| Message ID | 20210202112450.11932-2-osalvador@suse.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Cleanup and fixups for vmemmap handling | expand |
> @@ -962,7 +962,6 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end, > { > unsigned long next, pages = 0; > pte_t *pte; > - void *page_addr; > phys_addr_t phys_addr; > > pte = pte_start + pte_index(addr); > @@ -983,42 +982,19 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end, > if (phys_addr < (phys_addr_t)0x40000000) > return; > > - if (PAGE_ALIGNED(addr) && PAGE_ALIGNED(next)) { > - /* > - * Do not free direct mapping pages since they were > - * freed when offlining, or simplely not in use. > - */ > - if (!direct) > - free_pagetable(pte_page(*pte), 0); > - > - spin_lock(&init_mm.page_table_lock); > - pte_clear(&init_mm, addr, pte); > - spin_unlock(&init_mm.page_table_lock); > - > - /* For non-direct mapping, pages means nothing. */ > - pages++; > - } else { > - /* > - * If we are here, we are freeing vmemmap pages since > - * direct mapped memory ranges to be freed are aligned. > - * > - * If we are not removing the whole page, it means > - * other page structs in this page are being used and > - * we canot remove them. So fill the unused page_structs > - * with 0xFD, and remove the page when it is wholly > - * filled with 0xFD. > - */ > - memset((void *)addr, PAGE_INUSE, next - addr); > + /* > + * Do not free direct mapping pages since they were > + * freed when offlining, or simplely not in use. > + */ s/simplely/simply/ (I know, not your fault :) ) However, that comment is highly confusing. There is nothing to free in case of the a direct mapping; we never allocated anything. That's how a direct map works. I'd just get rid of the comment completely - we also don't have one at the other "if (!direct)" places. (side note: all this freeing before unmapping looks very weird, but at least we should have valid accesses anymore) > + if (!direct) > + free_pagetable(pte_page(*pte), 0); [...] > { > + /* > + * See comment in vmemmap_populate(). > + */ I'd drop this comment ... > + VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE)); > + VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE)); > + > remove_pagetable(start, end, false, altmap); > } > > @@ -1556,6 +1538,15 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, > { > int err; > > + /* > + * __populate_section_memmap enforces the range to be added to be > + * PMD aligned. Therefore we can be sure that, as long as the > + * struct page size is multiple of 8, the vmemmap range will be > + * PAGE aligned. > + */ ... and this comment, moving the details into the patch description. The commit should be easy to detect using git blame in case anybody wonders why. > + VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE)); > + VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE)); > + > if (end - start < PAGES_PER_SECTION * sizeof(struct page)) > err = vmemmap_populate_basepages(start, end, node, NULL); > else if (boot_cpu_has(X86_FEATURE_PSE)) > Apart from that looks good, thanks!
diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c index b5a3fa4033d3..4cfa902ec861 100644 --- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -962,7 +962,6 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end, { unsigned long next, pages = 0; pte_t *pte; - void *page_addr; phys_addr_t phys_addr; pte = pte_start + pte_index(addr); @@ -983,42 +982,19 @@ remove_pte_table(pte_t *pte_start, unsigned long addr, unsigned long end, if (phys_addr < (phys_addr_t)0x40000000) return; - if (PAGE_ALIGNED(addr) && PAGE_ALIGNED(next)) { - /* - * Do not free direct mapping pages since they were - * freed when offlining, or simplely not in use. - */ - if (!direct) - free_pagetable(pte_page(*pte), 0); - - spin_lock(&init_mm.page_table_lock); - pte_clear(&init_mm, addr, pte); - spin_unlock(&init_mm.page_table_lock); - - /* For non-direct mapping, pages means nothing. */ - pages++; - } else { - /* - * If we are here, we are freeing vmemmap pages since - * direct mapped memory ranges to be freed are aligned. - * - * If we are not removing the whole page, it means - * other page structs in this page are being used and - * we canot remove them. So fill the unused page_structs - * with 0xFD, and remove the page when it is wholly - * filled with 0xFD. - */ - memset((void *)addr, PAGE_INUSE, next - addr); + /* + * Do not free direct mapping pages since they were + * freed when offlining, or simplely not in use. + */ + if (!direct) + free_pagetable(pte_page(*pte), 0); - page_addr = page_address(pte_page(*pte)); - if (!memchr_inv(page_addr, PAGE_INUSE, PAGE_SIZE)) { - free_pagetable(pte_page(*pte), 0); + spin_lock(&init_mm.page_table_lock); + pte_clear(&init_mm, addr, pte); + spin_unlock(&init_mm.page_table_lock); - spin_lock(&init_mm.page_table_lock); - pte_clear(&init_mm, addr, pte); - spin_unlock(&init_mm.page_table_lock); - } - } + /* For non-direct mapping, pages means nothing. */ + pages++; } /* Call free_pte_table() in remove_pmd_table(). */ @@ -1197,6 +1173,12 @@ remove_pagetable(unsigned long start, unsigned long end, bool direct, void __ref vmemmap_free(unsigned long start, unsigned long end, struct vmem_altmap *altmap) { + /* + * See comment in vmemmap_populate(). + */ + VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE)); + VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE)); + remove_pagetable(start, end, false, altmap); } @@ -1556,6 +1538,15 @@ int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node, { int err; + /* + * __populate_section_memmap enforces the range to be added to be + * PMD aligned. Therefore we can be sure that, as long as the + * struct page size is multiple of 8, the vmemmap range will be + * PAGE aligned. + */ + VM_BUG_ON(!IS_ALIGNED(start, PAGE_SIZE)); + VM_BUG_ON(!IS_ALIGNED(end, PAGE_SIZE)); + if (end - start < PAGES_PER_SECTION * sizeof(struct page)) err = vmemmap_populate_basepages(start, end, node, NULL); else if (boot_cpu_has(X86_FEATURE_PSE))
remove_pte_table() is prepared to handle the case where either the start or the end of the range is not PAGE aligned. This cannot actually happen: __populate_section_memmap enforces the range to be PMD aligned, so as long as the size of the struct page remains multiple of 8, the vmemmap range will be aligned to PAGE_SIZE. Drop the unneeded handling of such case and place a VM_BUG_ON in vmemmap_{populate,free} to catch nasty cases. Signed-off-by: Oscar Salvador <osalvador@suse.de> Suggested-by: David Hildenbrand <david@redhat.com> --- arch/x86/mm/init_64.c | 61 ++++++++++++++++++------------------------- 1 file changed, 26 insertions(+), 35 deletions(-)