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Tweaked lfsr_file_open to only sync when LFS_O_SYNC + LFS_O_CREAT

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So we keep the behavior of creating reg files with lfsr_file_open +
LFS_O_SYNC, but only clear the desync flag if lfsr_file_open would
mutate the filesystem.

This is hopefully a simpler model to reason about, and makes LFS_O_SYNC
+ LFS_O_DESYNC a bit less weird.

Saves a little bit of code:

           code          stack          ctx
  before: 35836           2488          640
  after:  35820 (-0.0%)   2480 (-0.3%)  640 (+0.0%)
This commit is contained in:
Christopher Haster
2025-04-25 21:17:50 -05:00
parent 0f4ad6d842
commit 4b87499605
2 changed files with 164 additions and 98 deletions
Download Patch File Download Diff File Expand all files Collapse all files
lfs.c
+1 -8
View File
@@ -11459,19 +11459,12 @@ int lfsr_file_opencfg(lfs_t *lfs, lfsr_file_t *file,
lfsr_omdir_open(lfs, &file->b.o);
// sync if requested
if (lfsr_o_issync(flags) && !lfsr_o_isrdonly(flags)) {
if (lfsr_o_iscreat(flags) && lfsr_o_issync(flags)) {
err = lfsr_file_sync(lfs, file);
if (err) {
lfsr_omdir_close(lfs, &file->b.o);
goto failed;
}
// TODO should we do this for all LFS_O_SYNC operations?
// sync clears the desync flag, so reset it if we're desync
//
// note this matches the behavior of calling lfsr_file_sync and
// then lfsr_file_desync after opening the file
file->b.o.flags |= flags & LFS_O_DESYNC;
}
return 0;
tests/test_fsync.toml
+163 -90
View File
@@ -2463,15 +2463,18 @@ code = '''
// sync a
lfsr_file_sync(&lfs, &a) => 0;
// c should revert to a's contents
// c should still have b, this may be surprising, but the implicit
// sync in open+O_CREAT clears the desync flag
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("hello!");
assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// rewrite a
// write to a
lfsr_file_write(&lfs, &a, "bonjour!", strlen("bonjour!"))
=> strlen("bonjour!");
@@ -2498,6 +2501,13 @@ code = '''
assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// reopen a
lfsr_file_close(&lfs, &a) => 0;
lfsr_file_open(&lfs, &a, "jello",
LFS_O_WRONLY
| ((FLUSH == 2) ? LFS_O_FLUSH : 0)
| ((SYNC == 2) ? LFS_O_SYNC : 0)
| LFS_O_DESYNC) => 0;
// rewrite b
lfsr_file_rewind(&lfs, &b) => 0;
lfsr_file_write(&lfs, &b, "ohayo!", strlen("ohayo!"))
@@ -2516,22 +2526,19 @@ code = '''
// sync a
lfsr_file_sync(&lfs, &a) => 0;
// c should still have b, this may be surprising, but the implicit
// sync when we rewrote a clears the desync flag
// c should revert to a's contents
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("bonjour!");
assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// desync a
lfsr_file_desync(&lfs, &a) => 0;
// rewrite b
lfsr_file_rewind(&lfs, &b) => 0;
lfsr_file_write(&lfs, &b, "zdrasti!", strlen("zdrasti!"))
// rewrite a
lfsr_file_rewind(&lfs, &a) => 0;
lfsr_file_write(&lfs, &a, "zdrasti!", strlen("zdrasti!"))
=> strlen("zdrasti!");
// should immediately show up in c
@@ -2544,22 +2551,11 @@ code = '''
assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// sync a
lfsr_file_sync(&lfs, &a) => 0;
// c should revert to a's contents
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// lets rewrite a one last time
lfsr_file_rewind(&lfs, &a) => 0;
lfsr_file_write(&lfs, &a, "annyeong!", strlen("annyeong!"))
// desync a
lfsr_file_desync(&lfs, &a) => 0;
// rewrite b
lfsr_file_rewind(&lfs, &b) => 0;
lfsr_file_write(&lfs, &b, "annyeong!", strlen("annyeong!"))
=> strlen("annyeong!");
// should immediately show up in c
@@ -2572,18 +2568,46 @@ code = '''
assert(memcmp(rbuf, "annyeong!", strlen("annyeong!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// sync a
lfsr_file_sync(&lfs, &a) => 0;
// c should revert to a's contents
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("zdrasti!");
assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("zdrasti!");
assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// lets rewrite a one last time
lfsr_file_rewind(&lfs, &a) => 0;
lfsr_file_write(&lfs, &a, "czesc!", strlen("czesc!"))
=> strlen("czesc!");
// should immediately show up in c
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("czesc!i!");
assert(memcmp(rbuf, "czesc!i!", strlen("czesc!i!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("czesc!i!");
assert(memcmp(rbuf, "czesc!i!", strlen("czesc!i!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// close a and b
lfsr_file_close(&lfs, &a) => 0;
lfsr_file_close(&lfs, &b) => 0;
// should still have a
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("annyeong!");
assert(memcmp(rbuf, "annyeong!", strlen("annyeong!")) == 0);
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("czesc!i!");
assert(memcmp(rbuf, "czesc!i!", strlen("czesc!i!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("annyeong!");
assert(memcmp(rbuf, "annyeong!", strlen("annyeong!")) == 0);
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("czesc!i!");
assert(memcmp(rbuf, "czesc!i!", strlen("czesc!i!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
lfsr_file_close(&lfs, &c) => 0;
@@ -4280,12 +4304,15 @@ code = '''
// sync a
lfsr_file_sync(&lfs, &a) => 0;
// c should revert to a's contents
// c should still have b, this may be surprising, but the implicit
// sync in open+O_CREAT clears the desync flag
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("hello!");
assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// reopen a
@@ -4310,59 +4337,58 @@ code = '''
assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// resync a
lfsr_file_resync(&lfs, &a) => 0;
// sync a
lfsr_file_sync(&lfs, &a) => 0;
// c should still show b
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("bonjour!");
assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// desync a
lfsr_file_desync(&lfs, &a) => 0;
// rewrite b
lfsr_file_rewind(&lfs, &b) => 0;
lfsr_file_write(&lfs, &b, "ohayo!r!", strlen("ohayo!r!"))
=> strlen("ohayo!r!");
// should immediately show up in c
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!r!");
assert(memcmp(rbuf, "ohayo!r!", strlen("ohayo!r!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// sync a
lfsr_file_sync(&lfs, &a) => 0;
// c should revert to a's contents
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("bonjour!");
assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("hello!");
assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("bonjour!");
assert(memcmp(rbuf, "bonjour!", strlen("bonjour!")) == 0);
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("hello!");
assert(memcmp(rbuf, "hello!", strlen("hello!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// rewrite a
lfsr_file_rewind(&lfs, &a) => 0;
lfsr_file_write(&lfs, &a, "annyeong!", strlen("annyeong!"))
=> strlen("annyeong!");
// desync b
lfsr_file_desync(&lfs, &b) => 0;
// resync b
lfsr_file_resync(&lfs, &b) => 0;
// reopen a
lfsr_file_close(&lfs, &a) => 0;
lfsr_file_open(&lfs, &a, "jello",
LFS_O_WRONLY
| ((FLUSH == 2) ? LFS_O_FLUSH : 0)
| ((SYNC == 2) ? LFS_O_SYNC : 0)
| LFS_O_DESYNC) => 0;
// rewrite b
lfsr_file_rewind(&lfs, &b) => 0;
lfsr_file_write(&lfs, &b, "ohayo!", strlen("ohayo!"))
=> strlen("ohayo!");
// should immediately show up in c
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!");
assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!");
assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// resync a
lfsr_file_resync(&lfs, &a) => 0;
// sync a
lfsr_file_sync(&lfs, &a) => 0;
// c should still show b's changes
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!");
assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!");
assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// desync a
lfsr_file_desync(&lfs, &a) => 0;
// rewrite b
lfsr_file_rewind(&lfs, &b) => 0;
lfsr_file_write(&lfs, &b, "zdrasti!", strlen("zdrasti!"))
@@ -4370,12 +4396,59 @@ code = '''
// should immediately show up in c
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("zdrasti!!");
assert(memcmp(rbuf, "zdrasti!!", strlen("zdrasti!!")) == 0);
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("zdrasti!");
assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("zdrasti!!");
assert(memcmp(rbuf, "zdrasti!!", strlen("zdrasti!!")) == 0);
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("zdrasti!");
assert(memcmp(rbuf, "zdrasti!", strlen("zdrasti!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// sync a
lfsr_file_sync(&lfs, &a) => 0;
// c should revert to a's contents
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("ohayo!");
assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("ohayo!");
assert(memcmp(rbuf, "ohayo!", strlen("ohayo!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// rewrite a
lfsr_file_rewind(&lfs, &a) => 0;
lfsr_file_write(&lfs, &a, "annyeong!", strlen("annyeong!"))
=> strlen("annyeong!");
// should immediately show up in c
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("annyeong!");
assert(memcmp(rbuf, "annyeong!", strlen("annyeong!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("annyeong!");
assert(memcmp(rbuf, "annyeong!", strlen("annyeong!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// desync b
lfsr_file_desync(&lfs, &b) => 0;
// resync b
lfsr_file_resync(&lfs, &b) => 0;
// rewrite b
lfsr_file_rewind(&lfs, &b) => 0;
lfsr_file_write(&lfs, &b, "czesc!", strlen("czesc!"))
=> strlen("czesc!");
// should immediately show up in c
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("czesc!ng!");
assert(memcmp(rbuf, "czesc!ng!", strlen("czesc!ng!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("czesc!ng!");
assert(memcmp(rbuf, "czesc!ng!", strlen("czesc!ng!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
// close b
@@ -4385,12 +4458,12 @@ code = '''
// c should still show b's changes
lfsr_file_rewind(&lfs, &c) => 0;
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("zdrasti!!");
assert(memcmp(rbuf, "zdrasti!!", strlen("zdrasti!!")) == 0);
lfsr_file_read(&lfs, &c, rbuf, sizeof(rbuf)) => strlen("czesc!ng!");
assert(memcmp(rbuf, "czesc!ng!", strlen("czesc!ng!")) == 0);
// and on disk
lfsr_file_open(&lfs, &d, "jello", LFS_O_RDONLY) => 0;
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("zdrasti!!");
assert(memcmp(rbuf, "zdrasti!!", strlen("zdrasti!!")) == 0);
lfsr_file_read(&lfs, &d, rbuf, sizeof(rbuf)) => strlen("czesc!ng!");
assert(memcmp(rbuf, "czesc!ng!", strlen("czesc!ng!")) == 0);
lfsr_file_close(&lfs, &d) => 0;
lfsr_file_close(&lfs, &c) => 0;