http://bugzilla.kernel.org/show_bug.cgi?id=2645#c40
Update file times at write references to memory-mapped files.
Force file times update at the next write reference after
calling the msync() system call with the MS_ASYNC flag.
Signed-off-by: Anton Salikhmetov <[EMAIL PROTECTED]>
---
mm/memory.c | 6 ++++++
mm/msync.c | 57 ++++++++++++++++++++++++++++++++++++++++++++-------------
2 files changed, 50 insertions(+), 13 deletions(-)
diff --git a/mm/memory.c b/mm/memory.c
index 6dd1cd8..4b0144b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1670,6 +1670,9 @@ gotten:
unlock:
pte_unmap_unlock(page_table, ptl);
if (dirty_page) {
+ if (vma->vm_file)
+ file_update_time(vma->vm_file);
+
/*
* Yes, Virginia, this is actually required to prevent a race
* with clear_page_dirty_for_io() from clearing the page dirty
@@ -2343,6 +2346,9 @@ out_unlocked:
if (anon)
page_cache_release(vmf.page);
else if (dirty_page) {
+ if (vma->vm_file)
+ file_update_time(vma->vm_file);
+
set_page_dirty_balance(dirty_page, page_mkwrite);
put_page(dirty_page);
}
diff --git a/mm/msync.c b/mm/msync.c
index a4de868..394130d 100644
--- a/mm/msync.c
+++ b/mm/msync.c
@@ -5,6 +5,7 @@
* Copyright (C) 2008 Anton Salikhmetov <[EMAIL PROTECTED]>
*/
+#include <asm/tlbflush.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/mm.h>
@@ -13,11 +14,37 @@
#include <linux/syscalls.h>
/*
+ * Scan the PTEs for pages belonging to the VMA and mark them read-only.
+ * It will force a pagefault on the next write access.
+ */
+static void vma_wrprotect(struct vm_area_struct *vma)
+{
+ unsigned long addr;
+
+ for (addr = vma->vm_start; addr < vma->vm_end; addr += PAGE_SIZE) {
+ spinlock_t *ptl;
+ pgd_t *pgd = pgd_offset(vma->vm_mm, addr);
+ pud_t *pud = pud_offset(pgd, addr);
+ pmd_t *pmd = pmd_offset(pud, addr);
+ pte_t *pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl);
+
+ if (pte_dirty(*pte) && pte_write(*pte)) {
+ pte_t entry = ptep_clear_flush(vma, addr, pte);
+
+ entry = pte_wrprotect(entry);
+ set_pte_at(vma->vm_mm, addr, pte, entry);
+ }
+ pte_unmap_unlock(pte, ptl);
+ }
+}
+
+/*
* MS_SYNC syncs the entire file - including mappings.
*
- * MS_ASYNC does not start I/O (it used to, up to 2.5.67).
- * Nor does it mark the relevant pages dirty (it used to up to 2.6.17).
- * Now it doesn't do anything, since dirty pages are properly tracked.
+ * MS_ASYNC does not start I/O. Instead, it marks the relevant pages
+ * read-only by calling vma_wrprotect(). This is needed to catch the next
+ * write reference to the mapped region and update the file times
+ * accordingly.
*
* The application may now run fsync() to write out the dirty pages and
* wait on the writeout and check the result. Or the application may run
@@ -77,16 +104,20 @@ asmlinkage long sys_msync(unsigned long start, size_t len,
int flags)
error = 0;
start = vma->vm_end;
file = vma->vm_file;
- if (file && (vma->vm_flags & VM_SHARED) && (flags & MS_SYNC)) {
- get_file(file);
- up_read(&mm->mmap_sem);
- error = do_fsync(file, 0);
- fput(file);
- if (error || start >= end)
- goto out;
- down_read(&mm->mmap_sem);
- vma = find_vma(mm, start);
- continue;
+ if (file && (vma->vm_flags & VM_SHARED)) {
+ if (flags & MS_ASYNC)
+ vma_wrprotect(vma);
+ if (flags & MS_SYNC) {
+ get_file(file);
+ up_read(&mm->mmap_sem);
+ error = do_fsync(file, 0);
+ fput(file);
+ if (error || start >= end)
+ goto out;
+ down_read(&mm->mmap_sem);
+ vma = find_vma(mm, start);
+ continue;
+ }
}
vma = vma->vm_next;
--
1.4.4.4
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