From mboxrd@z Thu Jan 1 00:00:00 1970 From: Heming Zhao Date: Tue, 29 Oct 2019 05:07:30 +0000 Message-ID: <324885c4-a211-fb11-8315-979935391820@suse.com> References: <20191023213101.gpkorwubuobm5w5y@reti> <20191028154313.ibspu6qwqqsq54cc@reti> In-Reply-To: <20191028154313.ibspu6qwqqsq54cc@reti> Content-Language: en-US Content-ID: <3E762BD25E35E143BC2D16D2727ECB1B@namprd18.prod.outlook.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Subject: Re: [linux-lvm] resend patch - bcache may mistakenly write data to another disk when writes error Reply-To: LVM general discussion and development List-Id: LVM general discussion and development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , List-Id: Content-Type: text/plain; charset="us-ascii" To: LVM general discussion and development , Joe Thornber Cc: David Teigland 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 > 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 > 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 > > _______________________________________________ > linux-lvm mailing list > linux-lvm@redhat.com > https://www.redhat.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ >