kernel.git/mm/iov_iter.c, branch linux-3.18.y

Fix thinko in iov_iter_single_seg_count

2014-11-13T18:28:55Z

The branches of the if (i->type & ITER_BVEC) statement in iov_iter_single_seg_count() are the wrong way around; if ITER_BVEC is clear then we use i->bvec, when we should be using i->iov. This fixes it. In my case, the symptom that this caused was that a KVM guest doing filesystem operations on a virtual disk would result in one of qemu's threads on the host going into an infinite loop in generic_perform_write(). The loop would hit the copied == 0 case and call iov_iter_single_seg_count() to reduce the number of bytes to try to process, but because of the error, iov_iter_single_seg_count() would just return i->count and the loop made no progress and continued forever. Cc: stable@vger.kernel.org # 3.16+ Signed-off-by: Paul Mackerras Signed-off-by: Al Viro

Add copy_to_iter(), copy_from_iter() and iov_iter_zero()

2014-10-09T06:39:03Z

For DAX, we want to be able to copy between iovecs and kernel addresses that don't necessarily have a struct page. This is a fairly simple rearrangement for bvec iters to kmap the pages outside and pass them in, but for user iovecs it gets more complicated because we might try various different ways to kmap the memory. Duplicating the existing logic works out best in this case. We need to be able to write zeroes to an iovec for reads from unwritten ranges in a file. This is performed by the new iov_iter_zero() function, again patterned after the existing code that handles iovec iterators. [AV: and export the buggers...] Signed-off-by: Matthew Wilcox Signed-off-by: Al Viro

fuse: honour max_read and max_write in direct_io mode

2014-09-27T01:16:51Z

The third argument of fuse_get_user_pages() "nbytesp" refers to the number of bytes a caller asked to pack into fuse request. This value may be lesser than capacity of fuse request or iov_iter. So fuse_get_user_pages() must ensure that *nbytesp won't grow. Now, when helper iov_iter_get_pages() performs all hard work of extracting pages from iov_iter, it can be done by passing properly calculated "maxsize" to the helper. The other caller of iov_iter_get_pages() (dio_refill_pages()) doesn't need this capability, so pass LONG_MAX as the maxsize argument here. Fixes: c9c37e2e6378 ("fuse: switch to iov_iter_get_pages()") Reported-by: Werner Baumann Tested-by: Maxim Patlasov Signed-off-by: Miklos Szeredi Signed-off-by: Al Viro

switch iov_iter_get_pages() to passing maximal number of pages

2014-08-07T18:40:11Z

... instead of maximal size. Signed-off-by: Al Viro

bio_vec-backed iov_iter

2014-05-06T21:39:45Z

New variant of iov_iter - ITER_BVEC in iter->type, backed with bio_vec array instead of iovec one. Primitives taught to deal with such beasts, __swap_write() switched to using that kind of iov_iter. Note that bio_vec is just a triple - there's nothing block-specific about it. I've left the definition where it was, but took it from under ifdef CONFIG_BLOCK. Next target: ->splice_write()... Signed-off-by: Al Viro

optimize copy_page_{to,from}_iter()

2014-05-06T21:39:45Z

if we'd ended up in the end of a segment, jump to the beginning of the next one (iov_offset = 0, iov++), rather than having the next primitive deal with that. Ought to be folded back... Signed-off-by: Al Viro

new helper: copy_page_from_iter()

2014-05-06T21:39:42Z

parallel to copy_page_to_iter(). pipe_write() switched to it (and became ->write_iter()). Signed-off-by: Al Viro

new helper: iov_iter_get_pages_alloc()

2014-05-06T21:32:53Z

same as iov_iter_get_pages(), except that pages array is allocated (kmalloc if possible, vmalloc if that fails) and left for caller to free. Lustre and NFS ->direct_IO() switched to it. Signed-off-by: Al Viro

new helper: iov_iter_npages()

2014-05-06T21:32:52Z

counts the pages covered by iov_iter, up to given limit. do_block_direct_io() and fuse_iter_npages() switched to it. Signed-off-by: Al Viro

new helper: iov_iter_get_pages()

2014-05-06T21:32:50Z

iov_iter_get_pages(iter, pages, maxsize, &start) grabs references pinning the pages of up to maxsize of (contiguous) data from iter. Returns the amount of memory grabbed or -error. In case of success, the requested area begins at offset start in pages[0] and runs through pages[1], etc. Less than requested amount might be returned - either because the contiguous area in the beginning of iterator is smaller than requested, or because the kernel failed to pin that many pages. direct-io.c switched to using iov_iter_get_pages() Signed-off-by: Al Viro