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Date: Mon, 14 Jan 2008 12:08:17 +0100
From: Miklos Szeredi <miklos@...redi.hu>
To: salikhmetov@...il.com
CC: linux-mm@...ck.org, jakob@...hought.net,
linux-kernel@...r.kernel.org, valdis.kletnieks@...edu,
riel@...hat.com, ksm@...dk, staubach@...hat.com,
jesper.juhl@...il.com, torvalds@...ux-foundation.org,
a.p.zijlstra@...llo.nl, akpm@...ux-foundation.org,
protasnb@...il.com
Subject: Re: [PATCH 2/2] updating ctime and mtime at syncing
> http://bugzilla.kernel.org/show_bug.cgi?id=2645
>
> Changes for updating the ctime and mtime fields for memory-mapped files:
>
> 1) new flag triggering update of the inode data;
> 2) new function to update ctime and mtime for block device files;
> 3) new helper function to update ctime and mtime when needed;
> 4) updating time stamps for mapped files in sys_msync() and do_fsync();
> 5) implementing the feature of auto-updating ctime and mtime.
How exactly is this done?
Is this catering for this case:
1 page is dirtied through mapping
2 app calls msync(MS_ASYNC)
3 page is written again through mapping
4 app calls msync(MS_ASYNC)
5 ...
6 page is written back
What happens at 4? Do we care about this one at all?
More comments inline.
> Signed-off-by: Anton Salikhmetov <salikhmetov@...il.com>
> ---
> fs/buffer.c | 1 +
> fs/fs-writeback.c | 2 ++
> fs/inode.c | 42 +++++++++++++++++++++++++++++++++++-------
> fs/sync.c | 2 ++
> include/linux/fs.h | 9 ++++++++-
> include/linux/pagemap.h | 3 ++-
> mm/msync.c | 24 ++++++++++++++++--------
> mm/page-writeback.c | 1 +
> 8 files changed, 67 insertions(+), 17 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 7249e01..09adf7e 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -719,6 +719,7 @@ static int __set_page_dirty(struct page *page,
> }
> write_unlock_irq(&mapping->tree_lock);
> __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
> + set_bit(AS_MCTIME, &mapping->flags);
>
> return 1;
> }
> diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
> index 0fca820..c25ebd5 100644
> --- a/fs/fs-writeback.c
> +++ b/fs/fs-writeback.c
> @@ -243,6 +243,8 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
>
> spin_unlock(&inode_lock);
>
> + mapping_update_time(mapping);
> +
> ret = do_writepages(mapping, wbc);
>
> /* Don't write the inode if only I_DIRTY_PAGES was set */
> diff --git a/fs/inode.c b/fs/inode.c
> index ed35383..c02bfab 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -1243,8 +1243,8 @@ void touch_atime(struct vfsmount *mnt, struct dentry *dentry)
> EXPORT_SYMBOL(touch_atime);
>
> /**
> - * file_update_time - update mtime and ctime time
> - * @file: file accessed
> + * inode_update_time - update mtime and ctime time
> + * @inode: inode accessed
> *
> * Update the mtime and ctime members of an inode and mark the inode
> * for writeback. Note that this function is meant exclusively for
> @@ -1253,10 +1253,8 @@ EXPORT_SYMBOL(touch_atime);
> * S_NOCTIME inode flag, e.g. for network filesystem where these
> * timestamps are handled by the server.
> */
> -
> -void file_update_time(struct file *file)
> +void inode_update_time(struct inode *inode)
> {
> - struct inode *inode = file->f_path.dentry->d_inode;
> struct timespec now;
> int sync_it = 0;
>
> @@ -1279,8 +1277,39 @@ void file_update_time(struct file *file)
> if (sync_it)
> mark_inode_dirty_sync(inode);
> }
> +EXPORT_SYMBOL(inode_update_time);
> +
> +/*
> + * Update the ctime and mtime stamps for memory-mapped block device files.
> + */
> +static void bd_inode_update_time(struct inode *inode)
> +{
> + struct block_device *bdev = inode->i_bdev;
> + struct list_head *p;
> +
> + if (bdev == NULL)
> + return;
> +
> + mutex_lock(&bdev->bd_mutex);
> + list_for_each(p, &bdev->bd_inodes) {
> + inode = list_entry(p, struct inode, i_devices);
> + inode_update_time(inode);
> + }
> + mutex_unlock(&bdev->bd_mutex);
> +}
Umm, why not just call with file->f_dentry->d_inode, so that you don't
need to do this ugly search for the physical inode? The file pointer
is available in both msync and fsync.
> -EXPORT_SYMBOL(file_update_time);
> +/*
> + * Update the ctime and mtime stamps after checking if they are to be updated.
> + */
> +void mapping_update_time(struct address_space *mapping)
> +{
> + if (test_and_clear_bit(AS_MCTIME, &mapping->flags)) {
> + if (S_ISBLK(mapping->host->i_mode))
> + bd_inode_update_time(mapping->host);
> + else
> + inode_update_time(mapping->host);
> + }
> +}
>
> int inode_needs_sync(struct inode *inode)
> {
> @@ -1290,7 +1319,6 @@ int inode_needs_sync(struct inode *inode)
> return 1;
> return 0;
> }
> -
> EXPORT_SYMBOL(inode_needs_sync);
>
> int inode_wait(void *word)
> diff --git a/fs/sync.c b/fs/sync.c
> index 7cd005e..5561464 100644
> --- a/fs/sync.c
> +++ b/fs/sync.c
> @@ -87,6 +87,8 @@ long do_fsync(struct file *file, int datasync)
> goto out;
> }
>
> + mapping_update_time(mapping);
> +
> ret = filemap_fdatawrite(mapping);
>
> /*
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index b3ec4a4..1dccd4b 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -1977,7 +1977,14 @@ extern int buffer_migrate_page(struct address_space *,
> extern int inode_change_ok(struct inode *, struct iattr *);
> extern int __must_check inode_setattr(struct inode *, struct iattr *);
>
> -extern void file_update_time(struct file *file);
> +extern void inode_update_time(struct inode *);
> +
> +static inline void file_update_time(struct file *file)
> +{
> + inode_update_time(file->f_path.dentry->d_inode);
> +}
> +
> +extern void mapping_update_time(struct address_space *);
>
> static inline ino_t parent_ino(struct dentry *dentry)
> {
> diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
> index db8a410..bf0f9e7 100644
> --- a/include/linux/pagemap.h
> +++ b/include/linux/pagemap.h
> @@ -17,8 +17,9 @@
> * Bits in mapping->flags. The lower __GFP_BITS_SHIFT bits are the page
> * allocation mode flags.
> */
> -#define AS_EIO (__GFP_BITS_SHIFT + 0) /* IO error on async write */
> +#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_MCTIME (__GFP_BITS_SHIFT + 2) /* mtime and ctime to update */
>
> static inline void mapping_set_error(struct address_space *mapping, int error)
> {
> diff --git a/mm/msync.c b/mm/msync.c
> index ff654c9..07dc8fc 100644
> --- a/mm/msync.c
> +++ b/mm/msync.c
> @@ -5,6 +5,7 @@
> * Copyright (C) 1994-1999 Linus Torvalds
> *
> * Substantial code cleanup.
> + * Updating the ctime and mtime stamps for memory-mapped files.
> * Copyright (C) 2008 Anton Salikhmetov <salikhmetov@...il.com>
> */
>
> @@ -22,6 +23,10 @@
> * 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.
> *
> + * The msync() system call updates the ctime and mtime fields for
> + * the mapped file when called with the MS_SYNC or MS_ASYNC flags
> + * according to the POSIX standard.
> + *
> * 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 fadvise(FADV_DONTNEED) against the fd to start
> @@ -76,14 +81,17 @@ asmlinkage long sys_msync(unsigned long start, size_t len, int flags)
> break;
> }
> file = vma->vm_file;
> - if ((flags & MS_SYNC) && file && (vma->vm_flags & VM_SHARED)) {
> - get_file(file);
> - up_read(&mm->mmap_sem);
> - error = do_fsync(file, 0);
> - fput(file);
> - if (error)
> - return error;
> - down_read(&mm->mmap_sem);
> + if (file && (vma->vm_flags & VM_SHARED)) {
> + mapping_update_time(file->f_mapping);
> + if (flags & MS_SYNC) {
> + get_file(file);
> + up_read(&mm->mmap_sem);
> + error = do_fsync(file, 0);
> + fput(file);
> + if (error)
> + return error;
> + down_read(&mm->mmap_sem);
> + }
> }
>
> start = vma->vm_end;
> diff --git a/mm/page-writeback.c b/mm/page-writeback.c
> index d55cfca..a85df0b 100644
> --- a/mm/page-writeback.c
> +++ b/mm/page-writeback.c
> @@ -1025,6 +1025,7 @@ int __set_page_dirty_nobuffers(struct page *page)
> if (mapping->host) {
> /* !PageAnon && !swapper_space */
> __mark_inode_dirty(mapping->host, I_DIRTY_PAGES);
> + set_bit(AS_MCTIME, &mapping->flags);
> }
> return 1;
> }
> --
> 1.4.4.4
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