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Added sticky-bit for preventing file syncs after write errors

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Short story, files are no longer committed to directories during
file sync/close if the last write did not complete successfully.
This avoids a set of interesting user-experience issues related
to the end-of-life behaviour of the filesystem.

As a filesystem approaches end-of-life, the chances of running into
LFS_ERR_NOSPC grows rather quickly. Since this condition occurs after
at the end of a devices life, it's likely that operating in these
conditions hasn't been tested thoroughly.

In the specific case of file-writes, you can hit an LFS_ERR_NOSPC after
parts of the file have been written out. If the program simply continues
and closes the file, the file is written out half completed. Since
littlefs has a strong garuntee the prevents half-writes, it's unlikely
this state of the file would be expected.

To make things worse, since close is also responsible for memory
cleanup, it's actually _impossible_ to continue working as it was
without leaking memory.

By prevent the file commits, end-of-life behaviour should at least retain
a previous copy of the filesystem without any surprises.
This commit is contained in:
Christopher Haster
2017-11-16 17:25:41 -06:00
parent 2612e1b3fa
commit 843e3c6c75
3 changed files with 28 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files

9
lfs.c
View File

@@ -1403,7 +1403,9 @@ int lfs_file_sync(lfs_t *lfs, lfs_file_t *file) {
return err;
}
if ((file->flags & LFS_F_DIRTY) && !lfs_pairisnull(file->pair)) {
if ((file->flags & LFS_F_DIRTY) &&
!(file->flags & LFS_F_ERRED) &&
!lfs_pairisnull(file->pair)) {
// update dir entry
lfs_dir_t cwd;
int err = lfs_dir_fetch(lfs, &cwd, file->pair);
@@ -1537,6 +1539,7 @@ lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
file->head, file->size,
file->pos-1, &file->block, &file->off);
if (err) {
file->flags |= LFS_F_ERRED;
return err;
}
@@ -1550,6 +1553,7 @@ lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
file->block, file->pos,
&file->block, &file->off);
if (err) {
file->flags |= LFS_F_ERRED;
return err;
}
@@ -1565,6 +1569,7 @@ lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
if (err == LFS_ERR_CORRUPT) {
goto relocate;
}
file->flags |= LFS_F_ERRED;
return err;
}
@@ -1572,6 +1577,7 @@ lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
relocate:
err = lfs_file_relocate(lfs, file);
if (err) {
file->flags |= LFS_F_ERRED;
return err;
}
}
@@ -1584,6 +1590,7 @@ relocate:
lfs_alloc_ack(lfs);
}
file->flags &= ~LFS_F_ERRED;
return size;
}

1
lfs.h
View File

@@ -75,6 +75,7 @@ enum lfs_open_flags {
LFS_F_DIRTY = 0x10000, // File does not match storage
LFS_F_WRITING = 0x20000, // File has been written since last flush
LFS_F_READING = 0x40000, // File has been read since last flush
LFS_F_ERRED = 0x80000, // An error occured during write
};
// File seek flags

26
tests/test_alloc.sh
View File

@@ -121,6 +121,7 @@ tests/test.py << TEST
size = strlen("exhaustion");
memcpy(buffer, "exhaustion", size);
lfs_file_write(&lfs, &file[0], buffer, size) => size;
lfs_file_sync(&lfs, &file[0]) => 0;
size = strlen("blahblahblahblah");
memcpy(buffer, "blahblahblahblah", size);
@@ -142,6 +143,7 @@ tests/test.py << TEST
lfs_mount(&lfs, &cfg) => 0;
lfs_file_open(&lfs, &file[0], "exhaustion", LFS_O_RDONLY);
size = strlen("exhaustion");
lfs_file_size(&lfs, &file[0]) => size;
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "exhaustion", size) => 0;
lfs_file_close(&lfs, &file[0]) => 0;
@@ -166,6 +168,7 @@ tests/test.py << TEST
size = strlen("exhaustion");
memcpy(buffer, "exhaustion", size);
lfs_file_write(&lfs, &file[0], buffer, size) => size;
lfs_file_sync(&lfs, &file[0]) => 0;
size = strlen("blahblahblahblah");
memcpy(buffer, "blahblahblahblah", size);
@@ -187,6 +190,7 @@ tests/test.py << TEST
lfs_mount(&lfs, &cfg) => 0;
lfs_file_open(&lfs, &file[0], "exhaustion", LFS_O_RDONLY);
size = strlen("exhaustion");
lfs_file_size(&lfs, &file[0]) => size;
lfs_file_read(&lfs, &file[0], buffer, size) => size;
memcmp(buffer, "exhaustion", size) => 0;
lfs_file_close(&lfs, &file[0]) => 0;
@@ -196,14 +200,14 @@ TEST
echo "--- Dir exhaustion test ---"
tests/test.py << TEST
lfs_mount(&lfs, &cfg) => 0;
lfs_stat(&lfs, "exhaustion", &info) => 0;
lfs_size_t fullsize = info.size;
lfs_remove(&lfs, "exhaustion") => 0;
lfs_file_open(&lfs, &file[0], "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
size = strlen("blahblahblahblah");
memcpy(buffer, "blahblahblahblah", size);
for (lfs_size_t i = 0; i < fullsize - 2*512; i += size) {
for (lfs_size_t i = 0;
i < (cfg.block_count-6)*(cfg.block_size-8);
i += size) {
lfs_file_write(&lfs, &file[0], buffer, size) => size;
}
lfs_file_close(&lfs, &file[0]) => 0;
@@ -214,7 +218,11 @@ tests/test.py << TEST
lfs_file_open(&lfs, &file[0], "exhaustion", LFS_O_WRONLY | LFS_O_APPEND);
size = strlen("blahblahblahblah");
memcpy(buffer, "blahblahblahblah", size);
for (lfs_size_t i = 0;
i < (cfg.block_size-8);
i += size) {
lfs_file_write(&lfs, &file[0], buffer, size) => size;
}
lfs_file_close(&lfs, &file[0]) => 0;
lfs_mkdir(&lfs, "exhaustiondir") => LFS_ERR_NOSPC;
@@ -224,14 +232,14 @@ TEST
echo "--- Chained dir exhaustion test ---"
tests/test.py << TEST
lfs_mount(&lfs, &cfg) => 0;
lfs_stat(&lfs, "exhaustion", &info) => 0;
lfs_size_t fullsize = info.size;
lfs_remove(&lfs, "exhaustion") => 0;
lfs_file_open(&lfs, &file[0], "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
size = strlen("blahblahblahblah");
memcpy(buffer, "blahblahblahblah", size);
for (lfs_size_t i = 0; i < fullsize - 19*512; i += size) {
for (lfs_size_t i = 0;
i < (cfg.block_count-24)*(cfg.block_size-8);
i += size) {
lfs_file_write(&lfs, &file[0], buffer, size) => size;
}
lfs_file_close(&lfs, &file[0]) => 0;
@@ -247,7 +255,9 @@ tests/test.py << TEST
lfs_file_open(&lfs, &file[0], "exhaustion", LFS_O_WRONLY | LFS_O_CREAT);
size = strlen("blahblahblahblah");
memcpy(buffer, "blahblahblahblah", size);
for (lfs_size_t i = 0; i < fullsize - 20*512; i += size) {
for (lfs_size_t i = 0;
i < (cfg.block_count-26)*(cfg.block_size-8);
i += size) {
lfs_file_write(&lfs, &file[0], buffer, size) => size;
}
lfs_file_close(&lfs, &file[0]) => 0;