t: Replaced LFS_T_EXCL with LFS_I_DIRTY flag in lfsr_tinfo

This just forwards the internal LFS_I_DIRTY flag to the user via the
lfsr_tinfo flags field.

Benefits of this approach:

- Gives the user more flexibility on what to do if the filesystem is
  modified, maybe you want to keep traversing depending on some other
  logic.

- Can eventually add other flags to tinfo.flags, such as
  LFS_I_COMPACTED, LFS_I_REPAIRED, LFS_I_INCONSISTENT, etc.

- Avoids confusion around the very different behaviors of LFS_O_EXCL and
  LFS_T_EXCL.

  I tried to come up with a better name (maybe LFS_T_WATCH?) but it was
  a bit of a struggle... Switching to a flags approach sidesteps the
  issue.

- Can drop the LFS_ERR_BUSY error code for now.

Code changes were fairly insignificant:

           code          stack
  before: 35244           2680
  after:  35224 (-0.1%)   2680 (+0.0%)

The only concern is that the tests highlighted it's possible for our
flag scheme to miss mutation if it happens after/during the last set of
blocks... Not sure how to handle this yet...

lfs.c

@@ -5968,7 +5968,7 @@ static bool lfsr_omdir_ismidopen(lfs_t *lfs, lfsr_smid_t mid) {
 static void lfsr_fs_mkdirty(lfs_t *lfs) {
     for (lfsr_omdir_t *o = lfs->omdirs; o; o = o->next) {
         if (o->type == LFS_TYPE_TRAVERSAL) {
-            o->flags |= LFS_F_DIRTY;
+            o->flags |= LFS_I_DIRTY;
         }
     }
 }
@@ -8241,10 +8241,6 @@ static inline bool lfsr_t_ismtreeonly(uint32_t flags) {
     return flags & LFS_T_MTREEONLY;
 }
 
-static inline bool lfsr_t_isexcl(uint32_t flags) {
-    return flags & LFS_T_EXCL;
-}
-
 static inline bool lfsr_t_ismkconsistent(uint32_t flags) {
     return flags & LFS_T_MKCONSISTENT;
 }
@@ -8265,8 +8261,8 @@ static inline bool lfsr_t_isckdata(uint32_t flags) {
     return flags & (LFS_T_CKDATA ^ LFS_T_CKMETA);
 }
 
-static inline bool lfsr_f_isdirty(uint32_t flags) {
-    return flags & LFS_F_DIRTY;
+static inline bool lfsr_i_isdirty(uint32_t flags) {
+    return flags & LFS_I_DIRTY;
 }
 
 
@@ -8683,7 +8679,7 @@ static int lfsr_mtree_gc(lfs_t *lfs, lfsr_traversal_t *t,
         }
 
         // mark as dirty
-        t->o.o.flags |= LFS_F_DIRTY;
+        t->o.o.flags |= LFS_I_DIRTY;
     }
 
     // compacting btree nodes?
@@ -8761,7 +8757,7 @@ static int lfsr_mtree_gc(lfs_t *lfs, lfsr_traversal_t *t,
         t->u.bt.rid = t->u.bt.bid;
 
         // mark as dirty
-        t->o.o.flags |= LFS_F_DIRTY;
+        t->o.o.flags |= LFS_I_DIRTY;
     }
 
     if (tag_) {
@@ -8914,7 +8910,6 @@ static lfs_sblock_t lfs_alloc(lfs_t *lfs, bool erase) {
             int err = lfsr_mtree_traverse(lfs, &t,
                     NULL, NULL);
             if (err) {
-                LFS_ASSERT(err != LFS_ERR_BUSY);
                 if (err == LFS_ERR_NOENT) {
                     break;
                 }
@@ -12832,7 +12827,7 @@ int lfsr_traversal_open(lfs_t *lfs, lfsr_traversal_t *t, uint32_t flags) {
     LFS_ASSERT(!lfsr_t_ismtreeonly(flags) || !lfsr_t_islookahead(flags));
     LFS_ASSERT(!lfsr_t_ismtreeonly(flags) || !lfsr_t_isckdata(flags));
     // these flags are internal and shouldn't be provided by the user
-    LFS_ASSERT(!lfsr_f_isdirty(flags));
+    LFS_ASSERT(!lfsr_i_isdirty(flags));
 
     // some flags mutate the filesystem
     if (lfsr_t_ismkconsistent(flags)
@@ -12871,16 +12866,11 @@ int lfsr_traversal_read(lfs_t *lfs, lfsr_traversal_t *t,
         struct lfs_tinfo *tinfo) {
     LFS_ASSERT(lfsr_omdir_isopen(lfs, &t->o.o));
 
-    // traversal dirty and excl? terminate early
-    if (lfsr_t_isexcl(t->o.o.flags)
-            && lfsr_f_isdirty(t->o.o.flags)) {
-        return LFS_ERR_BUSY;
-    }
-
     while (true) {
         // some redund blocks left over?
         if (t->blocks[0] != -1) {
             // write our traversal info
+            tinfo->flags = t->o.o.flags & LFS_I_DIRTY;
             tinfo->btype = lfsr_t_btype(t->o.o.flags);
             tinfo->block = t->blocks[0];
 
@@ -12902,13 +12892,6 @@ int lfsr_traversal_read(lfs_t *lfs, lfsr_traversal_t *t,
             return err;
         }
 
-        // traversal may itself set the dirty flag if it required
-        // mutation to make progress
-        if (lfsr_t_isexcl(t->o.o.flags)
-                && lfsr_f_isdirty(t->o.o.flags)) {
-            return LFS_ERR_BUSY;
-        }
-
         // figure out type/blocks
         if (tag == LFSR_TAG_MDIR) {
             lfsr_mdir_t *mdir = (lfsr_mdir_t*)bptr.data.u.buffer;
@@ -12935,7 +12918,7 @@ int lfsr_traversal_read(lfs_t *lfs, lfsr_traversal_t *t,
 done:;
     // was a lookahead scan successful?
     if (lfsr_t_islookahead(t->o.o.flags)
-            && !lfsr_f_isdirty(t->o.o.flags)) {
+            && !lfsr_i_isdirty(t->o.o.flags)) {
         lfs_alloc_markfree(lfs);
     }
 
@@ -12978,7 +12961,7 @@ static void lfsr_traversal_clobber(lfs_t *lfs, lfsr_traversal_t *t) {
 static int lfsr_traversal_rewind_(lfs_t *lfs, lfsr_traversal_t *t) {
     (void)lfs;
     // reset traversal
-    t->o.o.flags &= ~LFS_F_DIRTY;
+    t->o.o.flags &= ~LFS_I_DIRTY;
     t->o.o.state = LFSR_TSTATE_MROOTANCHOR;
     t->o.o.mdir.mid = -1;
     t->o.o.mdir.rbyd.weight = 0;

lfs.h

@@ -98,7 +98,6 @@ enum lfs_error {
     LFS_ERR_UNKNOWN     = -1,   // Unknown error
     LFS_ERR_INVAL       = -22,  // Invalid parameter
     LFS_ERR_NOTSUP      = -95,  // Operation not supported
-    LFS_ERR_BUSY        = -16,  // Device or resource busy
     LFS_ERR_IO          = -5,   // Error during device operation
     LFS_ERR_CORRUPT     = -84,  // Corrupted
     LFS_ERR_NOENT       = -2,   // No directory entry
@@ -169,8 +168,7 @@ enum lfs_btype {
 // Traversal flags
 enum lfs_traversal_flags {
     // traversal open flags
-    LFS_T_MTREEONLY     = 0x0008, // Only traverse the mtree
-    LFS_T_EXCL          = 0x0010, // Terminate if filesystem modified
+    LFS_T_MTREEONLY     = 0x0010, // Only traverse the mtree
     LFS_T_MKCONSISTENT  = 0x0020, // Make the filesystem consistent
     LFS_T_LOOKAHEAD     = 0x0040, // Populate lookahead buffer
     LFS_T_COMPACT       = 0x0080, // Compact metadata logs
@@ -179,9 +177,11 @@ enum lfs_traversal_flags {
 // TODO
 //    LFS_T_REPAIRMETA    = 0x0400, // Repair metadata blocks
 //    LFS_T_REPAIRDATA    = 0x0c00, // Repair metadata + data blocks
+};
 
-    // internally used flags
-    LFS_F_DIRTY         = 0x1000, // Filesystem has been modified
+enum lfs_tinfo_flags {
+    // traversal info flags
+    LFS_I_DIRTY         = 0x1000, // Filesystem has been modified
 };
 
 
@@ -385,6 +385,9 @@ struct lfs_fsinfo {
 
 // Traversal info structure
 struct lfs_tinfo {
+    // Traversal flags
+    uint16_t flags;
+
     // Type of the block
     uint8_t btype;
 

scripts/dbgerr.py

@@ -6,7 +6,6 @@ ERRS = [
     ('UNKNOWN',         -1,     "Unknown error"                     ),
     ('INVAL',           -22,    "Invalid parameter"                 ),
     ('NOTSUP',          -95,    "Operation not supported"           ),
-    ('BUSY',            -16,    "Device or resource busy"           ),
     ('IO',              -5,     "Error during device operation"     ),
     ('CORRUPT',         -84,    "Corrupted"                         ),
     ('NOENT',           -2,     "No directory entry"                ),