diff mbox series

[v2,5/7] mm/vmalloc: skip the uninitilized vmalloc areas

Message ID 20221217015435.73889-6-bhe@redhat.com (mailing list archive)
State New
Headers show
Series mm/vmalloc.c: allow vread() to read out vm_map_ram areas | expand

Commit Message

Baoquan He Dec. 17, 2022, 1:54 a.m. UTC 
For areas allocated via vmalloc_xxx() APIs, it searches for unmapped area
to reserve and allocates new pages to map into, please see function
__vmalloc_node_range(). During the process, flag VM_UNINITIALIZED is set
in vm->flags to indicate that the pages allocation and mapping haven't
been done, until clear_vm_uninitialized_flag() is called to clear it.

For this kind of area, if VM_UNINITIALIZED is still set, let's ignore
it in vread() because pages newly allocated and being mapped in that
area only contains zero data. reading them out by aligned_vread() is
wasting time.

Signed-off-by: Baoquan He <bhe@redhat.com>
---
 mm/vmalloc.c | 5 +++++
 1 file changed, 5 insertions(+)

Comments

Lorenzo Stoakes Dec. 17, 2022, 12:07 p.m. UTC | #1 
On Sat, Dec 17, 2022 at 09:54:33AM +0800, Baoquan He wrote:
> @@ -3617,6 +3617,11 @@ long vread(char *buf, char *addr, unsigned long count)
>  		if (!vm && !flags)
>  			continue;
>
> +		if (vm->flags & VM_UNINITIALIZED)
> +			continue;

This comes immediately after asserting that vm _might be null_. This surely must become:-

if (vm && vm->flags & VM_UNINITIALIZED)
        continue;
Baoquan He Dec. 19, 2022, 7:16 a.m. UTC | #2 
On 12/17/22 at 12:07pm, Lorenzo Stoakes wrote:
> On Sat, Dec 17, 2022 at 09:54:33AM +0800, Baoquan He wrote:
> > @@ -3617,6 +3617,11 @@ long vread(char *buf, char *addr, unsigned long count)
> >  		if (!vm && !flags)
> >  			continue;
> >
> > +		if (vm->flags & VM_UNINITIALIZED)
> > +			continue;
> 
> This comes immediately after asserting that vm _might be null_. This surely must become:-
> 
> if (vm && vm->flags & VM_UNINITIALIZED)
>         continue;

You are right, will fix it in v3. Thanks for careful reivewing.
diff mbox series

Patch

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 3bfa872a4513..bdaceda1b878 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3617,6 +3617,11 @@  long vread(char *buf, char *addr, unsigned long count)
 		if (!vm && !flags)
 			continue;
 
+		if (vm->flags & VM_UNINITIALIZED)
+			continue;
+		/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
+		smp_rmb();
+
 		vaddr = (char *) va->va_start;
 		size = flags ? va_size(va) : get_vm_area_size(vm);