diff mbox series

[v3,5/7] mm/vmalloc: skip the uninitilized vmalloc areas

Message ID 20230113031921.64716-6-bhe@redhat.com
State New
Headers
Series mm/vmalloc.c: allow vread() to read out vm_map_ram areas |

Commit Message

Baoquan He Jan. 13, 2023, 3:19 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

Uladzislau Rezki Jan. 16, 2023, 11:44 a.m. UTC | #1 
On Fri, Jan 13, 2023 at 11:19:19AM +0800, Baoquan He wrote:
> 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(+)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 4a10b3b692fa..dbcdcad2276b 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3660,6 +3660,11 @@ long vread(char *buf, char *addr, unsigned long count)
>  		if (!vm && !flags)
>  			continue;
>  
> +		if (vm && (vm->flags & VM_UNINITIALIZED))
> +			continue;
> +		/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
> +		smp_rmb();
> +
>  		vaddr = (char *) va->va_start;
>  		size = vm ? get_vm_area_size(vm) : va_size(va);
>  
> -- 
> 2.34.1
> 
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>

--
Uladzislau Rezki
Lorenzo Stoakes Jan. 16, 2023, 12:24 p.m. UTC | #2 
On Fri, Jan 13, 2023 at 11:19:19AM +0800, Baoquan He wrote:
> 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(+)
>
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 4a10b3b692fa..dbcdcad2276b 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -3660,6 +3660,11 @@ long vread(char *buf, char *addr, unsigned long count)
>  		if (!vm && !flags)
>  			continue;
>
> +		if (vm && (vm->flags & VM_UNINITIALIZED))
> +			continue;
> +		/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
> +		smp_rmb();
> +
>  		vaddr = (char *) va->va_start;
>  		size = vm ? get_vm_area_size(vm) : va_size(va);
>
> --
> 2.34.1
>

Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com>
diff mbox series

Patch

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 4a10b3b692fa..dbcdcad2276b 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3660,6 +3660,11 @@  long vread(char *buf, char *addr, unsigned long count)
 		if (!vm && !flags)
 			continue;
 
+		if (vm && (vm->flags & VM_UNINITIALIZED))
+			continue;
+		/* Pair with smp_wmb() in clear_vm_uninitialized_flag() */
+		smp_rmb();
+
 		vaddr = (char *) va->va_start;
 		size = vm ? get_vm_area_size(vm) : va_size(va);