linux-kernel - Re: [PATCH v2 11/17] UBI: simplify recover

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Date:   Fri, 16 Sep 2016 15:27:24 +0200
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Richard Weinberger <richard@....at>
Cc:     Artem Bityutskiy <dedekind1@...il.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 11/17] UBI: simplify recover_peb() code

On Fri, 16 Sep 2016 15:23:31 +0200
Richard Weinberger <richard@....at> wrote:

> Boris,
> 
> On 16.09.2016 13:23, Boris Brezillon wrote:
> > On Fri, 16 Sep 2016 12:14:04 +0200
> > Richard Weinberger <richard@....at> wrote:
> >   
> >> Boris,
> >>
> >> On 05.09.2016 17:05, Boris Brezillon wrote:  
> >>> + * This function is called in case of a write failure and moves all good data
> >>> + * from the potentially bad physical eraseblock to a good physical eraseblock.
> >>> + * This function also writes the data which was not written due to the failure.
> >>> + * Returns 0 in case of success, and a negative error code in case of failure.
> >>> + * This function tries %UBI_IO_RETRIES before giving up.
> >>> + */
> >>> +static int recover_peb(struct ubi_device *ubi, int pnum, int vol_id, int lnum,
> >>> +		       const void *buf, int offset, int len)
> >>> +{
> >>> +	int err, idx = vol_id2idx(ubi, vol_id), tries;
> >>> +	struct ubi_volume *vol = ubi->volumes[idx];
> >>> +	struct ubi_vid_hdr *vid_hdr;
> >>> +
> >>> +	vid_hdr = ubi_zalloc_vid_hdr(ubi, GFP_NOFS);
> >>> +	if (!vid_hdr)
> >>> +		return -ENOMEM;
> >>> +
> >>> +	for (tries = 0; tries <= UBI_IO_RETRIES; tries++) {
> >>> +		err = try_recover_peb(vol, pnum, lnum, buf, offset, len,
> >>> +				      vid_hdr);
> >>> +		if (!err || err == -ENOSPC)
> >>> +			break;    
> >>
> >> Why do you handle ENOSPC as fatal error? Since the loop is bound by UBI_IO_RETRIES
> >> IMHO we can retry also upon ENOSPC.  
> > 
> > I was just trying to mimic the existing behavior: if ubi_wl_get_peb()
> > fails to return a free PEB it returns -ENOSPC, and the current
> > implementation does not retry in this case.  
> 
> Whoops. I thought the current code does retry upon -ENOSPC.
> 
> > I also realize that we should not retry if the error happened when
> > reading from the source PEB.
> > 
> > Maybe we should have an extra 'bool *retry' parameter to let
> > recover_peb() know whether the operation should be retried or not.
> > What do you think?  
> 
> Since your change does not change the current behaviour, let's keep it as-is.

Actually it does. Now I'm retrying even when we have errors on the
reads :-(.

> 
> Thanks,
> //richard