Revert "mm/vmalloc: interchage the implementation of vmalloc_to_{pfn,page}"
Revert commit ece86e222db4, which was intended as a small performance improvement. Despite the claim that the patch doesn't introduce any functional changes in fact it does. The "no page" path behaves different now. Originally, vmalloc_to_page might return NULL under some conditions, with new implementation it returns pfn_to_page(0) which is not the same as NULL. Simple test shows the difference. test.c #include <linux/kernel.h> #include <linux/module.h> #include <linux/vmalloc.h> #include <linux/mm.h> int __init myi(void) { struct page *p; void *v; v = vmalloc(PAGE_SIZE); /* trigger the "no page" path in vmalloc_to_page*/ vfree(v); p = vmalloc_to_page(v); pr_err("expected val = NULL, returned val = %p", p); return -EBUSY; } void __exit mye(void) { } module_init(myi) module_exit(mye) Before interchange: expected val = NULL, returned val = (null) After interchange: expected val = NULL, returned val = c7ebe000 Signed-off-by: Vladimir Murzin <murzin.v@gmail.com> Cc: Jianyu Zhan <nasa4836@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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fb5bb60cd0
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28
mm/vmalloc.c
28
mm/vmalloc.c
@ -220,12 +220,12 @@ int is_vmalloc_or_module_addr(const void *x)
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}
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/*
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* Walk a vmap address to the physical pfn it maps to.
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* Walk a vmap address to the struct page it maps.
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*/
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unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
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struct page *vmalloc_to_page(const void *vmalloc_addr)
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{
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unsigned long addr = (unsigned long) vmalloc_addr;
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unsigned long pfn = 0;
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struct page *page = NULL;
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pgd_t *pgd = pgd_offset_k(addr);
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/*
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@ -244,24 +244,24 @@ unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
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ptep = pte_offset_map(pmd, addr);
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pte = *ptep;
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if (pte_present(pte))
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pfn = pte_pfn(pte);
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page = pte_page(pte);
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pte_unmap(ptep);
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}
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}
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}
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return pfn;
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}
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EXPORT_SYMBOL(vmalloc_to_pfn);
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/*
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* Map a vmalloc()-space virtual address to the struct page.
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*/
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struct page *vmalloc_to_page(const void *vmalloc_addr)
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{
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return pfn_to_page(vmalloc_to_pfn(vmalloc_addr));
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return page;
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}
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EXPORT_SYMBOL(vmalloc_to_page);
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/*
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* Map a vmalloc()-space virtual address to the physical page frame number.
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*/
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unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
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{
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return page_to_pfn(vmalloc_to_page(vmalloc_addr));
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}
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EXPORT_SYMBOL(vmalloc_to_pfn);
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/*** Global kva allocator ***/
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