simple use wcache from drive (was)Re: [RFC/PATCH 0/7] enable honoring write cache setting of IDE drive

simple use wcache from drive (was)Re: [RFC/PATCH 0/7] enable honoring write cache setting of IDE drive

[Doug Maxey]

On Fri, 28 Jan 2005 23:32:53 +0100, Bartlomiej Zolnierkiewicz wrote:
>> The datacenters/server folks that would be using these drives would
>> expect them to remain as set.  I have to check, but unless something
>> has changed very recently in the kernel, setting with hdparm does not
>> "stick" in the sense that the command succeeds to the disk, but no change
>> is made to the barrier.
>
>It is not a problem for IDE driver (flushes become no-ops)
>and this way you can later enable wcache and still use barries.

Well that certainly simplfies things.

How about this?
===== drivers/ide/ide-disk.c 1.115 vs edited =====
--- 1.115/drivers/ide/ide-disk.c	2005-01-04 11:39:25 -06:00
+++ edited/drivers/ide/ide-disk.c	2005-01-28 16:48:24 -06:00
@@ -1083,7 +1083,7 @@ static void idedisk_setup (ide_drive_t *
 	if ((id->csfo & 1) || (id->cfs_enable_1 & (1 << 5)))
 		drive->wcache = 1;
 
-	write_cache(drive, 1);
+	write_cache(drive, drive->wcache);
 
 	/*
 	 * We must avoid issuing commands a drive does not understand

Re: simple use wcache from drive (was)Re: [RFC/PATCH 0/7] enable honoring write cache setting of IDE drive

[Bartlomiej Zolnierkiewicz]

On Fri, 28 Jan 2005 16:54:49 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
> 
> On Fri, 28 Jan 2005 23:32:53 +0100, Bartlomiej Zolnierkiewicz wrote:
> >> The datacenters/server folks that would be using these drives would
> >> expect them to remain as set.  I have to check, but unless something
> >> has changed very recently in the kernel, setting with hdparm does not
> >> "stick" in the sense that the command succeeds to the disk, but no change
> >> is made to the barrier.
> >
> >It is not a problem for IDE driver (flushes become no-ops)
> >and this way you can later enable wcache and still use barries.
> 
> Well that certainly simplfies things.
> 
> How about this?

No go until 'drive->wcache' bug is fixed.

> ===== drivers/ide/ide-disk.c 1.115 vs edited =====
> --- 1.115/drivers/ide/ide-disk.c        2005-01-04 11:39:25 -06:00
> +++ edited/drivers/ide/ide-disk.c       2005-01-28 16:48:24 -06:00
> @@ -1083,7 +1083,7 @@ static void idedisk_setup (ide_drive_t *
>         if ((id->csfo & 1) || (id->cfs_enable_1 & (1 << 5)))
>                 drive->wcache = 1;
> 
> -       write_cache(drive, 1);
> +       write_cache(drive, drive->wcache);
> 
>         /*
>          * We must avoid issuing commands a drive does not understand
>

Re: simple use wcache from drive (was)Re: [RFC/PATCH 0/7] enable honoring write cache setting of IDE drive

[Bartlomiej Zolnierkiewicz]

On Fri, 28 Jan 2005 23:56:41 +0100, Bartlomiej Zolnierkiewicz
<bzolnier@gmail.com> wrote:
> On Fri, 28 Jan 2005 16:54:49 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
> >
> > On Fri, 28 Jan 2005 23:32:53 +0100, Bartlomiej Zolnierkiewicz wrote:
> > >> The datacenters/server folks that would be using these drives would
> > >> expect them to remain as set.  I have to check, but unless something
> > >> has changed very recently in the kernel, setting with hdparm does not
> > >> "stick" in the sense that the command succeeds to the disk, but no change
> > >> is made to the barrier.
> > >
> > >It is not a problem for IDE driver (flushes become no-ops)
> > >and this way you can later enable wcache and still use barries.
> >
> > Well that certainly simplfies things.
> >
> > How about this?
> 
> No go until 'drive->wcache' bug is fixed.

And until user is informed about status of wcache (printk).

> > ===== drivers/ide/ide-disk.c 1.115 vs edited =====
> > --- 1.115/drivers/ide/ide-disk.c        2005-01-04 11:39:25 -06:00
> > +++ edited/drivers/ide/ide-disk.c       2005-01-28 16:48:24 -06:00
> > @@ -1083,7 +1083,7 @@ static void idedisk_setup (ide_drive_t *
> >         if ((id->csfo & 1) || (id->cfs_enable_1 & (1 << 5)))
> >                 drive->wcache = 1;
> >
> > -       write_cache(drive, 1);
> > +       write_cache(drive, drive->wcache);
> >
> >         /*
> >          * We must avoid issuing commands a drive does not understand
> >
>

Re: simple use wcache from drive

[Doug Maxey]

On Fri, 28 Jan 2005 23:59:18 +0100, Bartlomiej Zolnierkiewicz wrote:
>On Fri, 28 Jan 2005 23:56:41 +0100, Bartlomiej Zolnierkiewicz
><bzolnier@gmail.com> wrote:
>> On Fri, 28 Jan 2005 16:54:49 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
>> >
>> > On Fri, 28 Jan 2005 23:32:53 +0100, Bartlomiej Zolnierkiewicz wrote:
>> > >> The datacenters/server folks that would be using these drives would
>> > >> expect them to remain as set.  I have to check, but unless something
>> > >> has changed very recently in the kernel, setting with hdparm does not
>> > >> "stick" in the sense that the command succeeds to the disk, but no change
>> > >> is made to the barrier.
>> > >
>> > >It is not a problem for IDE driver (flushes become no-ops)
>> > >and this way you can later enable wcache and still use barries.
>> >
>> > Well that certainly simplfies things.
>> >
>> > How about this?
>> 
>> No go until 'drive->wcache' bug is fixed.
>
>And until user is informed about status of wcache (printk).
>

[PATCH] use IDE drive cache enabled setting by default.

  Enable the default setting of the driver use of write cache to be
  defined by the drive itself.

Signed-off-by: Doug Maxey <dwm@austin.ibm.com>

===== drivers/ide/ide-disk.c 1.115 vs 1.116 =====
--- 1.115/drivers/ide/ide-disk.c	2005-01-04 11:39:25 -06:00
+++ 1.116/drivers/ide/ide-disk.c	2005-01-29 15:13:24 -06:00
@@ -784,6 +784,7 @@ static int write_cache(ide_drive_t *driv
 	if (err)
 		return err;
 
+	printk(KERN_DEBUG "%s: %sabling write cache\n", drive->name, arg ? "en" : "dis");
 	drive->wcache = arg;
 	return 0;
 }
@@ -1080,10 +1081,10 @@ static void idedisk_setup (ide_drive_t *
 	drive->no_io_32bit = id->dword_io ? 1 : 0;
 
 	/* write cache enabled? */
-	if ((id->csfo & 1) || (id->cfs_enable_1 & (1 << 5)))
+	if ((id->csfo & 1) && (id->cfs_enable_1 & (1 << 5)))
 		drive->wcache = 1;
 
-	write_cache(drive, 1);
+	write_cache(drive, drive->wcache);
 
 	/*
 	 * We must avoid issuing commands a drive does not understand

Re: simple use wcache from drive

[Bartlomiej Zolnierkiewicz]

On Sat, 29 Jan 2005 17:54:47 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
> 
> On Fri, 28 Jan 2005 23:59:18 +0100, Bartlomiej Zolnierkiewicz wrote:
> >On Fri, 28 Jan 2005 23:56:41 +0100, Bartlomiej Zolnierkiewicz
> ><bzolnier@gmail.com> wrote:
> >> On Fri, 28 Jan 2005 16:54:49 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
> >> >
> >> > On Fri, 28 Jan 2005 23:32:53 +0100, Bartlomiej Zolnierkiewicz wrote:
> >> > >> The datacenters/server folks that would be using these drives would
> >> > >> expect them to remain as set.  I have to check, but unless something
> >> > >> has changed very recently in the kernel, setting with hdparm does not
> >> > >> "stick" in the sense that the command succeeds to the disk, but no change
> >> > >> is made to the barrier.
> >> > >
> >> > >It is not a problem for IDE driver (flushes become no-ops)
> >> > >and this way you can later enable wcache and still use barries.
> >> >
> >> > Well that certainly simplfies things.
> >> >
> >> > How about this?
> >>
> >> No go until 'drive->wcache' bug is fixed.
> >
> >And until user is informed about status of wcache (printk).
> >
> 
> [PATCH] use IDE drive cache enabled setting by default.
> 
>   Enable the default setting of the driver use of write cache to be
>   defined by the drive itself.
> 
> Signed-off-by: Doug Maxey <dwm@austin.ibm.com>
> 
> ===== drivers/ide/ide-disk.c 1.115 vs 1.116 =====
> --- 1.115/drivers/ide/ide-disk.c        2005-01-04 11:39:25 -06:00
> +++ 1.116/drivers/ide/ide-disk.c        2005-01-29 15:13:24 -06:00
> @@ -784,6 +784,7 @@ static int write_cache(ide_drive_t *driv
>         if (err)
>                 return err;
> 
> +       printk(KERN_DEBUG "%s: %sabling write cache\n", drive->name, arg ? "en" : "dis");
>         drive->wcache = arg;
>         return 0;
>  }
> @@ -1080,10 +1081,10 @@ static void idedisk_setup (ide_drive_t *
>         drive->no_io_32bit = id->dword_io ? 1 : 0;
> 
>         /* write cache enabled? */
> -       if ((id->csfo & 1) || (id->cfs_enable_1 & (1 << 5)))
> +       if ((id->csfo & 1) && (id->cfs_enable_1 & (1 << 5)))
>                 drive->wcache = 1;

This bogus... I was thinking about bug related to hdparm...

> -       write_cache(drive, 1);
> +       write_cache(drive, drive->wcache);

You still didn't answer my question what is the practical reason for this...

>         /*
>          * We must avoid issuing commands a drive does not understand
>

Re: simple use wcache from drive

[Doug Maxey]

On Sun, 30 Jan 2005 01:05:03 +0100, Bartlomiej Zolnierkiewicz wrote:
>On Sat, 29 Jan 2005 17:54:47 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
>> 
>> On Fri, 28 Jan 2005 23:59:18 +0100, Bartlomiej Zolnierkiewicz wrote:
>> >On Fri, 28 Jan 2005 23:56:41 +0100, Bartlomiej Zolnierkiewicz
>> ><bzolnier@gmail.com> wrote:
>> >> On Fri, 28 Jan 2005 16:54:49 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
>> >> >
>> >> > On Fri, 28 Jan 2005 23:32:53 +0100, Bartlomiej Zolnierkiewicz wrote:
>> >> > >> The datacenters/server folks that would be using these drives would
>> >> > >> expect them to remain as set.  I have to check, but unless something
>> >> > >> has changed very recently in the kernel, setting with hdparm does not
>> >> > >> "stick" in the sense that the command succeeds to the disk, but no change
>> >> > >> is made to the barrier.
>> >> > >
>> >> > >It is not a problem for IDE driver (flushes become no-ops)
>> >> > >and this way you can later enable wcache and still use barries.
>> >> >
>> >> > Well that certainly simplfies things.
>> >> >
>> >> > How about this?
>> >>
>> >> No go until 'drive->wcache' bug is fixed.
>> >
>> >And until user is informed about status of wcache (printk).
>> >
>> 
>> [PATCH] use IDE drive cache enabled setting by default.
>> 
>>   Enable the default setting of the driver use of write cache to be
>>   defined by the drive itself.
>> 
>> Signed-off-by: Doug Maxey <dwm@austin.ibm.com>
>> 
>> ===== drivers/ide/ide-disk.c 1.115 vs 1.116 =====
>> --- 1.115/drivers/ide/ide-disk.c        2005-01-04 11:39:25 -06:00
>> +++ 1.116/drivers/ide/ide-disk.c        2005-01-29 15:13:24 -06:00
>> @@ -784,6 +784,7 @@ static int write_cache(ide_drive_t *driv
>>         if (err)
>>                 return err;
>> 
>> +       printk(KERN_DEBUG "%s: %sabling write cache\n", drive->name, arg ? "en" : "dis");
>>         drive->wcache = arg;
>>         return 0;
>>  }
>> @@ -1080,10 +1081,10 @@ static void idedisk_setup (ide_drive_t *
>>         drive->no_io_32bit = id->dword_io ? 1 : 0;
>> 
>>         /* write cache enabled? */
>> -       if ((id->csfo & 1) || (id->cfs_enable_1 & (1 << 5)))
>> +       if ((id->csfo & 1) && (id->cfs_enable_1 & (1 << 5)))
>>                 drive->wcache = 1;
>
>This bogus... I was thinking about bug related to hdparm...

Sorry, my crystal ball is foggy today.  Do you have a specific bug number or 
message-id?

>
>> -       write_cache(drive, 1);
>> +       write_cache(drive, drive->wcache);
>
>You still didn't answer my question what is the practical reason for this...

Thought we had already cleared this up.  See above.

>
>>         /*
>>          * We must avoid issuing commands a drive does not understand
>>
>

Re: simple use wcache from drive

[Bartlomiej Zolnierkiewicz]

On Sat, 29 Jan 2005 18:19:50 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
> 
> On Sun, 30 Jan 2005 01:05:03 +0100, Bartlomiej Zolnierkiewicz wrote:
> >On Sat, 29 Jan 2005 17:54:47 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
> >>
> >> On Fri, 28 Jan 2005 23:59:18 +0100, Bartlomiej Zolnierkiewicz wrote:
> >> >On Fri, 28 Jan 2005 23:56:41 +0100, Bartlomiej Zolnierkiewicz
> >> ><bzolnier@gmail.com> wrote:
> >> >> On Fri, 28 Jan 2005 16:54:49 -0600, Doug Maxey <dwm@austin.ibm.com> wrote:
> >> >> >
> >> >> > On Fri, 28 Jan 2005 23:32:53 +0100, Bartlomiej Zolnierkiewicz wrote:
> >> >> > >> The datacenters/server folks that would be using these drives would
> >> >> > >> expect them to remain as set.  I have to check, but unless something
> >> >> > >> has changed very recently in the kernel, setting with hdparm does not
> >> >> > >> "stick" in the sense that the command succeeds to the disk, but no change
> >> >> > >> is made to the barrier.
> >> >> > >
> >> >> > >It is not a problem for IDE driver (flushes become no-ops)
> >> >> > >and this way you can later enable wcache and still use barries.
> >> >> >
> >> >> > Well that certainly simplfies things.
> >> >> >
> >> >> > How about this?
> >> >>
> >> >> No go until 'drive->wcache' bug is fixed.
> >> >
> >> >And until user is informed about status of wcache (printk).
> >> >
> >>
> >> [PATCH] use IDE drive cache enabled setting by default.
> >>
> >>   Enable the default setting of the driver use of write cache to be
> >>   defined by the drive itself.
> >>
> >> Signed-off-by: Doug Maxey <dwm@austin.ibm.com>
> >>
> >> ===== drivers/ide/ide-disk.c 1.115 vs 1.116 =====
> >> --- 1.115/drivers/ide/ide-disk.c        2005-01-04 11:39:25 -06:00
> >> +++ 1.116/drivers/ide/ide-disk.c        2005-01-29 15:13:24 -06:00
> >> @@ -784,6 +784,7 @@ static int write_cache(ide_drive_t *driv
> >>         if (err)
> >>                 return err;
> >>
> >> +       printk(KERN_DEBUG "%s: %sabling write cache\n", drive->name, arg ? "en" : "dis");
> >>         drive->wcache = arg;
> >>         return 0;
> >>  }
> >> @@ -1080,10 +1081,10 @@ static void idedisk_setup (ide_drive_t *
> >>         drive->no_io_32bit = id->dword_io ? 1 : 0;
> >>
> >>         /* write cache enabled? */
> >> -       if ((id->csfo & 1) || (id->cfs_enable_1 & (1 << 5)))
> >> +       if ((id->csfo & 1) && (id->cfs_enable_1 & (1 << 5)))
> >>                 drive->wcache = 1;
> >
> >This bogus... I was thinking about bug related to hdparm...
> 
> Sorry, my crystal ball is foggy today.  Do you have a specific bug number or
> message-id?

>From private mail to you:
On Wed, 13 Oct 2004 21:06:32 +0200, Bartlomiej Zolnierkiewicz
<bzolnier@gmail.com> wrote:
> the write cache handling is a bit more complicated, please look at
> write_cache():
> 
>         if (!ide_id_has_flush_cache(drive->id))
>                 return 1;
> 
> this means that the write cache will stay enabled for devices not supporting
> (or advertising) flush cache feature.  Anyway this is a minor issue,
> real problem is that hdparm doesn't use HDIO_SET_WCACHE ioctl but
> HDIO_DRIVE_CMD to [en,dis]able write cache.  Suppose the following scenario:
> 
> - disk supports write cache and cache flush
> - disk comes with write cache disabled by default
> - your patch disables write cache
> - user enables write cache with hdparm
> - driver is not aware that write cache has been enabled
>  (BAD)

> >
> >> -       write_cache(drive, 1);
> >> +       write_cache(drive, drive->wcache);
> >
> >You still didn't answer my question what is the practical reason for this...
> 
> Thought we had already cleared this up.  See above.

Nope, please see "[RFC/PATCH 0/7] enable honoring write cache setting
of IDE drive" thread.