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    SubjectRe: [PATCH v3 5/6] mm/memory_hotplug: Move and simplify walk_memory_blocks()
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    On 20.06.19 20:31, David Hildenbrand wrote:
    > Let's move walk_memory_blocks() to the place where memory block logic
    > resides and simplify it. While at it, add a type for the callback function.
    >
    > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    > Cc: "Rafael J. Wysocki" <rafael@kernel.org>
    > Cc: David Hildenbrand <david@redhat.com>
    > Cc: Andrew Morton <akpm@linux-foundation.org>
    > Cc: Stephen Rothwell <sfr@canb.auug.org.au>
    > Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
    > Cc: Andrew Banman <andrew.banman@hpe.com>
    > Cc: "mike.travis@hpe.com" <mike.travis@hpe.com>
    > Cc: Oscar Salvador <osalvador@suse.com>
    > Cc: Michal Hocko <mhocko@suse.com>
    > Cc: Wei Yang <richard.weiyang@gmail.com>
    > Cc: Arun KS <arunks@codeaurora.org>
    > Cc: Qian Cai <cai@lca.pw>
    > Signed-off-by: David Hildenbrand <david@redhat.com>
    > ---
    > drivers/base/memory.c | 42 ++++++++++++++++++++++++++
    > include/linux/memory.h | 3 ++
    > include/linux/memory_hotplug.h | 2 --
    > mm/memory_hotplug.c | 55 ----------------------------------
    > 4 files changed, 45 insertions(+), 57 deletions(-)
    >
    > diff --git a/drivers/base/memory.c b/drivers/base/memory.c
    > index c54e80fd25a8..0204384b4d1d 100644
    > --- a/drivers/base/memory.c
    > +++ b/drivers/base/memory.c
    > @@ -44,6 +44,11 @@ static inline unsigned long pfn_to_block_id(unsigned long pfn)
    > return base_memory_block_id(pfn_to_section_nr(pfn));
    > }
    >
    > +static inline unsigned long phys_to_block_id(unsigned long phys)
    > +{
    > + return pfn_to_block_id(PFN_DOWN(phys));
    > +}
    > +
    > static int memory_subsys_online(struct device *dev);
    > static int memory_subsys_offline(struct device *dev);
    >
    > @@ -851,3 +856,40 @@ int __init memory_dev_init(void)
    > printk(KERN_ERR "%s() failed: %d\n", __func__, ret);
    > return ret;
    > }
    > +
    > +/**
    > + * walk_memory_blocks - walk through all present memory blocks overlapped
    > + * by the range [start, start + size)
    > + *
    > + * @start: start address of the memory range
    > + * @size: size of the memory range
    > + * @arg: argument passed to func
    > + * @func: callback for each memory section walked
    > + *
    > + * This function walks through all present memory blocks overlapped by the
    > + * range [start, start + size), calling func on each memory block.
    > + *
    > + * In case func() returns an error, walking is aborted and the error is
    > + * returned.
    > + */
    > +int walk_memory_blocks(unsigned long start, unsigned long size,
    > + void *arg, walk_memory_blocks_func_t func)
    > +{
    > + const unsigned long start_block_id = phys_to_block_id(start);
    > + const unsigned long end_block_id = phys_to_block_id(start + size - 1);
    > + struct memory_block *mem;
    > + unsigned long block_id;
    > + int ret = 0;

    I *guess* the stall we are seeing is when size = 0.

    (via ACPI, if info->length is 0)

    if (!size)
    return 0;

    ... but that is just a wild guess. Will have a look after my vacation.

    --

    Thanks,

    David / dhildenb

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