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SubjectRe: [PATCH 3/4] ide: Implement disk shock protection support
Date

Hi,

On Wednesday 03 September 2008, Elias Oltmanns wrote:
> Bartlomiej Zolnierkiewicz <bzolnier@gmail.com> wrote:
> > On Friday 29 August 2008, Elias Oltmanns wrote:
> >> On user request (through sysfs), the IDLE IMMEDIATE command with UNLOAD
> >
> >> FEATURE as specified in ATA-7 is issued to the device and processing of
> >> the request queue is stopped thereafter until the speified timeout
> >> expires or user space asks to resume normal operation. This is supposed
> >> to prevent the heads of a hard drive from accidentally crashing onto the
> >> platter when a heavy shock is anticipated (like a falling laptop
> >> expected to hit the floor). In fact, the whole port stops processing
> >> commands until the timeout has expired in order to avoid resets due to
> >> failed commands on another device.
> >>
> >> Signed-off-by: Elias Oltmanns <eo@nebensachen.de>
> >
> > [ continuing the discussion from 'patch #2' thread ]
> >
> > While I'm still not fully convinced this is the best way to go in
> > the long-term I'm well aware that if we won't get in 2.6.28 it will
> > mean at least 3 more months until it hits users so lets concentrate
> > on existing user/kernel-space solution first...
> >
> > There are some issues to address before it can go in but once they
> > are fixed I'm fine with the patch and I'll merge it as soon as patches
> > #1-2 are in.
>
> Thank you very much Bart, I really do appreciate that. Some more
> questions though:

Thanks for rework, the code looks a lot simpler now.

> > [...]
> >
> >> @@ -842,6 +842,9 @@ static void ide_port_tune_devices(ide_hwif_t *hwif)
> >>
> >> if (hwif->dma_ops)
> >> ide_set_dma(drive);
> >> +
> >> + if (!ata_id_has_unload(drive->id))
> >> + drive->dev_flags |= IDE_DFLAG_NO_UNLOAD;
> >
> > ide_port_tune_devices() is not a best suited place for it,
> > please move it to ide_port_init_devices().
>
> ... We need to have IDENTIFY data present in drive->id at that point
> which is not the case before ide_probe_port() has been executed. Should
> I perhaps move it to ide_port_setup_devices() instead?

I think that do_identify() is the best place for it at the moment.

> [...]
> >> + spin_lock_irq(&ide_lock);
> >> + if (unlikely(!hwif->present || timer_pending(&hwif->park_timer)))
> >> + goto done;
> >> +
> >> + drive = hwif->hwgroup->drive;
> >> + while (drive->hwif != hwif)
> >> + drive = drive->next;
> >
> > How's about just looping on hwif->drives[] instead?
> >
> > [ this would also allow removal of loops in issue_park_cmd()
> > and simplify locking there ]
>
> Yes, I've reorganised it all a bit in order to account for all the
> issues addressed in the discussion. In particular, I loop over
> hwif->drives now as you suggested.
>
> [...]
> >> +static ssize_t park_store(struct device *dev, struct device_attribute *attr,
> >> + const char *buf, size_t len)
> >> +{
> >> +#define MAX_PARK_TIMEOUT 30
> >> + ide_drive_t *drive = to_ide_device(dev);
> >> + ide_hwif_t *hwif = drive->hwif;
> >> + DECLARE_COMPLETION_ONSTACK(wait);
> >> + unsigned long timeout;
> >> + int rc, count = 0;
> >> +
> >> + rc = strict_strtoul(buf, 10, &timeout);
> >> + if (rc || timeout > MAX_PARK_TIMEOUT)
> >> + return -EINVAL;
> >> +
> >> + mutex_lock(&ide_setting_mtx);
> >
> > No need to hold ide_settings_mtx here.
>
> Even though the next version of the patch is different in various ways,
> we have a similar problem. As far as I can see, we need to hold the
> ide_setting_mtx here because the spin_lock will be taken and released
> several times subsequently and therefore cannot protect hwif->park_timer
> (or hwif->park_timeout in the new patch) against concurrent writes to
> this sysfs attribute.

OK.

> >
> >> + spin_lock_irq(&ide_lock);
> >> + if (unlikely(!(drive->dev_flags & IDE_DFLAG_PRESENT))) {
> >> + rc = -ENODEV;
> >> + goto unlock;
> >> + }
>
> [...]
>
> > Also could you please move the new code to a separate file (i.e.
> > ide-park.c) instead of stuffing it all in ide.c?
>
> This is probably a sensible idea especially since there may be more once
> we go ahead with the in-kernel solution. This means, however, that some
> more random stuff is going into include/linux/ide.h. If it wasn't so
> huge and if I had an idea what was to be taken into account so as not to
> break user space applications, I'd offer to try my hand at moving things
> to a private header file drivers/ide/ide.h. But as it is, I'm rather
> scared.

<linux/ide.h> it is not exported to user-space at all so introducing
drivers/ide/ide.h shouldn't be a problem.

> >
> > Otherwise it looks OK (modulo PM notifiers concerns raised by Tejun
> > but the code is identical to libata's version so it is sufficient to
> > duplicate the potential fixes here).
>
> On popular request, they're gone now. With the new patches I can't
> reproduce the system freezes anymore.
>
> The patch below applies to next-20080903. I'll resend the whole series
> once this (and the libata one) has been reviewed and potential glitches
> have been ironed out.
>
> Regards,
>
> Elias
>
> ---
>
> drivers/ide/Makefile | 2 -
> drivers/ide/ide-io.c | 27 +++++++++
> drivers/ide/ide-park.c | 133 ++++++++++++++++++++++++++++++++++++++++++++
> drivers/ide/ide-probe.c | 3 +
> drivers/ide/ide-taskfile.c | 10 +++
> drivers/ide/ide.c | 1
> include/linux/ide.h | 16 +++++
> 7 files changed, 190 insertions(+), 2 deletions(-)
> create mode 100644 drivers/ide/ide-park.c
>
> diff --git a/drivers/ide/Makefile b/drivers/ide/Makefile
> index e6e7811..16795fe 100644
> --- a/drivers/ide/Makefile
> +++ b/drivers/ide/Makefile
> @@ -5,7 +5,7 @@
> EXTRA_CFLAGS += -Idrivers/ide
>
> ide-core-y += ide.o ide-ioctls.o ide-io.o ide-iops.o ide-lib.o ide-probe.o \
> - ide-taskfile.o ide-pio-blacklist.o
> + ide-taskfile.o ide-park.o ide-pio-blacklist.o
>
> # core IDE code
> ide-core-$(CONFIG_IDE_TIMINGS) += ide-timings.o
> diff --git a/drivers/ide/ide-io.c b/drivers/ide/ide-io.c
> index e205f46..c9f6325 100644
> --- a/drivers/ide/ide-io.c
> +++ b/drivers/ide/ide-io.c
> @@ -672,7 +672,30 @@ EXPORT_SYMBOL_GPL(ide_devset_execute);
>
> static ide_startstop_t ide_special_rq(ide_drive_t *drive, struct request *rq)
> {
> + ide_hwif_t *hwif = drive->hwif;
> + ide_task_t task;
> + struct ide_taskfile *tf = &task.tf;
> +
> + memset(&task, 0, sizeof(task));
> switch (rq->cmd[0]) {
> + case REQ_PARK_HEADS:
> + drive->sleep = drive->hwif->park_timeout;
> + drive->dev_flags |= IDE_DFLAG_SLEEPING;
> + complete((struct completion *)rq->end_io_data);
> + if (drive->dev_flags & IDE_DFLAG_NO_UNLOAD) {
> + ide_end_request(drive, 1, 0);
> + return ide_stopped;
> + }
> + tf->command = ATA_CMD_IDLEIMMEDIATE;
> + tf->feature = 0x44;
> + tf->lbal = 0x4c;
> + tf->lbam = 0x4e;
> + tf->lbah = 0x55;
> + task.tf_flags |= IDE_TFLAG_CUSTOM_HANDLER;
> + break;
> + case REQ_UNPARK_HEADS:
> + tf->command = ATA_CMD_CHK_POWER;
> + break;
> case REQ_DEVSET_EXEC:
> {
> int err, (*setfunc)(ide_drive_t *, int) = rq->special;
> @@ -692,6 +715,10 @@ static ide_startstop_t ide_special_rq(ide_drive_t *drive, struct request *rq)
> ide_end_request(drive, 0, 0);
> return ide_stopped;
> }
> + task.tf_flags |= IDE_TFLAG_TF | IDE_TFLAG_DEVICE;
> + task.rq = rq;
> + hwif->data_phase = task.data_phase = TASKFILE_NO_DATA;
> + return do_rw_taskfile(drive, &task);
> }
>
> static void ide_check_pm_state(ide_drive_t *drive, struct request *rq)
> diff --git a/drivers/ide/ide-park.c b/drivers/ide/ide-park.c
> new file mode 100644
> index 0000000..fd04cb7
> --- /dev/null
> +++ b/drivers/ide/ide-park.c
> @@ -0,0 +1,133 @@
> +#include <linux/kernel.h>
> +#include <linux/ide.h>
> +#include <linux/jiffies.h>
> +#include <linux/blkdev.h>
> +#include <linux/completion.h>
> +
> +static void issue_park_cmd(ide_drive_t *drive, unsigned long timeout)
> +{
> + ide_hwif_t *hwif = drive->hwif;
> + int i, restart;
> +
> + if (!timeout && time_before(hwif->park_timeout, jiffies))
> + return;

Maybe this check could be moved to the caller?

> + timeout += jiffies;
> + restart = time_before(timeout, hwif->park_timeout);
> + hwif->park_timeout = timeout;
> +
> + for (i = 0; i < MAX_DRIVES; i++) {

and the code under for-loop factored out to a separate helper?

> + ide_drive_t *drive = &hwif->drives[i];
> + struct request_queue *q;
> + struct request *rq;
> + DECLARE_COMPLETION_ONSTACK(wait);
> +
> + spin_lock_irq(&ide_lock);
> + if (!(drive->dev_flags & IDE_DFLAG_PRESENT) ||
> + ide_device_get(drive)) {
> + spin_unlock_irq(&ide_lock);
> + continue;
> + }

No need to ide_lock for IDE_DLAG_PRESENT check or ide_device_get().

> + if (drive->dev_flags & IDE_DFLAG_SLEEPING) {
> + drive->sleep = timeout;
> + spin_unlock_irq(&ide_lock);
> + goto next_step;
> + }
> + spin_unlock_irq(&ide_lock);
> +
> + q = drive->queue;
> + rq = blk_get_request(q, READ, __GFP_WAIT);
> + rq->cmd[0] = REQ_PARK_HEADS;
> + rq->cmd_len = 1;
> + rq->cmd_type = REQ_TYPE_SPECIAL;
> + rq->end_io_data = &wait;
> + blk_execute_rq_nowait(q, NULL, rq, 1, NULL);

Shouldn't this be skipped if 'restart' is true?

> + /*
> + * This really is only to make sure that the request
> + * has been started yet, not necessarily completed
> + * though.
> + */
> + wait_for_completion(&wait);
> + if (q->rq.count[READ] + q->rq.count[WRITE] <= 1 &&

What it is the point of 'q->rq.count[READ] + q->rq.count[WRITE] <= 1'
check?

> + !(drive->dev_flags & IDE_DFLAG_NO_UNLOAD)) {
> + rq = blk_get_request(q, READ, GFP_NOWAIT);
> +
> + if (unlikely(!rq))
> + goto next_step;
> +
> + rq->cmd[0] = REQ_UNPARK_HEADS;
> + rq->cmd_len = 1;
> + rq->cmd_type = REQ_TYPE_SPECIAL;
> + elv_add_request(q, rq, ELEVATOR_INSERT_FRONT, 0);
> + }
> +
> +next_step:
> + ide_device_put(drive);
> + }
> +
> + if (restart) {
> + ide_hwgroup_t *hwgroup = hwif->hwgroup;
> +
> + spin_lock_irq(&ide_lock);
> + if (hwgroup->sleeping && del_timer(&hwgroup->timer)) {
> + hwgroup->sleeping = 0;
> + hwgroup->busy = 0;
> + __blk_run_queue(drive->queue);

What about the other device?

> + }
> + spin_unlock_irq(&ide_lock);
> + }
> +}
> +
> +ide_devset_w_flag(no_unload, IDE_DFLAG_NO_UNLOAD);
> +
> +ssize_t ide_park_show(struct device *dev, struct device_attribute *attr,
> + char *buf)
> +{
> + ide_drive_t *drive = to_ide_device(dev);
> + ide_hwif_t *hwif = drive->hwif;
> + unsigned int seconds;
> +
> + mutex_lock(&ide_setting_mtx);
> + if (drive->dev_flags & IDE_DFLAG_SLEEPING &&
> + time_after(hwif->park_timeout, jiffies))
> + /*
> + * Adding 1 in order to guarantee nonzero value until timer
> + * has actually expired.
> + */
> + seconds = jiffies_to_msecs(hwif->park_timeout - jiffies)
> + / 1000 + 1;
> + else
> + seconds = 0;
> + mutex_unlock(&ide_setting_mtx);
> +
> + return snprintf(buf, 20, "%u\n", seconds);
> +}
> +
> +ssize_t ide_park_store(struct device *dev, struct device_attribute *attr,
> + const char *buf, size_t len)
> +{
> +#define MAX_PARK_TIMEOUT 30
> + ide_drive_t *drive = to_ide_device(dev);
> + long int input;
> + int rc;
> +
> + rc = strict_strtol(buf, 10, &input);
> + if (rc || input < -2 || input > MAX_PARK_TIMEOUT)
> + return -EINVAL;
> +
> + mutex_lock(&ide_setting_mtx);
> + if (input >= 0) {
> + if (drive->dev_flags & IDE_DFLAG_NO_UNLOAD) {
> + mutex_unlock(&ide_setting_mtx);
> + return -EOPNOTSUPP;
> + }
> +
> + issue_park_cmd(drive, msecs_to_jiffies(input * 1000));
> + } else
> + /* input can either be -1 or -2 at this point */

Since Tejun already raised concerns about multiplexing per-device
and per-port settings I'm not repeating them here. Please just
remember to backport fixes from libata version to ide one.

> + rc = ide_devset_execute(drive, &ide_devset_no_unload,
> + input + 1);

No need to use ide_devset_execute() - ide_setting_mtx already provides
the needed protection.

Thanks,
Bart


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