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Subject[PATCH 5/5] kvm/book3s: use pinned_vm instead of locked_vm to account pinned pages
Date
Memory used for TCE tables in kvm_vm_ioctl_create_spapr_tce is currently
accounted to locked_vm because it stays resident and its allocation is
directly triggered from userspace as explained in f8626985c7c2 ("KVM:
PPC: Account TCE-containing pages in locked_vm").

However, since the memory comes straight from the page allocator (and to
a lesser extent unreclaimable slab) and is effectively pinned, it should
be accounted with pinned_vm (see bc3e53f682d9 ("mm: distinguish between
mlocked and pinned pages")).

pinned_vm recently became atomic and so no longer relies on mmap_sem
held as writer: delete.

Signed-off-by: Daniel Jordan <daniel.m.jordan@oracle.com>
---
arch/powerpc/kvm/book3s_64_vio.c | 35 ++++++++++++++------------------
1 file changed, 15 insertions(+), 20 deletions(-)

diff --git a/arch/powerpc/kvm/book3s_64_vio.c b/arch/powerpc/kvm/book3s_64_vio.c
index 532ab79734c7..2f8d7c051e4e 100644
--- a/arch/powerpc/kvm/book3s_64_vio.c
+++ b/arch/powerpc/kvm/book3s_64_vio.c
@@ -56,39 +56,34 @@ static unsigned long kvmppc_stt_pages(unsigned long tce_pages)
return tce_pages + ALIGN(stt_bytes, PAGE_SIZE) / PAGE_SIZE;
}

-static long kvmppc_account_memlimit(unsigned long stt_pages, bool inc)
+static long kvmppc_account_memlimit(unsigned long pages, bool inc)
{
long ret = 0;
+ s64 pinned_vm;

if (!current || !current->mm)
return ret; /* process exited */

- down_write(&current->mm->mmap_sem);
-
if (inc) {
- unsigned long locked, lock_limit;
+ unsigned long lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;

- locked = current->mm->locked_vm + stt_pages;
- lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
- if (locked > lock_limit && !capable(CAP_IPC_LOCK))
+ pinned_vm = atomic64_add_return(pages, &current->mm->pinned_vm);
+ if (pinned_vm > lock_limit && !capable(CAP_IPC_LOCK)) {
ret = -ENOMEM;
- else
- current->mm->locked_vm += stt_pages;
+ atomic64_sub(pages, &current->mm->pinned_vm);
+ }
} else {
- if (WARN_ON_ONCE(stt_pages > current->mm->locked_vm))
- stt_pages = current->mm->locked_vm;
+ pinned_vm = atomic64_read(&current->mm->pinned_vm);
+ if (WARN_ON_ONCE(pages > pinned_vm))
+ pages = pinned_vm;

- current->mm->locked_vm -= stt_pages;
+ atomic64_sub(pages, &current->mm->pinned_vm);
}

- pr_debug("[%d] RLIMIT_MEMLOCK KVM %c%ld %ld/%ld%s\n", current->pid,
- inc ? '+' : '-',
- stt_pages << PAGE_SHIFT,
- current->mm->locked_vm << PAGE_SHIFT,
- rlimit(RLIMIT_MEMLOCK),
- ret ? " - exceeded" : "");
-
- up_write(&current->mm->mmap_sem);
+ pr_debug("[%d] RLIMIT_MEMLOCK KVM %c%lu %ld/%lu%s\n", current->pid,
+ inc ? '+' : '-', pages << PAGE_SHIFT,
+ atomic64_read(&current->mm->pinned_vm) << PAGE_SHIFT,
+ rlimit(RLIMIT_MEMLOCK), ret ? " - exceeded" : "");

return ret;
}
--
2.20.1
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