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Added out-of-order write testing to emubd

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Some forms of storage, mainly anything with an FTL, eMMC, SD, etc, do
not guarantee a strict write order for writes to different blocks. It
would be good to test that this doesn't break littlefs.

This adds LFS_EMUBD_POWERLOSS_OOO to lfs_emubd, which tells lfs_emubd to
try to break any order-dependent code on powerloss.

The behavior right now is a bit simple, but does result in test
breakage:

1. Save the state of the block on first write (erase really) after
   sync/init.

2. On powerloss, revert the first write to its original state.

This might be a bit confusing when debugging, since the block will
appear to time-travel, but doing anything fancier would make emubd quite
a bit more complicated.

You could also get a bit fancier with which/how many blocks to revert,
but this should at least be sufficient to make sure bd sync calls are in
the right place.
This commit is contained in:
Christopher Haster
2024-02-27 12:58:07 -06:00
parent f53a0cc961
commit f2a6f45eef
9 changed files with 125 additions and 13 deletions
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bd/lfs_emubd.h
+9 -6
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@@ -36,17 +36,18 @@ extern "C"
// Not that read-noop is not allowed. Read _must_ return a consistent (but
// may be arbitrary) value on every read.
typedef enum lfs_emubd_badblock_behavior {
LFS_EMUBD_BADBLOCK_PROGERROR,
LFS_EMUBD_BADBLOCK_ERASEERROR,
LFS_EMUBD_BADBLOCK_READERROR,
LFS_EMUBD_BADBLOCK_PROGNOOP,
LFS_EMUBD_BADBLOCK_ERASENOOP,
LFS_EMUBD_BADBLOCK_PROGERROR = 0, // Error on prog
LFS_EMUBD_BADBLOCK_ERASEERROR = 1, // Error on erase
LFS_EMUBD_BADBLOCK_READERROR = 2, // Error on read
LFS_EMUBD_BADBLOCK_PROGNOOP = 3, // Prog does nothing silently
LFS_EMUBD_BADBLOCK_ERASENOOP = 4, // Erase does nothing silently
} lfs_emubd_badblock_behavior_t;
// Mode determining how power-loss behaves during testing. For now this
// only supports a noop behavior, leaving the data on-disk untouched.
typedef enum lfs_emubd_powerloss_behavior {
LFS_EMUBD_POWERLOSS_NOOP,
LFS_EMUBD_POWERLOSS_NOOP = 0, // Progs are atomic
LFS_EMUBD_POWERLOSS_OOO = 1, // Blocks are written out-of-order
} lfs_emubd_powerloss_behavior_t;
// Type for measuring read/program/erase operations
@@ -152,6 +153,8 @@ typedef struct lfs_emubd {
lfs_emubd_io_t proged;
lfs_emubd_io_t erased;
lfs_emubd_powercycles_t power_cycles;
lfs_ssize_t ooo_block;
lfs_emubd_block_t *ooo_data;
lfs_emubd_disk_t *disk;
const struct lfs_emubd_config *cfg;