As evidenced by this bug report [1], userspace libraries are interested in whether a mapping is DAX mapped, i.e. no intervening page cache. Rather than using the ambiguous VM_MIXEDMAP flag in smaps, provide an explicit "is dax" indication as a new flag in the page vector populated by mincore. There are also cases, particularly for testing and validating a configuration to know the hardware mapping geometry of the pages in a given process address range. Consider filesystem-dax where a configuration needs to take care to align partitions and block allocations before huge page mappings might be used, or anonymous-transparent-huge-pages where a process is opportunistically assigned large pages. mincore2() allows these configurations to be surveyed and validated. The implementation takes advantage of the unused bits in the per-page byte returned for each PAGE_SIZE extent of a given address range. The new format of each vector byte is: (TLB_SHIFT - PAGE_SHIFT) << 2 | vma_is_dax() << 1 | page_present [1]: https://lkml.org/lkml/2016/9/7/61 Cc: Arnd Bergmann <arnd@xxxxxxxx> Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx> Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx> Cc: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx> Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx> --- include/linux/syscalls.h | 2 + include/uapi/asm-generic/mman-common.h | 3 + kernel/sys_ni.c | 1 mm/mincore.c | 126 +++++++++++++++++++++++++------- 4 files changed, 104 insertions(+), 28 deletions(-) diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index d02239022bd0..4aa2ee7e359a 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -467,6 +467,8 @@ asmlinkage long sys_munlockall(void); asmlinkage long sys_madvise(unsigned long start, size_t len, int behavior); asmlinkage long sys_mincore(unsigned long start, size_t len, unsigned char __user * vec); +asmlinkage long sys_mincore2(unsigned long start, size_t len, + unsigned char __user * vec, int flags); asmlinkage long sys_pivot_root(const char __user *new_root, const char __user *put_old); diff --git a/include/uapi/asm-generic/mman-common.h b/include/uapi/asm-generic/mman-common.h index 58274382a616..05037343f0da 100644 --- a/include/uapi/asm-generic/mman-common.h +++ b/include/uapi/asm-generic/mman-common.h @@ -72,4 +72,7 @@ #define MAP_HUGE_SHIFT 26 #define MAP_HUGE_MASK 0x3f +#define MINCORE_DAX 1 /* indicate pages that are dax-mapped */ +#define MINCORE_ORDER 2 /* retrieve hardware mapping-size-order */ + #endif /* __ASM_GENERIC_MMAN_COMMON_H */ diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c index 2c5e3a8e00d7..e14b87834054 100644 --- a/kernel/sys_ni.c +++ b/kernel/sys_ni.c @@ -197,6 +197,7 @@ cond_syscall(sys_mlockall); cond_syscall(sys_munlockall); cond_syscall(sys_mlock2); cond_syscall(sys_mincore); +cond_syscall(sys_mincore2); cond_syscall(sys_madvise); cond_syscall(sys_mremap); cond_syscall(sys_remap_file_pages); diff --git a/mm/mincore.c b/mm/mincore.c index c0b5ba965200..15f9eb5de65b 100644 --- a/mm/mincore.c +++ b/mm/mincore.c @@ -15,25 +15,62 @@ #include <linux/swap.h> #include <linux/swapops.h> #include <linux/hugetlb.h> +#include <linux/dax.h> #include <asm/uaccess.h> #include <asm/pgtable.h> +#define MINCORE_DAX_MASK 2 +#define MINCORE_DAX_SHIFT 1 + +#define MINCORE_ORDER_MASK 0x7c +#define MINCORE_ORDER_SHIFT 2 + +struct mincore_params { + unsigned char *vec; + int flags; +}; + +static void mincore_set(unsigned char *vec, struct vm_area_struct *vma, int nr, + int flags) +{ + unsigned char mincore = 1; + + if (!nr) { + *vec = 0; + return; + } + + if ((flags & MINCORE_DAX) && vma_is_dax(vma)) + mincore |= 1 << MINCORE_DAX_SHIFT; + if (flags & MINCORE_ORDER) { + unsigned char order = ilog2(nr); + + WARN_ON((order << MINCORE_ORDER_SHIFT) & ~MINCORE_ORDER_MASK); + mincore |= order << MINCORE_ORDER_SHIFT; + } + memset(vec, mincore, nr); +} + static int mincore_hugetlb(pte_t *pte, unsigned long hmask, unsigned long addr, unsigned long end, struct mm_walk *walk) { #ifdef CONFIG_HUGETLB_PAGE + struct mincore_params *p = walk->private; + int nr = (end - addr) >> PAGE_SHIFT; + unsigned char *vec = p->vec; unsigned char present; - unsigned char *vec = walk->private; /* * Hugepages under user process are always in RAM and never * swapped out, but theoretically it needs to be checked. */ present = pte && !huge_pte_none(huge_ptep_get(pte)); - for (; addr != end; vec++, addr += PAGE_SIZE) - *vec = present; - walk->private = vec; + if (!present) + memset(vec, 0, nr); + else + mincore_set(vec, walk->vma, nr, p->flags); + p->vec = vec + nr; #else BUG(); #endif @@ -82,20 +119,24 @@ static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff) } static int __mincore_unmapped_range(unsigned long addr, unsigned long end, - struct vm_area_struct *vma, unsigned char *vec) + struct vm_area_struct *vma, unsigned char *vec, + int flags) { unsigned long nr = (end - addr) >> PAGE_SHIFT; + unsigned char present; int i; if (vma->vm_file) { pgoff_t pgoff; pgoff = linear_page_index(vma, addr); - for (i = 0; i < nr; i++, pgoff++) - vec[i] = mincore_page(vma->vm_file->f_mapping, pgoff); + for (i = 0; i < nr; i++, pgoff++) { + present = mincore_page(vma->vm_file->f_mapping, pgoff); + mincore_set(vec + i, vma, present, flags); + } } else { for (i = 0; i < nr; i++) - vec[i] = 0; + mincore_set(vec + i, vma, 0, flags); } return nr; } @@ -103,8 +144,11 @@ static int __mincore_unmapped_range(unsigned long addr, unsigned long end, static int mincore_unmapped_range(unsigned long addr, unsigned long end, struct mm_walk *walk) { - walk->private += __mincore_unmapped_range(addr, end, - walk->vma, walk->private); + struct mincore_params *p = walk->private; + int nr = __mincore_unmapped_range(addr, end, walk->vma, p->vec, + p->flags); + + p->vec += nr; return 0; } @@ -114,18 +158,20 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, spinlock_t *ptl; struct vm_area_struct *vma = walk->vma; pte_t *ptep; - unsigned char *vec = walk->private; + struct mincore_params *p = walk->private; + unsigned char *vec = p->vec; int nr = (end - addr) >> PAGE_SHIFT; + int flags = p->flags; ptl = pmd_trans_huge_lock(pmd, vma); if (ptl) { - memset(vec, 1, nr); + mincore_set(vec, vma, nr, flags); spin_unlock(ptl); goto out; } if (pmd_trans_unstable(pmd)) { - __mincore_unmapped_range(addr, end, vma, vec); + __mincore_unmapped_range(addr, end, vma, vec, flags); goto out; } @@ -135,9 +181,9 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, if (pte_none(pte)) __mincore_unmapped_range(addr, addr + PAGE_SIZE, - vma, vec); + vma, vec, flags); else if (pte_present(pte)) - *vec = 1; + mincore_set(vec, vma, 1, flags); else { /* pte is a swap entry */ swp_entry_t entry = pte_to_swp_entry(pte); @@ -146,14 +192,17 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, * migration or hwpoison entries are always * uptodate */ - *vec = 1; + mincore_set(vec, vma, 1, flags); } else { #ifdef CONFIG_SWAP - *vec = mincore_page(swap_address_space(entry), - entry.val); + unsigned char present; + + present = mincore_page(swap_address_space(entry), + entry.val); + mincore_set(vec, vma, present, flags); #else WARN_ON(1); - *vec = 1; + mincore_set(vec, vma, 1, flags); #endif } } @@ -161,7 +210,7 @@ static int mincore_pte_range(pmd_t *pmd, unsigned long addr, unsigned long end, } pte_unmap_unlock(ptep - 1, ptl); out: - walk->private += nr; + p->vec = vec + nr; cond_resched(); return 0; } @@ -171,16 +220,21 @@ out: * all the arguments, we hold the mmap semaphore: we should * just return the amount of info we're asked for. */ -static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *vec) +static long do_mincore(unsigned long addr, unsigned long pages, + unsigned char *vec, int flags) { struct vm_area_struct *vma; unsigned long end; int err; + struct mincore_params p = { + .vec = vec, + .flags = flags, + }; struct mm_walk mincore_walk = { .pmd_entry = mincore_pte_range, .pte_hole = mincore_unmapped_range, .hugetlb_entry = mincore_hugetlb, - .private = vec, + .private = &p, }; vma = find_vma(current->mm, addr); @@ -195,13 +249,19 @@ static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *v } /* - * The mincore(2) system call. + * The mincore2(2) system call. * - * mincore() returns the memory residency status of the pages in the + * mincore2() returns the memory residency status of the pages in the * current process's address space specified by [addr, addr + len). * The status is returned in a vector of bytes. The least significant * bit of each byte is 1 if the referenced page is in memory, otherwise - * it is zero. + * it is zero. When 'flags' is non-zero each byte additionally contains + * an indication of whether the referenced page in memory is a DAX + * mapping (bit 2 of each vector byte), and/or the order of the mapping + * (bits 3 through 7 of each vector byte). Where the order relates to + * the hardware mapping size backing the given logical-page. For + * example, a 2MB-dax-mapped-huge-page would correspond to 512 vector + * entries with the value 0x27. * * Because the status of a page can change after mincore() checks it * but before it returns to the application, the returned vector may @@ -218,8 +278,8 @@ static long do_mincore(unsigned long addr, unsigned long pages, unsigned char *v * mapped * -EAGAIN - A kernel resource was temporarily unavailable. */ -SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, - unsigned char __user *, vec) +SYSCALL_DEFINE4(mincore2, unsigned long, start, size_t, len, + unsigned char __user *, vec, int, flags) { long retval; unsigned long pages; @@ -229,6 +289,10 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, if (start & ~PAGE_MASK) return -EINVAL; + /* Check that undefined flags are zero */ + if (flags & ~(MINCORE_DAX | MINCORE_ORDER)) + return -EINVAL; + /* ..and we need to be passed a valid user-space range */ if (!access_ok(VERIFY_READ, (void __user *) start, len)) return -ENOMEM; @@ -251,7 +315,7 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, * the temporary buffer size. */ down_read(¤t->mm->mmap_sem); - retval = do_mincore(start, min(pages, PAGE_SIZE), tmp); + retval = do_mincore(start, min(pages, PAGE_SIZE), tmp, flags); up_read(¤t->mm->mmap_sem); if (retval <= 0) @@ -268,3 +332,9 @@ SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, free_page((unsigned long) tmp); return retval; } + +SYSCALL_DEFINE3(mincore, unsigned long, start, size_t, len, + unsigned char __user *, vec) +{ + return sys_mincore2(start, len, vec, 0); +} -- To unsubscribe from this list: send the line "unsubscribe linux-api" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
