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Added handling for corrupt as initial state of blocks

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Before this, littlefs incorrectly assumed corrupt blocks were only the result
of our own modification. This would be fine for most cases of freshly
erased storage, but for storage with block-level ECC this wasn't always
true.

Fortunately, it's quite easy for littlefs to handle this case correctly,
as long as corrupt storage always reports that it is corrupt, which for
most forms of ECC is the case unless we perform a write on the storage.

found by rojer
This commit is contained in:
Christopher Haster
2018-07-16 15:22:02 -05:00
parent f94d233deb
commit 041e90a1ca
1 changed files with 11 additions and 2 deletions
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13
lfs.c
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@@ -417,11 +417,14 @@ static int lfs_dir_alloc(lfs_t *lfs, lfs_dir_t *dir) {
// rather than clobbering one of the blocks we just pretend // rather than clobbering one of the blocks we just pretend
// the revision may be valid // the revision may be valid
int err = lfs_bd_read(lfs, dir->pair[0], 0, &dir->d.rev, 4); int err = lfs_bd_read(lfs, dir->pair[0], 0, &dir->d.rev, 4);
dir->d.rev = lfs_fromle32(dir->d.rev); if (err && err != LFS_ERR_CORRUPT) {
if (err) {
return err; return err;
} }
if (err != LFS_ERR_CORRUPT) {
dir->d.rev = lfs_fromle32(dir->d.rev);
}
// set defaults // set defaults
dir->d.rev += 1; dir->d.rev += 1;
dir->d.size = sizeof(dir->d)+4; dir->d.size = sizeof(dir->d)+4;
@@ -445,6 +448,9 @@ static int lfs_dir_fetch(lfs_t *lfs,
int err = lfs_bd_read(lfs, tpair[i], 0, &test, sizeof(test)); int err = lfs_bd_read(lfs, tpair[i], 0, &test, sizeof(test));
lfs_dir_fromle32(&test); lfs_dir_fromle32(&test);
if (err) { if (err) {
if (err == LFS_ERR_CORRUPT) {
continue;
}
return err; return err;
} }
@@ -464,6 +470,9 @@ static int lfs_dir_fetch(lfs_t *lfs,
err = lfs_bd_crc(lfs, tpair[i], sizeof(test), err = lfs_bd_crc(lfs, tpair[i], sizeof(test),
(0x7fffffff & test.size) - sizeof(test), &crc); (0x7fffffff & test.size) - sizeof(test), &crc);
if (err) { if (err) {
if (err == LFS_ERR_CORRUPT) {
continue;
}
return err; return err;
} }