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Fixed issue with superblock breaking lfs_dir_seek

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The superblock entry takes up id 0 in the root directory (not all
entries are files, though currently the superblock is the only
exception). Normally, reading a directory correctly skips the
superblock and only reports non-superblock files.

However, this doesn't work perfectly for lfs_dir_seek, which tries
to be clever to not touch the disk.

Fortunately, we can fix this by adding an offset for the superblock.
This will only work while the superblock is the only non-file entry,
otherwise we would need to touch the disk to properly seek in a
directory (though we already touch the disk a bit to get dir-tails
during seeks).

Found by jhartika
This commit is contained in:
Christopher Haster
2019-11-27 11:27:30 -06:00
parent 6b65737715
commit 73fd57b1e4
2 changed files with 84 additions and 4 deletions
Download Patch File Download Diff File Expand all files Collapse all files

14
lfs.c
View File

@@ -2064,10 +2064,14 @@ int lfs_dir_seek(lfs_t *lfs, lfs_dir_t *dir, lfs_off_t off) {
dir->pos = lfs_min(2, off);
off -= dir->pos;
while (off != 0) {
dir->id = lfs_min(dir->m.count, off);
dir->pos += dir->id;
off -= dir->id;
// skip superblock entry
dir->id = (off > 0 && lfs_pair_cmp(dir->head, lfs->root) == 0);
while (off > 0) {
int diff = lfs_min(dir->m.count - dir->id, off);
dir->id += diff;
dir->pos += diff;
off -= diff;
if (dir->id == dir->m.count) {
if (!dir->m.split) {
@@ -2080,6 +2084,8 @@ int lfs_dir_seek(lfs_t *lfs, lfs_dir_t *dir, lfs_off_t off) {
LFS_TRACE("lfs_dir_seek -> %d", err);
return err;
}
dir->id = 0;
}
}

74
tests/test_seek.sh
View File

@@ -428,4 +428,78 @@ scripts/test.py << TEST
TEST
done
echo "--- Root seek test ---"
./scripts/test.py << TEST
lfs_mount(&lfs, &cfg) => 0;
for (int i = 3; i < $MEDIUMSIZE; i++) {
sprintf(path, "hi%03d", i);
lfs_mkdir(&lfs, path) => 0;
}
lfs_dir_open(&lfs, &dir, "/") => 0;
for (int i = 0; i < $MEDIUMSIZE; i++) {
if (i == 0) {
sprintf(path, ".");
} else if (i == 1) {
sprintf(path, "..");
} else if (i == 2) {
sprintf(path, "hello");
} else {
sprintf(path, "hi%03d", i);
}
lfs_dir_read(&lfs, &dir, &info) => 1;
strcmp(path, info.name) => 0;
}
lfs_dir_read(&lfs, &dir, &info) => 0;
lfs_dir_close(&lfs, &dir) => 0;
for (int j = 0; j < $MEDIUMSIZE; j++) {
lfs_soff_t off = -1;
lfs_dir_open(&lfs, &dir, "/") => 0;
for (int i = 0; i < $MEDIUMSIZE; i++) {
if (i == 0) {
sprintf(path, ".");
} else if (i == 1) {
sprintf(path, "..");
} else if (i == 2) {
sprintf(path, "hello");
} else {
sprintf(path, "hi%03d", i);
}
if (i == j) {
off = lfs_dir_tell(&lfs, &dir);
off >= 0 => true;
}
lfs_dir_read(&lfs, &dir, &info) => 1;
strcmp(path, info.name) => 0;
}
lfs_dir_read(&lfs, &dir, &info) => 0;
lfs_dir_close(&lfs, &dir) => 0;
lfs_dir_open(&lfs, &dir, "/") => 0;
lfs_dir_seek(&lfs, &dir, off) => 0;
for (int i = j; i < $MEDIUMSIZE; i++) {
if (i == 0) {
sprintf(path, ".");
} else if (i == 1) {
sprintf(path, "..");
} else if (i == 2) {
sprintf(path, "hello");
} else {
sprintf(path, "hi%03d", i);
}
lfs_dir_read(&lfs, &dir, &info) => 1;
strcmp(path, info.name) => 0;
}
lfs_dir_read(&lfs, &dir, &info) => 0;
lfs_dir_close(&lfs, &dir) => 0;
}
lfs_unmount(&lfs) => 0;
TEST
scripts/results.py