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linux/arch/x86/include/asm/pgalloc.h
Michal Hocko 32d6bd9059 tree wide: get rid of __GFP_REPEAT for order-0 allocations part I 
This is the third version of the patchset previously sent [1].  I have
basically only rebased it on top of 4.7-rc1 tree and dropped "dm: get
rid of superfluous gfp flags" which went through dm tree.  I am sending
it now because it is tree wide and chances for conflicts are reduced
considerably when we want to target rc2.  I plan to send the next step
and rename the flag and move to a better semantic later during this
release cycle so we will have a new semantic ready for 4.8 merge window
hopefully.

Motivation:

While working on something unrelated I've checked the current usage of
__GFP_REPEAT in the tree.  It seems that a majority of the usage is and
always has been bogus because __GFP_REPEAT has always been about costly
high order allocations while we are using it for order-0 or very small
orders very often.  It seems that a big pile of them is just a
copy&paste when a code has been adopted from one arch to another.

I think it makes some sense to get rid of them because they are just
making the semantic more unclear.  Please note that GFP_REPEAT is
documented as

* __GFP_REPEAT: Try hard to allocate the memory, but the allocation attempt

* _might_ fail.  This depends upon the particular VM implementation.
  while !costly requests have basically nofail semantic.  So one could
  reasonably expect that order-0 request with __GFP_REPEAT will not loop
  for ever.  This is not implemented right now though.

I would like to move on with __GFP_REPEAT and define a better semantic
for it.

  $ git grep __GFP_REPEAT origin/master | wc -l
  111
  $ git grep __GFP_REPEAT | wc -l
  36

So we are down to the third after this patch series.  The remaining
places really seem to be relying on __GFP_REPEAT due to large allocation
requests.  This still needs some double checking which I will do later
after all the simple ones are sorted out.

I am touching a lot of arch specific code here and I hope I got it right
but as a matter of fact I even didn't compile test for some archs as I
do not have cross compiler for them.  Patches should be quite trivial to
review for stupid compile mistakes though.  The tricky parts are usually
hidden by macro definitions and thats where I would appreciate help from
arch maintainers.

[1] http://lkml.kernel.org/r/1461849846-27209-1-git-send-email-mhocko@kernel.org

This patch (of 19):

__GFP_REPEAT has a rather weak semantic but since it has been introduced
around 2.6.12 it has been ignored for low order allocations.  Yet we
have the full kernel tree with its usage for apparently order-0
allocations.  This is really confusing because __GFP_REPEAT is
explicitly documented to allow allocation failures which is a weaker
semantic than the current order-0 has (basically nofail).

Let's simply drop __GFP_REPEAT from those places.  This would allow to
identify place which really need allocator to retry harder and formulate
a more specific semantic for what the flag is supposed to do actually.

Link: http://lkml.kernel.org/r/1464599699-30131-2-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: "Theodore Ts'o" <tytso@mit.edu>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Chen Liqin <liqin.linux@gmail.com>
Cc: Chris Metcalf <cmetcalf@mellanox.com> [for tile]
Cc: Guan Xuetao <gxt@mprc.pku.edu.cn>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Helge Deller <deller@gmx.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jan Kara <jack@suse.cz>
Cc: John Crispin <blogic@openwrt.org>
Cc: Lennox Wu <lennox.wu@gmail.com>
Cc: Ley Foon Tan <lftan@altera.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Matt Fleming <matt@codeblueprint.co.uk>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Rich Felker <dalias@libc.org>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-06-24 17:23:52 -07:00

149 lines
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#ifndef _ASM_X86_PGALLOC_H
#define _ASM_X86_PGALLOC_H
#include <linux/threads.h>
#include <linux/mm.h> /* for struct page */
#include <linux/pagemap.h>
static inline int __paravirt_pgd_alloc(struct mm_struct *mm) { return 0; }
#ifdef CONFIG_PARAVIRT
#include <asm/paravirt.h>
#else
#define paravirt_pgd_alloc(mm) __paravirt_pgd_alloc(mm)
static inline void paravirt_pgd_free(struct mm_struct *mm, pgd_t *pgd) {}
static inline void paravirt_alloc_pte(struct mm_struct *mm, unsigned long pfn) {}
static inline void paravirt_alloc_pmd(struct mm_struct *mm, unsigned long pfn) {}
static inline void paravirt_alloc_pmd_clone(unsigned long pfn, unsigned long clonepfn,
unsigned long start, unsigned long count) {}
static inline void paravirt_alloc_pud(struct mm_struct *mm, unsigned long pfn) {}
static inline void paravirt_release_pte(unsigned long pfn) {}
static inline void paravirt_release_pmd(unsigned long pfn) {}
static inline void paravirt_release_pud(unsigned long pfn) {}
#endif
/*
* Flags to use when allocating a user page table page.
*/
extern gfp_t __userpte_alloc_gfp;
/*
* Allocate and free page tables.
*/
extern pgd_t *pgd_alloc(struct mm_struct *);
extern void pgd_free(struct mm_struct *mm, pgd_t *pgd);
extern pte_t *pte_alloc_one_kernel(struct mm_struct *, unsigned long);
extern pgtable_t pte_alloc_one(struct mm_struct *, unsigned long);
/* Should really implement gc for free page table pages. This could be
done with a reference count in struct page. */
static inline void pte_free_kernel(struct mm_struct *mm, pte_t *pte)
{
BUG_ON((unsigned long)pte & (PAGE_SIZE-1));
free_page((unsigned long)pte);
}
static inline void pte_free(struct mm_struct *mm, struct page *pte)
{
pgtable_page_dtor(pte);
__free_page(pte);
}
extern void ___pte_free_tlb(struct mmu_gather *tlb, struct page *pte);
static inline void __pte_free_tlb(struct mmu_gather *tlb, struct page *pte,
unsigned long address)
{
___pte_free_tlb(tlb, pte);
}
static inline void pmd_populate_kernel(struct mm_struct *mm,
pmd_t *pmd, pte_t *pte)
{
paravirt_alloc_pte(mm, __pa(pte) >> PAGE_SHIFT);
set_pmd(pmd, __pmd(__pa(pte) | _PAGE_TABLE));
}
static inline void pmd_populate(struct mm_struct *mm, pmd_t *pmd,
struct page *pte)
{
unsigned long pfn = page_to_pfn(pte);
paravirt_alloc_pte(mm, pfn);
set_pmd(pmd, __pmd(((pteval_t)pfn << PAGE_SHIFT) | _PAGE_TABLE));
}
#define pmd_pgtable(pmd) pmd_page(pmd)
#if CONFIG_PGTABLE_LEVELS > 2
static inline pmd_t *pmd_alloc_one(struct mm_struct *mm, unsigned long addr)
{
struct page *page;
page = alloc_pages(GFP_KERNEL | __GFP_ZERO, 0);
if (!page)
return NULL;
if (!pgtable_pmd_page_ctor(page)) {
__free_pages(page, 0);
return NULL;
}
return (pmd_t *)page_address(page);
}
static inline void pmd_free(struct mm_struct *mm, pmd_t *pmd)
{
BUG_ON((unsigned long)pmd & (PAGE_SIZE-1));
pgtable_pmd_page_dtor(virt_to_page(pmd));
free_page((unsigned long)pmd);
}
extern void ___pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd);
static inline void __pmd_free_tlb(struct mmu_gather *tlb, pmd_t *pmd,
unsigned long address)
{
___pmd_free_tlb(tlb, pmd);
}
#ifdef CONFIG_X86_PAE
extern void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmd);
#else /* !CONFIG_X86_PAE */
static inline void pud_populate(struct mm_struct *mm, pud_t *pud, pmd_t *pmd)
{
paravirt_alloc_pmd(mm, __pa(pmd) >> PAGE_SHIFT);
set_pud(pud, __pud(_PAGE_TABLE | __pa(pmd)));
}
#endif /* CONFIG_X86_PAE */
#if CONFIG_PGTABLE_LEVELS > 3
static inline void pgd_populate(struct mm_struct *mm, pgd_t *pgd, pud_t *pud)
{
paravirt_alloc_pud(mm, __pa(pud) >> PAGE_SHIFT);
set_pgd(pgd, __pgd(_PAGE_TABLE | __pa(pud)));
}
static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
{
return (pud_t *)get_zeroed_page(GFP_KERNEL);
}
static inline void pud_free(struct mm_struct *mm, pud_t *pud)
{
BUG_ON((unsigned long)pud & (PAGE_SIZE-1));
free_page((unsigned long)pud);
}
extern void ___pud_free_tlb(struct mmu_gather *tlb, pud_t *pud);
static inline void __pud_free_tlb(struct mmu_gather *tlb, pud_t *pud,
unsigned long address)
{
___pud_free_tlb(tlb, pud);
}
#endif /* CONFIG_PGTABLE_LEVELS > 3 */
#endif /* CONFIG_PGTABLE_LEVELS > 2 */
#endif /* _ASM_X86_PGALLOC_H */
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