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SubjectRe: [PATCH v2] mm, zone_device: replace {get, put}_zone_device_page() with a single reference

* Dan Williams <> wrote:

> Kirill points out that the calls to {get,put}_dev_pagemap() can be
> removed from the mm fast path if we take a single get_dev_pagemap()
> reference to signify that the page is alive and use the final put of the
> page to drop that reference.
> This does require some care to make sure that any waits for the
> percpu_ref to drop to zero occur *after* devm_memremap_page_release(),
> since it now maintains its own elevated reference.
> Cc: Ingo Molnar <>
> Cc: Jérôme Glisse <>
> Cc: Andrew Morton <>
> Reviewed-by: Logan Gunthorpe <>
> Suggested-by: Kirill Shutemov <>
> Tested-by: Kirill Shutemov <>
> Signed-off-by: Dan Williams <>

This changelog is lacking an explanation about how this solves the crashes you
were seeing.



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