Add metadata_max and inline_file_max to config

We have seen poor read performance on NAND flashes with 128kB blocks.
The root cause is inline files having to traverse many sets of metadata
pairs inside the current block before being fully reconstructed. Simply
disabling inline files is not enough, as the metadata will still fill up
the block and eventually need to be compacted.

By allowing configuration of how much size metadata takes up, along with
limiting (or disabling) inline file size, we achieve read performance
improvements on an order of magnitude.

1 files changed, 19 insertions, 5 deletions

diff --git a/lfs.c b/lfs.c
index d7439fe..5585b40 100644
--- a/lfs.c
+++ b/lfs.c
@@ -1589,7 +1589,7 @@ static int lfs_dir_compact(lfs_t *lfs,
         // for metadata updates.
         if (end - begin < 0xff &&
                 size <= lfs_min(lfs->cfg->block_size - 36,
-                    lfs_alignup(lfs->cfg->block_size/2,
+                    lfs_alignup(lfs->metadata_max/2,
                         lfs->cfg->prog_size))) {
             break;
         }
@@ -1674,7 +1674,7 @@ static int lfs_dir_compact(lfs_t *lfs,
                 .crc = 0xffffffff,
 
                 .begin = 0,
-                .end = lfs->cfg->block_size - 8,
+                .end = lfs->metadata_max - 8,
             };
 
             // erase block to write to
@@ -1884,7 +1884,7 @@ static int lfs_dir_commit(lfs_t *lfs, lfs_mdir_t *dir,
             .crc = 0xffffffff,
 
             .begin = dir->off,
-            .end = lfs->cfg->block_size - 8,
+            .end = lfs->metadata_max - 8,
         };
 
         // traverse attrs that need to be written out
@@ -2966,7 +2966,7 @@ static lfs_ssize_t lfs_file_rawwrite(lfs_t *lfs, lfs_file_t *file,
     if ((file->flags & LFS_F_INLINE) &&
             lfs_max(file->pos+nsize, file->ctz.size) >
             lfs_min(0x3fe, lfs_min(
-                lfs->cfg->cache_size, lfs->cfg->block_size/8))) {
+                lfs->cfg->cache_size, lfs->inline_file_max))) {
         // inline file doesn't fit anymore
         int err = lfs_file_outline(lfs, file);
         if (err) {
@@ -3536,6 +3536,20 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
         lfs->attr_max = LFS_ATTR_MAX;
     }
 
+    LFS_ASSERT(lfs->cfg->metadata_max <= lfs->cfg->block_size);
+    lfs->metadata_max = lfs->cfg->metadata_max;
+    if (!lfs->metadata_max) {
+        lfs->metadata_max = lfs->cfg->block_size;
+    }
+
+    LFS_ASSERT(lfs->cfg->inline_file_max <= LFS_FILE_MAX);
+    lfs->inline_file_max = lfs->cfg->inline_file_max;
+    if (!lfs->inline_file_max) {
+        lfs->inline_file_max = lfs->cfg->block_size / 8;
+    } else if(lfs->inline_file_max == -1) {
+        lfs->inline_file_max = 0;
+    }
+
     // setup default state
     lfs->root[0] = LFS_BLOCK_NULL;
     lfs->root[1] = LFS_BLOCK_NULL;
@@ -3829,7 +3843,7 @@ int lfs_fs_rawtraverse(lfs_t *lfs,
                 if (err) {
                     return err;
                 }
-            } else if (includeorphans && 
+            } else if (includeorphans &&
                     lfs_tag_type3(tag) == LFS_TYPE_DIRSTRUCT) {
                 for (int i = 0; i < 2; i++) {
                     err = cb(data, (&ctz.head)[i]);