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1c628004e0
This patch introduces the mk_vma_flags() macro helper to allow easy
manipulation of VMA flags utilising the new bitmap representation
implemented of VMA flags defined by the vma_flags_t type.
It is a variadic macro which provides a bitwise-or'd representation of all
of each individual VMA flag specified.
Note that, while we maintain VM_xxx flags for backwards compatibility
until the conversion is complete, we define VMA flags of type vma_flag_t
using VMA_xxx_BIT to avoid confusing the two.
This helper macro therefore can be used thusly:
vma_flags_t flags = mk_vma_flags(VMA_READ_BIT, VMA_WRITE_BIT);
Testing has demonstrated that the compiler optimises this code such that
it generates the same assembly utilising this macro as it does if the
flags were specified manually, for instance:
vma_flags_t get_flags(void)
{
return mk_vma_flags(VMA_READ_BIT, VMA_WRITE_BIT, VMA_EXEC_BIT);
}
Generates the same code as:
vma_flags_t get_flags(void)
{
vma_flags_t flags;
vma_flags_clear_all(&flags);
vma_flag_set(&flags, VMA_READ_BIT);
vma_flag_set(&flags, VMA_WRITE_BIT);
vma_flag_set(&flags, VMA_EXEC_BIT);
return flags;
}
And:
vma_flags_t get_flags(void)
{
vma_flags_t flags;
unsigned long *bitmap = ACCESS_PRIVATE(&flags, __vma_flags);
*bitmap = 1UL << (__force int)VMA_READ_BIT;
*bitmap |= 1UL << (__force int)VMA_WRITE_BIT;
*bitmap |= 1UL << (__force int)VMA_EXEC_BIT;
return flags;
}
That is:
get_flags:
movl $7, %eax
ret
Link: https://lkml.kernel.org/r/fde00df6ff7fb8c4b42cc0defa5a4924c7a1943a.1769097829.git.lorenzo.stoakes@oracle.com
Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Suggested-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Pedro Falcato <pfalcato@suse.de>
Reviewed-by: Liam R. Howlett <Liam.Howlett@oracle.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Zi Yan <ziy@nvidia.com>
Cc: Damien Le Moal <dlemoal@kernel.org>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Cc: Yury Norov <ynorov@nvidia.com>
Cc: Chris Mason <clm@fb.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>