Sorry for delay, On 02/06, Hugh Dickins wrote: > > On Sun, 3 Feb 2008, Oleg Nesterov wrote: > > > mmap_region() checks "file != NULL" when we know "file && vma_merge() == T". > > Also, swap these if/else branches, imho make the code a bit more readable. > > > > Signed-off-by: Oleg Nesterov <[EMAIL PROTECTED]> > > Acked-with-a-but-by: Hugh Dickins <[EMAIL PROTECTED]> > > But my but is this: you can go one step further, it's silly to be > repeating the "if (correct_wcount) atomic_inc..." in both the if > and the else clauses.
Ah. Shame on me. Of course, I noticed these 2 correct_wcount's, but didn't realize we can safely use "inode" after fput(). Not only the caller should have a reference, vma_merge() requires that vm_file == file, so fput(file) can't destroy the last reference. > For several minutes I thought that must indicate we already had a > bug there. Eventually I realized not: we need deny_write_access() > above to test and deny atomically, then once we've merged or linked > the vma it's securely denying in the vma itself: so before returning > we need to undo our temporary denial. A brief comment might be > worthwhile, perhaps something like > > /* Once vma denies write, undo our temporary denial count */ > if (correct_wcount) > atomic_inc(&inode->i_writecount); Thanks Hugh, I'll redo this cleanup. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
