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Added proper handling of orphans

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Unfortunately, threading all dir blocks in a linked-list did
not come without problems.

While it's possible to atomically add a dir to the linked list
(by adding the new dir into the linked-list position immediately
after it's parent, requiring only one atomic update to the parent
block), it is not easy to make sure the linked-list is in a state
that always allows atomic removal of dirs.

The simple solution is to allow this non-atomic removal, with an
additional step to remove any orphans that could have been created
by a power-loss. This deorphan step is only run if the normal
allocator has failed.
This commit is contained in:
Christopher Haster
2017-04-01 12:23:15 -05:00
parent 8a674524fc
commit a3734eeb34
3 changed files with 216 additions and 40 deletions
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32
emubd/lfs_emubd.c
View File

@@ -14,6 +14,8 @@
#include <dirent.h>
#include <sys/stat.h>
#include <unistd.h>
#include <assert.h>
#include <stdbool.h>
// Block device emulated on existing filesystem
@@ -76,12 +78,10 @@ int lfs_emubd_read(lfs_emubd_t *emu, lfs_block_t block,
uint8_t *data = buffer;
// Check if read is valid
if (!(off % emu->info.read_size == 0 &&
size % emu->info.read_size == 0 &&
((uint64_t)block*emu->info.erase_size + off + size
< emu->info.total_size))) {
return -EINVAL;
}
assert(off % emu->info.read_size == 0);
assert(size % emu->info.read_size == 0);
assert((uint64_t)block*emu->info.erase_size + off + size
< emu->info.total_size);
// Zero out buffer for debugging
memset(data, 0, size);
@@ -128,12 +128,10 @@ int lfs_emubd_prog(lfs_emubd_t *emu, lfs_block_t block,
const uint8_t *data = buffer;
// Check if write is valid
if (!(off % emu->info.prog_size == 0 &&
size % emu->info.prog_size == 0 &&
((uint64_t)block*emu->info.erase_size + off + size
< emu->info.total_size))) {
return -EINVAL;
}
assert(off % emu->info.prog_size == 0);
assert(size % emu->info.prog_size == 0);
assert((uint64_t)block*emu->info.erase_size + off + size
< emu->info.total_size);
// Iterate over blocks until enough data is read
while (size > 0) {
@@ -177,12 +175,10 @@ int lfs_emubd_erase(lfs_emubd_t *emu, lfs_block_t block,
lfs_off_t off, lfs_size_t size) {
// Check if erase is valid
if (!(off % emu->info.erase_size == 0 &&
size % emu->info.erase_size == 0 &&
((uint64_t)block*emu->info.erase_size + off + size
< emu->info.total_size))) {
return -EINVAL;
}
assert(off % emu->info.erase_size == 0);
assert(size % emu->info.erase_size == 0);
assert((uint64_t)block*emu->info.erase_size + off + size
< emu->info.total_size);
// Iterate and erase blocks
while (size > 0) {