Sorry for delay, On 02/06, Hugh Dickins wrote: > > On Sun, 3 Feb 2008, Oleg Nesterov wrote: > > Off-topic question to all. sys_remap_file_pages() doesn't work with > > shared readonly mappings, why? > > Slight correction: it works with shared readonly mappings, doesn't > it, so long as the mmap'ed file was opened for reading and writing?
Yes sure. I meant, if the file was opened without FMODE_WRITE, then mmap(PROT_READ, MAP_SHARED) doesn't actually set VM_SHARED, it only sets VM_MAYSHARE. (this looks understandable, but means that !VM_SHARED doesn't necessary imply the possible cow). > > IOW, why it checks VM_SHARED but not VM_MAYSHARE? > > My guess has always been that it was just a misunderstanding of how > those VM_ flags end up working: assume so unless Ingo corrects me. > > By the time I realized that oddity, we'd been driven into several > tiresome corners by the very existence of sys_remap_file_pages. > So whereas my usual instinct would have been to relax the restriction > and generalize, in its case I wanted to hold on to every restriction > we had. OK, thanks a lot. I was afraid I missed some "obvious" reason why we can't do this. 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/
