I am writing an app which really wants to know if a file is on the
disk or not (ie. do I need to sync?).
mincore() bits other than 0 are undefined (as documented in the man
page); in fact my Ubuntu 12.10 i386 system seems to write 129 in some
bytes, so it really shouldn't break anyone.
Is PG_dirty the right choice? Is that right for huge pages? Should I
assume is_migration_entry(entry) means it's not dirty, or is there some
other check here?
Thanks,
Rusty
diff --git a/mm/mincore.c b/mm/mincore.c
index 936b4ce..e1e8f03 100644
--- a/mm/mincore.c
+++ b/mm/mincore.c
@@ -19,6 +19,9 @@
#include <asm/uaccess.h>
#include <asm/pgtable.h>
+#define MINCORE_INCORE 1
+#define MINCORE_DIRTY 2
+
static void mincore_hugetlb_page_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long end,
unsigned char *vec)
@@ -28,7 +31,7 @@ static void mincore_hugetlb_page_range(struct vm_area_struct
*vma,
h = hstate_vma(vma);
while (1) {
- unsigned char present;
+ unsigned char flags = 0;
pte_t *ptep;
/*
* Huge pages are always in RAM for now, but
@@ -36,7 +39,15 @@ static void mincore_hugetlb_page_range(struct vm_area_struct
*vma,
*/
ptep = huge_pte_offset(current->mm,
addr & huge_page_mask(h));
- present = ptep && !huge_pte_none(huge_ptep_get(ptep));
+ if (ptep) {
+ pte_t pte = huge_ptep_get(ptep);
+
+ if (!huge_pte_none(pte)) {
+ flags = MINCORE_INCORE;
+ if (pte_dirty(pte))
+ flags |= MINCORE_DIRTY;
+ }
+ }
while (1) {
*vec = present;
vec++;
@@ -61,7 +72,7 @@ static void mincore_hugetlb_page_range(struct vm_area_struct
*vma,
*/
static unsigned char mincore_page(struct address_space *mapping, pgoff_t pgoff)
{
- unsigned char present = 0;
+ unsigned char flags = 0;
struct page *page;
/*
@@ -79,11 +90,15 @@ static unsigned char mincore_page(struct address_space
*mapping, pgoff_t pgoff)
}
#endif
if (page) {
- present = PageUptodate(page);
+ if (PageUptodate(page)) {
+ flags = MINCORE_INCORE;
+ if (PageDirty(page))
+ flags |= MINCORE_DIRTY;
+ }
page_cache_release(page);
}
- return present;
+ return flags;
}
static void mincore_unmapped_range(struct vm_area_struct *vma,
@@ -121,9 +136,11 @@ static void mincore_pte_range(struct vm_area_struct *vma,
pmd_t *pmd,
next = addr + PAGE_SIZE;
if (pte_none(pte))
mincore_unmapped_range(vma, addr, next, vec);
- else if (pte_present(pte))
- *vec = 1;
- else if (pte_file(pte)) {
+ else if (pte_present(pte)) {
+ *vec = MINCORE_INCORE;
+ if (pte_dirty(pte))
+ *vec |= MINCORE_DIRTY;
+ } else if (pte_file(pte)) {
pgoff = pte_to_pgoff(pte);
*vec = mincore_page(vma->vm_file->f_mapping, pgoff);
} else { /* pte is a swap entry */
@@ -131,14 +148,15 @@ static void mincore_pte_range(struct vm_area_struct *vma,
pmd_t *pmd,
if (is_migration_entry(entry)) {
/* migration entries are always uptodate */
- *vec = 1;
+ *vec = MINCORE_INCORE;
+ /* FIXME: Can they be dirty? */
} else {
#ifdef CONFIG_SWAP
pgoff = entry.val;
*vec = mincore_page(&swapper_space, pgoff);
#else
WARN_ON(1);
- *vec = 1;
+ *vec = MINCORE_INCORE|MINCORE_DIRTY;
#endif
}
}
@@ -246,7 +264,7 @@ static long do_mincore(unsigned long addr, unsigned long
pages, unsigned char *v
* 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. The second bit indicates if page (may be) dirty.
*
* Because the status of a page can change after mincore() checks it
* but before it returns to the application, the returned vector may
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