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Moved away from bool exists, prefer tag != LFS3_ERR_NOENT

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The main motivation for the `bool exists` pattern was to avoid issues
with err clobbering. But now that lfs3_mtree_pathlookup returns a
muxed tag + err, this is less of a concern.

In littlefs, the err variable is frequently used as a short lived
temporary for propagating error codes. So frequent that I really
wouldn't trust its state after a couple of lines. Quickly converting
err -> bool exists reduced the risk that some necessary err state ends
up clobbered in a refactor.

This risk is still present for the tag variable, but it's already more
common for tags to hold persistent state (they hold file types after
all), so I think this risk is manageable.

And why get rid of a variable that's arguably more self-documenting?
When you're trying to keep a program's state in your head, less state is
better than more state.

No code changes.
This commit is contained in:
Christopher Haster
2025-07-17 18:38:45 -05:00
parent 35d8c36dd1
commit 9ac5ee4f53
1 changed files with 30 additions and 29 deletions
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lfs3.c
+30 -29
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@@ -10506,8 +10506,7 @@ int lfs3_mkdir(lfs3_t *lfs3, const char *path) {
return tag;
}
// already exists? pretend orphans don't exist
bool exists = (tag != LFS3_ERR_NOENT);
if (exists && tag != LFS3_TAG_ORPHAN) {
if (tag != LFS3_ERR_NOENT && tag != LFS3_TAG_ORPHAN) {
return LFS3_ERR_EXIST;
}
@@ -10581,13 +10580,13 @@ int lfs3_mkdir(lfs3_t *lfs3, const char *path) {
// check if we have a collision, if we do, search for the next
// available did
while (true) {
tag = lfs3_mtree_namelookup(lfs3, did_, NULL, 0,
lfs3_stag_t tag_ = lfs3_mtree_namelookup(lfs3, did_, NULL, 0,
&mdir, NULL);
if (tag < 0) {
if (tag == LFS3_ERR_NOENT) {
if (tag_ < 0) {
if (tag_ == LFS3_ERR_NOENT) {
break;
}
return tag;
return tag_;
}
// try the next did
@@ -10621,12 +10620,14 @@ int lfs3_mkdir(lfs3_t *lfs3, const char *path) {
// committing our bookmark may have changed the mid of our metadata entry,
// we need to look it up again, we can at least avoid the full path walk
tag = lfs3_mtree_namelookup(lfs3, did, name, name_len,
lfs3_stag_t tag_ = lfs3_mtree_namelookup(lfs3, did, name, name_len,
&mdir, NULL);
if (tag < 0 && tag != LFS3_ERR_NOENT) {
return tag;
if (tag_ < 0 && tag_ != LFS3_ERR_NOENT) {
return tag_;
}
LFS3_ASSERT((exists) ? tag >= 0 : tag == LFS3_ERR_NOENT);
LFS3_ASSERT((tag != LFS3_ERR_NOENT)
? tag_ >= 0
: tag_ == LFS3_ERR_NOENT);
// commit our new directory into our parent, zeroing the grm in the
// process
@@ -10634,7 +10635,8 @@ int lfs3_mkdir(lfs3_t *lfs3, const char *path) {
lfs3_alloc_ckpoint(lfs3);
err = lfs3_mdir_commit(lfs3, &mdir, LFS3_RATTRS(
LFS3_RATTR_NAME(
LFS3_TAG_MASK12 | LFS3_TAG_DIR, (!exists) ? +1 : 0,
LFS3_TAG_MASK12 | LFS3_TAG_DIR,
(tag == LFS3_ERR_NOENT) ? +1 : 0,
did, name, name_len),
LFS3_RATTR_LEB128(
LFS3_TAG_DID, 0, did_)));
@@ -10645,7 +10647,7 @@ int lfs3_mkdir(lfs3_t *lfs3, const char *path) {
// update in-device state
for (lfs3_omdir_t *o = lfs3->omdirs; o; o = o->next) {
// mark any clobbered uncreats as zombied
if (exists
if (tag != LFS3_ERR_NOENT
&& lfs3_o_type(o->flags) == LFS3_TYPE_REG
&& o->mdir.mid == mdir.mid) {
o->flags = (o->flags & ~LFS3_o_UNCREAT)
@@ -10654,7 +10656,7 @@ int lfs3_mkdir(lfs3_t *lfs3, const char *path) {
| LFS3_O_DESYNC;
// update dir positions
} else if (!exists
} else if (tag == LFS3_ERR_NOENT
&& lfs3_o_type(o->flags) == LFS3_TYPE_DIR
&& ((lfs3_dir_t*)o)->did == did
&& o->mdir.mid >= mdir.mid) {
@@ -10878,11 +10880,10 @@ int lfs3_rename(lfs3_t *lfs3, const char *old_path, const char *new_path) {
&& lfs3_path_islast(new_path))) {
return new_tag;
}
bool exists = (new_tag != LFS3_ERR_NOENT);
// there are a few cases we need to watch out for
lfs3_did_t new_did_ = 0;
if (!exists) {
if (new_tag == LFS3_ERR_NOENT) {
// if we're a file, don't allow trailing slashes
if (old_tag != LFS3_TAG_DIR && lfs3_path_isdir(new_path)) {
return LFS3_ERR_NOTDIR;
@@ -10921,14 +10922,14 @@ int lfs3_rename(lfs3_t *lfs3, const char *old_path, const char *new_path) {
if (new_tag == LFS3_TAG_DIR) {
// TODO deduplicate the isempty check with lfs3_remove?
// first lets figure out the did
lfs3_data_t data;
lfs3_stag_t tag = lfs3_mdir_lookup(lfs3, &new_mdir, LFS3_TAG_DID,
&data);
if (tag < 0) {
return tag;
lfs3_data_t data_;
lfs3_stag_t tag_ = lfs3_mdir_lookup(lfs3, &new_mdir, LFS3_TAG_DID,
&data_);
if (tag_ < 0) {
return tag_;
}
err = lfs3_data_readleb128(lfs3, &data, &new_did_);
err = lfs3_data_readleb128(lfs3, &data_, &new_did_);
if (err) {
return err;
}
@@ -10959,7 +10960,8 @@ int lfs3_rename(lfs3_t *lfs3, const char *old_path, const char *new_path) {
lfs3_alloc_ckpoint(lfs3);
err = lfs3_mdir_commit(lfs3, &new_mdir, LFS3_RATTRS(
LFS3_RATTR_NAME(
LFS3_TAG_MASK12 | old_tag, (!exists) ? +1 : 0,
LFS3_TAG_MASK12 | old_tag,
(new_tag == LFS3_ERR_NOENT) ? +1 : 0,
new_did, new_path, lfs3_path_namelen(new_path)),
LFS3_RATTR_MOVE(&old_mdir)));
if (err) {
@@ -10969,7 +10971,7 @@ int lfs3_rename(lfs3_t *lfs3, const char *old_path, const char *new_path) {
// update in-device state
for (lfs3_omdir_t *o = lfs3->omdirs; o; o = o->next) {
// mark any clobbered uncreats as zombied
if (exists
if (new_tag != LFS3_ERR_NOENT
&& lfs3_o_type(o->flags) == LFS3_TYPE_REG
&& o->mdir.mid == new_mdir.mid) {
o->flags = (o->flags & ~LFS3_o_UNCREAT)
@@ -10990,7 +10992,7 @@ int lfs3_rename(lfs3_t *lfs3, const char *old_path, const char *new_path) {
// update dir positions
} else if (lfs3_o_type(o->flags) == LFS3_TYPE_DIR) {
if (!exists
if (new_tag == LFS3_ERR_NOENT
&& ((lfs3_dir_t*)o)->did == new_did
&& o->mdir.mid >= new_mdir.mid) {
((lfs3_dir_t*)o)->pos += 1;
@@ -11007,7 +11009,7 @@ int lfs3_rename(lfs3_t *lfs3, const char *old_path, const char *new_path) {
// clobber entangled traversals
} else if (lfs3_o_type(o->flags) == LFS3_type_TRAVERSAL
&& ((exists && o->mdir.mid == new_mdir.mid)
&& ((new_tag != LFS3_ERR_NOENT && o->mdir.mid == new_mdir.mid)
|| o->mdir.mid == lfs3->grm.queue[0])) {
lfs3_traversal_clobber(lfs3, (lfs3_traversal_t*)o);
}
@@ -11669,10 +11671,9 @@ int lfs3_file_opencfg_(lfs3_t *lfs3, lfs3_file_t *file,
err = tag;
goto failed;
}
bool exists = (tag != LFS3_ERR_NOENT);
// creating a new entry?
if (!exists || tag == LFS3_TAG_ORPHAN) {
if (tag == LFS3_ERR_NOENT || tag == LFS3_TAG_ORPHAN) {
if (!lfs3_o_iscreat(file->b.o.flags)) {
err = LFS3_ERR_NOENT;
goto failed;
@@ -11693,7 +11694,7 @@ int lfs3_file_opencfg_(lfs3_t *lfs3, lfs3_file_t *file,
}
// if stickynote, mark as uncreated + unsync
if (exists) {
if (tag != LFS3_ERR_NOENT) {
file->b.o.flags |= LFS3_o_UNCREAT | LFS3_o_UNSYNC;
}
#endif
@@ -11729,7 +11730,7 @@ int lfs3_file_opencfg_(lfs3_t *lfs3, lfs3_file_t *file,
// need to create an entry?
#ifndef LFS3_RDONLY
if (!exists) {
if (tag == LFS3_ERR_NOENT) {
// small file wrset? can we atomically commit everything in one
// commit? currently this is only possible via lfs3_set
if (lfs3_o_iswrset(file->b.o.flags)