| Message ID | 20240125164256.4147-9-alexandru.elisei@arm.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Add support for arm64 MTE dynamic tag storage reuse | expand |
On 1/25/24 22:12, Alexandru Elisei wrote: > Today, cma_alloc() is used to allocate a contiguous memory region. The > function allows the caller to specify the number of pages to allocate, but > not the starting address. cma_alloc() will walk over the entire CMA region > trying to allocate the first available range of the specified size. > > Introduce cma_alloc_range(), which makes CMA more versatile by allowing the > caller to specify a particular range in the CMA region, defined by the > start pfn and the size. > > arm64 will make use of this function when tag storage management will be > implemented: cma_alloc_range() will be used to reserve the tag storage > associated with a tagged page. Basically, you would like to pass on a preferred start address and the allocation could just fail if a contig range is not available from such a starting address ? Then why not just change cma_alloc() to take a new argument 'start_pfn'. Why create a new but almost similar allocator ? But then I am wondering why this could not be done in the arm64 platform code itself operating on a CMA area reserved just for tag storage. Unless this new allocator has other usage beyond MTE, this could be implemented in the platform itself. > > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> > --- > > Changes since rfc v2: > > * New patch. > > include/linux/cma.h | 2 + > include/trace/events/cma.h | 59 ++++++++++++++++++++++++++ > mm/cma.c | 86 ++++++++++++++++++++++++++++++++++++++ > 3 files changed, 147 insertions(+) > > diff --git a/include/linux/cma.h b/include/linux/cma.h > index 63873b93deaa..e32559da6942 100644 > --- a/include/linux/cma.h > +++ b/include/linux/cma.h > @@ -50,6 +50,8 @@ extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size, > struct cma **res_cma); > extern struct page *cma_alloc(struct cma *cma, unsigned long count, unsigned int align, > bool no_warn); > +extern int cma_alloc_range(struct cma *cma, unsigned long start, unsigned long count, > + unsigned tries, gfp_t gfp); > extern bool cma_pages_valid(struct cma *cma, const struct page *pages, unsigned long count); > extern bool cma_release(struct cma *cma, const struct page *pages, unsigned long count); > > diff --git a/include/trace/events/cma.h b/include/trace/events/cma.h > index 25103e67737c..a89af313a572 100644 > --- a/include/trace/events/cma.h > +++ b/include/trace/events/cma.h > @@ -36,6 +36,65 @@ TRACE_EVENT(cma_release, > __entry->count) > ); > > +TRACE_EVENT(cma_alloc_range_start, > + > + TP_PROTO(const char *name, unsigned long start, unsigned long count, > + unsigned tries), > + > + TP_ARGS(name, start, count, tries), > + > + TP_STRUCT__entry( > + __string(name, name) > + __field(unsigned long, start) > + __field(unsigned long, count) > + __field(unsigned, tries) > + ), > + > + TP_fast_assign( > + __assign_str(name, name); > + __entry->start = start; > + __entry->count = count; > + __entry->tries = tries; > + ), > + > + TP_printk("name=%s start=%lx count=%lu tries=%u", > + __get_str(name), > + __entry->start, > + __entry->count, > + __entry->tries) > +); > + > +TRACE_EVENT(cma_alloc_range_finish, > + > + TP_PROTO(const char *name, unsigned long start, unsigned long count, > + unsigned attempts, int err), > + > + TP_ARGS(name, start, count, attempts, err), > + > + TP_STRUCT__entry( > + __string(name, name) > + __field(unsigned long, start) > + __field(unsigned long, count) > + __field(unsigned, attempts) > + __field(int, err) > + ), > + > + TP_fast_assign( > + __assign_str(name, name); > + __entry->start = start; > + __entry->count = count; > + __entry->attempts = attempts; > + __entry->err = err; > + ), > + > + TP_printk("name=%s start=%lx count=%lu attempts=%u err=%d", > + __get_str(name), > + __entry->start, > + __entry->count, > + __entry->attempts, > + __entry->err) > +); > + > TRACE_EVENT(cma_alloc_start, > > TP_PROTO(const char *name, unsigned long count, unsigned int align), > diff --git a/mm/cma.c b/mm/cma.c > index 543bb6b3be8e..4a0f68b9443b 100644 > --- a/mm/cma.c > +++ b/mm/cma.c > @@ -416,6 +416,92 @@ static void cma_debug_show_areas(struct cma *cma) > static inline void cma_debug_show_areas(struct cma *cma) { } > #endif > > +/** > + * cma_alloc_range() - allocate pages in a specific range > + * @cma: Contiguous memory region for which the allocation is performed. > + * @start: Starting pfn of the allocation. > + * @count: Requested number of pages > + * @tries: Number of tries if the range is busy > + * @no_warn: Avoid printing message about failed allocation > + * > + * This function allocates part of contiguous memory from a specific contiguous > + * memory area, from the specified starting address. The 'start' pfn and the the > + * 'count' number of pages must be aligned to the CMA bitmap order per bit. > + */ > +int cma_alloc_range(struct cma *cma, unsigned long start, unsigned long count, > + unsigned tries, gfp_t gfp) > +{ > + unsigned long bitmap_maxno, bitmap_no, bitmap_start, bitmap_count; > + unsigned long i = 0; > + struct page *page; > + int err = -EINVAL; > + > + if (!cma || !cma->count || !cma->bitmap) > + goto out_stats; > + > + trace_cma_alloc_range_start(cma->name, start, count, tries); > + > + if (!count || start < cma->base_pfn || > + start + count > cma->base_pfn + cma->count) > + goto out_stats; > + > + if (!IS_ALIGNED(start | count, 1 << cma->order_per_bit)) > + goto out_stats; > + > + bitmap_start = (start - cma->base_pfn) >> cma->order_per_bit; > + bitmap_maxno = cma_bitmap_maxno(cma); > + bitmap_count = cma_bitmap_pages_to_bits(cma, count); > + > + spin_lock_irq(&cma->lock); > + bitmap_no = bitmap_find_next_zero_area(cma->bitmap, bitmap_maxno, > + bitmap_start, bitmap_count, 0); > + if (bitmap_no != bitmap_start) { > + spin_unlock_irq(&cma->lock); > + err = -EEXIST; > + goto out_stats; > + } > + bitmap_set(cma->bitmap, bitmap_start, bitmap_count); > + spin_unlock_irq(&cma->lock); > + > + for (i = 0; i < tries; i++) { > + mutex_lock(&cma_mutex); > + err = alloc_contig_range(start, start + count, MIGRATE_CMA, gfp); > + mutex_unlock(&cma_mutex); > + > + if (err != -EBUSY) > + break; > + } > + > + if (err) { > + cma_clear_bitmap(cma, start, count); > + } else { > + page = pfn_to_page(start); > + > + /* > + * CMA can allocate multiple page blocks, which results in > + * different blocks being marked with different tags. Reset the > + * tags to ignore those page blocks. > + */ > + for (i = 0; i < count; i++) > + page_kasan_tag_reset(nth_page(page, i)); > + } > + > +out_stats: > + trace_cma_alloc_range_finish(cma->name, start, count, i, err); > + > + if (err) { > + count_vm_events(CMA_ALLOC_FAIL, count); > + if (cma) > + cma_sysfs_account_fail_pages(cma, count); > + } else { > + count_vm_events(CMA_ALLOC_SUCCESS, count); > + cma_sysfs_account_success_pages(cma, count); > + } > + > + return err; > +} > + > + > /** > * cma_alloc() - allocate pages from contiguous area > * @cma: Contiguous memory region for which the allocation is performed.
Hi, On Tue, Jan 30, 2024 at 10:50:00AM +0530, Anshuman Khandual wrote: > > > On 1/25/24 22:12, Alexandru Elisei wrote: > > Today, cma_alloc() is used to allocate a contiguous memory region. The > > function allows the caller to specify the number of pages to allocate, but > > not the starting address. cma_alloc() will walk over the entire CMA region > > trying to allocate the first available range of the specified size. > > > > Introduce cma_alloc_range(), which makes CMA more versatile by allowing the > > caller to specify a particular range in the CMA region, defined by the > > start pfn and the size. > > > > arm64 will make use of this function when tag storage management will be > > implemented: cma_alloc_range() will be used to reserve the tag storage > > associated with a tagged page. > > Basically, you would like to pass on a preferred start address and the > allocation could just fail if a contig range is not available from such > a starting address ? > > Then why not just change cma_alloc() to take a new argument 'start_pfn'. > Why create a new but almost similar allocator ? I tried doing that, and I gave up because: - It made cma_alloc() even more complex and hard to follow. - What value should 'start_pfn' be to tell cma_alloc() that it should be ignored? Or, to put it another way, what pfn number is invalid on **all** platforms that Linux supports? I can give it another go if we can come up with an invalid value for 'start_pfn'. > > But then I am wondering why this could not be done in the arm64 platform > code itself operating on a CMA area reserved just for tag storage. Unless > this new allocator has other usage beyond MTE, this could be implemented > in the platform itself. I had the same idea in the previous iteration, David Hildenbrand suggested this approach [1]. [1] https://lore.kernel.org/linux-fsdevel/2aafd53f-af1f-45f3-a08c-d11962254315@redhat.com/ Thanks, Alex > > > > > Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> > > --- > > > > Changes since rfc v2: > > > > * New patch. > > > > include/linux/cma.h | 2 + > > include/trace/events/cma.h | 59 ++++++++++++++++++++++++++ > > mm/cma.c | 86 ++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 147 insertions(+) > > > > diff --git a/include/linux/cma.h b/include/linux/cma.h > > index 63873b93deaa..e32559da6942 100644 > > --- a/include/linux/cma.h > > +++ b/include/linux/cma.h > > @@ -50,6 +50,8 @@ extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size, > > struct cma **res_cma); > > extern struct page *cma_alloc(struct cma *cma, unsigned long count, unsigned int align, > > bool no_warn); > > +extern int cma_alloc_range(struct cma *cma, unsigned long start, unsigned long count, > > + unsigned tries, gfp_t gfp); > > extern bool cma_pages_valid(struct cma *cma, const struct page *pages, unsigned long count); > > extern bool cma_release(struct cma *cma, const struct page *pages, unsigned long count); > > > > diff --git a/include/trace/events/cma.h b/include/trace/events/cma.h > > index 25103e67737c..a89af313a572 100644 > > --- a/include/trace/events/cma.h > > +++ b/include/trace/events/cma.h > > @@ -36,6 +36,65 @@ TRACE_EVENT(cma_release, > > __entry->count) > > ); > > > > +TRACE_EVENT(cma_alloc_range_start, > > + > > + TP_PROTO(const char *name, unsigned long start, unsigned long count, > > + unsigned tries), > > + > > + TP_ARGS(name, start, count, tries), > > + > > + TP_STRUCT__entry( > > + __string(name, name) > > + __field(unsigned long, start) > > + __field(unsigned long, count) > > + __field(unsigned, tries) > > + ), > > + > > + TP_fast_assign( > > + __assign_str(name, name); > > + __entry->start = start; > > + __entry->count = count; > > + __entry->tries = tries; > > + ), > > + > > + TP_printk("name=%s start=%lx count=%lu tries=%u", > > + __get_str(name), > > + __entry->start, > > + __entry->count, > > + __entry->tries) > > +); > > + > > +TRACE_EVENT(cma_alloc_range_finish, > > + > > + TP_PROTO(const char *name, unsigned long start, unsigned long count, > > + unsigned attempts, int err), > > + > > + TP_ARGS(name, start, count, attempts, err), > > + > > + TP_STRUCT__entry( > > + __string(name, name) > > + __field(unsigned long, start) > > + __field(unsigned long, count) > > + __field(unsigned, attempts) > > + __field(int, err) > > + ), > > + > > + TP_fast_assign( > > + __assign_str(name, name); > > + __entry->start = start; > > + __entry->count = count; > > + __entry->attempts = attempts; > > + __entry->err = err; > > + ), > > + > > + TP_printk("name=%s start=%lx count=%lu attempts=%u err=%d", > > + __get_str(name), > > + __entry->start, > > + __entry->count, > > + __entry->attempts, > > + __entry->err) > > +); > > + > > TRACE_EVENT(cma_alloc_start, > > > > TP_PROTO(const char *name, unsigned long count, unsigned int align), > > diff --git a/mm/cma.c b/mm/cma.c > > index 543bb6b3be8e..4a0f68b9443b 100644 > > --- a/mm/cma.c > > +++ b/mm/cma.c > > @@ -416,6 +416,92 @@ static void cma_debug_show_areas(struct cma *cma) > > static inline void cma_debug_show_areas(struct cma *cma) { } > > #endif > > > > +/** > > + * cma_alloc_range() - allocate pages in a specific range > > + * @cma: Contiguous memory region for which the allocation is performed. > > + * @start: Starting pfn of the allocation. > > + * @count: Requested number of pages > > + * @tries: Number of tries if the range is busy > > + * @no_warn: Avoid printing message about failed allocation > > + * > > + * This function allocates part of contiguous memory from a specific contiguous > > + * memory area, from the specified starting address. The 'start' pfn and the the > > + * 'count' number of pages must be aligned to the CMA bitmap order per bit. > > + */ > > +int cma_alloc_range(struct cma *cma, unsigned long start, unsigned long count, > > + unsigned tries, gfp_t gfp) > > +{ > > + unsigned long bitmap_maxno, bitmap_no, bitmap_start, bitmap_count; > > + unsigned long i = 0; > > + struct page *page; > > + int err = -EINVAL; > > + > > + if (!cma || !cma->count || !cma->bitmap) > > + goto out_stats; > > + > > + trace_cma_alloc_range_start(cma->name, start, count, tries); > > + > > + if (!count || start < cma->base_pfn || > > + start + count > cma->base_pfn + cma->count) > > + goto out_stats; > > + > > + if (!IS_ALIGNED(start | count, 1 << cma->order_per_bit)) > > + goto out_stats; > > + > > + bitmap_start = (start - cma->base_pfn) >> cma->order_per_bit; > > + bitmap_maxno = cma_bitmap_maxno(cma); > > + bitmap_count = cma_bitmap_pages_to_bits(cma, count); > > + > > + spin_lock_irq(&cma->lock); > > + bitmap_no = bitmap_find_next_zero_area(cma->bitmap, bitmap_maxno, > > + bitmap_start, bitmap_count, 0); > > + if (bitmap_no != bitmap_start) { > > + spin_unlock_irq(&cma->lock); > > + err = -EEXIST; > > + goto out_stats; > > + } > > + bitmap_set(cma->bitmap, bitmap_start, bitmap_count); > > + spin_unlock_irq(&cma->lock); > > + > > + for (i = 0; i < tries; i++) { > > + mutex_lock(&cma_mutex); > > + err = alloc_contig_range(start, start + count, MIGRATE_CMA, gfp); > > + mutex_unlock(&cma_mutex); > > + > > + if (err != -EBUSY) > > + break; > > + } > > + > > + if (err) { > > + cma_clear_bitmap(cma, start, count); > > + } else { > > + page = pfn_to_page(start); > > + > > + /* > > + * CMA can allocate multiple page blocks, which results in > > + * different blocks being marked with different tags. Reset the > > + * tags to ignore those page blocks. > > + */ > > + for (i = 0; i < count; i++) > > + page_kasan_tag_reset(nth_page(page, i)); > > + } > > + > > +out_stats: > > + trace_cma_alloc_range_finish(cma->name, start, count, i, err); > > + > > + if (err) { > > + count_vm_events(CMA_ALLOC_FAIL, count); > > + if (cma) > > + cma_sysfs_account_fail_pages(cma, count); > > + } else { > > + count_vm_events(CMA_ALLOC_SUCCESS, count); > > + cma_sysfs_account_success_pages(cma, count); > > + } > > + > > + return err; > > +} > > + > > + > > /** > > * cma_alloc() - allocate pages from contiguous area > > * @cma: Contiguous memory region for which the allocation is performed. >
On 1/30/24 17:05, Alexandru Elisei wrote: > Hi, > > On Tue, Jan 30, 2024 at 10:50:00AM +0530, Anshuman Khandual wrote: >> >> On 1/25/24 22:12, Alexandru Elisei wrote: >>> Today, cma_alloc() is used to allocate a contiguous memory region. The >>> function allows the caller to specify the number of pages to allocate, but >>> not the starting address. cma_alloc() will walk over the entire CMA region >>> trying to allocate the first available range of the specified size. >>> >>> Introduce cma_alloc_range(), which makes CMA more versatile by allowing the >>> caller to specify a particular range in the CMA region, defined by the >>> start pfn and the size. >>> >>> arm64 will make use of this function when tag storage management will be >>> implemented: cma_alloc_range() will be used to reserve the tag storage >>> associated with a tagged page. >> Basically, you would like to pass on a preferred start address and the >> allocation could just fail if a contig range is not available from such >> a starting address ? >> >> Then why not just change cma_alloc() to take a new argument 'start_pfn'. >> Why create a new but almost similar allocator ? > I tried doing that, and I gave up because: > > - It made cma_alloc() even more complex and hard to follow. > > - What value should 'start_pfn' be to tell cma_alloc() that it should be > ignored? Or, to put it another way, what pfn number is invalid on **all** > platforms that Linux supports? > > I can give it another go if we can come up with an invalid value for > 'start_pfn'. Something negative might work. How about -1/-1UL ? A quick search gives some instances such as ... git grep "pfn == -1" mm/mm_init.c: if (*start_pfn == -1UL) mm/vmscan.c: if (pfn == -1) mm/vmscan.c: if (pfn == -1) mm/vmscan.c: if (pfn == -1) tools/testing/selftests/mm/hugepage-vmemmap.c: if (pfn == -1UL) { Could not -1UL be abstracted as common macro MM_INVALID_PFN to be used in such scenarios including here ? > >> But then I am wondering why this could not be done in the arm64 platform >> code itself operating on a CMA area reserved just for tag storage. Unless >> this new allocator has other usage beyond MTE, this could be implemented >> in the platform itself. > I had the same idea in the previous iteration, David Hildenbrand suggested > this approach [1]. > > [1] https://lore.kernel.org/linux-fsdevel/2aafd53f-af1f-45f3-a08c-d11962254315@redhat.com/ There are two different cma_alloc() proposals here - including the next patch i.e mm: cma: Fast track allocating memory when the pages are free 1) Augment cma_alloc() or add cma_alloc_range() with start_pfn parameter 2) Speed up cma_alloc() for small allocation requests when pages are free The second one if separated out from this series could be considered on its own as it will help all existing cma_alloc() callers. The first one definitely needs an use case as provided in this series.
Hi, On Wed, Jan 31, 2024 at 11:54:17AM +0530, Anshuman Khandual wrote: > > > On 1/30/24 17:05, Alexandru Elisei wrote: > > Hi, > > > > On Tue, Jan 30, 2024 at 10:50:00AM +0530, Anshuman Khandual wrote: > >> > >> On 1/25/24 22:12, Alexandru Elisei wrote: > >>> Today, cma_alloc() is used to allocate a contiguous memory region. The > >>> function allows the caller to specify the number of pages to allocate, but > >>> not the starting address. cma_alloc() will walk over the entire CMA region > >>> trying to allocate the first available range of the specified size. > >>> > >>> Introduce cma_alloc_range(), which makes CMA more versatile by allowing the > >>> caller to specify a particular range in the CMA region, defined by the > >>> start pfn and the size. > >>> > >>> arm64 will make use of this function when tag storage management will be > >>> implemented: cma_alloc_range() will be used to reserve the tag storage > >>> associated with a tagged page. > >> Basically, you would like to pass on a preferred start address and the > >> allocation could just fail if a contig range is not available from such > >> a starting address ? > >> > >> Then why not just change cma_alloc() to take a new argument 'start_pfn'. > >> Why create a new but almost similar allocator ? > > I tried doing that, and I gave up because: > > > > - It made cma_alloc() even more complex and hard to follow. > > > > - What value should 'start_pfn' be to tell cma_alloc() that it should be > > ignored? Or, to put it another way, what pfn number is invalid on **all** > > platforms that Linux supports? > > > > I can give it another go if we can come up with an invalid value for > > 'start_pfn'. > > Something negative might work. How about -1/-1UL ? A quick search gives > some instances such as ... > > git grep "pfn == -1" > > mm/mm_init.c: if (*start_pfn == -1UL) > mm/vmscan.c: if (pfn == -1) > mm/vmscan.c: if (pfn == -1) > mm/vmscan.c: if (pfn == -1) > tools/testing/selftests/mm/hugepage-vmemmap.c: if (pfn == -1UL) { > > Could not -1UL be abstracted as common macro MM_INVALID_PFN to be used in > such scenarios including here ? Ah yes, you are right, get_pte_pfn() already uses -1 as an invalid pfn, so I can just use that. Will definitely give it a go on the next iteration, thanks for the suggestion! > > > > >> But then I am wondering why this could not be done in the arm64 platform > >> code itself operating on a CMA area reserved just for tag storage. Unless > >> this new allocator has other usage beyond MTE, this could be implemented > >> in the platform itself. > > I had the same idea in the previous iteration, David Hildenbrand suggested > > this approach [1]. > > > > [1] https://lore.kernel.org/linux-fsdevel/2aafd53f-af1f-45f3-a08c-d11962254315@redhat.com/ > > There are two different cma_alloc() proposals here - including the next > patch i.e mm: cma: Fast track allocating memory when the pages are free > > 1) Augment cma_alloc() or add cma_alloc_range() with start_pfn parameter > 2) Speed up cma_alloc() for small allocation requests when pages are free > > The second one if separated out from this series could be considered on > its own as it will help all existing cma_alloc() callers. The first one > definitely needs an use case as provided in this series. I understand, thanks for the input! Alex
diff --git a/include/linux/cma.h b/include/linux/cma.h index 63873b93deaa..e32559da6942 100644 --- a/include/linux/cma.h +++ b/include/linux/cma.h @@ -50,6 +50,8 @@ extern int cma_init_reserved_mem(phys_addr_t base, phys_addr_t size, struct cma **res_cma); extern struct page *cma_alloc(struct cma *cma, unsigned long count, unsigned int align, bool no_warn); +extern int cma_alloc_range(struct cma *cma, unsigned long start, unsigned long count, + unsigned tries, gfp_t gfp); extern bool cma_pages_valid(struct cma *cma, const struct page *pages, unsigned long count); extern bool cma_release(struct cma *cma, const struct page *pages, unsigned long count); diff --git a/include/trace/events/cma.h b/include/trace/events/cma.h index 25103e67737c..a89af313a572 100644 --- a/include/trace/events/cma.h +++ b/include/trace/events/cma.h @@ -36,6 +36,65 @@ TRACE_EVENT(cma_release, __entry->count) ); +TRACE_EVENT(cma_alloc_range_start, + + TP_PROTO(const char *name, unsigned long start, unsigned long count, + unsigned tries), + + TP_ARGS(name, start, count, tries), + + TP_STRUCT__entry( + __string(name, name) + __field(unsigned long, start) + __field(unsigned long, count) + __field(unsigned, tries) + ), + + TP_fast_assign( + __assign_str(name, name); + __entry->start = start; + __entry->count = count; + __entry->tries = tries; + ), + + TP_printk("name=%s start=%lx count=%lu tries=%u", + __get_str(name), + __entry->start, + __entry->count, + __entry->tries) +); + +TRACE_EVENT(cma_alloc_range_finish, + + TP_PROTO(const char *name, unsigned long start, unsigned long count, + unsigned attempts, int err), + + TP_ARGS(name, start, count, attempts, err), + + TP_STRUCT__entry( + __string(name, name) + __field(unsigned long, start) + __field(unsigned long, count) + __field(unsigned, attempts) + __field(int, err) + ), + + TP_fast_assign( + __assign_str(name, name); + __entry->start = start; + __entry->count = count; + __entry->attempts = attempts; + __entry->err = err; + ), + + TP_printk("name=%s start=%lx count=%lu attempts=%u err=%d", + __get_str(name), + __entry->start, + __entry->count, + __entry->attempts, + __entry->err) +); + TRACE_EVENT(cma_alloc_start, TP_PROTO(const char *name, unsigned long count, unsigned int align), diff --git a/mm/cma.c b/mm/cma.c index 543bb6b3be8e..4a0f68b9443b 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -416,6 +416,92 @@ static void cma_debug_show_areas(struct cma *cma) static inline void cma_debug_show_areas(struct cma *cma) { } #endif +/** + * cma_alloc_range() - allocate pages in a specific range + * @cma: Contiguous memory region for which the allocation is performed. + * @start: Starting pfn of the allocation. + * @count: Requested number of pages + * @tries: Number of tries if the range is busy + * @no_warn: Avoid printing message about failed allocation + * + * This function allocates part of contiguous memory from a specific contiguous + * memory area, from the specified starting address. The 'start' pfn and the the + * 'count' number of pages must be aligned to the CMA bitmap order per bit. + */ +int cma_alloc_range(struct cma *cma, unsigned long start, unsigned long count, + unsigned tries, gfp_t gfp) +{ + unsigned long bitmap_maxno, bitmap_no, bitmap_start, bitmap_count; + unsigned long i = 0; + struct page *page; + int err = -EINVAL; + + if (!cma || !cma->count || !cma->bitmap) + goto out_stats; + + trace_cma_alloc_range_start(cma->name, start, count, tries); + + if (!count || start < cma->base_pfn || + start + count > cma->base_pfn + cma->count) + goto out_stats; + + if (!IS_ALIGNED(start | count, 1 << cma->order_per_bit)) + goto out_stats; + + bitmap_start = (start - cma->base_pfn) >> cma->order_per_bit; + bitmap_maxno = cma_bitmap_maxno(cma); + bitmap_count = cma_bitmap_pages_to_bits(cma, count); + + spin_lock_irq(&cma->lock); + bitmap_no = bitmap_find_next_zero_area(cma->bitmap, bitmap_maxno, + bitmap_start, bitmap_count, 0); + if (bitmap_no != bitmap_start) { + spin_unlock_irq(&cma->lock); + err = -EEXIST; + goto out_stats; + } + bitmap_set(cma->bitmap, bitmap_start, bitmap_count); + spin_unlock_irq(&cma->lock); + + for (i = 0; i < tries; i++) { + mutex_lock(&cma_mutex); + err = alloc_contig_range(start, start + count, MIGRATE_CMA, gfp); + mutex_unlock(&cma_mutex); + + if (err != -EBUSY) + break; + } + + if (err) { + cma_clear_bitmap(cma, start, count); + } else { + page = pfn_to_page(start); + + /* + * CMA can allocate multiple page blocks, which results in + * different blocks being marked with different tags. Reset the + * tags to ignore those page blocks. + */ + for (i = 0; i < count; i++) + page_kasan_tag_reset(nth_page(page, i)); + } + +out_stats: + trace_cma_alloc_range_finish(cma->name, start, count, i, err); + + if (err) { + count_vm_events(CMA_ALLOC_FAIL, count); + if (cma) + cma_sysfs_account_fail_pages(cma, count); + } else { + count_vm_events(CMA_ALLOC_SUCCESS, count); + cma_sysfs_account_success_pages(cma, count); + } + + return err; +} + + /** * cma_alloc() - allocate pages from contiguous area * @cma: Contiguous memory region for which the allocation is performed.
Today, cma_alloc() is used to allocate a contiguous memory region. The function allows the caller to specify the number of pages to allocate, but not the starting address. cma_alloc() will walk over the entire CMA region trying to allocate the first available range of the specified size. Introduce cma_alloc_range(), which makes CMA more versatile by allowing the caller to specify a particular range in the CMA region, defined by the start pfn and the size. arm64 will make use of this function when tag storage management will be implemented: cma_alloc_range() will be used to reserve the tag storage associated with a tagged page. Signed-off-by: Alexandru Elisei <alexandru.elisei@arm.com> --- Changes since rfc v2: * New patch. include/linux/cma.h | 2 + include/trace/events/cma.h | 59 ++++++++++++++++++++++++++ mm/cma.c | 86 ++++++++++++++++++++++++++++++++++++++ 3 files changed, 147 insertions(+)