mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2024-12-28 16:53:49 +00:00
529ce23a76
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>
56 lines
1.5 KiB
C
56 lines
1.5 KiB
C
/* file-mmu.c: ramfs MMU-based file operations
|
|
*
|
|
* Resizable simple ram filesystem for Linux.
|
|
*
|
|
* Copyright (C) 2000 Linus Torvalds.
|
|
* 2000 Transmeta Corp.
|
|
*
|
|
* Usage limits added by David Gibson, Linuxcare Australia.
|
|
* This file is released under the GPL.
|
|
*/
|
|
|
|
/*
|
|
* NOTE! This filesystem is probably most useful
|
|
* not as a real filesystem, but as an example of
|
|
* how virtual filesystems can be written.
|
|
*
|
|
* It doesn't get much simpler than this. Consider
|
|
* that this file implements the full semantics of
|
|
* a POSIX-compliant read-write filesystem.
|
|
*
|
|
* Note in particular how the filesystem does not
|
|
* need to implement any data structures of its own
|
|
* to keep track of the virtual data: using the VFS
|
|
* caches is sufficient.
|
|
*/
|
|
|
|
#include <linux/fs.h>
|
|
#include <linux/mm.h>
|
|
#include <linux/ramfs.h>
|
|
#include <linux/sched.h>
|
|
|
|
#include "internal.h"
|
|
|
|
static unsigned long ramfs_mmu_get_unmapped_area(struct file *file,
|
|
unsigned long addr, unsigned long len, unsigned long pgoff,
|
|
unsigned long flags)
|
|
{
|
|
return mm_get_unmapped_area(current->mm, file, addr, len, pgoff, flags);
|
|
}
|
|
|
|
const struct file_operations ramfs_file_operations = {
|
|
.read_iter = generic_file_read_iter,
|
|
.write_iter = generic_file_write_iter,
|
|
.mmap = generic_file_mmap,
|
|
.fsync = noop_fsync,
|
|
.splice_read = filemap_splice_read,
|
|
.splice_write = iter_file_splice_write,
|
|
.llseek = generic_file_llseek,
|
|
.get_unmapped_area = ramfs_mmu_get_unmapped_area,
|
|
};
|
|
|
|
const struct inode_operations ramfs_file_inode_operations = {
|
|
.setattr = simple_setattr,
|
|
.getattr = simple_getattr,
|
|
};
|