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author | Rick Edgecombe <rick.p.edgecombe@intel.com> | 2024-03-25 19:16:44 -0700 |
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committer | Andrew Morton <akpm@linux-foundation.org> | 2024-04-25 20:56:25 -0700 |
commit | 529ce23a764f25d172198b4c6ba90f1e2ad17f93 (patch) | |
tree | 7a3c033c5c09cfc0c2345134291e059afa66d47f /drivers/dax | |
parent | 5def1e0f476da713141269d86815aba7c2817cb5 (diff) | |
download | linux-stable-529ce23a764f25d172198b4c6ba90f1e2ad17f93.tar.gz linux-stable-529ce23a764f25d172198b4c6ba90f1e2ad17f93.tar.bz2 linux-stable-529ce23a764f25d172198b4c6ba90f1e2ad17f93.zip |
mm: switch mm->get_unmapped_area() to a flag
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>
Diffstat (limited to 'drivers/dax')
-rw-r--r-- | drivers/dax/device.c | 6 |
1 files changed, 3 insertions, 3 deletions
diff --git a/drivers/dax/device.c b/drivers/dax/device.c index 93ebedc5ec8c..47c126d37b59 100644 --- a/drivers/dax/device.c +++ b/drivers/dax/device.c @@ -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 = { |