On Wed, 2007-02-21 at 18:51 +0100, Miklos Szeredi wrote:

From: Miklos Szeredi <redacted>

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

Why not also check inside vfs_getattr?

Cheers
  Trond

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