Re: [PATCH 1/3] staging: erofs: fix error handling when failed to read compresssed data

[Gao Xiang]

Hi Chao,

On 2019/3/25 10:05, Chao Yu wrote:
> On 2019/3/22 11:25, Gao Xiang wrote:
>> ping?
>>
>> Hi Chao,
>> could you take some time looking into this series?
> 
> Done, sorry for the delay.

It doesn't matter. It is helpful for our kernel upgrade
since it keeps up with the latest community code now ;)

Thanks for keeping on taking time on erofs. *thumb*

Thanks,
Gao Xiang

> 
> Thanks,
> 
>>
>> Thanks,
>> Gao Xiang
>>
>> On 2019/3/19 21:54, Gao Xiang wrote:
>>> Complete read error handling paths for all three kinds of
>>> compressed pages:
>>>
>>>  1) For cache-managed pages, PG_uptodate will be checked since
>>>     read_endio will unlock and SetPageUptodate for these pages;
>>>
>>>  2) For inplaced pages, read_endio cannot SetPageUptodate directly
>>>     since it should be used to mark the final decompressed data,
>>>     PG_error will be set with page locked for IO error instead;
>>>
>>>  3) For staging pages, PG_error is used, which is similar to
>>>     what we do for inplaced pages.
>>>
>>> Fixes: 3883a79abd02 ("staging: erofs: introduce VLE decompression support")
>>> Cc: <stable@xxxxxxxxxxxxxxx> # 4.19+
>>> Signed-off-by: Gao Xiang <gaoxiang25@xxxxxxxxxx>
>>> ---
>>>
>>> This series focus on fixing error handling when failed to read
>>> compresssed data due to previous incomplete paths.
>>>
>>> In addition, the last 2 patches add IO error fault injection
>>> for reading paths, which I have used to test the first patch as well.
>>>
>>> Thanks,
>>> Gao Xiang
>>>
>>>  drivers/staging/erofs/unzip_vle.c | 41 ++++++++++++++++++++++++++-------------
>>>  1 file changed, 28 insertions(+), 13 deletions(-)
>>>
>>> diff --git a/drivers/staging/erofs/unzip_vle.c b/drivers/staging/erofs/unzip_vle.c
>>> index 8715bc50e09c..3416d3f10324 100644
>>> --- a/drivers/staging/erofs/unzip_vle.c
>>> +++ b/drivers/staging/erofs/unzip_vle.c
>>> @@ -972,6 +972,7 @@ static int z_erofs_vle_unzip(struct super_block *sb,
>>>  	overlapped = false;
>>>  	compressed_pages = grp->compressed_pages;
>>>  
>>> +	err = 0;
>>>  	for (i = 0; i < clusterpages; ++i) {
>>>  		unsigned int pagenr;
>>>  
>>> @@ -981,26 +982,39 @@ static int z_erofs_vle_unzip(struct super_block *sb,
>>>  		DBG_BUGON(!page);
>>>  		DBG_BUGON(!page->mapping);
>>>  
>>> -		if (z_erofs_is_stagingpage(page))
>>> -			continue;
>>> +		if (!z_erofs_is_stagingpage(page)) {
>>>  #ifdef EROFS_FS_HAS_MANAGED_CACHE
>>> -		if (page->mapping == MNGD_MAPPING(sbi)) {
>>> -			DBG_BUGON(!PageUptodate(page));
>>> -			continue;
>>> -		}
>>> +			if (page->mapping == MNGD_MAPPING(sbi)) {
>>> +				if (unlikely(!PageUptodate(page)))
>>> +					err = -EIO;
>>> +				continue;
>>> +			}
>>>  #endif
>>>  
>>> -		/* only non-head page could be reused as a compressed page */
>>> -		pagenr = z_erofs_onlinepage_index(page);
>>> +			/*
>>> +			 * only if non-head page can be selected
>>> +			 * for inplace decompression
>>> +			 */
>>> +			pagenr = z_erofs_onlinepage_index(page);
>>>  
>>> -		DBG_BUGON(pagenr >= nr_pages);
>>> -		DBG_BUGON(pages[pagenr]);
>>> -		++sparsemem_pages;
>>> -		pages[pagenr] = page;
>>> +			DBG_BUGON(pagenr >= nr_pages);
>>> +			DBG_BUGON(pages[pagenr]);
>>> +			++sparsemem_pages;
>>> +			pages[pagenr] = page;
>>> +
>>> +			overlapped = true;
>>> +		}
>>>  
>>> -		overlapped = true;
>>> +		/* PG_error needs checking for inplaced and staging pages */
>>> +		if (unlikely(PageError(page))) {
>>> +			DBG_BUGON(PageUptodate(page));
>>> +			err = -EIO;
>>> +		}
>>>  	}
>>>  
>>> +	if (unlikely(err))
>>> +		goto out;
>>> +
>>>  	llen = (nr_pages << PAGE_SHIFT) - work->pageofs;
>>>  
>>>  	if (z_erofs_vle_workgrp_fmt(grp) == Z_EROFS_VLE_WORKGRP_FMT_PLAIN) {
>>> @@ -1194,6 +1208,7 @@ pickup_page_for_submission(struct z_erofs_vle_workgroup *grp,
>>>  	if (page->mapping == mc) {
>>>  		WRITE_ONCE(grp->compressed_pages[nr], page);
>>>  
>>> +		ClearPageError(page);
>>>  		if (!PagePrivate(page)) {
>>>  			/*
>>>  			 * impossible to be !PagePrivate(page) for
>>>
>> .
>>