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Subject[PATCH] update ctime and mtime for mmaped write
From
Date
From: Miklos Szeredi <mszeredi@suse.cz>

This patch makes writing to shared memory mappings update st_ctime and
st_mtime as defined by SUSv3:

The st_ctime and st_mtime fields of a file that is mapped with
MAP_SHARED and PROT_WRITE shall be marked for update at some point
in the interval between a write reference to the mapped region and
the next call to msync() with MS_ASYNC or MS_SYNC for that portion
of the file by any process. If there is no such call and if the
underlying file is modified as a result of a write reference, then
these fields shall be marked for update at some time after the
write reference.

A new address_space flag is introduced: AS_CMTIME. This is set each
time a page is dirtied through a userspace memory mapping. This
includes write accesses via get_user_pages().

Note, the flag is set unconditionally, even if the page is already
dirty. This is important, because the page might have been dirtied
earlier by a non-mmap write.

This flag is checked in msync() and __fput(), and if set, the file
times are updated and the flag is cleared

The flag is also cleared, if the time update is triggered by a normal
write. This is not mandated by the standard, but seems to be a sane
thing to do.

Fixes Novell Bugzilla #206431.

Inspired by Peter Staubach's patch and the resulting comments.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
---
Index: linux/include/linux/pagemap.h
===================================================================
--- linux.orig/include/linux/pagemap.h 2007-02-21 14:15:06.000000000 +0100
+++ linux/include/linux/pagemap.h 2007-02-21 14:16:04.000000000 +0100
@@ -18,6 +18,7 @@
*/
#define AS_EIO (__GFP_BITS_SHIFT + 0) /* IO error on async write */
#define AS_ENOSPC (__GFP_BITS_SHIFT + 1) /* ENOSPC on async write */
+#define AS_CMTIME (__GFP_BITS_SHIFT + 2) /* ctime/mtime update needed */

static inline gfp_t mapping_gfp_mask(struct address_space * mapping)
{
Index: linux/mm/msync.c
===================================================================
--- linux.orig/mm/msync.c 2007-02-21 14:14:43.000000000 +0100
+++ linux/mm/msync.c 2007-02-21 14:16:04.000000000 +0100
@@ -77,6 +77,7 @@ asmlinkage long sys_msync(unsigned long
}
file = vma->vm_file;
start = vma->vm_end;
+ mapping_update_time(file);
if ((flags & MS_SYNC) && file &&
(vma->vm_flags & VM_SHARED)) {
get_file(file);
Index: linux/fs/file_table.c
===================================================================
--- linux.orig/fs/file_table.c 2007-02-21 14:14:43.000000000 +0100
+++ linux/fs/file_table.c 2007-02-21 14:16:04.000000000 +0100
@@ -165,6 +165,7 @@ void fastcall __fput(struct file *file)
*/
eventpoll_release(file);
locks_remove_flock(file);
+ mapping_update_time(file);

if (file->f_op && file->f_op->release)
file->f_op->release(inode, file);
Index: linux/fs/inode.c
===================================================================
--- linux.orig/fs/inode.c 2007-02-21 14:14:43.000000000 +0100
+++ linux/fs/inode.c 2007-02-21 14:16:04.000000000 +0100
@@ -1219,6 +1219,7 @@ void file_update_time(struct file *file)
struct timespec now;
int sync_it = 0;

+ clear_bit(AS_CMTIME, &file->f_mapping->flags);
if (IS_NOCMTIME(inode))
return;
if (IS_RDONLY(inode))
@@ -1241,6 +1242,12 @@ void file_update_time(struct file *file)

EXPORT_SYMBOL(file_update_time);

+void mapping_update_time(struct file *file)
+{
+ if (test_bit(AS_CMTIME, &file->f_mapping->flags))
+ file_update_time(file);
+}
+
int inode_needs_sync(struct inode *inode)
{
if (IS_SYNC(inode))
Index: linux/include/linux/fs.h
===================================================================
--- linux.orig/include/linux/fs.h 2007-02-21 14:15:06.000000000 +0100
+++ linux/include/linux/fs.h 2007-02-21 14:16:04.000000000 +0100
@@ -1887,6 +1887,7 @@ extern int inode_change_ok(struct inode
extern int __must_check inode_setattr(struct inode *, struct iattr *);

extern void file_update_time(struct file *file);
+extern void mapping_update_time(struct file *file);

static inline ino_t parent_ino(struct dentry *dentry)
{
Index: linux/include/linux/mm.h
===================================================================
--- linux.orig/include/linux/mm.h 2007-02-21 14:14:43.000000000 +0100
+++ linux/include/linux/mm.h 2007-02-21 14:16:04.000000000 +0100
@@ -790,6 +790,7 @@ int redirty_page_for_writepage(struct wr
struct page *page);
int FASTCALL(set_page_dirty(struct page *page));
int set_page_dirty_lock(struct page *page);
+int set_page_dirty_mapping(struct page *page);
int clear_page_dirty_for_io(struct page *page);

extern unsigned long do_mremap(unsigned long addr,
Index: linux/mm/memory.c
===================================================================
--- linux.orig/mm/memory.c 2007-02-21 14:15:06.000000000 +0100
+++ linux/mm/memory.c 2007-02-21 14:16:04.000000000 +0100
@@ -676,7 +676,7 @@ static unsigned long zap_pte_range(struc
anon_rss--;
else {
if (pte_dirty(ptent))
- set_page_dirty(page);
+ set_page_dirty_mapping(page);
if (pte_young(ptent))
mark_page_accessed(page);
file_rss--;
@@ -954,7 +954,7 @@ struct page *follow_page(struct vm_area_
if (flags & FOLL_TOUCH) {
if ((flags & FOLL_WRITE) &&
!pte_dirty(pte) && !PageDirty(page))
- set_page_dirty(page);
+ set_page_dirty_mapping(page);
mark_page_accessed(page);
}
unlock:
@@ -1469,6 +1469,15 @@ static inline void cow_user_page(struct
copy_user_highpage(dst, src, va, vma);
}

+static void set_page_dirty_mapping_balance(struct page *page)
+{
+ if (set_page_dirty_mapping(page)) {
+ struct address_space *mapping = page_mapping(page);
+ if (mapping)
+ balance_dirty_pages_ratelimited(mapping);
+ }
+}
+
/*
* This routine handles present pages, when users try to write
* to a shared page. It is done by copying the page to a new address
@@ -1620,7 +1629,7 @@ gotten:
unlock:
pte_unmap_unlock(page_table, ptl);
if (dirty_page) {
- set_page_dirty_balance(dirty_page);
+ set_page_dirty_mapping_balance(dirty_page);
put_page(dirty_page);
}
return ret;
@@ -2274,7 +2283,7 @@ retry:
unlock:
pte_unmap_unlock(page_table, ptl);
if (dirty_page) {
- set_page_dirty_balance(dirty_page);
+ set_page_dirty_mapping_balance(dirty_page);
put_page(dirty_page);
}
return ret;
Index: linux/mm/page-writeback.c
===================================================================
--- linux.orig/mm/page-writeback.c 2007-02-21 14:15:54.000000000 +0100
+++ linux/mm/page-writeback.c 2007-02-21 14:16:04.000000000 +0100
@@ -244,16 +244,6 @@ static void balance_dirty_pages(struct a
pdflush_operation(background_writeout, 0);
}

-void set_page_dirty_balance(struct page *page)
-{
- if (set_page_dirty(page)) {
- struct address_space *mapping = page_mapping(page);
-
- if (mapping)
- balance_dirty_pages_ratelimited(mapping);
- }
-}
-
/**
* balance_dirty_pages_ratelimited_nr - balance dirty memory state
* @mapping: address_space which was dirtied
@@ -819,6 +809,30 @@ int fastcall set_page_dirty(struct page
EXPORT_SYMBOL(set_page_dirty);

/*
+ * Special set_page_dirty() variant for dirtiness coming from a memory
+ * mapping. In this case the ctime/mtime update flag needs to be set.
+ */
+int set_page_dirty_mapping(struct page *page)
+{
+ struct address_space *mapping = page_mapping(page);
+
+ if (likely(mapping)) {
+ int (*spd)(struct page *) = mapping->a_ops->set_page_dirty;
+#ifdef CONFIG_BLOCK
+ if (!spd)
+ spd = __set_page_dirty_buffers;
+#endif
+ set_bit(AS_CMTIME, &mapping->flags);
+ return (*spd)(page);
+ }
+ if (!PageDirty(page)) {
+ if (!TestSetPageDirty(page))
+ return 1;
+ }
+ return 0;
+}
+
+/*
* set_page_dirty() is racy if the caller has no reference against
* page->mapping->host, and if the page is unlocked. This is because another
* CPU could truncate the page off the mapping and then free the mapping.
Index: linux/mm/rmap.c
===================================================================
--- linux.orig/mm/rmap.c 2007-02-21 14:14:43.000000000 +0100
+++ linux/mm/rmap.c 2007-02-21 14:16:04.000000000 +0100
@@ -598,7 +598,7 @@ void page_remove_rmap(struct page *page,
* faster for those pages still in swapcache.
*/
if (page_test_and_clear_dirty(page))
- set_page_dirty(page);
+ set_page_dirty_mapping(page);
__dec_zone_page_state(page,
PageAnon(page) ? NR_ANON_PAGES : NR_FILE_MAPPED);
}
@@ -643,7 +643,7 @@ static int try_to_unmap_one(struct page

/* Move the dirty bit to the physical page now the pte is gone. */
if (pte_dirty(pteval))
- set_page_dirty(page);
+ set_page_dirty_mapping(page);

/* Update high watermark before we lower rss */
update_hiwater_rss(mm);
@@ -777,7 +777,7 @@ static void try_to_unmap_cluster(unsigne

/* Move the dirty bit to the physical page now the pte is gone. */
if (pte_dirty(pteval))
- set_page_dirty(page);
+ set_page_dirty_mapping(page);

page_remove_rmap(page, vma);
page_cache_release(page);
Index: linux/include/linux/writeback.h
===================================================================
--- linux.orig/include/linux/writeback.h 2007-02-21 14:15:05.000000000 +0100
+++ linux/include/linux/writeback.h 2007-02-21 14:16:04.000000000 +0100
@@ -117,7 +117,6 @@ int sync_page_range(struct inode *inode,
loff_t pos, loff_t count);
int sync_page_range_nolock(struct inode *inode, struct address_space *mapping,
loff_t pos, loff_t count);
-void set_page_dirty_balance(struct page *page);
void writeback_set_ratelimit(void);

/* pdflush.c */
-
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