On Fri, 16 Mar 2007 08:44:46 +0200 "Pekka Enberg" <[EMAIL PROTECTED]> wrote:
> On 3/16/07, Andrew Morton <[EMAIL PROTECTED]> wrote: > > Why is this code using invalidate_inode_pages2()? That function keeps on > > breaking, has ill-defined semantics and will probably change in the future. > > > > Exactly what semantics are you looking for here, and why? > > What the comment says "make pending reads fail." When revoking an > inode, we need to make sure there are no pending I/O that will > complete after revocation and thus leak information. hm, let's define "pending". I assume that any future callers to sys_read() will reliably do the right thing at this stage, so we are concerned with threads which are presently partway through a read from this inode? If that's not accurate then please describe with some detail exactly what semantics you're looking for here. If it _is_ accurate then hm, tricky. It all rather depends upon how the relevant filesystem implements reading (and writing?). Which is why you made it a file_operation, fair enough. But even for ext2 and ext3 (please keep ext4 in sync with ext3 changes, btw), if some process is partway through a big page_cache_readahead() operation then a concurrent invalidate_inode_pages2() call won't worry it at all: the pagecache will be reinstantiated and do_generic_mapping_read() will proceed to copy that pagecache out to the user after the revoke() has returned. I think. I'm afraid I havent paid any attention to this revoke proposal before, I don't understand the usecases nor the implementation details so things which are implicitly-obvious-to-you must be explained to me. But others will benefit from that explanation too ;) What, exactly, are we trying to do with the already-opened files and the currently-in-progress syscalls? (A concurrent direct-io read might be a problem too?) - 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/
