[PATCH v2] PM: HIBERNATION: skip the swap size check if the snapshot image size is anticipative

[Pavel Machek]

Hi!

Is the check even useful these days? Should we remove it altogether?

       	     	  	       	     	       Pavel


> Pavel ,Rafael, any feedback?
> -barry
> 
> 2011/11/25 Barry Song <Barry.Song at csr.com>:
> > From: Barry Song <baohua.song at csr.com>
> >
> > Current swsusp requires swap partitions even larger than real saved pages
> > based on the worst compression ratio:
> > but for an embedded system, which has limited storage space, then it might
> > can't give the large partition to save snapshot.
> > In the another way, some embedded systems can definitely know the most size
> > needed for snapshot since they run some specific application lists.
> > So this patch provides the possibility for users to tell kernel even
> > the system has a little snapshot partition, but it is still enough.
> > For example, if the system need to save 120MB memory, origin swsusp will require
> > a 130MB partition to save snapshot. but if users know 30MB is enough for them(
> > compressed image will be less than 30MB), they just make a 30MB partition by
> > echo 0 > /sys/power/check_swap_size
> >
> > Signed-off-by: Barry Song <Baohua.Song at csr.com>
> > Cc: Xiangzhen Ye <Xiangzhen.Ye at csr.com>
> > ---
> >  -v2:drop swap_enough bootargs and use /sys/power/check_swap_size node
> >
> >  Documentation/power/interface.txt |    5 +++++
> >  kernel/power/hibernate.c          |   22 ++++++++++++++++++++++
> >  kernel/power/power.h              |    2 ++
> >  kernel/power/swap.c               |    9 +++++++++
> >  4 files changed, 38 insertions(+), 0 deletions(-)
> >
> > diff --git a/Documentation/power/interface.txt b/Documentation/power/interface.txt
> > index c537834..5e205f0 100644
> > --- a/Documentation/power/interface.txt
> > +++ b/Documentation/power/interface.txt
> > @@ -47,6 +47,11 @@ Writing to this file will accept one of
> >        'testproc'
> >        'test'
> >
> > +/sys/power/check_swap_size controls whether we can skip checking the swap
> > +partition size by worst compression ratio. If users know the swap partition
> > +is enough for compressed snapshot, write 0 to /sys/power/check_swap_size.
> > +It is useful for an embedded system with known running softwares.
> > +
> >  /sys/power/image_size controls the size of the image created by
> >  the suspend-to-disk mechanism.  It can be written a string
> >  representing a non-negative integer that will be used as an upper
> > diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> > index 1c53f7f..5552473 100644
> > --- a/kernel/power/hibernate.c
> > +++ b/kernel/power/hibernate.c
> > @@ -1024,11 +1024,33 @@ static ssize_t reserved_size_store(struct kobject *kobj,
> >
> >  power_attr(reserved_size);
> >
> > +static ssize_t check_swap_size_show(struct kobject *kobj, struct kobj_attribute *attr,
> > +                              char *buf)
> > +{
> > +       return sprintf(buf, "%d\n", check_swap_size);
> > +}
> > +
> > +static ssize_t check_swap_size_store(struct kobject *kobj, struct kobj_attribute *attr,
> > +                               const char *buf, size_t n)
> > +{
> > +       int check_size;
> > +
> > +       if (sscanf(buf, "%d", &check_size) == 1) {
> > +               check_swap_size = check_size;
> > +               return n;
> > +       }
> > +
> > +       return -EINVAL;
> > +}
> > +
> > +power_attr(check_swap_size);
> > +
> >  static struct attribute * g[] = {
> >        &disk_attr.attr,
> >        &resume_attr.attr,
> >        &image_size_attr.attr,
> >        &reserved_size_attr.attr,
> > +       &check_swap_size_attr.attr,
> >        NULL,
> >  };
> >
> > diff --git a/kernel/power/power.h b/kernel/power/power.h
> > index 23a2db1..4f0fa78 100644
> > --- a/kernel/power/power.h
> > +++ b/kernel/power/power.h
> > @@ -74,6 +74,8 @@ static struct kobj_attribute _name##_attr = { \
> >
> >  /* Preferred image size in bytes (default 500 MB) */
> >  extern unsigned long image_size;
> > +/* If 0, skip checking whether the swap size is enough for compressed snapshot */
> > +extern int check_swap_size;
> >  /* Size of memory reserved for drivers (default SPARE_PAGES x PAGE_SIZE) */
> >  extern unsigned long reserved_size;
> >  extern int in_suspend;
> > diff --git a/kernel/power/swap.c b/kernel/power/swap.c
> > index 11a594c..db90195 100644
> > --- a/kernel/power/swap.c
> > +++ b/kernel/power/swap.c
> > @@ -37,6 +37,12 @@
> >  #define HIBERNATE_SIG  "S1SUSPEND"
> >
> >  /*
> > + * if users know swap partitions are enough for compressed snapshots,
> > + * echo 0 > /sys/power/check_swap_size
> > + */
> > +int check_swap_size = 1;
> > +
> > +/*
> >  *     The swap map is a data structure used for keeping track of each page
> >  *     written to a swap partition.  It consists of many swap_map_page
> >  *     structures that contain each an array of MAP_PAGE_ENTRIES swap entries.
> > @@ -772,6 +778,9 @@ static int enough_swap(unsigned int nr_pages, unsigned int flags)
> >        unsigned int free_swap = count_swap_pages(root_swap, 1);
> >        unsigned int required;
> >
> > +       if (!check_swap_size)
> > +               return 1;
> > +
> >        pr_debug("PM: Free swap pages: %u\n", free_swap);
> >
> >        required = PAGES_FOR_IO + ((flags & SF_NOCOMPRESS_MODE) ?
> > --
> > 1.7.1

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