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Subject: Re: [PATCH v2 11/17] UBI: simplify recover_peb() code
To: Boris Brezillon <boris.brezillon@free-electrons.com>
References: <1473087908-27862-1-git-send-email-boris.brezillon@free-electrons.com>
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Cc: Artem Bityutskiy <dedekind1@gmail.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Brian Norris <computersforpeace@gmail.com>,
        linux-mtd@lists.infradead.org, linux-kernel@vger.kernel.org
From: Richard Weinberger <richard@nod.at>
Message-ID: <bca2db4f-8bef-8a62-dee7-267e9947c521@nod.at>
Date: Fri, 16 Sep 2016 15:23:31 +0200
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Boris,

On 16.09.2016 13:23, Boris Brezillon wrote:
> On Fri, 16 Sep 2016 12:14:04 +0200
> Richard Weinberger <richard@nod.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.

Thanks,
//richard