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    Subject[PATCH] update ctime and mtime for mmaped write
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    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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