On Tue, 28 Jan 2014 23:01:26 +0200 "Kirill A. Shutemov" <[email protected]> wrote:
> On Tue, Jan 28, 2014 at 12:03:01PM -0800, Andrew Morton wrote: > > On Tue, 28 Jan 2014 11:14:19 +0000 Mark Rutland <[email protected]> > > wrote: > > > > > Commit 63d0f0a3c7e1 (mm/readahead.c:do_readhead(): don't check for > > > ->readpage) unintentionally made do_readahead return 0 for all valid > > > files regardless of whether readahead was supported, rather than the > > > expected -EINVAL. This gets forwarded on to userspace, and results in > > > sys_readahead appearing to succeed in cases that don't make sense (e.g. > > > when called on pipes or sockets). This issue is detected by the LTP > > > readahead01 testcase. > > > > How can this be? > > > > : static ssize_t > > : do_readahead(struct address_space *mapping, struct file *filp, > > : pgoff_t index, unsigned long nr) > > : { > > : if (!mapping || !mapping->a_ops) > > : return -EINVAL; > > : > > : return force_page_cache_readahead(mapping, filp, index, nr); > > It's not what we have in Linus' tree. force_page_cache_readahead() return > code is unused: > > force_page_cache_readahead(mapping, filp, index, nr); > return 0; > ah, oops, I was looking at the code with Mark's patch applied. Yes, the force_page_cache_readahead() return value should be propagated. And I guess the lobotomising of the force_page_cache_readahead() return value is OK. force_page_cache_readahead() presently returns an errno even if it has performed some reads. A read()-style function shouldn't do that - it should return a short read in that case. -- 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/
