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authorBaoquan He <bhe@redhat.com>2023-02-06 11:40:18 +0300
committerAndrew Morton <akpm@linux-foundation.org>2023-02-10 03:51:43 +0300
commit30a7a9b17c4b0331ec67aadb4b30ff2a951b4ed5 (patch)
tree8a2210d7965eb95eded6fc8041566c9c8c972bb9 /mm/vmalloc.c
parentbba9697b42ead45687352fdd0fd498735bc4361d (diff)
downloadlinux-30a7a9b17c4b0331ec67aadb4b30ff2a951b4ed5.tar.xz
mm/vmalloc: skip the uninitilized vmalloc areas
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 VM_UNINITIALIZED. 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. Link: https://lkml.kernel.org/r/20230206084020.174506-6-bhe@redhat.com Signed-off-by: Baoquan He <bhe@redhat.com> Reviewed-by: Lorenzo Stoakes <lstoakes@gmail.com> Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Cc: Dan Carpenter <error27@gmail.com> Cc: Stephen Brennan <stephen.s.brennan@oracle.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'mm/vmalloc.c')
-rw-r--r--mm/vmalloc.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 87d71c783646..3b57260b6d39 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3587,6 +3587,11 @@ 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);