pass = 0;
+    while (pass < 2) {
         // Fix any orphans
         lfs_mdir_t pdir = {.split = true, .tail = {0, 1}};
         lfs_mdir_t dir;
+        bool moreorphans = false;
 
         // iterate over all directory directory entries
         while (!lfs_pair_isnull(pdir.tail)) {
@@ -4600,7 +4711,7 @@ restart:
 
                         // did our commit create more orphans?
                         if (state == LFS_OK_ORPHANED) {
-                            goto restart;
+                            moreorphans = true;
                         }
 
                         // refetch tail
@@ -4636,7 +4747,7 @@ restart:
 
                     // did our commit create more orphans?
                     if (state == LFS_OK_ORPHANED) {
-                        goto restart;
+                        moreorphans = true;
                     }
 
                     // refetch tail
@@ -4646,6 +4757,8 @@ restart:
 
             pdir = dir;
         }
+
+        pass = moreorphans ? 0 : pass+1;
     }
 
     // mark orphans as fixed

lfs.h

@@ -112,6 +112,8 @@ enum lfs_type {
     LFS_TYPE_SOFTTAIL       = 0x600,
     LFS_TYPE_HARDTAIL       = 0x601,
     LFS_TYPE_MOVESTATE      = 0x7ff,
+    LFS_TYPE_CCRC           = 0x500,
+    LFS_TYPE_FCRC           = 0x5ff,
 
     // internal chip sources
     LFS_FROM_NOOP           = 0x000,

scripts/readmdir.py

@@ -24,6 +24,8 @@ TAG_TYPES = {
     'gstate':       (0x700, 0x700),
     'movestate':    (0x7ff, 0x7ff),
     'crc':          (0x700, 0x500),
+    'ccrc':         (0x780, 0x500),
+    'fcrc':         (0x7ff, 0x5ff),
 }
 
 class Tag:
@@ -99,7 +101,16 @@ class Tag:
         return struct.unpack('b', struct.pack('B', self.chunk))[0]
 
     def is_(self, type):
-        return (self.type & TAG_TYPES[type][0]) == TAG_TYPES[type][1]
+        try:
+            if ' ' in type:
+                type1, type3 = type.split()
+                return (self.is_(type1) and
+                    (self.type & ~TAG_TYPES[type1][0]) == int(type3, 0))
+
+            return self.type == int(type, 0)
+
+        except (ValueError, KeyError):
+            return (self.type & TAG_TYPES[type][0]) == TAG_TYPES[type][1]
 
     def mkmask(self):
         return Tag(
@@ -109,14 +120,20 @@ class Tag:
 
     def chid(self, nid):
         ntag = Tag(self.type, nid, self.size)
-        if hasattr(self, 'off'):  ntag.off  = self.off
-        if hasattr(self, 'data'): ntag.data = self.data
-        if hasattr(self, 'crc'):  ntag.crc  = self.crc
+        if hasattr(self, 'off'):    ntag.off    = self.off
+        if hasattr(self, 'data'):   ntag.data   = self.data
+        if hasattr(self, 'ccrc'):   ntag.crc    = self.crc
+        if hasattr(self, 'erased'): ntag.erased = self.erased
         return ntag
 
     def typerepr(self):
-        if self.is_('crc') and getattr(self, 'crc', 0xffffffff) != 0xffffffff:
-            return 'crc (bad)'
+        if (self.is_('ccrc')
+                and getattr(self, 'ccrc', 0xffffffff) != 0xffffffff):
+            crc_status = ' (bad)'
+        elif self.is_('fcrc') and getattr(self, 'erased', False):
+            crc_status = ' (era)'
+        else:
+            crc_status = ''
 
         reverse_types = {v: k for k, v in TAG_TYPES.items()}
         for prefix in range(12):
@@ -124,12 +141,12 @@ class Tag:
             if (mask, self.type & mask) in reverse_types:
                 type = reverse_types[mask, self.type & mask]
                 if prefix > 0:
-                    return '%s %#0*x' % (
-                        type, prefix//4, self.type & ((1 << prefix)-1))
+                    return '%s %#x%s' % (
+                        type, self.type & ((1 << prefix)-1), crc_status)
                 else:
-                    return type
+                    return '%s%s' % (type, crc_status)
         else:
-            return '%02x' % self.type
+            return '%02x%s' % (self.type, crc_status)
 
     def idrepr(self):
         return repr(self.id) if self.id != 0x3ff else '.'
@@ -172,6 +189,8 @@ class MetadataPair:
 
         self.rev, = struct.unpack('<I', block[0:4])
         crc = binascii.crc32(block[0:4])
+        fcrctag = None
+        fcrcdata = None
 
         # parse tags
         corrupt = False
@@ -182,11 +201,11 @@ class MetadataPair:
         while len(block) - off >= 4:
             ntag, = struct.unpack('>I', block[off:off+4])
 
-            tag = Tag(int(tag) ^ ntag)
+            tag = Tag((int(tag) ^ ntag) & 0x7fffffff)
             tag.off = off + 4
             tag.data = block[off+4:off+tag.dsize]
-            if tag.is_('crc'):
-                crc = binascii.crc32(block[off:off+4+4], crc)
+            if tag.is_('ccrc'):
+                crc = binascii.crc32(block[off:off+2*4], crc)
             else:
                 crc = binascii.crc32(block[off:off+tag.dsize], crc)
             tag.crc = crc
@@ -194,16 +213,29 @@ class MetadataPair:
 
             self.all_.append(tag)
 
-            if tag.is_('crc'):
+            if tag.is_('fcrc') and len(tag.data) == 8:
+                fcrctag = tag
+                fcrcdata = struct.unpack('<II', tag.data)
+            elif tag.is_('ccrc'):
                 # is valid commit?
                 if crc != 0xffffffff:
                     corrupt = True
                 if not corrupt:
                     self.log = self.all_.copy()
+                    # end of commit?
+                    if fcrcdata:
+                        fcrcsize, fcrc = fcrcdata
+                        fcrc_ = 0xffffffff ^ binascii.crc32(
+                            block[off:off+fcrcsize])
+                        if fcrc_ == fcrc:
+                            fcrctag.erased = True
+                            corrupt = True
 
                 # reset tag parsing
                 crc = 0
                 tag = Tag(int(tag) ^ ((tag.type & 1) << 31))
+                fcrctag = None
+                fcrcdata = None
 
         # find active ids
         self.ids = list(it.takewhile(
@@ -280,7 +312,7 @@ class MetadataPair:
         f.write('\n')
 
         for tag in tags:
-            f.write("%08x: %08x  %-13s %4s %4s" % (
+            f.write("%08x: %08x  %-14s %3s %4s" % (
                 tag.off, tag,
                 tag.typerepr(), tag.idrepr(), tag.sizerepr()))
             if truncate:

tests/test_powerloss.toml

@@ -0,0 +1,182 @@
+# There are already a number of tests that test general operations under
+# power-loss (see the reentrant attribute). These tests are for explicitly
+# testing specific corner cases.
+
+# only a revision count
+[cases.test_powerloss_only_rev]
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+
+    lfs_mount(&lfs, cfg) => 0;
+    lfs_mkdir(&lfs, "notebook") => 0;
+    lfs_file_t file;
+    lfs_file_open(&lfs, &file, "notebook/paper",
+            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
+    char buffer[256];
+    strcpy(buffer, "hello");
+    lfs_size_t size = strlen("hello");
+    for (int i = 0; i < 5; i++) {
+        lfs_file_write(&lfs, &file, buffer, size) => size;
+        lfs_file_sync(&lfs, &file) => 0;
+    }
+    lfs_file_close(&lfs, &file) => 0;
+
+    char rbuffer[256];
+    lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
+    for (int i = 0; i < 5; i++) {
+        lfs_file_read(&lfs, &file, rbuffer, size) => size;
+        assert(memcmp(rbuffer, buffer, size) == 0);
+    }
+    lfs_file_close(&lfs, &file) => 0;
+    lfs_unmount(&lfs) => 0;
+
+    // get pair/rev count
+    lfs_mount(&lfs, cfg) => 0;
+    lfs_dir_t dir;
+    lfs_dir_open(&lfs, &dir, "notebook") => 0;
+    lfs_block_t pair[2] = {dir.m.pair[0], dir.m.pair[1]};
+    uint32_t rev = dir.m.rev;
+    lfs_dir_close(&lfs, &dir) => 0;
+    lfs_unmount(&lfs) => 0;
+
+    // write just the revision count
+    uint8_t bbuffer[BLOCK_SIZE];
+    cfg->read(cfg, pair[1], 0, bbuffer, BLOCK_SIZE) => 0;
+
+    memcpy(bbuffer, &(uint32_t){lfs_tole32(rev+1)}, sizeof(uint32_t));
+
+    cfg->erase(cfg, pair[1]) => 0;
+    cfg->prog(cfg, pair[1], 0, bbuffer, BLOCK_SIZE) => 0;
+
+    lfs_mount(&lfs, cfg) => 0;
+
+    // can read?
+    lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
+    for (int i = 0; i < 5; i++) {
+        lfs_file_read(&lfs, &file, rbuffer, size) => size;
+        assert(memcmp(rbuffer, buffer, size) == 0);
+    }
+    lfs_file_close(&lfs, &file) => 0;
+
+    // can write?
+    lfs_file_open(&lfs, &file, "notebook/paper",
+            LFS_O_WRONLY | LFS_O_APPEND) => 0;
+    strcpy(buffer, "goodbye");
+    size = strlen("goodbye");
+    for (int i = 0; i < 5; i++) {
+        lfs_file_write(&lfs, &file, buffer, size) => size;
+        lfs_file_sync(&lfs, &file) => 0;
+    }
+    lfs_file_close(&lfs, &file) => 0;
+
+    lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
+    strcpy(buffer, "hello");
+    size = strlen("hello");
+    for (int i = 0; i < 5; i++) {
+        lfs_file_read(&lfs, &file, rbuffer, size) => size;
+        assert(memcmp(rbuffer, buffer, size) == 0);
+    }
+    strcpy(buffer, "goodbye");
+    size = strlen("goodbye");
+    for (int i = 0; i < 5; i++) {
+        lfs_file_read(&lfs, &file, rbuffer, size) => size;
+        assert(memcmp(rbuffer, buffer, size) == 0);
+    }
+    lfs_file_close(&lfs, &file) => 0;
+
+    lfs_unmount(&lfs) => 0;
+'''
+
+# partial prog, may not be byte in order!
+[cases.test_powerloss_partial_prog]
+if = "PROG_SIZE < BLOCK_SIZE"
+defines.BYTE_OFF = ["0", "PROG_SIZE-1", "PROG_SIZE/2"]
+defines.BYTE_VALUE = [0x33, 0xcc]
+in = "lfs.c"
+code = '''
+    lfs_t lfs;
+    lfs_format(&lfs, cfg) => 0;
+
+    lfs_mount(&lfs, cfg) => 0;
+    lfs_mkdir(&lfs, "notebook") => 0;
+    lfs_file_t file;
+    lfs_file_open(&lfs, &file, "notebook/paper",
+            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
+    char buffer[256];
+    strcpy(buffer, "hello");
+    lfs_size_t size = strlen("hello");
+    for (int i = 0; i < 5; i++) {
+        lfs_file_write(&lfs, &file, buffer, size) => size;
+        lfs_file_sync(&lfs, &file) => 0;
+    }
+    lfs_file_close(&lfs, &file) => 0;
+
+    char rbuffer[256];
+    lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
+    for (int i = 0; i < 5; i++) {
+        lfs_file_read(&lfs, &file, rbuffer, size) => size;
+        assert(memcmp(rbuffer, buffer, size) == 0);
+    }
+    lfs_file_close(&lfs, &file) => 0;
+    lfs_unmount(&lfs) => 0;
+
+    // imitate a partial prog, value should not matter, if littlefs
+    // doesn't notice the partial prog testbd will assert
+
+    // get offset to next prog
+    lfs_mount(&lfs, cfg) => 0;
+    lfs_dir_t dir;
+    lfs_dir_open(&lfs, &dir, "notebook") => 0;
+    lfs_block_t block = dir.m.pair[0];
+    lfs_off_t off = dir.m.off;
+    lfs_dir_close(&lfs, &dir) => 0;
+    lfs_unmount(&lfs) => 0;
+
+    // tweak byte
+    uint8_t bbuffer[BLOCK_SIZE];
+    cfg->read(cfg, block, 0, bbuffer, BLOCK_SIZE) => 0;
+
+    bbuffer[off + BYTE_OFF] = BYTE_VALUE;
+
+    cfg->erase(cfg, block) => 0;
+    cfg->prog(cfg, block, 0, bbuffer, BLOCK_SIZE) => 0;
+
+    lfs_mount(&lfs, cfg) => 0;
+
+    // can read?
+    lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
+    for (int i = 0; i < 5; i++) {
+        lfs_file_read(&lfs, &file, rbuffer, size) => size;
+        assert(memcmp(rbuffer, buffer, size) == 0);
+    }
+    lfs_file_close(&lfs, &file) => 0;
+
+    // can write?
+    lfs_file_open(&lfs, &file, "notebook/paper",
+            LFS_O_WRONLY | LFS_O_APPEND) => 0;
+    strcpy(buffer, "goodbye");
+    size = strlen("goodbye");
+    for (int i = 0; i < 5; i++) {
+        lfs_file_write(&lfs, &file, buffer, size) => size;
+        lfs_file_sync(&lfs, &file) => 0;
+    }
+    lfs_file_close(&lfs, &file) => 0;
+
+    lfs_file_open(&lfs, &file, "notebook/paper", LFS_O_RDONLY) => 0;
+    strcpy(buffer, "hello");
+    size = strlen("hello");
+    for (int i = 0; i < 5; i++) {
+        lfs_file_read(&lfs, &file, rbuffer, size) => size;
+        assert(memcmp(rbuffer, buffer, size) == 0);
+    }
+    strcpy(buffer, "goodbye");
+    size = strlen("goodbye");
+    for (int i = 0; i < 5; i++) {
+        lfs_file_read(&lfs, &file, rbuffer, size) => size;
+        assert(memcmp(rbuffer, buffer, size) == 0);
+    }
+    lfs_file_close(&lfs, &file) => 0;
+
+    lfs_unmount(&lfs) => 0;
+'''