[PATCH] Fix some problems with truncate and mtime semantics.

SUS requires that when truncating a file to the size that it currently
is:
  truncate and ftruncate should NOT modify ctime or mtime
  O_TRUNC SHOULD modify ctime and mtime.

Currently mtime and ctime are always modified on most local
filesystems (side effect of ->truncate) or never modified (on NFS).

With this patch:
  ATTR_CTIME|ATTR_MTIME are sent with ATTR_SIZE precisely when
    an update of these times is required whether size changes or not
    (via a new argument to do_truncate).  This allows NFS to do
    the right thing for O_TRUNC.
  inode_setattr nolonger forces ATTR_MTIME|ATTR_CTIME when the ATTR_SIZE
    sets the size to it's current value.  This allows local filesystems
    to do the right thing for f?truncate.

Also, the logic in inode_setattr is changed a bit so there are two return
points.  One returns the error from vmtruncate if it failed, the other
returns 0 (there can be no other failure).

Finally, if vmtruncate succeeds, and ATTR_SIZE is the only change
requested, we now fall-through and mark_inode_dirty.  If a filesystem did
not have a ->truncate function, then vmtruncate will have changed i_size,
without marking the inode as 'dirty', and I think this is wrong.

Signed-off-by: Neil Brown <neilb@suse.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Trond Myklebust <trond.myklebust@fys.uio.no>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 1 insertions, 1 deletions

diff --git a/fs/exec.c b/fs/exec.c
index e9650cd22a3b..2075b674d85e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1505,7 +1505,7 @@ int do_coredump(long signr, int exit_code, struct pt_regs * regs)
 		goto close_fail;
 	if (!file->f_op->write)
 		goto close_fail;
-	if (do_truncate(file->f_dentry, 0, file) != 0)
+	if (do_truncate(file->f_dentry, 0, 0, file) != 0)
 		goto close_fail;
 
 	retval = binfmt->core_dump(signr, regs, file);