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| author | Baoquan He <bhe@redhat.com> | 2023-02-06 16:40:18 +0800 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2023-02-09 16:51:43 -0800 |
| commit | 30a7a9b17c4b0331ec67aadb4b30ff2a951b4ed5 (patch) | |
| tree | 8a2210d7965eb95eded6fc8041566c9c8c972bb9 /mm/vmalloc.c | |
| parent | bba9697b42ead45687352fdd0fd498735bc4361d (diff) | |
| download | lwn-30a7a9b17c4b0331ec67aadb4b30ff2a951b4ed5.tar.gz lwn-30a7a9b17c4b0331ec67aadb4b30ff2a951b4ed5.zip | |
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.c | 5 |
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); |