On Thu, Nov 29, 2012 at 2:45 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: > On Wed, Nov 28, 2012 at 10:37:27PM -0800, Linus Torvalds wrote: >> On Wed, Nov 28, 2012 at 10:30 PM, Al Viro <viro@xxxxxxxxxxxxxxxxxx> wrote: >> > >> > Note that sync_blockdev() a few lines prior to that is good only if we >> > have no other processes doing write(2) (or dirtying the mmapped pages, >> > for that matter). The window isn't too wide, but... >> >> So with Mikulas' patches, the write actually would block (at write >> level) due to the locking. The mmap'ed patches may be around and >> flushed, but the logic to not allow currently *active* mmaps (with the >> rather nasty random -EBUSY return value) should mean that there is no >> race. >> >> Or rather, there's a race, but it results in that EBUSY thing. > > Same as with fs mounted on it, or the sucker having been claimed for > RAID array, etc. Frankly, I'm more than slightly tempted to make > bdev mmap() just claim the sodding device exclusive for as long as > it's mmapped... > > In principle, I agree, but... I still have nightmares from mmap/truncate > races way back. You are stepping into what used to be a really nasty > minefield. I'll look into that, but it's *definitely* not -rc8 fodder. Just let me know which relevant patch(es) you want me to test or break. Thanks, Jeff -- 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
