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Adopted similar mark-if-truncate-to-zero logic for file caches

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It worked well for file leaves, so we might as well adopt the same
post-truncate/fruncate logic for caches.

This moves checks for cache.size==0 from lfs3_file_write into
lfs3_file_truncate/fruncate.

Note that lfs3_file_truncate/fruncate are the only functions (for now)
that can reduce the size of a file.

Adds a bit of code, which is probably why this wasn't adopted earlier,
but it reduces the state we need to worry about and makes things easier
to understand:

           code          stack          ctx
  before: 37468           2464          656
  after:  37492 (+0.1%)   2464 (+0.0%)  656 (+0.0%)
This commit is contained in:
Christopher Haster
2025-07-03 15:06:28 -05:00
parent 8365b27dea
commit 35e407372c
1 changed files with 11 additions and 6 deletions
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lfs3.c
+11 -6
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@@ -13332,8 +13332,7 @@ lfs3_ssize_t lfs3_file_write(lfs3_t *lfs3, lfs3_file_t *file,
// strictly necessary, but enforces a more intuitive write order
// and avoids weird cases with low-level write heuristics
//
if ((!lfs3_o_isunflush(file->b.o.flags)
|| file->cache.size == 0)
if (!lfs3_o_isunflush(file->b.o.flags)
&& size >= lfs3_file_cachesize(lfs3, file)) {
err = lfs3_file_flush_(lfs3, file,
pos, buffer_, size);
@@ -13369,16 +13368,14 @@ lfs3_ssize_t lfs3_file_write(lfs3_t *lfs3, lfs3_file_t *file,
// 2. Bypassing the cache above means we only write to the
// cache once, and flush at most twice.
//
if ((!lfs3_o_isunflush(file->b.o.flags)
|| file->cache.size == 0)
if (!lfs3_o_isunflush(file->b.o.flags)
|| (pos >= file->cache.pos
&& pos <= file->cache.pos + file->cache.size
&& pos
< file->cache.pos
+ lfs3_file_cachesize(lfs3, file))) {
// unused cache? we can move it where we need it
if ((!lfs3_o_isunflush(file->b.o.flags)
|| file->cache.size == 0)) {
if (!lfs3_o_isunflush(file->b.o.flags)) {
file->cache.pos = pos;
file->cache.size = 0;
}
@@ -14006,6 +14003,10 @@ int lfs3_file_truncate(lfs3_t *lfs3, lfs3_file_t *file, lfs3_off_t size_) {
file->cache.size,
size_ - lfs3_min(file->cache.pos, size_));
file->cache.pos = lfs3_min(file->cache.pos, size_);
// mark as flushed if this completely truncates our cache
if (file->cache.size == 0) {
lfs3_file_discardcache(file);
}
return 0;
@@ -14102,6 +14103,10 @@ int lfs3_file_fruncate(lfs3_t *lfs3, lfs3_file_t *file, lfs3_off_t size_) {
file->cache.pos -= lfs3_smin(
size - size_,
file->cache.pos);
// mark as flushed if this completely truncates our cache
if (file->cache.size == 0) {
lfs3_file_discardcache(file);
}
// fruncate _does_ update pos, to keep the same pos relative to end
// of file, though we can't let pos go negative