fix omission of check on FOLL_LONGTERM in gup fast path

FOLL_LONGTERM suggests a pin which is going to be given to hardware and can't move. It would truncate CMA permanently and should be excluded.

FOLL_LONGTERM has already been checked in the slow path, but not checked in the fast path, which means a possible leak of CMA page to longterm pinned requirement through this crack.

Place a check in try_get_compound_head() in the fast path.

Some note about the check:
Huge page's subpages have the same migrate type due to either allocation from a free_list[] or alloc_contig_range() with param MIGRATE_MOVABLE. So it is enough to check on a single subpage by is_migrate_cma_page(subpage)

Signed-off-by Pingfan Liu <[email protected]>

Cc Ira Weiny <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Dan Williams <[email protected]>

Cc Matthew Wilcox <[email protected]>

Cc John Hubbard <[email protected]>

Cc "Aneesh Kumar K.V" <[email protected]>

Cc Keith Busch <[email protected]>

Cc Christoph Hellwig <[email protected]>

Cc Shuah Khan <[email protected]>

To: [email protected]
Cc: [email protected]

 mm/gup.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

mm/gup.c +3 -2

index cd8075e..f0d6804 100644
+++ b/mm/gup.c

@@ -33,9 +33,21 @@ struct follow_page_context {
  * Return the compound head page with ref appropriately incremented,
  * or NULL if that failed.
  */
-static inline struct page *try_get_compound_head(struct page *page, int refs)
+static inline struct page *try_get_compound_head(struct page *page, int refs,
+	unsigned int flags)
 {
-	struct page *head = compound_head(page);

Quoted 43 lines · Pingfan Liu

FOLL_LONGTERM suggests a pin which is going to be given to hardware and can't move. It would truncate CMA permanently and should be excluded.

FOLL_LONGTERM has already been checked in the slow path, but not checked in the fast path, which means a possible leak of CMA page to longterm pinned requirement through this crack.

Place a check in try_get_compound_head() in the fast path.

Some note about the check:
Huge page's subpages have the same migrate type due to either allocation from a free_list[] or alloc_contig_range() with param MIGRATE_MOVABLE. So it is enough to check on a single subpage by is_migrate_cma_page(subpage)

Signed-off-by Pingfan Liu <[email protected]>

Cc Ira Weiny <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Dan Williams <[email protected]>

Cc Matthew Wilcox <[email protected]>

Cc John Hubbard <[email protected]>

Cc "Aneesh Kumar K.V" <[email protected]>

Cc Keith Busch <[email protected]>

Cc Christoph Hellwig <[email protected]>

Cc Shuah Khan <[email protected]>

To: [email protected]
Cc: [email protected]

 mm/gup.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

mm/gup.c +3 -2

index cd8075e..f0d6804 100644
+++ b/mm/gup.c

@@ -33,9 +33,21 @@ struct follow_page_context {
  * Return the compound head page with ref appropriately incremented,
  * or NULL if that failed.
  */
-static inline struct page *try_get_compound_head(struct page *page, int refs)
+static inline struct page *try_get_compound_head(struct page *page, int refs,
+     unsigned int flags)
 {
-     struct page *head = compound_head(page);

mm/gup.c struct follow_page_context { · line 48

Quoted 10 lines

mm/gup.c +10 -0

+     struct page *head;
+
+     /*
+      * Huge page's subpages have the same migrate type due to either
+      * allocation from a free_list[] or alloc_contig_range() with param
+      * MIGRATE_MOVABLE. So it is enough to check on a single subpage.
+      */
+     if (unlikely(flags & FOLL_LONGTERM) &&
+             is_migrate_cma_page(page))
+             return NULL;

This doesn't seem very good actually.

If I understand properly, if the system has randomly decided to place, say, an anonymous page in a CMA region when an application did mmap(), then when the application tries to use this page with a LONGTERM pin it gets an immediate failure because of the above.

This not OK - the application should not be subject to random failures related to long term pins beyond its direct control.

Essentially, failures should only originate from the application using specific mmap scenarios, not randomly based on something the MM did, and certainly never for anonymous memory.

I think the correct action here is to trigger migration of the page so it is not in CMA.

Quoted 58 lines · Jason Gunthorpe

Quoted 43 lines · Pingfan Liu

FOLL_LONGTERM suggests a pin which is going to be given to hardware and can't move. It would truncate CMA permanently and should be excluded.

FOLL_LONGTERM has already been checked in the slow path, but not checked in the fast path, which means a possible leak of CMA page to longterm pinned requirement through this crack.

Place a check in try_get_compound_head() in the fast path.

Some note about the check:
Huge page's subpages have the same migrate type due to either allocation from a free_list[] or alloc_contig_range() with param MIGRATE_MOVABLE. So it is enough to check on a single subpage by is_migrate_cma_page(subpage)

Signed-off-by Pingfan Liu <[email protected]>

Cc Ira Weiny <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Dan Williams <[email protected]>

Cc Matthew Wilcox <[email protected]>

Cc John Hubbard <[email protected]>

Cc "Aneesh Kumar K.V" <[email protected]>

Cc Keith Busch <[email protected]>

Cc Christoph Hellwig <[email protected]>

Cc Shuah Khan <[email protected]>

To: [email protected]
Cc: [email protected]

 mm/gup.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

mm/gup.c +3 -2

index cd8075e..f0d6804 100644
+++ b/mm/gup.c

@@ -33,9 +33,21 @@ struct follow_page_context {
  * Return the compound head page with ref appropriately incremented,
  * or NULL if that failed.
  */
-static inline struct page *try_get_compound_head(struct page *page, int refs)
+static inline struct page *try_get_compound_head(struct page *page, int refs,
+     unsigned int flags)
 {
-     struct page *head = compound_head(page);

mm/gup.c struct follow_page_context { · line 48

Quoted 10 lines

mm/gup.c +10 -0

+     struct page *head;
+
+     /*
+      * Huge page's subpages have the same migrate type due to either
+      * allocation from a free_list[] or alloc_contig_range() with param
+      * MIGRATE_MOVABLE. So it is enough to check on a single subpage.
+      */
+     if (unlikely(flags & FOLL_LONGTERM) &&
+             is_migrate_cma_page(page))
+             return NULL;

This doesn't seem very good actually.

Quoted 4 lines

If I understand properly, if the system has randomly decided to place, say, an anonymous page in a CMA region when an application did mmap(), then when the application tries to use this page with a LONGTERM pin it gets an immediate failure because of the above.

No, actually, it will fall back to slow path, which migrates and sever the LONGTERM pin.

This patch just aims to fix the leakage in gup fast path, while in gup slow path, there is already logic to guard CMA against LONGTERM pin.

Quoted 8 lines

This not OK - the application should not be subject to random failures related to long term pins beyond its direct control.

Essentially, failures should only originate from the application using specific mmap scenarios, not randomly based on something the MM did, and certainly never for anonymous memory.

Quoted 2 lines

I think the correct action here is to trigger migration of the page so it is not in CMA.

In fact, it does this. The failure in gup fast path will fall back to slow path, where __gup_longterm_locked->check_and_migrate_cma_pages() does the migration.

Quoted 76 lines · Pingfan Liu

Quoted 58 lines · Jason Gunthorpe

Quoted 43 lines · Pingfan Liu

FOLL_LONGTERM suggests a pin which is going to be given to hardware and can't move. It would truncate CMA permanently and should be excluded.

FOLL_LONGTERM has already been checked in the slow path, but not checked in the fast path, which means a possible leak of CMA page to longterm pinned requirement through this crack.

Place a check in try_get_compound_head() in the fast path.

Some note about the check:
Huge page's subpages have the same migrate type due to either allocation from a free_list[] or alloc_contig_range() with param MIGRATE_MOVABLE. So it is enough to check on a single subpage by is_migrate_cma_page(subpage)

Signed-off-by Pingfan Liu <[email protected]>

Cc Ira Weiny <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Dan Williams <[email protected]>

Cc Matthew Wilcox <[email protected]>

Cc John Hubbard <[email protected]>

Cc "Aneesh Kumar K.V" <[email protected]>

Cc Keith Busch <[email protected]>

Cc Christoph Hellwig <[email protected]>

Cc Shuah Khan <[email protected]>

To: [email protected]
Cc: [email protected]

 mm/gup.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

mm/gup.c +3 -2

index cd8075e..f0d6804 100644
+++ b/mm/gup.c

@@ -33,9 +33,21 @@ struct follow_page_context {
  * Return the compound head page with ref appropriately incremented,
  * or NULL if that failed.
  */
-static inline struct page *try_get_compound_head(struct page *page, int refs)
+static inline struct page *try_get_compound_head(struct page *page, int refs,
+     unsigned int flags)
 {
-     struct page *head = compound_head(page);

mm/gup.c struct follow_page_context { · line 48

Quoted 10 lines

mm/gup.c +10 -0

+     struct page *head;
+
+     /*
+      * Huge page's subpages have the same migrate type due to either
+      * allocation from a free_list[] or alloc_contig_range() with param
+      * MIGRATE_MOVABLE. So it is enough to check on a single subpage.
+      */
+     if (unlikely(flags & FOLL_LONGTERM) &&
+             is_migrate_cma_page(page))
+             return NULL;

This doesn't seem very good actually.

Quoted 4 lines

If I understand properly, if the system has randomly decided to place, say, an anonymous page in a CMA region when an application did mmap(), then when the application tries to use this page with a LONGTERM pin it gets an immediate failure because of the above.

No, actually, it will fall back to slow path, which migrates and sever the LONGTERM pin.

This patch just aims to fix the leakage in gup fast path, while in gup slow path, there is already logic to guard CMA against LONGTERM pin.

Quoted 8 lines

This not OK - the application should not be subject to random failures related to long term pins beyond its direct control.

Essentially, failures should only originate from the application using specific mmap scenarios, not randomly based on something the MM did, and certainly never for anonymous memory.

Quoted 5 lines

Quoted 2 lines

I think the correct action here is to trigger migration of the page so it is not in CMA.

In fact, it does this. The failure in gup fast path will fall back to slow path, where __gup_longterm_locked->check_and_migrate_cma_pages() does the migration.

It is probably worth revising the commit message so this flow is clear

FOLL_LONGTERM suggests a pin which is going to be given to hardware and can't move. It would truncate CMA permanently and should be excluded.

FOLL_LONGTERM has already been checked in the slow path, but not checked in the fast path, which means a possible leak of CMA page to longterm pinned requirement through this crack.

Place a check in try_get_compound_head() in the fast path.

Some note about the check:
Huge page's subpages have the same migrate type due to either allocation from a free_list[] or alloc_contig_range() with param MIGRATE_MOVABLE. So it is enough to check on a single subpage by is_migrate_cma_page(subpage)

Signed-off-by Pingfan Liu <[email protected]>

Cc Ira Weiny <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Dan Williams <[email protected]>

Cc Matthew Wilcox <[email protected]>

Cc John Hubbard <[email protected]>

Cc "Aneesh Kumar K.V" <[email protected]>

Cc Keith Busch <[email protected]>

Cc Christoph Hellwig <[email protected]>

Cc Shuah Khan <[email protected]>

To: [email protected]
Cc: [email protected]

---
 mm/gup.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

mm/gup.c +19 -7

index cd8075e..f0d6804 100644
@@ -33,9 +33,21 @@ struct follow_page_context {
  * Return the compound head page with ref appropriately incremented,
  * or NULL if that failed.
  */
-static inline struct page *try_get_compound_head(struct page *page, int refs)
+static inline struct page *try_get_compound_head(struct page *page, int refs,
+	unsigned int flags)
 {
-	struct page *head = compound_head(page);
+	struct page *head;
+
+	/*
+	 * Huge page's subpages have the same migrate type due to either
+	 * allocation from a free_list[] or alloc_contig_range() with param
+	 * MIGRATE_MOVABLE. So it is enough to check on a single subpage.
+	 */
+	if (unlikely(flags & FOLL_LONGTERM) &&
+		is_migrate_cma_page(page))
+		return NULL;
+
+	head = compound_head(page);
 
 	if (WARN_ON_ONCE(page_ref_count(head) < 0))
 		return NULL;

@@ -1908,7 +1920,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 		page = pte_page(pte);
 
-		head = try_get_compound_head(page, 1);
+		head = try_get_compound_head(page, 1, flags);
 		if (!head)
 			goto pte_unmap;
 

@@ -2083,7 +2095,7 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 	page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(head, refs);
+	head = try_get_compound_head(head, refs, flags);
 	if (!head)
 		return 0;
 

@@ -2142,7 +2154,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
 	page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(pmd_page(orig), refs);
+	head = try_get_compound_head(pmd_page(orig), refs, flags);
 	if (!head)
 		return 0;
 

@@ -2174,7 +2186,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
 	page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(pud_page(orig), refs);
+	head = try_get_compound_head(pud_page(orig), refs, flags);
 	if (!head)
 		return 0;
 

@@ -2203,7 +2215,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
 	page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(pgd_page(orig), refs);
+	head = try_get_compound_head(pgd_page(orig), refs, flags);
 	if (!head)
 		return 0;
 

Signature · 1 line

2.7.5

Quoted 2 lines · Pingfan Liu

FOLL_LONGTERM suggests a pin which is going to be given to hardware and can't move. It would truncate CMA permanently and should be excluded.

I don't understand what is 'truncated' here?

I generally agree with Jason that this is going to be confusing to the user.

FOLL_LONGTERM suggests a pin which is going to be given to hardware and can't move. It would truncate CMA permanently and should be excluded.

FOLL_LONGTERM has already been checked in the slow path, but not checked in the fast path, which means a possible leak of CMA page to longterm pinned requirement through this crack.

Place a check in try_get_compound_head() in the fast path.

Some note about the check:
Huge page's subpages have the same migrate type due to either allocation from a free_list[] or alloc_contig_range() with param MIGRATE_MOVABLE. So it is enough to check on a single subpage by is_migrate_cma_page(subpage)

Signed-off-by Pingfan Liu <[email protected]>

Cc Ira Weiny <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Dan Williams <[email protected]>

Cc Matthew Wilcox <[email protected]>

Cc John Hubbard <[email protected]>

Cc "Aneesh Kumar K.V" <[email protected]>

Cc Keith Busch <[email protected]>

Cc Christoph Hellwig <[email protected]>

Cc Shuah Khan <[email protected]>

To: [email protected]
Cc: [email protected]

---
 mm/gup.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

mm/gup.c +0 -0

index cd8075e..f0d6804 100644

mm/gup.c +17 -6

 {
-	struct page *head = compound_head(page);
+	struct page *head;
+
+	/*
+	 * Huge page's subpages have the same migrate type due to either
+	 * allocation from a free_list[] or alloc_contig_range() with param
+	 * MIGRATE_MOVABLE. So it is enough to check on a single subpage.
+	 */
+	if (unlikely(flags & FOLL_LONGTERM) &&
+		is_migrate_cma_page(page))
+		return NULL;
+
+	head = compound_head(page);
 
 	if (WARN_ON_ONCE(page_ref_count(head) < 0))
 		return NULL;

@@ -1908,7 +1920,7 @@ static int gup_pte_range(pmd_t pmd, unsigned long addr, unsigned long end,
 		VM_BUG_ON(!pfn_valid(pte_pfn(pte)));
 		page = pte_page(pte);
 
-		head = try_get_compound_head(page, 1);
+		head = try_get_compound_head(page, 1, flags);
 		if (!head)
 			goto pte_unmap;
 

@@ -2083,7 +2095,7 @@ static int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
 	page = head + ((addr & (sz-1)) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(head, refs);
+	head = try_get_compound_head(head, refs, flags);
 	if (!head)
 		return 0;
 

@@ -2142,7 +2154,7 @@ static int gup_huge_pmd(pmd_t orig, pmd_t *pmdp, unsigned long addr,
 	page = pmd_page(orig) + ((addr & ~PMD_MASK) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(pmd_page(orig), refs);
+	head = try_get_compound_head(pmd_page(orig), refs, flags);
 	if (!head)
 		return 0;
 

@@ -2174,7 +2186,7 @@ static int gup_huge_pud(pud_t orig, pud_t *pudp, unsigned long addr,
 	page = pud_page(orig) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(pud_page(orig), refs);
+	head = try_get_compound_head(pud_page(orig), refs, flags);
 	if (!head)
 		return 0;
 

@@ -2203,7 +2215,7 @@ static int gup_huge_pgd(pgd_t orig, pgd_t *pgdp, unsigned long addr,
 	page = pgd_page(orig) + ((addr & ~PGDIR_MASK) >> PAGE_SHIFT);
 	refs = record_subpages(page, addr, end, pages + *nr);
 
-	head = try_get_compound_head(pgd_page(orig), refs);
+	head = try_get_compound_head(pgd_page(orig), refs, flags);
 	if (!head)
 		return 0;
 

Quoted 37 lines · Pingfan Liu

FOLL_LONGTERM suggests a pin which is going to be given to hardware and can't move. It would truncate CMA permanently and should be excluded.

FOLL_LONGTERM has already been checked in the slow path, but not checked in the fast path, which means a possible leak of CMA page to longterm pinned requirement through this crack.

Place a check in try_get_compound_head() in the fast path.

Some note about the check:
Huge page's subpages have the same migrate type due to either allocation from a free_list[] or alloc_contig_range() with param MIGRATE_MOVABLE. So it is enough to check on a single subpage by is_migrate_cma_page(subpage)

Signed-off-by Pingfan Liu <[email protected]>

Cc Ira Weiny <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Dan Williams <[email protected]>

Cc Matthew Wilcox <[email protected]>

Cc John Hubbard <[email protected]>

Cc "Aneesh Kumar K.V" <[email protected]>

Cc Keith Busch <[email protected]>

Cc Christoph Hellwig <[email protected]>

Cc Shuah Khan <[email protected]>

To: [email protected]
Cc: [email protected]

---
 mm/gup.c | 26 +++++++++++++++++++-------
 1 file changed, 19 insertions(+), 7 deletions(-)

mm/gup.c +0 -0

index cd8075e..f0d6804 100644

mm/gup.c struct follow_page_context { · line 37

Quoted 6 lines

mm/gup.c +2 -1

@@ -33,9 +33,21 @@ struct follow_page_context {
  * Return the compound head page with ref appropriately incremented,
  * or NULL if that failed.
  */
-static inline struct page *try_get_compound_head(struct page *page, int refs)
+static inline struct page *try_get_compound_head(struct page *page, int refs,
+     unsigned int flags)

ohhh...please please look at the latest gup.c in mmotm, and this one in particular:

commit 0ea2781c3de4 mm/gup: track FOLL_PIN pages

...where you'll see that there is a concept of "try_get*" vs. "try_grab*"). This is going to be a huge mess if we do it as above, from a code structure point of view.

The "grab" functions take gup flags, the "get" functions do not.

Anyway, as I said in reply to the cover letter, I'm really uncomfortable with this being applied to linux.git. So maybe if we see a fix to mmotm, it will be clearer how to port that back to linux.git (assuming that you need 5.6 fixed--do you though?)

Introduce a GUP_LONGTERM_BENCHMARK ioctl to test longterm pin in gup fast path.

Signed-off-by Pingfan Liu <[email protected]>

Cc Ira Weiny <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Dan Williams <[email protected]>

Cc Matthew Wilcox <[email protected]>

Cc John Hubbard <[email protected]>

Cc "Aneesh Kumar K.V" <[email protected]>

Cc Keith Busch <[email protected]>

Cc Christoph Hellwig <[email protected]>

Cc Shuah Khan <[email protected]>

To: [email protected]
Cc: [email protected]

---
 mm/gup_benchmark.c                         | 7 +++++++
 tools/testing/selftests/vm/gup_benchmark.c | 6 +++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

mm/gup_benchmark.c +1 -0

index 8dba38e..bf61e7a 100644
@@ -8,6 +8,7 @@
 #define GUP_FAST_BENCHMARK     _IOWR('g', 1, struct gup_benchmark)
 #define GUP_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark)
 #define GUP_BENCHMARK          _IOWR('g', 3, struct gup_benchmark)
+#define GUP_FAST_LONGTERM_BENCHMARK    _IOWR('g', 4, struct gup_benchmark)
 
 struct gup_benchmark {
        __u64 get_delta_usec;

mm/gup_benchmark.c +1 -0

                case GUP_LONGTERM_BENCHMARK:
                        nr = get_user_pages(addr, nr,
                                            gup->flags | FOLL_LONGTERM,

@@ -103,6 +109,7 @@ static long gup_benchmark_ioctl(struct file *filep, unsigned int cmd,
 
        switch (cmd) {
        case GUP_FAST_BENCHMARK:
+       case GUP_FAST_LONGTERM_BENCHMARK:
        case GUP_LONGTERM_BENCHMARK:
        case GUP_BENCHMARK:
                break;

tools/testing/selftests/vm/gup_benchmark.c +5 -2

index 389327e..5a01c538 100644
@@ -17,6 +17,7 @@
 #define GUP_FAST_BENCHMARK     _IOWR('g', 1, struct gup_benchmark)
 #define GUP_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark)
 #define GUP_BENCHMARK          _IOWR('g', 3, struct gup_benchmark)
+#define GUP_FAST_LONGTERM_BENCHMARK    _IOWR('g', 4, struct gup_benchmark)
 
 /* Just the flags we need, copied from mm.h: */
 #define FOLL_WRITE     0x01    /* check pte is writable */

@@ -40,7 +41,7 @@ int main(int argc, char **argv)
        char *file = "/dev/zero";
        char *p;
 
-       while ((opt = getopt(argc, argv, "m:r:n:f:tTLUwSH")) != -1) {
+       while ((opt = getopt(argc, argv, "m:r:n:f:tTlLUwSH")) != -1) {
                switch (opt) {
                case 'm':
                        size = atoi(optarg) * MB;

@@ -57,6 +58,9 @@ int main(int argc, char **argv)
                case 'T':
                        thp = 0;
                        break;
+               case 'l':
+                       cmd = GUP_FAST_LONGTERM_BENCHMARK;
+                       break;
                case 'L':
                        cmd = GUP_LONGTERM_BENCHMARK;
                        break;
--

2.7.5

Quoted 3 lines · Pingfan Liu

Introduce a GUP_LONGTERM_BENCHMARK ioctl to test longterm pin in gup fast path.

The title of the patch has a typo in it. There is only one 'e' in "benchmark".

Quoted 29 lines

Signed-off-by Pingfan Liu <[email protected]>

Cc Ira Weiny <[email protected]>

Cc Andrew Morton <[email protected]>

Cc Mike Rapoport <[email protected]>

Cc Dan Williams <[email protected]>

Cc Matthew Wilcox <[email protected]>

Cc John Hubbard <[email protected]>

Cc "Aneesh Kumar K.V" <[email protected]>

Cc Keith Busch <[email protected]>

Cc Christoph Hellwig <[email protected]>

Cc Shuah Khan <[email protected]>

To: [email protected]
Cc: [email protected]

---
 mm/gup_benchmark.c                         | 7 +++++++
 tools/testing/selftests/vm/gup_benchmark.c | 6 +++++-
 2 files changed, 12 insertions(+), 1 deletion(-)

mm/gup_benchmark.c +1 -0

index 8dba38e..bf61e7a 100644
@@ -8,6 +8,7 @@
 #define GUP_FAST_BENCHMARK     _IOWR('g', 1, struct gup_benchmark)
 #define GUP_LONGTERM_BENCHMARK _IOWR('g', 2, struct gup_benchmark)
 #define GUP_BENCHMARK          _IOWR('g', 3, struct gup_benchmark)
+#define GUP_FAST_LONGTERM_BENCHMARK    _IOWR('g', 4, struct gup_benchmark)
 

mm/gup_benchmark.c static int __gup_benchmark_ioctl(unsigned int cmd, · line 65

Quoted 11 lines

mm/gup_benchmark.c +5 -0

 struct gup_benchmark {
        __u64 get_delta_usec;

@@ -57,6 +58,11 @@ static int __gup_benchmark_ioctl(unsigned int cmd,
                        nr = get_user_pages_fast(addr, nr, gup->flags,
                                                 pages + i);
                        break;
+               case GUP_FAST_LONGTERM_BENCHMARK:
+                       nr = get_user_pages_fast(addr, nr,
+                                       (gup->flags & 1) | FOLL_LONGTERM,
+                                        pages + i);
+                       break;

If I am not mistaken the mask of gup->flags is redundant. It is already masked by FOLL_WRITE several lines before this switch statement.

The last V4 series:
https://lore.kernel.org/patchwork/project/lkml/list/?series=397950, and be dropped from mm tree due to conflict with "RFC: switch the remaining architectures to use generic GUP" [1]

I rebase it and sent out V5.
V4 -> V5: move around the patched code due to code change.

[1]: https://lore.kernel.org/linux-mm/[email protected]/

Cc: Ira Weiny <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Mike Rapoport <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: John Hubbard <[email protected]>
Cc: "Aneesh Kumar K.V" <[email protected]>
Cc: Keith Busch <[email protected]>
Cc: Christoph Hellwig <[email protected]>
Cc: Shuah Khan <[email protected]>
To: [email protected]
Cc: [email protected]

---
Pingfan Liu (3):
mm/gup: rename nr as nr_pinned in get_user_pages_fast() mm/gup: fix omission of check on FOLL_LONGTERM in gup fast path mm/gup_benchemark: add LONGTERM_BENCHMARK test in gup fast path

 mm/gup.c                                   | 46 +++++++++++++++++++-----------
 mm/gup_benchmark.c                         |  7 +++++
 tools/testing/selftests/vm/gup_benchmark.c |  6 +++-
 3 files changed, 41 insertions(+), 18 deletions(-)