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mm/vmalloc: use physical page count in vread_iter() for VM_ALLOC areas

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For VM_ALLOC areas in vread_iter(), derive the vm area size from
vm->nr_pages rather than get_vm_area_size().

Only VM_ALLOC areas are subject to vrealloc() shrinking, which frees pages
without reducing the virtual reservation size.  Switch to using
vm->nr_pages for VM_ALLOC areas so the reader remains correct once shrink
support is added.  Other mapping types (vmap, ioremap) do not initialize
nr_pages and will continue using get_vm_area_size().

[shivamkalra98@zohomail.in: add an nr_pages check]
  Link: https://lore.kernel.org/aff47da5-4fd5-481d-be18-e1eb99639490@zohomail.in
Link: https://lore.kernel.org/20260519-vmalloc-shrink-v14-3-70b96ee3e9c9@zohomail.in
Signed-off-by: Shivam Kalra <shivamkalra98@zohomail.in>
Reviewed-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Cc: Alice Ryhl <aliceryhl@google.com>
Cc: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Shivam Kalra 2026-05-19 17:42:16 +05:30 committed by Andrew Morton
parent d57ac904ff
commit 0bca238046
1 changed files with 12 additions and 1 deletions
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13
mm/vmalloc.c
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@ -4666,7 +4666,18 @@ long vread_iter(struct iov_iter *iter, const char *addr, size_t count)
smp_rmb();
vaddr = (char *) va->va_start;
size = vm ? get_vm_area_size(vm) : va_size(va);
if (vm)
/*
* For VM_ALLOC areas, use nr_pages rather than
* get_vm_area_size() because vrealloc() may shrink
* the mapping without updating area->size. Other
* mapping types (vmap, ioremap) don't set nr_pages.
*/
size = (vm->flags & VM_ALLOC && vm->nr_pages) ?
(vm->nr_pages << PAGE_SHIFT) :
get_vm_area_size(vm);
else
size = va_size(va);
if (addr >= vaddr + size)
goto next_va;