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Re: [PATCH v2 11/17] UBI: simplify recover_peb() code

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  Re: [PATCH v2 11/17] UBI: simplify recover_peb() code Richard Weinberger <richard@nod.at> - 2016-09-16 12:20 +0200
    Re: [PATCH v2 11/17] UBI: simplify recover_peb() code Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-09-16 13:30 +0200
      Re: [PATCH v2 11/17] UBI: simplify recover_peb() code Richard Weinberger <richard@nod.at> - 2016-09-16 15:30 +0200
        Re: [PATCH v2 11/17] UBI: simplify recover_peb() code Boris Brezillon <boris.brezillon@free-electrons.com> - 2016-09-16 15:30 +0200

#1484856 — Re: [PATCH v2 11/17] UBI: simplify recover_peb() code

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.

Thanks,
//richard

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#1484905

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.

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?

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#1484987

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

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#1484990

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

> 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.

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

> 
> Thanks,
> //richard

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