Github/littlefs
1
Fork 0
Code Actions Activity

Reimplemented the internal opened-mdir linked-list

Browse Source 
littlefs uses an invasive linked-list in open mdirs to keep any open
files/dirs (and some special mdirs) in sync during filesystem
operations. The main benefit of this is that the filesystem doesn't need
to know the number of open files at compile time.

The implementation here introduces a new type, lfsr_openedmdir_t, for
mdirs that want to participate in the opened-mdir linked-list. This
saves a couple words of memory in the cases where the mdir does not need
to participate in the opend-mdir linked-list.

Since we are creating quite a few more mdir structs in lfsr_mdir_commit now,
the size of this struct is valuable.

The implementation of lfsr_mdir_commit knew this was coming, so aside
from the new type, adding this feature was straightforward:

1. Update opened-mdirs based on in-flight attrs.
2. Update opened-mdirs rbyd state.
3. Mark any deleted opened-mdirs with the reserved mid -2.
4. Test.
This commit is contained in:
Christopher Haster
2023-05-24 16:17:46 -05:00
parent c60fa69ce1
commit 565c8cb9c7
3 changed files with 518 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lfs.c
+65 -1
View File
@@ -4420,6 +4420,31 @@ static inline lfs_size_t lfsr_mdir_weight(const lfsr_mdir_t *mdir) {
return mdir->rbyd.weight;
}
// track "opened" mdirs that may need to by updated
static void lfsr_mdir_addopened(lfs_t *lfs, lfsr_openedmdir_t *opened) {
opened->next = lfs->opened;
lfs->opened = opened;
}
static void lfsr_mdir_removeopened(lfs_t *lfs, lfsr_openedmdir_t *opened) {
for (lfsr_openedmdir_t **p = &lfs->opened; *p; p = &(*p)->next) {
if (*p == opened) {
*p = (*p)->next;
break;
}
}
}
static bool lfsr_mdir_isopened(lfs_t *lfs, const lfsr_openedmdir_t *opened) {
for (lfsr_openedmdir_t *p = lfs->opened; p; p = p->next) {
if (p == opened) {
return true;
}
}
return false;
}
static int lfsr_mdir_alloc(lfs_t *lfs, lfsr_mdir_t *mdir, lfs_ssize_t mid) {
// allocate two blocks
lfs_block_t blocks[2];
@@ -4756,6 +4781,7 @@ compact:;
static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir, lfs_ssize_t *rid,
const lfsr_attr_t *attrs, lfs_size_t attr_count) {
LFS_ASSERT(mdir->mid != -2);
// attempt to commit/compact the mdir normally
lfsr_mdir_t mdir_ = *mdir;
@@ -5321,10 +5347,46 @@ static int lfsr_mdir_commit(lfs_t *lfs, lfsr_mdir_t *mdir, lfs_ssize_t *rid,
lfs->mroot = mroot_;
lfs->mtree = mtree_;
// update any opened mdirs
for (lfsr_openedmdir_t *opened = lfs->opened;
opened;
opened = opened->next) {
if (opened->mdir.mid == mdir->mid
// avoid double-updating our current mdir
&& &opened->mdir != mdir) {
LFS_ASSERT(opened->rid < (lfs_ssize_t)opened->mdir.rbyd.weight);
LFS_ASSERT(opened->rid != -1);
// first play out any attrs that change our rid
for (lfs_size_t i = 0; i < attr_count; i++) {
if (opened->rid >= attrs[i].id) {
// removed?
if (opened->rid + attrs[i].delta < attrs[i].id) {
opened->rid = -2;
opened->mdir.mid = -2;
} else {
opened->rid += attrs[i].delta;
}
}
}
// update mdir to follow rid
if (opened->rid == -2) {
// skip removed mdirs
} else if ((lfs_size_t)opened->rid < mdir_.rbyd.weight) {
opened->mdir = mdir_;
} else {
opened->rid = opened->rid - mdir_.rbyd.weight;
opened->mdir = msibling_;
}
}
}
// update mdir to follow requested rid
lfs_ssize_t rid_ = *rid;
LFS_ASSERT(rid_ <= (lfs_ssize_t)mdir->rbyd.weight);
if (rid_ < 0) {
LFS_ASSERT(rid_ != -2);
if (rid_ == -1) {
*mdir = mroot_;
} else if ((lfs_size_t)rid_ < mdir_.rbyd.weight) {
*mdir = mdir_;
@@ -10222,6 +10284,8 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
lfs->lfs1 = NULL;
#endif
lfs->opened = NULL;
return 0;
cleanup: