mm: introduce vma_flags_count() and vma[_flags]_test_single_mask()

vma_flags_count() determines how many bits are set in VMA flags, using
bitmap_weight().

vma_flags_test_single_mask() determines if a vma_flags_t set of flags
contains a single flag specified as another vma_flags_t value, or if the
sought flag mask is empty, it is defined to return false.

This is useful when we want to declare a VMA flag as optionally a single
flag in a mask or empty depending on kernel configuration.

This allows us to have VM_NONE-like semantics when checking whether the
flag is set.

In a subsequent patch, we introduce the use of VMA_DROPPABLE of type
vma_flags_t using precisely these semantics.

It would be actively confusing to use vma_flags_test_any_single_mask() for
this (and vma_flags_test_all_mask() is not correct to use here, as it
trivially returns true when tested against an empty vma flags mask).

We introduce vma_flags_count() to be able to assert that the compared flag
mask is singular or empty, checked when CONFIG_DEBUG_VM is enabled.

Also update the VMA tests as part of this change.

Link: https://lkml.kernel.org/r/cd778dd02b9f2a01eb54d25a49dea8ec2ddf7753.1774034900.git.ljs@kernel.org
Signed-off-by: Lorenzo Stoakes (Oracle) <ljs@kernel.org>
Acked-by: Vlastimil Babka (SUSE) <vbabka@kernel.org>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Anton Ivanov <anton.ivanov@cambridgegreys.com>
Cc: "Borislav Petkov (AMD)" <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Christian Brauner <brauner@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dinh Nguyen <dinguyen@kernel.org>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Huacai Chen <chenhuacai@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Johannes Berg <johannes@sipsolutions.net>
Cc: Kees Cook <kees@kernel.org>
Cc: Liam Howlett <liam.howlett@oracle.com>
Cc: Madhavan Srinivasan <maddy@linux.ibm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Ondrej Mosnacek <omosnace@redhat.com>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Paul Moore <paul@paul-moore.com>
Cc: Pedro Falcato <pfalcato@suse.de>
Cc: Richard Weinberger <richard@nod.at>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Stephen Smalley <stephen.smalley.work@gmail.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@kernel.org>
Cc: WANG Xuerui <kernel@xen0n.name>
Cc: Will Deacon <will@kernel.org>
Cc: xu xin <xu.xin16@zte.com.cn>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/mm.h b/include/linux/mm.h
index f704d7cf287146f83c46f0f59febd0931c81865e..de72382efac2250facde1436b837975179a99995 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1078,6 +1078,14 @@ static __always_inline vma_flags_t __mk_vma_flags(vma_flags_t flags,
 #define append_vma_flags(flags, ...) __mk_vma_flags(flags,                     \
                COUNT_ARGS(__VA_ARGS__), (const vma_flag_t []){__VA_ARGS__})
 
+/* Calculates the number of set bits in the specified VMA flags. */
+static __always_inline int vma_flags_count(const vma_flags_t *flags)
+{
+       const unsigned long *bitmap = flags->__vma_flags;
+
+       return bitmap_weight(bitmap, NUM_VMA_FLAG_BITS);
+}
+
 /*
  * Test whether a specific VMA flag is set, e.g.:
  *
@@ -1153,6 +1161,26 @@ static __always_inline bool vma_flags_test_all_mask(const vma_flags_t *flags,
 #define vma_flags_test_all(flags, ...) \
        vma_flags_test_all_mask(flags, mk_vma_flags(__VA_ARGS__))
 
+/*
+ * Helper to test that a flag mask of type vma_flags_t has a SINGLE flag set
+ * (returning false if flagmask has no flags set).
+ *
+ * This is defined to make the semantics clearer when testing an optionally
+ * defined VMA flags mask, e.g.:
+ *
+ * if (vma_flags_test_single_mask(&flags, VMA_DROPPABLE)) { ... }
+ *
+ * When VMA_DROPPABLE is defined if available, or set to EMPTY_VMA_FLAGS
+ * otherwise.
+ */
+static __always_inline bool vma_flags_test_single_mask(const vma_flags_t *flags,
+               vma_flags_t flagmask)
+{
+       VM_WARN_ON_ONCE(vma_flags_count(&flagmask) > 1);
+
+       return vma_flags_test_any_mask(flags, flagmask);
+}
+
 /* Set each of the to_set flags in flags, non-atomically. */
 static __always_inline void vma_flags_set_mask(vma_flags_t *flags,
                vma_flags_t to_set)
@@ -1281,6 +1309,24 @@ static __always_inline bool vma_test_all_mask(const struct vm_area_struct *vma,
 #define vma_test_all(vma, ...) \
        vma_test_all_mask(vma, mk_vma_flags(__VA_ARGS__))
 
+/*
+ * Helper to test that a flag mask of type vma_flags_t has a SINGLE flag set
+ * (returning false if flagmask has no flags set).
+ *
+ * This is useful when a flag needs to be either defined or not depending upon
+ * kernel configuration, e.g.:
+ *
+ * if (vma_test_single_mask(vma, VMA_DROPPABLE)) { ... }
+ *
+ * When VMA_DROPPABLE is defined if available, or set to EMPTY_VMA_FLAGS
+ * otherwise.
+ */
+static __always_inline bool
+vma_test_single_mask(const struct vm_area_struct *vma, vma_flags_t flagmask)
+{
+       return vma_flags_test_single_mask(&vma->flags, flagmask);
+}
+
 /*
  * Helper to set all VMA flags in a VMA.
  *

diff --git a/tools/testing/vma/include/custom.h b/tools/testing/vma/include/custom.h
index 2c498e713fbda1992764f90986f4c6269437b097..b7d9eb0a44e41298ca648c56e5d43c3540e6de01 100644 (file)
--- a/tools/testing/vma/include/custom.h
+++ b/tools/testing/vma/include/custom.h
@@ -15,12 +15,6 @@ extern unsigned long dac_mmap_min_addr;
 #define dac_mmap_min_addr      0UL
 #endif
 
-#define VM_WARN_ON(_expr) (WARN_ON(_expr))
-#define VM_WARN_ON_ONCE(_expr) (WARN_ON_ONCE(_expr))
-#define VM_WARN_ON_VMG(_expr, _vmg) (WARN_ON(_expr))
-#define VM_BUG_ON(_expr) (BUG_ON(_expr))
-#define VM_BUG_ON_VMA(_expr, _vma) (BUG_ON(_expr))
-
 #define TASK_SIZE ((1ul << 47)-PAGE_SIZE)
 
 /*

diff --git a/tools/testing/vma/include/dup.h b/tools/testing/vma/include/dup.h
index f9fe07a8a443a6b69771da770fae6a3b6e0552ad..244ee02dc21d3563a6739a72bd26cee48b41c6d3 100644 (file)
--- a/tools/testing/vma/include/dup.h
+++ b/tools/testing/vma/include/dup.h
@@ -905,6 +905,13 @@ static __always_inline vma_flags_t __mk_vma_flags(vma_flags_t flags,
 #define append_vma_flags(flags, ...) __mk_vma_flags(flags,                     \
                COUNT_ARGS(__VA_ARGS__), (const vma_flag_t []){__VA_ARGS__})
 
+static __always_inline int vma_flags_count(const vma_flags_t *flags)
+{
+       const unsigned long *bitmap = flags->__vma_flags;
+
+       return bitmap_weight(bitmap, NUM_VMA_FLAG_BITS);
+}
+
 static __always_inline bool vma_flags_test(const vma_flags_t *flags,
                vma_flag_t bit)
 {
@@ -952,6 +959,14 @@ static __always_inline bool vma_flags_test_all_mask(const vma_flags_t *flags,
 #define vma_flags_test_all(flags, ...) \
        vma_flags_test_all_mask(flags, mk_vma_flags(__VA_ARGS__))
 
+static __always_inline bool vma_flags_test_single_mask(const vma_flags_t *flags,
+                                               vma_flags_t flagmask)
+{
+       VM_WARN_ON_ONCE(vma_flags_count(&flagmask) > 1);
+
+       return vma_flags_test_any_mask(flags, flagmask);
+}
+
 static __always_inline void vma_flags_set_mask(vma_flags_t *flags, vma_flags_t to_set)
 {
        unsigned long *bitmap = flags->__vma_flags;
@@ -1031,6 +1046,12 @@ static __always_inline bool vma_test_all_mask(const struct vm_area_struct *vma,
 #define vma_test_all(vma, ...) \
        vma_test_all_mask(vma, mk_vma_flags(__VA_ARGS__))
 
+static __always_inline bool
+vma_test_single_mask(const struct vm_area_struct *vma, vma_flags_t flagmask)
+{
+       return vma_flags_test_single_mask(&vma->flags, flagmask);
+}
+
 static __always_inline void vma_set_flags_mask(struct vm_area_struct *vma,
                vma_flags_t flags)
 {

diff --git a/tools/testing/vma/vma_internal.h b/tools/testing/vma/vma_internal.h
index 0e1121e2ef23e73a471726e8499666f738c13210..e12ab2c80f95077a3923ffeae1c1d9daf714524f 100644 (file)
--- a/tools/testing/vma/vma_internal.h
+++ b/tools/testing/vma/vma_internal.h
@@ -51,6 +51,12 @@ typedef unsigned long        pgprotval_t;
 typedef struct pgprot { pgprotval_t pgprot; } pgprot_t;
 typedef __bitwise unsigned int vm_fault_t;
 
+#define VM_WARN_ON(_expr) (WARN_ON(_expr))
+#define VM_WARN_ON_ONCE(_expr) (WARN_ON_ONCE(_expr))
+#define VM_WARN_ON_VMG(_expr, _vmg) (WARN_ON(_expr))
+#define VM_BUG_ON(_expr) (BUG_ON(_expr))
+#define VM_BUG_ON_VMA(_expr, _vma) (BUG_ON(_expr))
+
 #include "include/stubs.h"
 #include "include/dup.h"
 #include "include/custom.h"