On Wed, 21 Feb 2007 18:51:52 +0100 Miklos Szeredi <miklos@xxxxxxxxxx> 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 from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
