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SubjectRe: [RFC PATCH 2/2] mm: Batch page_check_references in shrink_page_list sharing the same i_mmap_mutex
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On Tue, 2012-08-21 at 09:21 -0400, Matthew Wilcox wrote:

>
> The only clunky bit would seem to be this bit:
>
> > if (page_mapped(page) && mapping) {
> > - switch (try_to_unmap(page, TTU_UNMAP)) {
> > + switch (try_to_unmap(page, TTU_UNMAP,
> > + mmap_mutex_locked)) {
>
> Which I think has to look like this:
>
> if (page_mapped(page) && mapping) {
> - switch (try_to_unmap(page, TTU_UNMAP)) {
> + int result;
> + if (i_mmap_mutex)
> + result = __try_to_unmap(page, TTU_UNMAP);
> + else
> + result = try_to_unmap(page, TTU_UNMAP);
> + switch (result) {
>

I think

- switch (try_to_unmap(page, TTU_UNMAP)) {
+ switch (__try_to_unmap(page, TTU_UNMAP)) {
should be enough when your changes are adopted. Because if the page
mmap mutex needs to be locked, we will have locked it here before
__try_to_unmap gets used.

+ if (needs_page_mmap_mutex(page) &&
+ i_mmap_mutex != &page->mapping->i_mmap_mutex) {
+ if (i_mmap_mutex)
+ mutex_unlock(i_mmap_mutex);
+ i_mmap_mutex = &page->mapping->i_mmap_mutex;
+ mutex_lock(i_mmap_mutex);
+ }

Tim



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