| Message ID | 20181219034047.16305-2-aneesh.kumar@linux.ibm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm/kvm/vfio/ppc64: Migrate compound pages out of CMA region | expand |
On 19/12/2018 14:40, Aneesh Kumar K.V wrote: > This helper does a get_user_pages_fast and if it find pages in the CMA area > it will try to migrate them before taking page reference. This makes sure that > we don't keep non-movable pages (due to page reference count) in the CMA area. > Not able to move pages out of CMA area result in CMA allocation failures. > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > --- > include/linux/hugetlb.h | 2 + > include/linux/migrate.h | 3 + > mm/hugetlb.c | 4 +- > mm/migrate.c | 139 ++++++++++++++++++++++++++++++++++++++++ > 4 files changed, 146 insertions(+), 2 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 087fd5f48c91..1eed0cdaec0e 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -371,6 +371,8 @@ struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid, > nodemask_t *nmask); > struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma, > unsigned long address); > +struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask, > + int nid, nodemask_t *nmask); > int huge_add_to_page_cache(struct page *page, struct address_space *mapping, > pgoff_t idx); > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > index f2b4abbca55e..d82b35afd2eb 100644 > --- a/include/linux/migrate.h > +++ b/include/linux/migrate.h > @@ -286,6 +286,9 @@ static inline int migrate_vma(const struct migrate_vma_ops *ops, > } > #endif /* IS_ENABLED(CONFIG_MIGRATE_VMA_HELPER) */ > > +extern int get_user_pages_cma_migrate(unsigned long start, int nr_pages, int write, > + struct page **pages); > + > #endif /* CONFIG_MIGRATION */ > > #endif /* _LINUX_MIGRATE_H */ > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > index 7f2a28ab46d5..faf3102ae45e 100644 > --- a/mm/hugetlb.c > +++ b/mm/hugetlb.c > @@ -1585,8 +1585,8 @@ static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask, > return page; > } > > -static struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask, > - int nid, nodemask_t *nmask) > +struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask, > + int nid, nodemask_t *nmask) > { > struct page *page; > > diff --git a/mm/migrate.c b/mm/migrate.c > index f7e4bfdc13b7..d564558fba03 100644 > --- a/mm/migrate.c > +++ b/mm/migrate.c > @@ -2946,3 +2946,142 @@ int migrate_vma(const struct migrate_vma_ops *ops, > } > EXPORT_SYMBOL(migrate_vma); > #endif /* defined(MIGRATE_VMA_HELPER) */ > + > +static struct page *new_non_cma_page(struct page *page, unsigned long private) > +{ > + /* > + * We want to make sure we allocate the new page from the same node > + * as the source page. > + */ > + int nid = page_to_nid(page); > + /* > + * Trying to allocate a page for migration. Ignore allocation > + * failure warnings > + */ > + gfp_t gfp_mask = GFP_USER | __GFP_THISNODE | __GFP_NOWARN; > + > + if (PageHighMem(page)) > + gfp_mask |= __GFP_HIGHMEM; > + > +#ifdef CONFIG_HUGETLB_PAGE > + if (PageHuge(page)) { > + struct hstate *h = page_hstate(page); > + /* > + * We don't want to dequeue from the pool because pool pages will > + * mostly be from the CMA region. > + */ > + return alloc_migrate_huge_page(h, gfp_mask, nid, NULL); > + } > +#endif > + if (PageTransHuge(page)) { > + struct page *thp; > + /* > + * ignore allocation failure warnings > + */ > + gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_THISNODE | __GFP_NOWARN; > + > + /* > + * Remove the movable mask so that we don't allocate from > + * CMA area again. > + */ > + thp_gfpmask &= ~__GFP_MOVABLE; > + thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER); > + if (!thp) > + return NULL; > + prep_transhuge_page(thp); > + return thp; > + } > + > + return __alloc_pages_node(nid, gfp_mask, 0); > +} > + > +/** > + * get_user_pages_cma_migrate() - pin user pages in memory by migrating pages in CMA region > + * @start: starting user address > + * @nr_pages: number of pages from start to pin > + * @write: whether pages will be written to > + * @pages: array that receives pointers to the pages pinned. > + * Should be at least nr_pages long. > + * > + * Attempt to pin user pages in memory without taking mm->mmap_sem. > + * If not successful, it will fall back to taking the lock and > + * calling get_user_pages(). > + * > + * If the pinned pages are backed by CMA region, we migrate those pages out, > + * allocating new pages from non-CMA region. This helps in avoiding keeping > + * pages pinned in the CMA region for a long time thereby resulting in > + * CMA allocation failures. > + * > + * Returns number of pages pinned. This may be fewer than the number > + * requested. If nr_pages is 0 or negative, returns 0. If no pages > + * were pinned, returns -errno. > + */ > + > +int get_user_pages_cma_migrate(unsigned long start, int nr_pages, int write, > + struct page **pages) > +{ > + int i, ret; > + bool drain_allow = true; > + bool migrate_allow = true; > + LIST_HEAD(cma_page_list); > + > +get_user_again: > + ret = get_user_pages_fast(start, nr_pages, write, pages); > + if (ret <= 0) > + return ret; > + > + for (i = 0; i < ret; ++i) { > + /* > + * If we get a page from the CMA zone, since we are going to > + * be pinning these entries, we might as well move them out > + * of the CMA zone if possible. > + */ > + if (is_migrate_cma_page(pages[i]) && migrate_allow) { > + > + struct page *head = compound_head(pages[i]); > + > + if (PageHuge(head)) > + isolate_huge_page(head, &cma_page_list); You need curly braces in both branches as per https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/process/coding-style.rst#n191 > + else { > + if (!PageLRU(head) && drain_allow) { > + lru_add_drain_all(); > + drain_allow = false; > + } > + > + if (!isolate_lru_page(head)) { > + list_add_tail(&head->lru, &cma_page_list); > + mod_node_page_state(page_pgdat(head), > + NR_ISOLATED_ANON + > + page_is_file_cache(head), > + hpage_nr_pages(head)); > + } > + } > + } > + } > + if (!list_empty(&cma_page_list)) { > + /* > + * drop the above get_user_pages reference. > + */ Can be a single line comment. > + for (i = 0; i < ret; ++i) > + put_page(pages[i]); > + > + if (migrate_pages(&cma_page_list, new_non_cma_page, > + NULL, 0, MIGRATE_SYNC, MR_CONTIG_RANGE)) { > + /* > + * some of the pages failed migration. Do get_user_pages > + * without migration. > + */ > + migrate_allow = false; > + > + if (!list_empty(&cma_page_list)) > + putback_movable_pages(&cma_page_list); > + } > + /* > + * We did migrate all the pages, Try to get the page references again > + * migrating any new CMA pages which we failed to isolate earlier. > + */ > + drain_allow = true; > + goto get_user_again; So it is possible to have pages pinned, then successfully migrated (migrate_pages() returned 0), then pinned again, then some pages may end up in CMA again and migrate again and nothing seems to prevent this loop from being endless. What do I miss? (ps I hate such "goto"s, confuse a lot) > + } > + return ret; > +} >
On 19/12/2018 14:40, Aneesh Kumar K.V wrote: > This helper does a get_user_pages_fast and if it find pages in the CMA area > it will try to migrate them before taking page reference. This makes sure that > we don't keep non-movable pages (due to page reference count) in the CMA area. > Not able to move pages out of CMA area result in CMA allocation failures. > > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > --- > include/linux/hugetlb.h | 2 + > include/linux/migrate.h | 3 + > mm/hugetlb.c | 4 +- > mm/migrate.c | 139 ++++++++++++++++++++++++++++++++++++++++ > 4 files changed, 146 insertions(+), 2 deletions(-) > > diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h > index 087fd5f48c91..1eed0cdaec0e 100644 > --- a/include/linux/hugetlb.h > +++ b/include/linux/hugetlb.h > @@ -371,6 +371,8 @@ struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid, > nodemask_t *nmask); > struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma, > unsigned long address); > +struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask, > + int nid, nodemask_t *nmask); > int huge_add_to_page_cache(struct page *page, struct address_space *mapping, > pgoff_t idx); > > diff --git a/include/linux/migrate.h b/include/linux/migrate.h > index f2b4abbca55e..d82b35afd2eb 100644 > --- a/include/linux/migrate.h > +++ b/include/linux/migrate.h > @@ -286,6 +286,9 @@ static inline int migrate_vma(const struct migrate_vma_ops *ops, > } > #endif /* IS_ENABLED(CONFIG_MIGRATE_VMA_HELPER) */ > > +extern int get_user_pages_cma_migrate(unsigned long start, int nr_pages, int write, > + struct page **pages); ah, sorry for commenting the same patch again but ./scripts/checkpatch.pl complains a log on this patch.
On 12/20/18 9:49 AM, Alexey Kardashevskiy wrote: > > > On 19/12/2018 14:40, Aneesh Kumar K.V wrote: >> This helper does a get_user_pages_fast and if it find pages in the CMA area >> it will try to migrate them before taking page reference. This makes sure that >> we don't keep non-movable pages (due to page reference count) in the CMA area. >> Not able to move pages out of CMA area result in CMA allocation failures. >> >> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> > ..... >> + * We did migrate all the pages, Try to get the page references again >> + * migrating any new CMA pages which we failed to isolate earlier. >> + */ >> + drain_allow = true; >> + goto get_user_again; > > > So it is possible to have pages pinned, then successfully migrated > (migrate_pages() returned 0), then pinned again, then some pages may end > up in CMA again and migrate again and nothing seems to prevent this loop > from being endless. What do I miss? > pages used as target page for migration won't be allocated from CMA region. -aneesh
On 20/12/2018 16:22, Aneesh Kumar K.V wrote: > On 12/20/18 9:49 AM, Alexey Kardashevskiy wrote: >> >> >> On 19/12/2018 14:40, Aneesh Kumar K.V wrote: >>> This helper does a get_user_pages_fast and if it find pages in the >>> CMA area >>> it will try to migrate them before taking page reference. This makes >>> sure that >>> we don't keep non-movable pages (due to page reference count) in the >>> CMA area. >>> Not able to move pages out of CMA area result in CMA allocation >>> failures. >>> >>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> >> > > ..... >>> + * We did migrate all the pages, Try to get the page >>> references again >>> + * migrating any new CMA pages which we failed to isolate >>> earlier. >>> + */ >>> + drain_allow = true; >>> + goto get_user_again; >> >> >> So it is possible to have pages pinned, then successfully migrated >> (migrate_pages() returned 0), then pinned again, then some pages may end >> up in CMA again and migrate again and nothing seems to prevent this loop >> from being endless. What do I miss? >> > > pages used as target page for migration won't be allocated from CMA region. Then migrate_allow should be set to "false" regardless what migrate_pages() returned and then I am totally missing the point of this goto and going through the loop again even when we know for sure it won't do literally anything but checking is_migrate_cma_page() even though we know pages won't be allocated from CMA. It should be simple gup_fast() instead of goto and then we won't need goto/migrate_allow.
On 12/20/18 11:18 AM, Alexey Kardashevskiy wrote: > > > On 20/12/2018 16:22, Aneesh Kumar K.V wrote: >> On 12/20/18 9:49 AM, Alexey Kardashevskiy wrote: >>> >>> >>> On 19/12/2018 14:40, Aneesh Kumar K.V wrote: >>>> This helper does a get_user_pages_fast and if it find pages in the >>>> CMA area >>>> it will try to migrate them before taking page reference. This makes >>>> sure that >>>> we don't keep non-movable pages (due to page reference count) in the >>>> CMA area. >>>> Not able to move pages out of CMA area result in CMA allocation >>>> failures. >>>> >>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> >>> >> >> ..... >>>> + * We did migrate all the pages, Try to get the page >>>> references again >>>> + * migrating any new CMA pages which we failed to isolate >>>> earlier. >>>> + */ >>>> + drain_allow = true; >>>> + goto get_user_again; >>> >>> >>> So it is possible to have pages pinned, then successfully migrated >>> (migrate_pages() returned 0), then pinned again, then some pages may end >>> up in CMA again and migrate again and nothing seems to prevent this loop >>> from being endless. What do I miss? >>> >> >> pages used as target page for migration won't be allocated from CMA region. > > > Then migrate_allow should be set to "false" regardless what > migrate_pages() returned and then I am totally missing the point of this > goto and going through the loop again even when we know for sure it > won't do literally anything but checking is_migrate_cma_page() even > though we know pages won't be allocated from CMA. > Because we might have failed to isolate all the pages in the first attempt. -aneesh
On 20/12/2018 16:52, Aneesh Kumar K.V wrote: > On 12/20/18 11:18 AM, Alexey Kardashevskiy wrote: >> >> >> On 20/12/2018 16:22, Aneesh Kumar K.V wrote: >>> On 12/20/18 9:49 AM, Alexey Kardashevskiy wrote: >>>> >>>> >>>> On 19/12/2018 14:40, Aneesh Kumar K.V wrote: >>>>> This helper does a get_user_pages_fast and if it find pages in the >>>>> CMA area >>>>> it will try to migrate them before taking page reference. This makes >>>>> sure that >>>>> we don't keep non-movable pages (due to page reference count) in the >>>>> CMA area. >>>>> Not able to move pages out of CMA area result in CMA allocation >>>>> failures. >>>>> >>>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> >>>> >>> >>> ..... >>>>> + * We did migrate all the pages, Try to get the page >>>>> references again >>>>> + * migrating any new CMA pages which we failed to isolate >>>>> earlier. >>>>> + */ >>>>> + drain_allow = true; >>>>> + goto get_user_again; >>>> >>>> >>>> So it is possible to have pages pinned, then successfully migrated >>>> (migrate_pages() returned 0), then pinned again, then some pages may >>>> end >>>> up in CMA again and migrate again and nothing seems to prevent this >>>> loop >>>> from being endless. What do I miss? >>>> >>> >>> pages used as target page for migration won't be allocated from CMA >>> region. >> >> >> Then migrate_allow should be set to "false" regardless what >> migrate_pages() returned and then I am totally missing the point of this >> goto and going through the loop again even when we know for sure it >> won't do literally anything but checking is_migrate_cma_page() even >> though we know pages won't be allocated from CMA. >> > > Because we might have failed to isolate all the pages in the first attempt. isolate==migrate? If we failed to migrate, then migrate_pages() returns non zero (positive or negative), we set migrate_allow to false, empty the cma_page_list and repeat but we won't add anything to cma_page_list as migrate_allow==false. If we succeeded to migrate, then we repeat the loop with migrate_allow==true but it does not matter as is_migrate_cma_page() is expected to return false because we just successfully migrated _everything_ so we won't be adding anything to cma_page_list either. What have I missed?
On 12/20/18 11:50 AM, Alexey Kardashevskiy wrote: > > > On 20/12/2018 16:52, Aneesh Kumar K.V wrote: >> On 12/20/18 11:18 AM, Alexey Kardashevskiy wrote: >>> >>> >>> On 20/12/2018 16:22, Aneesh Kumar K.V wrote: >>>> On 12/20/18 9:49 AM, Alexey Kardashevskiy wrote: >>>>> >>>>> >>>>> On 19/12/2018 14:40, Aneesh Kumar K.V wrote: >>>>>> This helper does a get_user_pages_fast and if it find pages in the >>>>>> CMA area >>>>>> it will try to migrate them before taking page reference. This makes >>>>>> sure that >>>>>> we don't keep non-movable pages (due to page reference count) in the >>>>>> CMA area. >>>>>> Not able to move pages out of CMA area result in CMA allocation >>>>>> failures. >>>>>> >>>>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> >>>>> >>>> >>>> ..... >>>>>> + * We did migrate all the pages, Try to get the page >>>>>> references again >>>>>> + * migrating any new CMA pages which we failed to isolate >>>>>> earlier. >>>>>> + */ >>>>>> + drain_allow = true; >>>>>> + goto get_user_again; >>>>> >>>>> >>>>> So it is possible to have pages pinned, then successfully migrated >>>>> (migrate_pages() returned 0), then pinned again, then some pages may >>>>> end >>>>> up in CMA again and migrate again and nothing seems to prevent this >>>>> loop >>>>> from being endless. What do I miss? >>>>> >>>> >>>> pages used as target page for migration won't be allocated from CMA >>>> region. >>> >>> >>> Then migrate_allow should be set to "false" regardless what >>> migrate_pages() returned and then I am totally missing the point of this >>> goto and going through the loop again even when we know for sure it >>> won't do literally anything but checking is_migrate_cma_page() even >>> though we know pages won't be allocated from CMA. >>> >> >> Because we might have failed to isolate all the pages in the first attempt. > > isolate==migrate? no The call to isolate_lru_page and isolate_huge_page. We can fail because the percpu pagevec is not fully drained -aneesh
diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h index 087fd5f48c91..1eed0cdaec0e 100644 --- a/include/linux/hugetlb.h +++ b/include/linux/hugetlb.h @@ -371,6 +371,8 @@ struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid, nodemask_t *nmask); struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma, unsigned long address); +struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask, + int nid, nodemask_t *nmask); int huge_add_to_page_cache(struct page *page, struct address_space *mapping, pgoff_t idx); diff --git a/include/linux/migrate.h b/include/linux/migrate.h index f2b4abbca55e..d82b35afd2eb 100644 --- a/include/linux/migrate.h +++ b/include/linux/migrate.h @@ -286,6 +286,9 @@ static inline int migrate_vma(const struct migrate_vma_ops *ops, } #endif /* IS_ENABLED(CONFIG_MIGRATE_VMA_HELPER) */ +extern int get_user_pages_cma_migrate(unsigned long start, int nr_pages, int write, + struct page **pages); + #endif /* CONFIG_MIGRATION */ #endif /* _LINUX_MIGRATE_H */ diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 7f2a28ab46d5..faf3102ae45e 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1585,8 +1585,8 @@ static struct page *alloc_surplus_huge_page(struct hstate *h, gfp_t gfp_mask, return page; } -static struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask, - int nid, nodemask_t *nmask) +struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask, + int nid, nodemask_t *nmask) { struct page *page; diff --git a/mm/migrate.c b/mm/migrate.c index f7e4bfdc13b7..d564558fba03 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -2946,3 +2946,142 @@ int migrate_vma(const struct migrate_vma_ops *ops, } EXPORT_SYMBOL(migrate_vma); #endif /* defined(MIGRATE_VMA_HELPER) */ + +static struct page *new_non_cma_page(struct page *page, unsigned long private) +{ + /* + * We want to make sure we allocate the new page from the same node + * as the source page. + */ + int nid = page_to_nid(page); + /* + * Trying to allocate a page for migration. Ignore allocation + * failure warnings + */ + gfp_t gfp_mask = GFP_USER | __GFP_THISNODE | __GFP_NOWARN; + + if (PageHighMem(page)) + gfp_mask |= __GFP_HIGHMEM; + +#ifdef CONFIG_HUGETLB_PAGE + if (PageHuge(page)) { + struct hstate *h = page_hstate(page); + /* + * We don't want to dequeue from the pool because pool pages will + * mostly be from the CMA region. + */ + return alloc_migrate_huge_page(h, gfp_mask, nid, NULL); + } +#endif + if (PageTransHuge(page)) { + struct page *thp; + /* + * ignore allocation failure warnings + */ + gfp_t thp_gfpmask = GFP_TRANSHUGE | __GFP_THISNODE | __GFP_NOWARN; + + /* + * Remove the movable mask so that we don't allocate from + * CMA area again. + */ + thp_gfpmask &= ~__GFP_MOVABLE; + thp = __alloc_pages_node(nid, thp_gfpmask, HPAGE_PMD_ORDER); + if (!thp) + return NULL; + prep_transhuge_page(thp); + return thp; + } + + return __alloc_pages_node(nid, gfp_mask, 0); +} + +/** + * get_user_pages_cma_migrate() - pin user pages in memory by migrating pages in CMA region + * @start: starting user address + * @nr_pages: number of pages from start to pin + * @write: whether pages will be written to + * @pages: array that receives pointers to the pages pinned. + * Should be at least nr_pages long. + * + * Attempt to pin user pages in memory without taking mm->mmap_sem. + * If not successful, it will fall back to taking the lock and + * calling get_user_pages(). + * + * If the pinned pages are backed by CMA region, we migrate those pages out, + * allocating new pages from non-CMA region. This helps in avoiding keeping + * pages pinned in the CMA region for a long time thereby resulting in + * CMA allocation failures. + * + * Returns number of pages pinned. This may be fewer than the number + * requested. If nr_pages is 0 or negative, returns 0. If no pages + * were pinned, returns -errno. + */ + +int get_user_pages_cma_migrate(unsigned long start, int nr_pages, int write, + struct page **pages) +{ + int i, ret; + bool drain_allow = true; + bool migrate_allow = true; + LIST_HEAD(cma_page_list); + +get_user_again: + ret = get_user_pages_fast(start, nr_pages, write, pages); + if (ret <= 0) + return ret; + + for (i = 0; i < ret; ++i) { + /* + * If we get a page from the CMA zone, since we are going to + * be pinning these entries, we might as well move them out + * of the CMA zone if possible. + */ + if (is_migrate_cma_page(pages[i]) && migrate_allow) { + + struct page *head = compound_head(pages[i]); + + if (PageHuge(head)) + isolate_huge_page(head, &cma_page_list); + else { + if (!PageLRU(head) && drain_allow) { + lru_add_drain_all(); + drain_allow = false; + } + + if (!isolate_lru_page(head)) { + list_add_tail(&head->lru, &cma_page_list); + mod_node_page_state(page_pgdat(head), + NR_ISOLATED_ANON + + page_is_file_cache(head), + hpage_nr_pages(head)); + } + } + } + } + if (!list_empty(&cma_page_list)) { + /* + * drop the above get_user_pages reference. + */ + for (i = 0; i < ret; ++i) + put_page(pages[i]); + + if (migrate_pages(&cma_page_list, new_non_cma_page, + NULL, 0, MIGRATE_SYNC, MR_CONTIG_RANGE)) { + /* + * some of the pages failed migration. Do get_user_pages + * without migration. + */ + migrate_allow = false; + + if (!list_empty(&cma_page_list)) + putback_movable_pages(&cma_page_list); + } + /* + * We did migrate all the pages, Try to get the page references again + * migrating any new CMA pages which we failed to isolate earlier. + */ + drain_allow = true; + goto get_user_again; + } + return ret; +}
This helper does a get_user_pages_fast and if it find pages in the CMA area it will try to migrate them before taking page reference. This makes sure that we don't keep non-movable pages (due to page reference count) in the CMA area. Not able to move pages out of CMA area result in CMA allocation failures. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com> --- include/linux/hugetlb.h | 2 + include/linux/migrate.h | 3 + mm/hugetlb.c | 4 +- mm/migrate.c | 139 ++++++++++++++++++++++++++++++++++++++++ 4 files changed, 146 insertions(+), 2 deletions(-)