Github/littlefs
1
Fork 0
Code Actions Activity

Adopted internal LFSR_TAG_GRMPUSH for atomic self-grming commits

Browse Source 
So instead of special behavior for only bookmark tags, LFSR_TAG_GRMPUSH
allows pushing any mid to the grm queue.

The benefit of LFSR_TAG_GRMPUSH, vs just calling lfsr_grm_push before
lfsr_mdir_commit, is that you can push mids that don't exist yet. This
lets you to create self-grming mids that effectively don't exist until
some other work has completed.

We currently use this to atomically create directory + bookmark entries,
but it may have some other uses in the future.

---

The extra rattr does add a bit of code, but fortunately no stack, since
lfsr_mkdir is not on the stack hot-path:

           code          stack          ctx
  before: 35768           2368          640
  after:  35796 (+0.1%)   2368 (+0.0%)  640 (+0.0%)
This commit is contained in:
Christopher Haster
2025-04-29 00:48:39 -05:00
parent e6f28e202e
commit ee406c1709
1 changed files with 14 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lfs.c
+14 -5
View File
@@ -1163,8 +1163,9 @@ enum lfsr_tag {
LFSR_TAG_INTERNAL = 0x0800,
LFSR_TAG_RATTRS = 0x0800,
LFSR_TAG_SHRUBCOMMIT = 0x0801,
LFSR_TAG_MOVE = 0x0802,
LFSR_TAG_ATTRS = 0x0803,
LFSR_TAG_GRMPUSH = 0x0802,
LFSR_TAG_MOVE = 0x0803,
LFSR_TAG_ATTRS = 0x0804,
// some in-device only tag modifiers
LFSR_TAG_RM = 0x8000,
@@ -7894,6 +7895,11 @@ static int lfsr_mdir_commit__(lfs_t *lfs, lfsr_mdir_t *mdir,
return err;
}
// push a new grm, this tag lets us push grms atomically when
// creating new mids
} else if (rattrs[i].tag == LFSR_TAG_GRMPUSH) {
// do nothing here, this is handled up in lfsr_mdir_commit
// move tags copy over any tags associated with the source's rid
// TODO can this be deduplicated with lfsr_mdir_compact__ more?
// it _really_ wants to be deduplicated
@@ -8512,8 +8518,9 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir,
// keep in mind we revert to on-disk gstate if we run into an error
lfsr_smid_t mid_ = mdir->mid;
for (lfs_size_t i = 0; i < rattr_count; i++) {
// automatically create grms for new bookmarks
if (rattrs[i].tag == LFSR_TAG_BOOKMARK) {
// push a new grm, this tag lets us push grms atomically when
// creating new mids
if (rattrs[i].tag == LFSR_TAG_GRMPUSH) {
lfsr_grm_push(lfs, mid_);
// adjust pending grms?
@@ -10273,7 +10280,9 @@ int lfsr_mkdir(lfs_t *lfs, const char *path) {
lfs_alloc_ckpoint(lfs);
err = lfsr_mdir_commit(lfs, &mdir, LFSR_RATTRS(
LFSR_RATTR_NAME(
LFSR_TAG_BOOKMARK, +1, did_, NULL, 0)));
LFSR_TAG_BOOKMARK, +1, did_, NULL, 0),
LFSR_RATTR(
LFSR_TAG_GRMPUSH, 0)));
if (err) {
return err;
}