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mm: switch mm->get_unmapped_area() to a flag

Browse Source 
The mm_struct contains a function pointer *get_unmapped_area(), which is
set to either arch_get_unmapped_area() or arch_get_unmapped_area_topdown()
during the initialization of the mm.

Since the function pointer only ever points to two functions that are
named the same across all arch's, a function pointer is not really
required.  In addition future changes will want to add versions of the
functions that take additional arguments.  So to save a pointers worth of
bytes in mm_struct, and prevent adding additional function pointers to
mm_struct in future changes, remove it and keep the information about
which get_unmapped_area() to use in a flag.

Add the new flag to MMF_INIT_MASK so it doesn't get clobbered on fork by
mmf_init_flags().  Most MM flags get clobbered on fork.  In the
pre-existing behavior mm->get_unmapped_area() would get copied to the new
mm in dup_mm(), so not clobbering the flag preserves the existing behavior
around inheriting the topdown-ness.

Introduce a helper, mm_get_unmapped_area(), to easily convert code that
refers to the old function pointer to instead select and call either
arch_get_unmapped_area() or arch_get_unmapped_area_topdown() based on the
flag.  Then drop the mm->get_unmapped_area() function pointer.  Leave the
get_unmapped_area() pointer in struct file_operations alone.  The main
purpose of this change is to reorganize in preparation for future changes,
but it also converts the calls of mm->get_unmapped_area() from indirect
branches into a direct ones.

The stress-ng bigheap benchmark calls realloc a lot, which calls through
get_unmapped_area() in the kernel.  On x86, the change yielded a ~1%
improvement there on a retpoline config.

In testing a few x86 configs, removing the pointer unfortunately didn't
result in any actual size reductions in the compiled layout of mm_struct. 
But depending on compiler or arch alignment requirements, the change could
shrink the size of mm_struct.

Link: https://lkml.kernel.org/r/20240326021656.202649-3-rick.p.edgecombe@intel.com
Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Aneesh Kumar K.V <aneesh.kumar@kernel.org>
Cc: Borislav Petkov (AMD) <bp@alien8.de>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Deepak Gupta <debug@rivosinc.com>
Cc: Guo Ren <guoren@kernel.org>
Cc: Helge Deller <deller@gmx.de>
Cc: H. Peter Anvin (Intel) <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "James E.J. Bottomley" <James.Bottomley@HansenPartnership.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Brown <broonie@kernel.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Naveen N. Rao <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Rick Edgecombe 2024-03-25 19:16:44 -07:00 committed by Andrew Morton
parent 5def1e0f47
commit 529ce23a76
23 changed files with 66 additions and 57 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/s390/mm/hugetlbpage.c
View File

@ -318,7 +318,7 @@ unsigned long hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
goto check_asce_limit;
}
if (mm->get_unmapped_area == arch_get_unmapped_area)
if (!test_bit(MMF_TOPDOWN, &mm->flags))
addr = hugetlb_get_unmapped_area_bottomup(file, addr, len,
pgoff, flags);
else

4
arch/s390/mm/mmap.c
View File

@ -185,10 +185,10 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
*/
if (mmap_is_legacy(rlim_stack)) {
mm->mmap_base = mmap_base_legacy(random_factor);
mm->get_unmapped_area = arch_get_unmapped_area;
clear_bit(MMF_TOPDOWN, &mm->flags);
} else {
mm->mmap_base = mmap_base(random_factor, rlim_stack);
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
set_bit(MMF_TOPDOWN, &mm->flags);
}
}

15
arch/sparc/kernel/sys_sparc_64.c
View File

@ -218,14 +218,10 @@ arch_get_unmapped_area_topdown(struct file *filp, const unsigned long addr0,
unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, unsigned long len, unsigned long pgoff, unsigned long flags)
{
unsigned long align_goal, addr = -ENOMEM;
unsigned long (*get_area)(struct file *, unsigned long,
unsigned long, unsigned long, unsigned long);
get_area = current->mm->get_unmapped_area;
if (flags & MAP_FIXED) {
/* Ok, don't mess with it. */
return get_area(NULL, orig_addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, NULL, orig_addr, len, pgoff, flags);
}
flags &= ~MAP_SHARED;
@ -238,7 +234,8 @@ unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, u
align_goal = (64UL * 1024);
do {
addr = get_area(NULL, orig_addr, len + (align_goal - PAGE_SIZE), pgoff, flags);
addr = mm_get_unmapped_area(current->mm, NULL, orig_addr,
len + (align_goal - PAGE_SIZE), pgoff, flags);
if (!(addr & ~PAGE_MASK)) {
addr = (addr + (align_goal - 1UL)) & ~(align_goal - 1UL);
break;
@ -256,7 +253,7 @@ unsigned long get_fb_unmapped_area(struct file *filp, unsigned long orig_addr, u
* be obtained.
*/
if (addr & ~PAGE_MASK)
addr = get_area(NULL, orig_addr, len, pgoff, flags);
addr = mm_get_unmapped_area(current->mm, NULL, orig_addr, len, pgoff, flags);
return addr;
}
@ -292,7 +289,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
gap == RLIM_INFINITY ||
sysctl_legacy_va_layout) {
mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
mm->get_unmapped_area = arch_get_unmapped_area;
clear_bit(MMF_TOPDOWN, &mm->flags);
} else {
/* We know it's 32-bit */
unsigned long task_size = STACK_TOP32;
@ -303,7 +300,7 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
gap = (task_size / 6 * 5);
mm->mmap_base = PAGE_ALIGN(task_size - gap - random_factor);
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
set_bit(MMF_TOPDOWN, &mm->flags);
}
}

2
arch/sparc/mm/hugetlbpage.c
View File

@ -123,7 +123,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
(!vma || addr + len <= vm_start_gap(vma)))
return addr;
}
if (mm->get_unmapped_area == arch_get_unmapped_area)
if (!test_bit(MMF_TOPDOWN, &mm->flags))
return hugetlb_get_unmapped_area_bottomup(file, addr, len,
pgoff, flags);
else

2
arch/x86/kernel/cpu/sgx/driver.c
View File

@ -113,7 +113,7 @@ static unsigned long sgx_get_unmapped_area(struct file *file,
if (flags & MAP_FIXED)
return addr;
return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
}
#ifdef CONFIG_COMPAT

2
arch/x86/mm/hugetlbpage.c
View File

@ -115,7 +115,7 @@ hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
}
get_unmapped_area:
if (mm->get_unmapped_area == arch_get_unmapped_area)
if (!test_bit(MMF_TOPDOWN, &mm->flags))
return hugetlb_get_unmapped_area_bottomup(file, addr, len,
pgoff, flags);
else

4
arch/x86/mm/mmap.c
View File

@ -129,9 +129,9 @@ static void arch_pick_mmap_base(unsigned long *base, unsigned long *legacy_base,
void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
{
if (mmap_is_legacy())
mm->get_unmapped_area = arch_get_unmapped_area;
clear_bit(MMF_TOPDOWN, &mm->flags);
else
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
set_bit(MMF_TOPDOWN, &mm->flags);
arch_pick_mmap_base(&mm->mmap_base, &mm->mmap_legacy_base,
arch_rnd(mmap64_rnd_bits), task_size_64bit(0),

2
drivers/char/mem.c
View File

@ -544,7 +544,7 @@ static unsigned long get_unmapped_area_zero(struct file *file,
}
/* Otherwise flags & MAP_PRIVATE: with no shmem object beneath it */
return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
#else
return -ENOSYS;
#endif

6
drivers/dax/device.c
View File

@ -329,14 +329,14 @@ static unsigned long dax_get_unmapped_area(struct file *filp,
if ((off + len_align) < off)
goto out;
addr_align = current->mm->get_unmapped_area(filp, addr, len_align,
pgoff, flags);
addr_align = mm_get_unmapped_area(current->mm, filp, addr, len_align,
pgoff, flags);
if (!IS_ERR_VALUE(addr_align)) {
addr_align += (off - addr_align) & (align - 1);
return addr_align;
}
out:
return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags);
}
static const struct address_space_operations dev_dax_aops = {

4
fs/hugetlbfs/inode.c
View File

@ -249,11 +249,11 @@ generic_hugetlb_get_unmapped_area(struct file *file, unsigned long addr,
}
/*
* Use mm->get_unmapped_area value as a hint to use topdown routine.
* Use MMF_TOPDOWN flag as a hint to use topdown routine.
* If architectures have special needs, they should define their own
* version of hugetlb_get_unmapped_area.
*/
if (mm->get_unmapped_area == arch_get_unmapped_area_topdown)
if (test_bit(MMF_TOPDOWN, &mm->flags))
return hugetlb_get_unmapped_area_topdown(file, addr, len,
pgoff, flags);
return hugetlb_get_unmapped_area_bottomup(file, addr, len,

3
fs/proc/inode.c
View File

@ -455,8 +455,9 @@ pde_get_unmapped_area(struct proc_dir_entry *pde, struct file *file, unsigned lo
return pde->proc_ops->proc_get_unmapped_area(file, orig_addr, len, pgoff, flags);
#ifdef CONFIG_MMU
return current->mm->get_unmapped_area(file, orig_addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, file, orig_addr, len, pgoff, flags);
#endif
return orig_addr;
}

2
fs/ramfs/file-mmu.c
View File

@ -35,7 +35,7 @@ static unsigned long ramfs_mmu_get_unmapped_area(struct file *file,
unsigned long addr, unsigned long len, unsigned long pgoff,
unsigned long flags)
{
return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
}
const struct file_operations ramfs_file_operations = {

6
include/linux/mm_types.h
View File

@ -777,11 +777,7 @@ struct mm_struct {
} ____cacheline_aligned_in_smp;
struct maple_tree mm_mt;
#ifdef CONFIG_MMU
unsigned long (*get_unmapped_area) (struct file *filp,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags);
#endif
unsigned long mmap_base; /* base of mmap area */
unsigned long mmap_legacy_base; /* base of mmap area in bottom-up allocations */
#ifdef CONFIG_HAVE_ARCH_COMPAT_MMAP_BASES

5
include/linux/sched/coredump.h
View File

@ -92,9 +92,12 @@ static inline int get_dumpable(struct mm_struct *mm)
#define MMF_VM_MERGE_ANY 30
#define MMF_VM_MERGE_ANY_MASK (1 << MMF_VM_MERGE_ANY)
#define MMF_TOPDOWN 31 /* mm searches top down by default */
#define MMF_TOPDOWN_MASK (1 << MMF_TOPDOWN)
#define MMF_INIT_MASK (MMF_DUMPABLE_MASK | MMF_DUMP_FILTER_MASK |\
MMF_DISABLE_THP_MASK | MMF_HAS_MDWE_MASK |\
MMF_VM_MERGE_ANY_MASK)
MMF_VM_MERGE_ANY_MASK | MMF_TOPDOWN_MASK)
static inline unsigned long mmf_init_flags(unsigned long flags)
{

5
include/linux/sched/mm.h
View File

@ -8,6 +8,7 @@
#include <linux/mm_types.h>
#include <linux/gfp.h>
#include <linux/sync_core.h>
#include <linux/sched/coredump.h>
/*
* Routines for handling mm_structs
@ -186,6 +187,10 @@ arch_get_unmapped_area_topdown(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff,
unsigned long flags);
unsigned long mm_get_unmapped_area(struct mm_struct *mm, struct file *filp,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags);
unsigned long
generic_get_unmapped_area(struct file *filp, unsigned long addr,
unsigned long len, unsigned long pgoff,

2
io_uring/io_uring.c
View File

@ -3525,7 +3525,7 @@ static unsigned long io_uring_mmu_get_unmapped_area(struct file *filp,
#else
addr = 0UL;
#endif
return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags);
}
#else /* !CONFIG_MMU */

2
kernel/bpf/arena.c
View File

@ -314,7 +314,7 @@ static unsigned long arena_get_unmapped_area(struct file *filp, unsigned long ad
return -EINVAL;
}
ret = current->mm->get_unmapped_area(filp, addr, len * 2, 0, flags);
ret = mm_get_unmapped_area(current->mm, filp, addr, len * 2, 0, flags);
if (IS_ERR_VALUE(ret))
return ret;
if ((ret >> 32) == ((ret + len - 1) >> 32))

2
kernel/bpf/syscall.c
View File

@ -980,7 +980,7 @@ static unsigned long bpf_get_unmapped_area(struct file *filp, unsigned long addr
if (map->ops->map_get_unmapped_area)
return map->ops->map_get_unmapped_area(filp, addr, len, pgoff, flags);
#ifdef CONFIG_MMU
return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags);
#else
return addr;
#endif

6
mm/debug.c
View File

@ -177,9 +177,6 @@ EXPORT_SYMBOL(dump_vma);
void dump_mm(const struct mm_struct *mm)
{
pr_emerg("mm %px task_size %lu\n"
#ifdef CONFIG_MMU
"get_unmapped_area %px\n"
#endif
"mmap_base %lu mmap_legacy_base %lu\n"
"pgd %px mm_users %d mm_count %d pgtables_bytes %lu map_count %d\n"
"hiwater_rss %lx hiwater_vm %lx total_vm %lx locked_vm %lx\n"
@ -205,9 +202,6 @@ void dump_mm(const struct mm_struct *mm)
"def_flags: %#lx(%pGv)\n",
mm, mm->task_size,
#ifdef CONFIG_MMU
mm->get_unmapped_area,
#endif
mm->mmap_base, mm->mmap_legacy_base,
mm->pgd, atomic_read(&mm->mm_users),
atomic_read(&mm->mm_count),

9
mm/huge_memory.c
View File

@ -816,8 +816,8 @@ static unsigned long __thp_get_unmapped_area(struct file *filp,
if (len_pad < len || (off + len_pad) < off)
return 0;
ret = current->mm->get_unmapped_area(filp, addr, len_pad,
off >> PAGE_SHIFT, flags);
ret = mm_get_unmapped_area(current->mm, filp, addr, len_pad,
off >> PAGE_SHIFT, flags);
/*
* The failure might be due to length padding. The caller will retry
@ -835,8 +835,7 @@ static unsigned long __thp_get_unmapped_area(struct file *filp,
off_sub = (off - ret) & (size - 1);
if (current->mm->get_unmapped_area == arch_get_unmapped_area_topdown &&
!off_sub)
if (test_bit(MMF_TOPDOWN, &current->mm->flags) && !off_sub)
return ret + size;
ret += off_sub;
@ -853,7 +852,7 @@ unsigned long thp_get_unmapped_area(struct file *filp, unsigned long addr,
if (ret)
return ret;
return current->mm->get_unmapped_area(filp, addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, filp, addr, len, pgoff, flags);
}
EXPORT_SYMBOL_GPL(thp_get_unmapped_area);

21
mm/mmap.c
View File

@ -1812,7 +1812,8 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
unsigned long (*get_area)(struct file *, unsigned long,
unsigned long, unsigned long, unsigned long);
unsigned long, unsigned long, unsigned long)
= NULL;
unsigned long error = arch_mmap_check(addr, len, flags);
if (error)
@ -1822,7 +1823,6 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
if (len > TASK_SIZE)
return -ENOMEM;
get_area = current->mm->get_unmapped_area;
if (file) {
if (file->f_op->get_unmapped_area)
get_area = file->f_op->get_unmapped_area;
@ -1841,7 +1841,11 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
if (!file)
pgoff = 0;
addr = get_area(file, addr, len, pgoff, flags);
if (get_area)
addr = get_area(file, addr, len, pgoff, flags);
else
addr = mm_get_unmapped_area(current->mm, file, addr, len,
pgoff, flags);
if (IS_ERR_VALUE(addr))
return addr;
@ -1856,6 +1860,17 @@ get_unmapped_area(struct file *file, unsigned long addr, unsigned long len,
EXPORT_SYMBOL(get_unmapped_area);
unsigned long
mm_get_unmapped_area(struct mm_struct *mm, struct file *file,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
if (test_bit(MMF_TOPDOWN, &mm->flags))
return arch_get_unmapped_area_topdown(file, addr, len, pgoff, flags);
return arch_get_unmapped_area(file, addr, len, pgoff, flags);
}
EXPORT_SYMBOL(mm_get_unmapped_area);
/**
* find_vma_intersection() - Look up the first VMA which intersects the interval
* @mm: The process address space.

11
mm/shmem.c
View File

@ -2267,8 +2267,6 @@ unsigned long shmem_get_unmapped_area(struct file *file,
unsigned long uaddr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
unsigned long (*get_area)(struct file *,
unsigned long, unsigned long, unsigned long, unsigned long);
unsigned long addr;
unsigned long offset;
unsigned long inflated_len;
@ -2278,8 +2276,8 @@ unsigned long shmem_get_unmapped_area(struct file *file,
if (len > TASK_SIZE)
return -ENOMEM;
get_area = current->mm->get_unmapped_area;
addr = get_area(file, uaddr, len, pgoff, flags);
addr = mm_get_unmapped_area(current->mm, file, uaddr, len, pgoff,
flags);
if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE))
return addr;
@ -2336,7 +2334,8 @@ unsigned long shmem_get_unmapped_area(struct file *file,
if (inflated_len < len)
return addr;
inflated_addr = get_area(NULL, uaddr, inflated_len, 0, flags);
inflated_addr = mm_get_unmapped_area(current->mm, NULL, uaddr,
inflated_len, 0, flags);
if (IS_ERR_VALUE(inflated_addr))
return addr;
if (inflated_addr & ~PAGE_MASK)
@ -4801,7 +4800,7 @@ unsigned long shmem_get_unmapped_area(struct file *file,
unsigned long addr, unsigned long len,
unsigned long pgoff, unsigned long flags)
{
return current->mm->get_unmapped_area(file, addr, len, pgoff, flags);
return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
}
#endif

6
mm/util.c
View File

@ -469,17 +469,17 @@ void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
if (mmap_is_legacy(rlim_stack)) {
mm->mmap_base = TASK_UNMAPPED_BASE + random_factor;
mm->get_unmapped_area = arch_get_unmapped_area;
clear_bit(MMF_TOPDOWN, &mm->flags);
} else {
mm->mmap_base = mmap_base(random_factor, rlim_stack);
mm->get_unmapped_area = arch_get_unmapped_area_topdown;
set_bit(MMF_TOPDOWN, &mm->flags);
}
}
#elif defined(CONFIG_MMU) && !defined(HAVE_ARCH_PICK_MMAP_LAYOUT)
void arch_pick_mmap_layout(struct mm_struct *mm, struct rlimit *rlim_stack)
{
mm->mmap_base = TASK_UNMAPPED_BASE;
mm->get_unmapped_area = arch_get_unmapped_area;
clear_bit(MMF_TOPDOWN, &mm->flags);
}
#endif