From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Wed, 21 Feb 2007 20:26:15 -0800 From: Andrew Morton Subject: Re: [PATCH] update ctime and mtime for mmaped write Message-Id: <20070221202615.a0a167f4.akpm@linux-foundation.org> In-Reply-To: References: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Miklos Szeredi Cc: staubach@redhat.com, hugh@veritas.com, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-ID: On Wed, 21 Feb 2007 18:51:52 +0100 Miklos Szeredi wrote: > 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. Why is the flag checked in __fput()? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org