Merge pull request #5761 from geky/littlefs-fix-lookahead-rewind

littlefs: Fix issue with immediate exhaustion and small unaligned storage

Author: cmonr

.travis.yml

@@ -142,11 +142,10 @@ matrix:
         # Run local littlefs tests
         - CFLAGS="-Wno-format" make -C$LITTLEFS/littlefs test QUIET=1
         # Run local littlefs tests with set of variations
-        - CFLAGS="-Wno-format -DLFS_READ_SIZE=64 -DLFS_PROG_SIZE=64" make -C$LITTLEFS/littlefs test QUIET=1
-        - CFLAGS="-Wno-format -DLFS_READ_SIZE=1 -DLFS_PROG_SIZE=1" make -C$LITTLEFS/littlefs test QUIET=1
-        - CFLAGS="-Wno-format -DLFS_READ_SIZE=512 -DLFS_PROG_SIZE=512" make -C$LITTLEFS/littlefs test QUIET=1
-        - CFLAGS="-Wno-format -DLFS_BLOCK_COUNT=1023" make -C$LITTLEFS/littlefs test QUIET=1
-        - CFLAGS="-Wno-format -DLFS_LOOKAHEAD=2048" make -C$LITTLEFS/littlefs test QUIET=1
+        - CFLAGS="-Wno-format -DLFS_READ_SIZE=64  -DLFS_PROG_SIZE=64"      make -C$LITTLEFS/littlefs test QUIET=1
+        - CFLAGS="-Wno-format -DLFS_READ_SIZE=1   -DLFS_PROG_SIZE=1"       make -C$LITTLEFS/littlefs test QUIET=1
+        - CFLAGS="-Wno-format -DLFS_READ_SIZE=512 -DLFS_PROG_SIZE=512"     make -C$LITTLEFS/littlefs test QUIET=1
+        - CFLAGS="-Wno-format -DLFS_BLOCK_COUNT=1023 -DLFS_LOOKAHEAD=2048" make -C$LITTLEFS/littlefs test QUIET=1
         # Self-hosting littlefs fuzz test with littlefs-fuse
         - make -Clittlefs_fuse
         - littlefs_fuse/lfs --format /dev/loop0

features/filesystem/littlefs/littlefs/.travis.yml

@@ -12,10 +12,9 @@ script:
     - make test QUIET=1
 
     # run tests with a few different configurations
-    - CFLAGS="-DLFS_READ_SIZE=1   -DLFS_PROG_SIZE=1"   make test QUIET=1
-    - CFLAGS="-DLFS_READ_SIZE=512 -DLFS_PROG_SIZE=512" make test QUIET=1
-    - CFLAGS="-DLFS_BLOCK_COUNT=1023" make test QUIET=1
-    - CFLAGS="-DLFS_LOOKAHEAD=2048"   make test QUIET=1
+    - CFLAGS="-DLFS_READ_SIZE=1   -DLFS_PROG_SIZE=1"       make test QUIET=1
+    - CFLAGS="-DLFS_READ_SIZE=512 -DLFS_PROG_SIZE=512"     make test QUIET=1
+    - CFLAGS="-DLFS_BLOCK_COUNT=1023 -DLFS_LOOKAHEAD=2048" make test QUIET=1
 
     # self-host with littlefs-fuse for fuzz test
     - make -C littlefs-fuse

features/filesystem/littlefs/littlefs/lfs.c

@@ -2039,9 +2039,9 @@ int lfs_mount(lfs_t *lfs, const struct lfs_config *cfg) {
         return err;
     }
 
-    // setup free lookahead
-    lfs->free.begin = -lfs->cfg->lookahead;
-    lfs->free.off = lfs->cfg->lookahead;
+    // setup free lookahead, rewind so first allocation triggers a scan
+    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;
 
     // load superblock