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From: Miklos Szeredi <miklos@szeredi.hu>
To: staubach@redhat.com
Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org,
	linux-fsdevel@vger.kernel.org
Subject: Re: [patch 01/22] update ctime and mtime for mmaped write
Date: Wed, 28 Feb 2007 18:06:38 +0100	[thread overview]
Message-ID: <E1HMSGE-000886-00@dorka.pomaz.szeredi.hu> (raw)
In-Reply-To: <45E58EB8.6030502@redhat.com> (message from Peter Staubach on Wed, 28 Feb 2007 09:16:24 -0500)

> These change still have the undesirable property that although the
> modified pages may be flushed to stable storage, the metadata on
> the file will not be updated until the application takes positive
> action.  This is permissible given the current wording in the
> specifications, but it would be much more desirable if sync(2),
> fsync(P), or the inode being written out due to normal system
> activity would also cause the metadata to be updated.
> 
> Perhaps the setting of the flag could be checked in some places
> like __sync_single_inode() and do_fsync()?

I don't see the point in updating the timestamp from these functions.

The file isn't _modified_ by sync() or fsync().  Just as it's not
modified by stat().

sync() and fsync() do cache->disk, while the file itself stays the
same.

OTOH msync(MS_ASYNC) does memory->file, which is a conceptually file
modifying operation.  OK, msync(MS_ASYNC) is actually a no-op on
2.6.18+, but that's purely an implementation detail and no application
should be relying on it.

Before 2.6.18 sync() or fsync() acually didn't flush data written
through a shared mapping to disk, only msync(MS_SYNC), because the
dirty state was only available in the page tables, not in the page or
the inode.

Miklos

  reply	other threads:[~2007-02-28 17:07 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-02-27 23:14 [patch 00/22] misc VFS/VM patches and fuse writable shared mapping support Miklos Szeredi
2007-02-27 23:14 ` [patch 01/22] update ctime and mtime for mmaped write Miklos Szeredi
2007-02-28 14:16   ` Peter Staubach
2007-02-28 17:06     ` Miklos Szeredi [this message]
2007-02-28 17:21       ` Peter Staubach
2007-02-28 17:51         ` Miklos Szeredi
2007-02-28 20:01           ` Peter Staubach
2007-02-28 20:35             ` Miklos Szeredi
2007-02-28 20:58               ` Miklos Szeredi
2007-02-28 21:09                 ` Peter Staubach
2007-03-01  7:25                   ` Miklos Szeredi
2007-02-27 23:14 ` [patch 02/22] fix quadratic behavior of shrink_dcache_parent() Miklos Szeredi
2007-02-27 23:14 ` [patch 03/22] fix deadlock in balance_dirty_pages Miklos Szeredi
2007-02-27 23:14 ` [patch 04/22] fix deadlock in throttle_vm_writeout Miklos Szeredi
2007-02-27 23:14 ` [patch 05/22] balance dirty pages from loop device Miklos Szeredi
2007-02-27 23:14 ` [patch 06/22] consolidate generic_writepages and mpage_writepages Miklos Szeredi
2007-02-27 23:14 ` [patch 07/22] add filesystem subtype support Miklos Szeredi
2007-02-27 23:14 ` [patch 08/22] fuse: update backing_dev_info congestion state Miklos Szeredi
2007-02-27 23:14 ` [patch 09/22] fuse: fix reserved request wake up Miklos Szeredi
2007-02-27 23:14 ` [patch 10/22] fuse: add reference counting to fuse_file Miklos Szeredi
2007-02-27 23:14 ` [patch 11/22] fuse: add truncation semaphore Miklos Szeredi
2007-02-27 23:14 ` [patch 12/22] fuse: fix page invalidation Miklos Szeredi
2007-02-27 23:14 ` [patch 13/22] fuse: add list of writable files to fuse_inode Miklos Szeredi
2007-02-27 23:14 ` [patch 14/22] fuse: add helper for asynchronous writes Miklos Szeredi
2007-02-27 23:14 ` [patch 15/22] add non-owner variant of down_read_trylock() Miklos Szeredi
2007-02-27 23:14 ` [patch 16/22] fuse: add fuse_writepage() function Miklos Szeredi
2007-02-27 23:14 ` [patch 17/22] fuse: writable shared mmap support Miklos Szeredi
2007-02-27 23:15 ` [patch 18/22] fuse: add fuse_writepages() function Miklos Szeredi
2007-02-27 23:15 ` [patch 19/22] export sync_sb() to modules Miklos Szeredi
2007-02-27 23:15 ` [patch 20/22] fuse: make dirty stats available Miklos Szeredi
2007-02-27 23:15 ` [patch 21/22] fuse: limit dirty pages Miklos Szeredi
2007-02-27 23:15 ` [patch 22/22] fuse: allow big write requests Miklos Szeredi

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