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mm: pagewalk: add p4d_entry() and pgd_entry() 

pgd_entry() and pud_entry() were removed by commit 0b1fbfe500
("mm/pagewalk: remove pgd_entry() and pud_entry()") because there were no
users.  We're about to add users so reintroduce them, along with
p4d_entry() as we now have 5 levels of tables.

Note that commit a00cc7d9dd ("mm, x86: add support for PUD-sized
transparent hugepages") already re-added pud_entry() but with different
semantics to the other callbacks.  This commit reverts the semantics back
to match the other callbacks.

To support hmm.c which now uses the new semantics of pud_entry() a new
member ('action') of struct mm_walk is added which allows the callbacks to
either descend (ACTION_SUBTREE, the default), skip (ACTION_CONTINUE) or
repeat the callback (ACTION_AGAIN).  hmm.c is then updated to call
pud_trans_huge_lock() itself and make use of the splitting/retry logic of
the core code.

After this change pud_entry() is called for all entries, not just
transparent huge pages.

[arnd@arndb.de: fix unused variable warning]
 Link: http://lkml.kernel.org/r/20200107204607.1533842-1-arnd@arndb.de
Link: http://lkml.kernel.org/r/20191218162402.45610-12-steven.price@arm.com
Signed-off-by: Steven Price <steven.price@arm.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Albert Ou <aou@eecs.berkeley.edu>
Cc: Alexandre Ghiti <alex@ghiti.fr>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Hogan <jhogan@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Jerome Glisse <jglisse@redhat.com>
Cc: "Liang, Kan" <kan.liang@linux.intel.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Paul Burton <paul.burton@mips.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Paul Walmsley <paul.walmsley@sifive.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Will Deacon <will@kernel.org>
Cc: Zong Li <zong.li@sifive.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Steven Price 2020-02-03 17:35:45 -08:00 committed by Linus Torvalds
parent 757b2a4ab5
commit 3afc423632
3 changed files with 95 additions and 47 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
include/linux/pagewalk.h
View File

@ -8,15 +8,15 @@ struct mm_walk;
/** /**
* mm_walk_ops - callbacks for walk_page_range * mm_walk_ops - callbacks for walk_page_range
* @pud_entry: if set, called for each non-empty PUD (2nd-level) entry * @pgd_entry: if set, called for each non-empty PGD (top-level) entry
* this handler should only handle pud_trans_huge() puds. * @p4d_entry: if set, called for each non-empty P4D entry
* the pmd_entry or pte_entry callbacks will be used for * @pud_entry: if set, called for each non-empty PUD entry
* regular PUDs. * @pmd_entry: if set, called for each non-empty PMD entry
* @pmd_entry: if set, called for each non-empty PMD (3rd-level) entry
* this handler is required to be able to handle * this handler is required to be able to handle
* pmd_trans_huge() pmds. They may simply choose to * pmd_trans_huge() pmds. They may simply choose to
* split_huge_page() instead of handling it explicitly. * split_huge_page() instead of handling it explicitly.
* @pte_entry: if set, called for each non-empty PTE (4th-level) entry * @pte_entry: if set, called for each non-empty PTE (lowest-level)
* entry
* @pte_hole: if set, called for each hole at all levels * @pte_hole: if set, called for each hole at all levels
* @hugetlb_entry: if set, called for each hugetlb entry * @hugetlb_entry: if set, called for each hugetlb entry
* @test_walk: caller specific callback function to determine whether * @test_walk: caller specific callback function to determine whether
@ -27,8 +27,15 @@ struct mm_walk;
* @pre_vma: if set, called before starting walk on a non-null vma. * @pre_vma: if set, called before starting walk on a non-null vma.
* @post_vma: if set, called after a walk on a non-null vma, provided * @post_vma: if set, called after a walk on a non-null vma, provided
* that @pre_vma and the vma walk succeeded. * that @pre_vma and the vma walk succeeded.
*
* p?d_entry callbacks are called even if those levels are folded on a
* particular architecture/configuration.
*/ */
struct mm_walk_ops { struct mm_walk_ops {
int (*pgd_entry)(pgd_t *pgd, unsigned long addr,
unsigned long next, struct mm_walk *walk);
int (*p4d_entry)(p4d_t *p4d, unsigned long addr,
unsigned long next, struct mm_walk *walk);
int (*pud_entry)(pud_t *pud, unsigned long addr, int (*pud_entry)(pud_t *pud, unsigned long addr,
unsigned long next, struct mm_walk *walk); unsigned long next, struct mm_walk *walk);
int (*pmd_entry)(pmd_t *pmd, unsigned long addr, int (*pmd_entry)(pmd_t *pmd, unsigned long addr,
@ -47,11 +54,25 @@ struct mm_walk_ops {
void (*post_vma)(struct mm_walk *walk); void (*post_vma)(struct mm_walk *walk);
}; };
/*
* Action for pud_entry / pmd_entry callbacks.
* ACTION_SUBTREE is the default
*/
enum page_walk_action {
/* Descend to next level, splitting huge pages if needed and possible */
ACTION_SUBTREE = 0,
/* Continue to next entry at this level (ignoring any subtree) */
ACTION_CONTINUE = 1,
/* Call again for this entry */
ACTION_AGAIN = 2
};
/** /**
* mm_walk - walk_page_range data * mm_walk - walk_page_range data
* @ops: operation to call during the walk * @ops: operation to call during the walk
* @mm: mm_struct representing the target process of page table walk * @mm: mm_struct representing the target process of page table walk
* @vma: vma currently walked (NULL if walking outside vmas) * @vma: vma currently walked (NULL if walking outside vmas)
* @action: next action to perform (see enum page_walk_action)
* @private: private data for callbacks' usage * @private: private data for callbacks' usage
* *
* (see the comment on walk_page_range() for more details) * (see the comment on walk_page_range() for more details)
@ -60,6 +81,7 @@ struct mm_walk {
const struct mm_walk_ops *ops; const struct mm_walk_ops *ops;
struct mm_struct *mm; struct mm_struct *mm;
struct vm_area_struct *vma; struct vm_area_struct *vma;
enum page_walk_action action;
void *private; void *private;
}; };

58
mm/hmm.c
View File

@ -474,23 +474,32 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
{ {
struct hmm_vma_walk *hmm_vma_walk = walk->private; struct hmm_vma_walk *hmm_vma_walk = walk->private;
struct hmm_range *range = hmm_vma_walk->range; struct hmm_range *range = hmm_vma_walk->range;
unsigned long addr = start, next; unsigned long addr = start;
pmd_t *pmdp;
pud_t pud; pud_t pud;
int ret; int ret = 0;
spinlock_t *ptl = pud_trans_huge_lock(pudp, walk->vma);
if (!ptl)
return 0;
/* Normally we don't want to split the huge page */
walk->action = ACTION_CONTINUE;
again:
pud = READ_ONCE(*pudp); pud = READ_ONCE(*pudp);
if (pud_none(pud)) if (pud_none(pud)) {
return hmm_vma_walk_hole(start, end, walk); ret = hmm_vma_walk_hole(start, end, walk);
goto out_unlock;
}
if (pud_huge(pud) && pud_devmap(pud)) { if (pud_huge(pud) && pud_devmap(pud)) {
unsigned long i, npages, pfn; unsigned long i, npages, pfn;
uint64_t *pfns, cpu_flags; uint64_t *pfns, cpu_flags;
bool fault, write_fault; bool fault, write_fault;
if (!pud_present(pud)) if (!pud_present(pud)) {
return hmm_vma_walk_hole(start, end, walk); ret = hmm_vma_walk_hole(start, end, walk);
goto out_unlock;
}
i = (addr - range->start) >> PAGE_SHIFT; i = (addr - range->start) >> PAGE_SHIFT;
npages = (end - addr) >> PAGE_SHIFT; npages = (end - addr) >> PAGE_SHIFT;
@ -499,16 +508,20 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
cpu_flags = pud_to_hmm_pfn_flags(range, pud); cpu_flags = pud_to_hmm_pfn_flags(range, pud);
hmm_range_need_fault(hmm_vma_walk, pfns, npages, hmm_range_need_fault(hmm_vma_walk, pfns, npages,
cpu_flags, &fault, &write_fault); cpu_flags, &fault, &write_fault);
if (fault || write_fault) if (fault || write_fault) {
return hmm_vma_walk_hole_(addr, end, fault, ret = hmm_vma_walk_hole_(addr, end, fault,
write_fault, walk); write_fault, walk);
goto out_unlock;
}
pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT); pfn = pud_pfn(pud) + ((addr & ~PUD_MASK) >> PAGE_SHIFT);
for (i = 0; i < npages; ++i, ++pfn) { for (i = 0; i < npages; ++i, ++pfn) {
hmm_vma_walk->pgmap = get_dev_pagemap(pfn, hmm_vma_walk->pgmap = get_dev_pagemap(pfn,
hmm_vma_walk->pgmap); hmm_vma_walk->pgmap);
if (unlikely(!hmm_vma_walk->pgmap)) if (unlikely(!hmm_vma_walk->pgmap)) {
return -EBUSY; ret = -EBUSY;
goto out_unlock;
}
pfns[i] = hmm_device_entry_from_pfn(range, pfn) | pfns[i] = hmm_device_entry_from_pfn(range, pfn) |
cpu_flags; cpu_flags;
} }
@ -517,22 +530,15 @@ static int hmm_vma_walk_pud(pud_t *pudp, unsigned long start, unsigned long end,
hmm_vma_walk->pgmap = NULL; hmm_vma_walk->pgmap = NULL;
} }
hmm_vma_walk->last = end; hmm_vma_walk->last = end;
return 0; goto out_unlock;
} }
split_huge_pud(walk->vma, pudp, addr); /* Ask for the PUD to be split */
if (pud_none(*pudp)) walk->action = ACTION_SUBTREE;
goto again;
pmdp = pmd_offset(pudp, addr); out_unlock:
do { spin_unlock(ptl);
next = pmd_addr_end(addr, end); return ret;
ret = hmm_vma_walk_pmd(pmdp, addr, next, walk);
if (ret)
return ret;
} while (pmdp++, addr = next, addr != end);
return 0;
} }
#else #else
#define hmm_vma_walk_pud NULL #define hmm_vma_walk_pud NULL

50
mm/pagewalk.c
View File

@ -46,6 +46,9 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
break; break;
continue; continue;
} }
walk->action = ACTION_SUBTREE;
/* /*
* This implies that each ->pmd_entry() handler * This implies that each ->pmd_entry() handler
* needs to know about pmd_trans_huge() pmds * needs to know about pmd_trans_huge() pmds
@ -55,16 +58,21 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr, unsigned long end,
if (err) if (err)
break; break;
if (walk->action == ACTION_AGAIN)
goto again;
/* /*
* Check this here so we only break down trans_huge * Check this here so we only break down trans_huge
* pages when we _need_ to * pages when we _need_ to
*/ */
if (!ops->pte_entry) if (walk->action == ACTION_CONTINUE ||
!(ops->pte_entry))
continue; continue;
split_huge_pmd(walk->vma, pmd, addr); split_huge_pmd(walk->vma, pmd, addr);
if (pmd_trans_unstable(pmd)) if (pmd_trans_unstable(pmd))
goto again; goto again;
err = walk_pte_range(pmd, addr, next, walk); err = walk_pte_range(pmd, addr, next, walk);
if (err) if (err)
break; break;
@ -93,24 +101,25 @@ static int walk_pud_range(p4d_t *p4d, unsigned long addr, unsigned long end,
continue; continue;
} }
if (ops->pud_entry) { walk->action = ACTION_SUBTREE;
spinlock_t *ptl = pud_trans_huge_lock(pud, walk->vma);
if (ptl) { if (ops->pud_entry)
err = ops->pud_entry(pud, addr, next, walk); err = ops->pud_entry(pud, addr, next, walk);
spin_unlock(ptl); if (err)
if (err) break;
break;
continue; if (walk->action == ACTION_AGAIN)
} goto again;
}
if (walk->action == ACTION_CONTINUE ||
!(ops->pmd_entry || ops->pte_entry))
continue;
split_huge_pud(walk->vma, pud, addr); split_huge_pud(walk->vma, pud, addr);
if (pud_none(*pud)) if (pud_none(*pud))
goto again; goto again;
if (ops->pmd_entry || ops->pte_entry) err = walk_pmd_range(pud, addr, next, walk);
err = walk_pmd_range(pud, addr, next, walk);
if (err) if (err)
break; break;
} while (pud++, addr = next, addr != end); } while (pud++, addr = next, addr != end);
@ -136,7 +145,12 @@ static int walk_p4d_range(pgd_t *pgd, unsigned long addr, unsigned long end,
break; break;
continue; continue;
} }
if (ops->pmd_entry || ops->pte_entry) if (ops->p4d_entry) {
err = ops->p4d_entry(p4d, addr, next, walk);
if (err)
break;
}
if (ops->pud_entry || ops->pmd_entry || ops->pte_entry)
err = walk_pud_range(p4d, addr, next, walk); err = walk_pud_range(p4d, addr, next, walk);
if (err) if (err)
break; break;
@ -163,7 +177,13 @@ static int walk_pgd_range(unsigned long addr, unsigned long end,
break; break;
continue; continue;
} }
if (ops->pmd_entry || ops->pte_entry) if (ops->pgd_entry) {
err = ops->pgd_entry(pgd, addr, next, walk);
if (err)
break;
}
if (ops->p4d_entry || ops->pud_entry || ops->pmd_entry ||
ops->pte_entry)
err = walk_p4d_range(pgd, addr, next, walk); err = walk_p4d_range(pgd, addr, next, walk);
if (err) if (err)
break; break;