[linux-lvm] resend patch - bcache may mistakenly write data to another disk when writes error
Heming Zhao
heming.zhao at suse.com
Tue Oct 29 05:07:30 UTC 2019
Hello Joe,
Please check my comments for your commit 2938b4dcc & 6b0d969b
1. b->ref_count is non-zero, and write error happens, the data never release?
(no place to call _unlink_block & _free_block)
2. when dev_write_bytes failed, call dev_unset_last_byte with "fd=-1" is wrong.
3. I still think below error handling should be added.
Below base on stable-2.02, but the core idea is same, should access the return value of io_submit & io_getevents.
```
static bool _async_issue(struct io_engine *ioe, enum dir d, int fd,
... ...
if (r < 0) {
_cb_free(e->cbs, cb);
+ ((struct block *)context)->error = r; <== assign errno & print warning
+ log_warn("io_submit <%c> off %llu bytes %llu return %d:%s",
+ (d == DIR_READ) ? 'R' : 'W', (long long unsigned)offset,
+ (long long unsigned)nbytes, r, strerror(-r));
return false;
}
static void _issue_low_level(struct block *b, enum dir d)
... ...
dm_list_move(&cache->io_pending, &b->list);
if (!cache->engine->issue(cache->engine, d, b->fd, sb, se, b->data, b)) {
- /* FIXME: if io_submit() set an errno, return that instead of EIO? */
- _complete_io(b, -EIO);
+ _complete_io(b, b->error); <=== this pass the right errno to caller.
return;
}
}
-static void _wait_all(struct bcache *cache)
+static bool _wait_all(struct bcache *cache) <=== change to return error
{
+ bool ret = true;
while (!dm_list_empty(&cache->io_pending))
- _wait_io(cache);
+ ret = _wait_io(cache);
+ return ret;
}
-static void _wait_specific(struct block *b)
+static bool _wait_specific(struct block *b) <=== change to return error
{
+ bool ret = true;
while (_test_flags(b, BF_IO_PENDING))
- _wait_io(b->cache);
+ ret = _wait_io(b->cache);
+ return ret;
}
bool bcache_flush(struct bcache *cache) <==== add more error handling
{
+ bool write_ret = true, wait_ret = true;
... ...
_issue_write(b);
+ if (b->error) write_ret = false;
}
- _wait_all(cache);
+ wait_ret = _wait_all(cache);
- return dm_list_empty(&cache->errored);
+ if (write_ret == false || wait_ret == false ||
+ !dm_list_empty(&cache->errored))
+ return false;
+ else
+ return true;
}
```
Thanks,
zhm
On 10/28/19 11:43 PM, Joe Thornber wrote:
> On Thu, Oct 24, 2019 at 03:06:18AM +0000, Heming Zhao wrote:
>> First fail is in bcache_flush, then bcache_invalidate_fd does nothing because the data
>> in cache->errored, which not belongs to dirty & clean list. Then the data mistakenly
>> move from cache->errored into cache->dirty by "bcache_get => _lookup_or_read_block"
>> (because the data holds BF_DIRTY flag).
>
> I just pushed a couple of patches that will hopefully fix this issue for you:
>
> commit 6b0d969b2a85ba69046afa26af4d7bcddddbccd5 (HEAD -> master, origin/master, origin/HEAD, 2019-10-11-bcache-purge)
> Author: Joe Thornber <ejt at redhat.com>
> Date: Mon Oct 28 15:01:47 2019 +0000
>
> [label] Use bcache_abort_fd() to ensure blocks are no longer in the cache.
>
> The return value from bcache_invalidate_fd() was not being checked.
>
> So I've introduced a little function, _invalidate_fd() that always
> calls bcache_abort_fd() if the write fails.
>
> commit 2938b4dcca0a1df661758abfab7f402ea7aab018
> Author: Joe Thornber <ejt at redhat.com>
> Date: Mon Oct 28 14:29:47 2019 +0000
>
> [bcache] add bcache_abort()
>
> This gives us a way to cope with write failures.
>
>
>
>
> Also there are big changes to bcache coming, that remove file descriptors from
> the interface completely. See the branch 2019-09-05-add-io-manager for more info
> (bcache has been renamed io_manager).
>
> - Joe
>
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