Fixed lookahead overflow and removed unbounded lookahead pointers

As pointed out by davidefer, the lookahead pointer modular arithmetic
does not work around integer overflow when the pointer size is not a
multiple of the block count.

To avoid overflow problems, the easy solution is to stop trying to
work around integer overflows and keep the lookahead offset inside the
block device. To make this work, the ack was modified into a resetable
counter that is decremented every block allocation.

As a plus, quite a bit of the allocation logic ended up simplified.

.travis.yml

@@ -35,7 +35,7 @@ script:
     if [ "$TRAVIS_TEST_RESULT" -eq 0 ]
     then
         CURR=$(tail -n1 sizes | awk '{print $1}')
-        PREV=$(curl https://api.github.com/repos/$TRAVIS_REPO_SLUG/status/master \
+        PREV=$(curl -u $GEKY_BOT_STATUSES https://api.github.com/repos/$TRAVIS_REPO_SLUG/status/master \
             | jq -re "select(.sha != \"$TRAVIS_COMMIT\")
                 | .statuses[] | select(.context == \"$STAGE/$NAME\").description
                 | capture(\"code size is (?<size>[0-9]+)\").size" \
@@ -165,7 +165,8 @@ jobs:
                     \"name\": \"$LFS_VERSION\"
                 }"
             RELEASE=$(
-                curl -f https://api.github.com/repos/$TRAVIS_REPO_SLUG/releases/tags/$LFS_VERSION
+                curl -f -u $GEKY_BOT_RELEASES \
+                    https://api.github.com/repos/$TRAVIS_REPO_SLUG/releases/tags/$LFS_VERSION
             )
             CHANGES=$(
                 git log --oneline $LFS_PREV_VERSION.. --grep='^Merge' --invert-grep

Makefile

@@ -33,8 +33,8 @@ size: $(OBJ)
 	$(SIZE) -t $^
 
 .SUFFIXES:
-test: test_format test_dirs test_files test_seek test_truncate test_parallel \
-	test_alloc test_paths test_orphan test_move test_corrupt
+test: test_format test_dirs test_files test_seek test_truncate \
+	test_interspersed test_alloc test_paths test_orphan test_move test_corrupt
 test_%: tests/test_%.sh
 ifdef QUIET
 	@./$< | sed -n '/^[-=]/p'

lfs.c

@@ -270,8 +270,7 @@ int lfs_deorphan(lfs_t *lfs);
 static int lfs_alloc_lookahead(void *p, lfs_block_t block) {
     lfs_t *lfs = p;
 
-    lfs_block_t off = (((lfs_soff_t)(block - lfs->free.begin)
-                % (lfs_soff_t)(lfs->cfg->block_count))
+    lfs_block_t off = ((block - lfs->free.off)
             + lfs->cfg->block_count) % lfs->cfg->block_count;
 
     if (off < lfs->free.size) {
@@ -283,27 +282,39 @@ 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 (lfs->free.off != lfs->free.size) {
-            lfs_block_t off = lfs->free.off;
-            lfs->free.off += 1;
+        while (lfs->free.i != lfs->free.size) {
+            lfs_block_t off = lfs->free.i;
+            lfs->free.i += 1;
+            lfs->free.ack -= 1;
 
             if (!(lfs->free.buffer[off / 32] & (1U << (off % 32)))) {
                 // found a free block
-                *block = (lfs->free.begin + off) % lfs->cfg->block_count;
+                *block = (lfs->free.off + off) % lfs->cfg->block_count;
+
+                // eagerly find next off so an alloc ack can
+                // discredit old lookahead blocks
+                while (lfs->free.i != lfs->free.size &&
+                        (lfs->free.buffer[lfs->free.i / 32]
+                            & (1U << (lfs->free.i % 32)))) {
+                    lfs->free.i += 1;
+                    lfs->free.ack -= 1;
+                }
+
                 return 0;
             }
         }
 
         // 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);
+        //if (lfs->free.i == lfs->free.ack - lfs->free.off) {
+        if (lfs->free.ack == 0) {
+            LFS_WARN("No more free space %d", lfs->free.i + lfs->free.off);
             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;
+        lfs->free.off = (lfs->free.off + lfs->free.size)
+                % lfs->cfg->block_count;
+        lfs->free.size = lfs_min(lfs->cfg->lookahead, lfs->free.ack);
+        lfs->free.i = 0;
 
         // find mask of free blocks from tree
         memset(lfs->free.buffer, 0, lfs->cfg->lookahead/8);
@@ -315,7 +326,7 @@ static int lfs_alloc(lfs_t *lfs, lfs_block_t *block) {
 }
 
 static void lfs_alloc_ack(lfs_t *lfs) {
-    lfs->free.ack = lfs->free.off-1 + lfs->free.begin + lfs->cfg->block_count;
+    lfs->free.ack = lfs->cfg->block_count;
 }
 
 
@@ -386,6 +397,10 @@ static inline bool lfs_pairsync(
            (paira[0] == pairb[1] && paira[1] == pairb[0]);
 }
 
+static inline lfs_size_t lfs_entry_size(const lfs_entry_t *entry) {
+    return 4 + entry->d.elen + entry->d.alen + entry->d.nlen;
+}
+
 static int lfs_dir_alloc(lfs_t *lfs, lfs_dir_t *dir) {
     // allocate pair of dir blocks
     for (int i = 0; i < 2; i++) {
@@ -469,93 +484,27 @@ static int lfs_dir_fetch(lfs_t *lfs,
     return 0;
 }
 
-struct lfs_commit {
-    uint32_t crc;
-    lfs_block_t block;
-    lfs_off_t off;
-};
-
-static int lfs_commit(lfs_t *lfs, struct lfs_commit *c,
-        const void *data, lfs_size_t size) {
-    lfs_crc(&c->crc, data, size);
-    int err = lfs_bd_prog(lfs, c->block, c->off, data, size);
-    c->off += size;
-    return err;
-}
-
 struct lfs_region {
-    lfs_off_t off;
-    lfs_ssize_t diff;
-
-    int (*commit)(lfs_t *lfs, struct lfs_commit *c,
-            const void *data, lfs_size_t size);
-    const void *data;
-    lfs_size_t size;
-    struct lfs_region *next;
+    lfs_off_t oldoff;
+    lfs_size_t oldlen;
+    const void *newdata;
+    lfs_size_t newlen;
 };
 
-static int lfs_commit_mem(lfs_t *lfs, struct lfs_commit *c,
-        const void *data, lfs_size_t size) {
-    return lfs_commit(lfs, c, data, size);
-}
-
-struct lfs_commit_disk {
-    lfs_block_t block;
-    lfs_off_t off;
-    struct lfs_region *regions;
-};
-
-static int lfs_commit_disk(lfs_t *lfs, struct lfs_commit *c,
-        const void *p, lfs_size_t size) {
-    const struct lfs_commit_disk *d = p;
-
-    struct lfs_region *r = d->regions;
-    lfs_off_t off = 0;
-    while (true) {
-        if (r && r->off == off) {
-            lfs_off_t orig = c->off;
-            int err = r->commit(lfs, c, r->data, r->size);
-            if (err) {
-                return err;
-            }
-
-            off += (c->off - orig) - r->diff;
-            r = r->next;
-        } else if (off < size) {
-            uint8_t data;
-            int err = lfs_bd_read(lfs, d->block, d->off + off, &data, 1);
-            if (err) {
-                return err;
-            }
-
-            err = lfs_commit(lfs, c, &data, 1);
-            if (err) {
-                return err;
-            }
-
-            off += 1;
-        } else {
-            return 0;
-        }
-    }
-}
-
 static int lfs_dir_commit(lfs_t *lfs, lfs_dir_t *dir,
-        struct lfs_region *regions) {
-    // state for copying over
-    const lfs_block_t oldpair[2] = {dir->pair[1], dir->pair[0]};
-    lfs_size_t oldsize = (0x7fffffff & dir->d.size) - 4;
-    bool relocated = false;
-
+        const struct lfs_region *regions, int count) {
     // increment revision count
     dir->d.rev += 1;
 
     // keep pairs in order such that pair[0] is most recent
     lfs_pairswap(dir->pair);
-    for (struct lfs_region *r = regions; r; r = r->next) {
-        dir->d.size += r->diff;
+    for (int i = 0; i < count; i++) {
+        dir->d.size += regions[i].newlen - regions[i].oldlen;
     }
 
+    const lfs_block_t oldpair[2] = {dir->pair[0], dir->pair[1]};
+    bool relocated = false;
+
     while (true) {
         if (true) {
             int err = lfs_bd_erase(lfs, dir->pair[0]);
@@ -566,19 +515,10 @@ static int lfs_dir_commit(lfs_t *lfs, lfs_dir_t *dir,
                 return err;
             }
 
-            struct lfs_commit c = {
-                .crc = 0xffffffff,
-                .block = dir->pair[0],
-                .off = 0,
-            };
-
+            uint32_t crc = 0xffffffff;
             lfs_dir_tole32(&dir->d);
-            err = lfs_commit_disk(lfs, &c, &(struct lfs_commit_disk){
-                    oldpair[1], 0,
-                    &(struct lfs_region){
-                        0, 0,
-                        lfs_commit_mem, &dir->d, sizeof(dir->d),
-                        regions}}, oldsize);
+            lfs_crc(&crc, &dir->d, sizeof(dir->d));
+            err = lfs_bd_prog(lfs, dir->pair[0], 0, &dir->d, sizeof(dir->d));
             lfs_dir_fromle32(&dir->d);
             if (err) {
                 if (err == LFS_ERR_CORRUPT) {
@@ -587,9 +527,48 @@ static int lfs_dir_commit(lfs_t *lfs, lfs_dir_t *dir,
                 return err;
             }
 
-            c.crc = lfs_tole32(c.crc);
-            err = lfs_bd_prog(lfs, dir->pair[0], c.off, &c.crc, 4);
-            c.crc = lfs_fromle32(c.crc);
+            int i = 0;
+            lfs_off_t oldoff = sizeof(dir->d);
+            lfs_off_t newoff = sizeof(dir->d);
+            while (newoff < (0x7fffffff & dir->d.size)-4) {
+                if (i < count && regions[i].oldoff == oldoff) {
+                    lfs_crc(&crc, regions[i].newdata, regions[i].newlen);
+                    err = lfs_bd_prog(lfs, dir->pair[0],
+                            newoff, regions[i].newdata, regions[i].newlen);
+                    if (err) {
+                        if (err == LFS_ERR_CORRUPT) {
+                            goto relocate;
+                        }
+                        return err;
+                    }
+
+                    oldoff += regions[i].oldlen;
+                    newoff += regions[i].newlen;
+                    i += 1;
+                } else {
+                    uint8_t data;
+                    err = lfs_bd_read(lfs, oldpair[1], oldoff, &data, 1);
+                    if (err) {
+                        return err;
+                    }
+
+                    lfs_crc(&crc, &data, 1);
+                    err = lfs_bd_prog(lfs, dir->pair[0], newoff, &data, 1);
+                    if (err) {
+                        if (err == LFS_ERR_CORRUPT) {
+                            goto relocate;
+                        }
+                        return err;
+                    }
+
+                    oldoff += 1;
+                    newoff += 1;
+                }
+            }
+
+            crc = lfs_tole32(crc);
+            err = lfs_bd_prog(lfs, dir->pair[0], newoff, &crc, 4);
+            crc = lfs_fromle32(crc);
             if (err) {
                 if (err == LFS_ERR_CORRUPT) {
                     goto relocate;
@@ -613,13 +592,12 @@ static int lfs_dir_commit(lfs_t *lfs, lfs_dir_t *dir,
                 return err;
             }
 
-            if (ncrc != c.crc) {
+            if (ncrc != crc) {
                 goto relocate;
             }
         }
 
         break;
-
 relocate:
         //commit was corrupted
         LFS_DEBUG("Bad block at %d", dir->pair[0]);
@@ -662,18 +640,29 @@ relocate:
     return 0;
 }
 
+static int lfs_dir_update(lfs_t *lfs, lfs_dir_t *dir,
+        lfs_entry_t *entry, const void *data) {
+    lfs_entry_tole32(&entry->d);
+    int err = lfs_dir_commit(lfs, dir, (struct lfs_region[]){
+            {entry->off, sizeof(entry->d), &entry->d, sizeof(entry->d)},
+            {entry->off+sizeof(entry->d), entry->d.nlen, data, entry->d.nlen}
+        }, data ? 2 : 1);
+    lfs_entry_fromle32(&entry->d);
+    return err;
+}
+
 static int lfs_dir_append(lfs_t *lfs, lfs_dir_t *dir,
-        lfs_entry_t *entry, struct lfs_region *regions) {
+        lfs_entry_t *entry, const void *data) {
     // check if we fit, if top bit is set we do not and move on
     while (true) {
-        if ((0x7fffffff & dir->d.size) + entry->size <= lfs->cfg->block_size) {
+        if (dir->d.size + lfs_entry_size(entry) <= lfs->cfg->block_size) {
             entry->off = dir->d.size - 4;
-            for (struct lfs_region *r = regions; r; r = r->next) {
-                r->off += entry->off;
-            }
 
             lfs_entry_tole32(&entry->d);
-            int err = lfs_dir_commit(lfs, dir, regions);
+            int err = lfs_dir_commit(lfs, dir, (struct lfs_region[]){
+                    {entry->off, 0, &entry->d, sizeof(entry->d)},
+                    {entry->off, 0, data, entry->d.nlen}
+                }, 2);
             lfs_entry_fromle32(&entry->d);
             return err;
         }
@@ -689,12 +678,11 @@ static int lfs_dir_append(lfs_t *lfs, lfs_dir_t *dir,
             dir->d.tail[0] = olddir.d.tail[0];
             dir->d.tail[1] = olddir.d.tail[1];
             entry->off = dir->d.size - 4;
-            for (struct lfs_region *r = regions; r; r = r->next) {
-                r->off += entry->off;
-            }
-
             lfs_entry_tole32(&entry->d);
-            err = lfs_dir_commit(lfs, dir, regions);
+            err = lfs_dir_commit(lfs, dir, (struct lfs_region[]){
+                    {entry->off, 0, &entry->d, sizeof(entry->d)},
+                    {entry->off, 0, data, entry->d.nlen}
+                }, 2);
             lfs_entry_fromle32(&entry->d);
             if (err) {
                 return err;
@@ -703,7 +691,7 @@ static int lfs_dir_append(lfs_t *lfs, lfs_dir_t *dir,
             olddir.d.size |= 0x80000000;
             olddir.d.tail[0] = dir->pair[0];
             olddir.d.tail[1] = dir->pair[1];
-            return lfs_dir_commit(lfs, &olddir, NULL);
+            return lfs_dir_commit(lfs, &olddir, NULL, 0);
         }
 
         int err = lfs_dir_fetch(lfs, dir, dir->d.tail);
@@ -713,10 +701,10 @@ static int lfs_dir_append(lfs_t *lfs, lfs_dir_t *dir,
     }
 }
 
-static int lfs_dir_remove(lfs_t *lfs, lfs_dir_t *dir,
-        const lfs_entry_t *entry) {
+static int lfs_dir_remove(lfs_t *lfs, lfs_dir_t *dir, lfs_entry_t *entry) {
     // check if we should just drop the directory block
-    if ((dir->d.size & 0x7fffffff) == sizeof(dir->d)+4 + entry->size) {
+    if ((dir->d.size & 0x7fffffff) == sizeof(dir->d)+4
+            + lfs_entry_size(entry)) {
         lfs_dir_t pdir;
         int res = lfs_pred(lfs, dir->pair, &pdir);
         if (res < 0) {
@@ -727,15 +715,14 @@ static int lfs_dir_remove(lfs_t *lfs, lfs_dir_t *dir,
             pdir.d.size &= dir->d.size | 0x7fffffff;
             pdir.d.tail[0] = dir->d.tail[0];
             pdir.d.tail[1] = dir->d.tail[1];
-            return lfs_dir_commit(lfs, &pdir, NULL);
+            return lfs_dir_commit(lfs, &pdir, NULL, 0);
         }
     }
 
     // shift out the entry
-    int err = lfs_dir_commit(lfs, dir,
-            &(struct lfs_region){
-                entry->off, -entry->size,
-                lfs_commit_mem, NULL, 0});
+    int err = lfs_dir_commit(lfs, dir, (struct lfs_region[]){
+            {entry->off, lfs_entry_size(entry), NULL, 0},
+        }, 1);
     if (err) {
         return err;
     }
@@ -747,7 +734,7 @@ static int lfs_dir_remove(lfs_t *lfs, lfs_dir_t *dir,
                 f->pair[0] = 0xffffffff;
                 f->pair[1] = 0xffffffff;
             } else if (f->poff > entry->off) {
-                f->poff -= entry->size;
+                f->poff -= lfs_entry_size(entry);
             }
         }
     }
@@ -755,8 +742,8 @@ static int lfs_dir_remove(lfs_t *lfs, lfs_dir_t *dir,
     for (lfs_dir_t *d = lfs->dirs; d; d = d->next) {
         if (lfs_paircmp(d->pair, dir->pair) == 0) {
             if (d->off > entry->off) {
-                d->off -= entry->size;
-                d->pos -= entry->size;
+                d->off -= lfs_entry_size(entry);
+                d->pos -= lfs_entry_size(entry);
             }
         }
     }
@@ -764,82 +751,6 @@ static int lfs_dir_remove(lfs_t *lfs, lfs_dir_t *dir,
     return 0;
 }
 
-static int lfs_dir_update(lfs_t *lfs, lfs_dir_t *dir,
-        lfs_entry_t *entry, struct lfs_region *regions) {
-    lfs_ssize_t diff = 0;
-    for (struct lfs_region *r = regions; r; r = r->next) {
-        diff += r->diff;
-    }
-
-    // do we still fit?
-    if ((0x7fffffff & dir->d.size) + diff <= lfs->cfg->block_size) {
-        for (struct lfs_region *r = regions; r; r = r->next) {
-            r->off += entry->off;
-        }
-
-        lfs_entry_tole32(&entry->d);
-        int err = lfs_dir_commit(lfs, dir, regions);
-        lfs_entry_fromle32(&entry->d);
-        if (err) {
-            return err;
-        }
-
-        // shift over any files/directories that are affected
-        for (lfs_file_t *f = lfs->files; f; f = f->next) {
-            if (lfs_paircmp(f->pair, dir->pair) == 0) {
-                if (f->poff > entry->off) {
-                    f->poff += diff;
-                }
-            }
-        }
-
-        for (lfs_dir_t *d = lfs->dirs; d; d = d->next) {
-            if (lfs_paircmp(d->pair, dir->pair) == 0) {
-                if (d->off > entry->off) {
-                    d->off += diff;
-                    d->pos += diff;
-                }
-            }
-        }
-    } else {
-        lfs_dir_t olddir = *dir;
-        lfs_entry_t oldentry = {
-            .off = entry->off,
-            .size = entry->size - diff,
-            .d.type = entry->d.type | LFS_STRUCT_MOVED,
-        };
-
-        // mark as moving
-        int err = lfs_dir_commit(lfs, &olddir,
-                &(struct lfs_region){
-                    oldentry.off, 0,
-                    lfs_commit_mem, &oldentry.d.type, 1});
-        if (err) {
-            return err;
-        }
-
-        // append updated entry
-        lfs_entry_tole32(&entry->d);
-        err = lfs_dir_append(lfs, dir, entry,
-                &(struct lfs_region){
-                    0, +entry->size,
-                    lfs_commit_disk, &(struct lfs_commit_disk){
-                        olddir.pair[0], entry->off, regions}, oldentry.size});
-        lfs_entry_fromle32(&entry->d);
-        if (err) {
-            return err;
-        }
-
-        // remove old entry
-        err = lfs_dir_remove(lfs, dir, &oldentry);
-        if (err) {
-            return err;
-        }
-    }
-
-    return 0;
-}
-
 static int lfs_dir_next(lfs_t *lfs, lfs_dir_t *dir, lfs_entry_t *entry) {
     while (dir->off + sizeof(entry->d) > (0x7fffffff & dir->d.size)-4) {
         if (!(0x80000000 & dir->d.size)) {
@@ -864,9 +775,8 @@ static int lfs_dir_next(lfs_t *lfs, lfs_dir_t *dir, lfs_entry_t *entry) {
     }
 
     entry->off = dir->off;
-    entry->size = 4 + entry->d.elen + entry->d.alen + entry->d.nlen;
-    dir->off += entry->size;
-    dir->pos += entry->size;
+    dir->off += lfs_entry_size(entry);
+    dir->pos += lfs_entry_size(entry);
     return 0;
 }
 
@@ -884,7 +794,10 @@ static int lfs_dir_find(lfs_t *lfs, lfs_dir_t *dir,
         // special case for root dir
         if (pathname[0] == '\0') {
             *entry = (lfs_entry_t){
-                .d.type = LFS_STRUCT_DIR | LFS_TYPE_DIR,
+                .d.type = LFS_TYPE_DIR,
+                .d.elen = sizeof(entry->d) - 4,
+                .d.alen = 0,
+                .d.nlen = 0,
                 .d.u.dir[0] = lfs->root[0],
                 .d.u.dir[1] = lfs->root[1],
             };
@@ -932,14 +845,14 @@ static int lfs_dir_find(lfs_t *lfs, lfs_dir_t *dir,
                 return err;
             }
 
-            if (((0x7f & entry->d.type) != (LFS_STRUCT_CTZ | LFS_TYPE_REG) &&
-                 (0x7f & entry->d.type) != (LFS_STRUCT_DIR | LFS_TYPE_DIR)) ||
+            if (((0x7f & entry->d.type) != LFS_TYPE_REG &&
+                 (0x7f & entry->d.type) != LFS_TYPE_DIR) ||
                 entry->d.nlen != pathlen) {
                 continue;
             }
 
             int res = lfs_bd_cmp(lfs, dir->pair[0],
-                    entry->off + entry->size - pathlen,
+                    entry->off + 4+entry->d.elen+entry->d.alen,
                     pathname, pathlen);
             if (res < 0) {
                 return res;
@@ -952,13 +865,13 @@ static int lfs_dir_find(lfs_t *lfs, lfs_dir_t *dir,
         }
 
         // check that entry has not been moved
-        if (entry->d.type & LFS_STRUCT_MOVED) {
+        if (entry->d.type & 0x80) {
             int moved = lfs_moved(lfs, &entry->d.u);
             if (moved < 0 || moved) {
                 return (moved < 0) ? moved : LFS_ERR_NOENT;
             }
 
-            entry->d.type &= ~LFS_STRUCT_MOVED;
+            entry->d.type &= ~0x80;
         }
 
         pathname += pathlen;
@@ -968,7 +881,7 @@ static int lfs_dir_find(lfs_t *lfs, lfs_dir_t *dir,
         }
 
         // continue on if we hit a directory
-        if ((0xf & entry->d.type) != LFS_TYPE_DIR) {
+        if (entry->d.type != LFS_TYPE_DIR) {
             return LFS_ERR_NOTDIR;
         }
 
@@ -1014,29 +927,22 @@ int lfs_mkdir(lfs_t *lfs, const char *path) {
     dir.d.tail[0] = cwd.d.tail[0];
     dir.d.tail[1] = cwd.d.tail[1];
 
-    err = lfs_dir_commit(lfs, &dir, NULL);
+    err = lfs_dir_commit(lfs, &dir, NULL, 0);
     if (err) {
         return err;
     }
 
-    entry.d.type = LFS_STRUCT_DIR | LFS_TYPE_DIR;
+    entry.d.type = LFS_TYPE_DIR;
     entry.d.elen = sizeof(entry.d) - 4;
     entry.d.alen = 0;
     entry.d.nlen = strlen(path);
     entry.d.u.dir[0] = dir.pair[0];
     entry.d.u.dir[1] = dir.pair[1];
-    entry.size = 4 + entry.d.elen + entry.d.alen + entry.d.nlen;
 
     cwd.d.tail[0] = dir.pair[0];
     cwd.d.tail[1] = dir.pair[1];
 
-    err = lfs_dir_append(lfs, &cwd, &entry,
-            &(struct lfs_region){
-                0, +sizeof(entry.d),
-                lfs_commit_mem, &entry.d, sizeof(entry.d),
-            &(struct lfs_region){
-                0, +entry.d.nlen,
-                lfs_commit_mem, path, entry.d.nlen}});
+    err = lfs_dir_append(lfs, &cwd, &entry, path);
     if (err) {
         return err;
     }
@@ -1058,7 +964,7 @@ int lfs_dir_open(lfs_t *lfs, lfs_dir_t *dir, const char *path) {
     err = lfs_dir_find(lfs, dir, &entry, &path);
     if (err) {
         return err;
-    } else if (entry.d.type != (LFS_STRUCT_DIR | LFS_TYPE_DIR)) {
+    } else if (entry.d.type != LFS_TYPE_DIR) {
         return LFS_ERR_NOTDIR;
     }
 
@@ -1116,13 +1022,13 @@ int lfs_dir_read(lfs_t *lfs, lfs_dir_t *dir, struct lfs_info *info) {
             return (err == LFS_ERR_NOENT) ? 0 : err;
         }
 
-        if ((0x7f & entry.d.type) != (LFS_STRUCT_CTZ | LFS_TYPE_REG) &&
-            (0x7f & entry.d.type) != (LFS_STRUCT_DIR | LFS_TYPE_DIR)) {
+        if ((0x7f & entry.d.type) != LFS_TYPE_REG &&
+            (0x7f & entry.d.type) != LFS_TYPE_DIR) {
             continue;
         }
 
         // check that entry has not been moved
-        if (entry.d.type & LFS_STRUCT_MOVED) {
+        if (entry.d.type & 0x80) {
             int moved = lfs_moved(lfs, &entry.d.u);
             if (moved < 0) {
                 return moved;
@@ -1132,19 +1038,19 @@ int lfs_dir_read(lfs_t *lfs, lfs_dir_t *dir, struct lfs_info *info) {
                 continue;
             }
 
-            entry.d.type &= ~LFS_STRUCT_MOVED;
+            entry.d.type &= ~0x80;
         }
 
         break;
     }
 
-    info->type = 0xf & entry.d.type;
+    info->type = entry.d.type;
     if (info->type == LFS_TYPE_REG) {
         info->size = entry.d.u.file.size;
     }
 
     int err = lfs_bd_read(lfs, dir->pair[0],
-            entry.off + entry.size - entry.d.nlen,
+            entry.off + 4+entry.d.elen+entry.d.alen,
             info->name, entry.d.nlen);
     if (err) {
         return err;
@@ -1414,25 +1320,17 @@ int lfs_file_open(lfs_t *lfs, lfs_file_t *file,
         }
 
         // create entry to remember name
-        entry.d.type = LFS_STRUCT_CTZ | LFS_TYPE_REG;
+        entry.d.type = LFS_TYPE_REG;
         entry.d.elen = sizeof(entry.d) - 4;
         entry.d.alen = 0;
         entry.d.nlen = strlen(path);
         entry.d.u.file.head = 0xffffffff;
         entry.d.u.file.size = 0;
-        entry.size = 4 + entry.d.elen + entry.d.alen + entry.d.nlen;
-
-        err = lfs_dir_append(lfs, &cwd, &entry,
-                &(struct lfs_region){
-                    0, +sizeof(entry.d),
-                    lfs_commit_mem, &entry.d, sizeof(entry.d),
-                &(struct lfs_region){
-                    0, +entry.d.nlen,
-                    lfs_commit_mem, path, entry.d.nlen}});
+        err = lfs_dir_append(lfs, &cwd, &entry, path);
         if (err) {
             return err;
         }
-    } else if ((0xf & entry.d.type) == LFS_TYPE_DIR) {
+    } else if (entry.d.type == LFS_TYPE_DIR) {
         return LFS_ERR_ISDIR;
     } else if (flags & LFS_O_EXCL) {
         return LFS_ERR_EXIST;
@@ -1640,16 +1538,11 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
             return err;
         }
 
-        LFS_ASSERT(entry.d.type == (LFS_STRUCT_CTZ | LFS_TYPE_REG));
+        LFS_ASSERT(entry.d.type == LFS_TYPE_REG);
         entry.d.u.file.head = file->head;
         entry.d.u.file.size = file->size;
 
-        lfs_entry_tole32(&entry.d);
-        err = lfs_dir_update(lfs, &cwd, &entry,
-            &(struct lfs_region){
-                0, 0,
-                lfs_commit_mem, &entry.d, sizeof(entry.d)});
-        lfs_entry_fromle32(&entry.d);
+        err = lfs_dir_update(lfs, &cwd, &entry, NULL);
         if (err) {
             return err;
         }
@@ -1934,7 +1827,7 @@ int lfs_stat(lfs_t *lfs, const char *path, struct lfs_info *info) {
     }
 
     memset(info, 0, sizeof(*info));
-    info->type = 0xf & entry.d.type;
+    info->type = entry.d.type;
     if (info->type == LFS_TYPE_REG) {
         info->size = entry.d.u.file.size;
     }
@@ -1943,7 +1836,7 @@ int lfs_stat(lfs_t *lfs, const char *path, struct lfs_info *info) {
         strcpy(info->name, "/");
     } else {
         err = lfs_bd_read(lfs, cwd.pair[0],
-                entry.off + entry.size - entry.d.nlen,
+                entry.off + 4+entry.d.elen+entry.d.alen,
                 info->name, entry.d.nlen);
         if (err) {
             return err;
@@ -1975,7 +1868,7 @@ int lfs_remove(lfs_t *lfs, const char *path) {
     }
 
     lfs_dir_t dir;
-    if ((0xf & entry.d.type) == LFS_TYPE_DIR) {
+    if (entry.d.type == LFS_TYPE_DIR) {
         // must be empty before removal, checking size
         // without masking top bit checks for any case where
         // dir is not empty
@@ -1994,7 +1887,7 @@ int lfs_remove(lfs_t *lfs, const char *path) {
     }
 
     // if we were a directory, find pred, replace tail
-    if ((0xf & entry.d.type) == LFS_TYPE_DIR) {
+    if (entry.d.type == LFS_TYPE_DIR) {
         int res = lfs_pred(lfs, dir.pair, &cwd);
         if (res < 0) {
             return res;
@@ -2004,7 +1897,7 @@ int lfs_remove(lfs_t *lfs, const char *path) {
         cwd.d.tail[0] = dir.d.tail[0];
         cwd.d.tail[1] = dir.d.tail[1];
 
-        err = lfs_dir_commit(lfs, &cwd, NULL);
+        err = lfs_dir_commit(lfs, &cwd, NULL, 0);
         if (err) {
             return err;
         }
@@ -2057,7 +1950,7 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     }
 
     lfs_dir_t dir;
-    if (prevexists && (0xf & preventry.d.type) == LFS_TYPE_DIR) {
+    if (prevexists && preventry.d.type == LFS_TYPE_DIR) {
         // must be empty before removal, checking size
         // without masking top bit checks for any case where
         // dir is not empty
@@ -2070,11 +1963,8 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     }
 
     // mark as moving
-    oldentry.d.type |= LFS_STRUCT_MOVED;
-    err = lfs_dir_update(lfs, &oldcwd, &oldentry,
-            &(struct lfs_region){
-                0, 0,
-                lfs_commit_mem, &oldentry.d.type, 1});
+    oldentry.d.type |= 0x80;
+    err = lfs_dir_update(lfs, &oldcwd, &oldentry, NULL);
     if (err) {
         return err;
     }
@@ -2087,28 +1977,16 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     // move to new location
     lfs_entry_t newentry = preventry;
     newentry.d = oldentry.d;
-    newentry.d.type &= ~LFS_STRUCT_MOVED;
+    newentry.d.type &= ~0x80;
     newentry.d.nlen = strlen(newpath);
 
     if (prevexists) {
-        err = lfs_dir_update(lfs, &newcwd, &newentry,
-                &(struct lfs_region){
-                    0, 0,
-                    lfs_commit_mem, &newentry.d, sizeof(newentry.d),
-                &(struct lfs_region){
-                    sizeof(newentry.d), 0,
-                    lfs_commit_mem, newpath, newentry.d.nlen}});
+        err = lfs_dir_update(lfs, &newcwd, &newentry, newpath);
         if (err) {
             return err;
         }
     } else {
-        err = lfs_dir_append(lfs, &newcwd, &newentry,
-                &(struct lfs_region){
-                    0, +sizeof(newentry.d),
-                    lfs_commit_mem, &newentry.d, sizeof(newentry.d),
-                &(struct lfs_region){
-                    0, +newentry.d.nlen,
-                    lfs_commit_mem, newpath, newentry.d.nlen}});
+        err = lfs_dir_append(lfs, &newcwd, &newentry, newpath);
         if (err) {
             return err;
         }
@@ -2126,7 +2004,7 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
     }
 
     // if we were a directory, find pred, replace tail
-    if (prevexists && (0xf & preventry.d.type) == LFS_TYPE_DIR) {
+    if (prevexists && preventry.d.type == LFS_TYPE_DIR) {
         int res = lfs_pred(lfs, dir.pair, &newcwd);
         if (res < 0) {
             return res;
@@ -2136,7 +2014,7 @@ int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath) {
         newcwd.d.tail[0] = dir.d.tail[0];
         newcwd.d.tail[1] = dir.d.tail[1];
 
-        err = lfs_dir_commit(lfs, &newcwd, NULL);
+        err = lfs_dir_commit(lfs, &newcwd, NULL, 0);
         if (err) {
             return err;
         }
@@ -2227,9 +2105,9 @@ 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.size = lfs_min(lfs->cfg->lookahead, lfs->cfg->block_count);
+    lfs->free.i = 0;
     lfs_alloc_ack(lfs);
 
     // create superblock dir
@@ -2246,7 +2124,7 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
         return err;
     }
 
-    err = lfs_dir_commit(lfs, &root, NULL);
+    err = lfs_dir_commit(lfs, &root, NULL, 0);
     if (err) {
         return err;
     }
@@ -2256,7 +2134,8 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
 
     // write superblocks
     lfs_superblock_t superblock = {
-        .d.type = LFS_STRUCT_DIR | LFS_TYPE_SUPERBLOCK,
+        .off = sizeof(superdir.d),
+        .d.type = LFS_TYPE_SUPERBLOCK,
         .d.elen = sizeof(superblock.d) - sizeof(superblock.d.magic) - 4,
         .d.nlen = sizeof(superblock.d.magic),
         .d.version = LFS_DISK_VERSION,
@@ -2273,9 +2152,10 @@ int lfs_format(lfs_t *lfs, const struct lfs_config *cfg) {
     lfs_superblock_tole32(&superblock.d);
     bool valid = false;
     for (int i = 0; i < 2; i++) {
-        err = lfs_dir_commit(lfs, &superdir, &(struct lfs_region){
-                sizeof(superdir.d), 0,
-                lfs_commit_mem, &superblock.d, sizeof(superblock.d)});
+        err = lfs_dir_commit(lfs, &superdir, (struct lfs_region[]){
+                {sizeof(superdir.d), sizeof(superblock.d),
+                 &superblock.d, sizeof(superblock.d)}
+            }, 1);
         if (err && err != LFS_ERR_CORRUPT) {
             return err;
         }
@@ -2304,9 +2184,9 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
     }
 
     // setup free lookahead
-    lfs->free.begin = 0;
-    lfs->free.size = 0;
     lfs->free.off = 0;
+    lfs->free.size = 0;
+    lfs->free.i = 0;
     lfs_alloc_ack(lfs);
 
     // load superblock
@@ -2330,7 +2210,7 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
     }
 
     if (err || memcmp(superblock.d.magic, "littlefs", 8) != 0) {
-        LFS_ERROR("Invalid superblock at %d %d", dir.pair[0], dir.pair[1]);
+        LFS_ERROR("Invalid superblock at %d %d", 0, 1);
         return LFS_ERR_CORRUPT;
     }
 
@@ -2357,6 +2237,8 @@ int lfs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data) {
     }
 
     // iterate over metadata pairs
+    lfs_dir_t dir;
+    lfs_entry_t entry;
     lfs_block_t cwd[2] = {0, 1};
 
     while (true) {
@@ -2367,14 +2249,12 @@ int lfs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data) {
             }
         }
 
-        lfs_dir_t dir;
         int err = lfs_dir_fetch(lfs, &dir, cwd);
         if (err) {
             return err;
         }
 
         // iterate over contents
-        lfs_entry_t entry;
         while (dir.off + sizeof(entry.d) <= (0x7fffffff & dir.d.size)-4) {
             err = lfs_bd_read(lfs, dir.pair[0], dir.off,
                     &entry.d, sizeof(entry.d));
@@ -2383,8 +2263,8 @@ int lfs_traverse(lfs_t *lfs, int (*cb)(void*, lfs_block_t), void *data) {
                 return err;
             }
 
-            dir.off += 4 + entry.d.elen + entry.d.alen + entry.d.nlen;
-            if ((0x70 & entry.d.type) == LFS_STRUCT_CTZ) {
+            dir.off += lfs_entry_size(&entry);
+            if ((0x70 & entry.d.type) == (0x70 & LFS_TYPE_REG)) {
                 err = lfs_ctz_traverse(lfs, &lfs->rcache, NULL,
                         entry.d.u.file.head, entry.d.u.file.size, cb, data);
                 if (err) {
@@ -2474,7 +2354,7 @@ static int lfs_parent(lfs_t *lfs, const lfs_block_t dir[2],
                 break;
             }
 
-            if (((0x70 & entry->d.type) == LFS_STRUCT_DIR) &&
+            if (((0x70 & entry->d.type) == (0x70 & LFS_TYPE_DIR)) &&
                  lfs_paircmp(entry->d.u.dir, dir) == 0) {
                 return true;
             }
@@ -2514,7 +2394,7 @@ static int lfs_moved(lfs_t *lfs, const void *e) {
                 break;
             }
 
-            if (!(LFS_STRUCT_MOVED & entry.d.type) &&
+            if (!(0x80 & entry.d.type) &&
                  memcmp(&entry.d.u, e, sizeof(entry.d.u)) == 0) {
                 return true;
             }
@@ -2539,10 +2419,7 @@ static int lfs_relocate(lfs_t *lfs,
         entry.d.u.dir[0] = newpair[0];
         entry.d.u.dir[1] = newpair[1];
 
-        int err = lfs_dir_update(lfs, &parent, &entry,
-                &(struct lfs_region){
-                    0, 0,
-                    lfs_commit_mem, &entry.d, sizeof(entry.d)});
+        int err = lfs_dir_update(lfs, &parent, &entry, NULL);
         if (err) {
             return err;
         }
@@ -2569,7 +2446,7 @@ static int lfs_relocate(lfs_t *lfs,
         parent.d.tail[0] = newpair[0];
         parent.d.tail[1] = newpair[1];
 
-        return lfs_dir_commit(lfs, &parent, NULL);
+        return lfs_dir_commit(lfs, &parent, NULL, 0);
     }
 
     // couldn't find dir, must be new
@@ -2611,7 +2488,7 @@ int lfs_deorphan(lfs_t *lfs) {
                 pdir.d.tail[0] = cwd.d.tail[0];
                 pdir.d.tail[1] = cwd.d.tail[1];
 
-                err = lfs_dir_commit(lfs, &pdir, NULL);
+                err = lfs_dir_commit(lfs, &pdir, NULL, 0);
                 if (err) {
                     return err;
                 }
@@ -2627,7 +2504,7 @@ int lfs_deorphan(lfs_t *lfs) {
                 pdir.d.tail[0] = entry.d.u.dir[0];
                 pdir.d.tail[1] = entry.d.u.dir[1];
 
-                err = lfs_dir_commit(lfs, &pdir, NULL);
+                err = lfs_dir_commit(lfs, &pdir, NULL, 0);
                 if (err) {
                     return err;
                 }
@@ -2649,7 +2526,7 @@ int lfs_deorphan(lfs_t *lfs) {
             }
 
             // found moved entry
-            if (entry.d.type & LFS_STRUCT_MOVED) {
+            if (entry.d.type & 0x80) {
                 int moved = lfs_moved(lfs, &entry.d.u);
                 if (moved < 0) {
                     return moved;
@@ -2665,11 +2542,8 @@ int lfs_deorphan(lfs_t *lfs) {
                 } else {
                     LFS_DEBUG("Found partial move %d %d",
                             entry.d.u.dir[0], entry.d.u.dir[1]);
-                    entry.d.type &= ~LFS_STRUCT_MOVED;
-                    err = lfs_dir_update(lfs, &cwd, &entry,
-                            &(struct lfs_region){
-                                0, 0,
-                                lfs_commit_mem, &entry.d, sizeof(entry.d)});
+                    entry.d.type &= ~0x80;
+                    err = lfs_dir_update(lfs, &cwd, &entry, NULL);
                     if (err) {
                         return err;
                     }

lfs.h

@@ -74,15 +74,9 @@ enum lfs_error {
 
 // File types
 enum lfs_type {
-    // file type
-    LFS_TYPE_REG        = 0x01,
-    LFS_TYPE_DIR        = 0x02,
-    LFS_TYPE_SUPERBLOCK = 0x0e,
-
-    // on disk structure
-    LFS_STRUCT_CTZ      = 0x10,
-    LFS_STRUCT_DIR      = 0x20,
-    LFS_STRUCT_MOVED    = 0x80,
+    LFS_TYPE_REG        = 0x11,
+    LFS_TYPE_DIR        = 0x22,
+    LFS_TYPE_SUPERBLOCK = 0x2e,
 };
 
 // File open flags
@@ -196,7 +190,6 @@ struct lfs_info {
 /// littlefs data structures ///
 typedef struct lfs_entry {
     lfs_off_t off;
-    lfs_size_t size;
 
     struct lfs_disk_entry {
         uint8_t type;
@@ -250,6 +243,8 @@ typedef struct lfs_dir {
 } lfs_dir_t;
 
 typedef struct lfs_superblock {
+    lfs_off_t off;
+
     struct lfs_disk_superblock {
         uint8_t type;
         uint8_t elen;
@@ -264,9 +259,9 @@ typedef struct lfs_superblock {
 } lfs_superblock_t;
 
 typedef struct lfs_free {
-    lfs_block_t begin;
-    lfs_block_t size;
     lfs_block_t off;
+    lfs_block_t size;
+    lfs_block_t i;
     lfs_block_t ack;
     uint32_t *buffer;
 } lfs_free_t;
@@ -325,10 +320,6 @@ int lfs_remove(lfs_t *lfs, const char *path);
 // If the destination exists, it must match the source in type.
 // If the destination is a directory, the directory must be empty.
 //
-// Note: If power loss occurs, it is possible that the file or directory
-// will exist in both the oldpath and newpath simultaneously after the
-// next mount.
-//
 // Returns a negative error code on failure.
 int lfs_rename(lfs_t *lfs, const char *oldpath, const char *newpath);
 

tests/test_alloc.sh

@@ -110,10 +110,35 @@ lfs_alloc_singleproc multiprocreuse
 lfs_verify multiprocreuse
 lfs_verify singleprocreuse
 
-echo "--- Cleanup ---"
 lfs_remove multiprocreuse
 lfs_remove singleprocreuse
 
+echo "--- Lookahead overflow test ---"
+lfs_mkdir overflow
+for name in bacon eggs pancakes
+do
+tests/test.py << TEST
+    lfs_mount(&lfs, &cfg) => 0;
+
+//    // setup lookahead to almost overflow
+//    lfs.free.begin = ((lfs_size_t)-1) - 2*$SIZE;
+//    lfs.free.size = 0;
+//    lfs.free.off = 0;
+
+    lfs_file_open(&lfs, &file[0], "overflow/$name",
+            LFS_O_WRONLY | LFS_O_CREAT | LFS_O_APPEND) => 0;
+    size = strlen("$name");
+    memcpy(buffer, "$name", size);
+    for (int i = 0; i < $SIZE; i++) {
+        lfs_file_write(&lfs, &file[0], buffer, size) => size;
+    }
+    lfs_file_close(&lfs, &file[0]) => 0;
+    lfs_unmount(&lfs) => 0;
+TEST
+done
+lfs_verify overflow
+lfs_remove overflow
+
 echo "--- Exhaustion test ---"
 tests/test.py << TEST
     lfs_mount(&lfs, &cfg) => 0;
@@ -289,7 +314,7 @@ tests/test.py << TEST
     }
     lfs_file_close(&lfs, &file[0]) => 0;
 
-    // open whole
+    // open hole
     lfs_remove(&lfs, "bump") => 0;
 
     lfs_mkdir(&lfs, "splitdir") => 0;
@@ -301,5 +326,130 @@ tests/test.py << TEST
     lfs_unmount(&lfs) => 0;
 TEST
 
+echo "--- Outdated lookahead test ---"
+rm -rf blocks
+tests/test.py << TEST
+    lfs_format(&lfs, &cfg) => 0;
+
+    lfs_mount(&lfs, &cfg) => 0;
+
+    // fill completely with two files
+    lfs_file_open(&lfs, &file[0], "exhaustion1",
+            LFS_O_WRONLY | LFS_O_CREAT) => 0;
+    size = strlen("blahblahblahblah");
+    memcpy(buffer, "blahblahblahblah", size);
+    for (lfs_size_t i = 0;
+            i < ((cfg.block_count-4)/2)*(cfg.block_size-8);
+            i += size) {
+        lfs_file_write(&lfs, &file[0], buffer, size) => size;
+    }
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    lfs_file_open(&lfs, &file[0], "exhaustion2",
+            LFS_O_WRONLY | LFS_O_CREAT) => 0;
+    size = strlen("blahblahblahblah");
+    memcpy(buffer, "blahblahblahblah", size);
+    for (lfs_size_t i = 0;
+            i < ((cfg.block_count-4+1)/2)*(cfg.block_size-8);
+            i += size) {
+        lfs_file_write(&lfs, &file[0], buffer, size) => size;
+    }
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    // remount to force reset of lookahead
+    lfs_unmount(&lfs) => 0;
+
+    lfs_mount(&lfs, &cfg) => 0;
+
+    // rewrite one file
+    lfs_file_open(&lfs, &file[0], "exhaustion1",
+            LFS_O_WRONLY | LFS_O_TRUNC) => 0;
+    lfs_file_sync(&lfs, &file[0]) => 0;
+    size = strlen("blahblahblahblah");
+    memcpy(buffer, "blahblahblahblah", size);
+    for (lfs_size_t i = 0;
+            i < ((cfg.block_count-4)/2)*(cfg.block_size-8);
+            i += size) {
+        lfs_file_write(&lfs, &file[0], buffer, size) => size;
+    }
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    // rewrite second file, this requires lookahead does not
+    // use old population
+    lfs_file_open(&lfs, &file[0], "exhaustion2",
+            LFS_O_WRONLY | LFS_O_TRUNC) => 0;
+    lfs_file_sync(&lfs, &file[0]) => 0;
+    size = strlen("blahblahblahblah");
+    memcpy(buffer, "blahblahblahblah", size);
+    for (lfs_size_t i = 0;
+            i < ((cfg.block_count-4+1)/2)*(cfg.block_size-8);
+            i += size) {
+        lfs_file_write(&lfs, &file[0], buffer, size) => size;
+    }
+    lfs_file_close(&lfs, &file[0]) => 0;
+TEST
+
+echo "--- Outdated lookahead and split dir test ---"
+rm -rf blocks
+tests/test.py << TEST
+    lfs_format(&lfs, &cfg) => 0;
+    lfs_mount(&lfs, &cfg) => 0;
+
+    // fill completely with two files
+    lfs_file_open(&lfs, &file[0], "exhaustion1",
+            LFS_O_WRONLY | LFS_O_CREAT) => 0;
+    size = strlen("blahblahblahblah");
+    memcpy(buffer, "blahblahblahblah", size);
+    for (lfs_size_t i = 0;
+            i < ((cfg.block_count-4)/2)*(cfg.block_size-8);
+            i += size) {
+        lfs_file_write(&lfs, &file[0], buffer, size) => size;
+    }
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    lfs_file_open(&lfs, &file[0], "exhaustion2",
+            LFS_O_WRONLY | LFS_O_CREAT) => 0;
+    size = strlen("blahblahblahblah");
+    memcpy(buffer, "blahblahblahblah", size);
+    for (lfs_size_t i = 0;
+            i < ((cfg.block_count-4+1)/2)*(cfg.block_size-8);
+            i += size) {
+        lfs_file_write(&lfs, &file[0], buffer, size) => size;
+    }
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    // remount to force reset of lookahead
+    lfs_unmount(&lfs) => 0;
+
+    lfs_mount(&lfs, &cfg) => 0;
+
+    // rewrite one file with a hole of one block
+    lfs_file_open(&lfs, &file[0], "exhaustion1",
+            LFS_O_WRONLY | LFS_O_TRUNC) => 0;
+    lfs_file_sync(&lfs, &file[0]) => 0;
+    size = strlen("blahblahblahblah");
+    memcpy(buffer, "blahblahblahblah", size);
+    for (lfs_size_t i = 0;
+            i < ((cfg.block_count-4)/2 - 1)*(cfg.block_size-8);
+            i += size) {
+        lfs_file_write(&lfs, &file[0], buffer, size) => size;
+    }
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    // try to allocate a directory, should fail!
+    lfs_mkdir(&lfs, "split") => LFS_ERR_NOSPC;
+
+    // file should not fail
+    lfs_file_open(&lfs, &file[0], "notasplit",
+            LFS_O_WRONLY | LFS_O_CREAT) => 0;
+    lfs_file_write(&lfs, &file[0], "hi", 2) => 2;
+    lfs_file_close(&lfs, &file[0]) => 0;
+
+    lfs_unmount(&lfs) => 0;
+TEST
+
+
+
+
 echo "--- Results ---"
 tests/stats.py

tests/test_interspersed.sh

@@ -1,13 +1,13 @@
 #!/bin/bash
 set -eu
 
-echo "=== Parallel tests ==="
+echo "=== Interspersed tests ==="
 rm -rf blocks
 tests/test.py << TEST
     lfs_format(&lfs, &cfg) => 0;
 TEST
 
-echo "--- Parallel file test ---"
+echo "--- Interspersed file test ---"
 tests/test.py << TEST
     lfs_mount(&lfs, &cfg) => 0;
     lfs_file_open(&lfs, &file[0], "a", LFS_O_WRONLY | LFS_O_CREAT) => 0;
@@ -77,7 +77,7 @@ tests/test.py << TEST
     lfs_unmount(&lfs) => 0;
 TEST
 
-echo "--- Parallel remove file test ---"
+echo "--- Interspersed remove file test ---"
 tests/test.py << TEST
     lfs_mount(&lfs, &cfg) => 0;
     lfs_file_open(&lfs, &file[0], "e", LFS_O_WRONLY | LFS_O_CREAT) => 0;