By mistake the ITER_PIPE early-exit / warning from copy_from_iter() was
cargo-culted in _copy_to_iter_mcsafe() rather than a machine-check-safe
version of copy_to_iter_pipe().
Implement copy_pipe_to_iter_mcsafe() being careful to return the
indication of short copies due to a CPU exception.
Without this regression-fix all splice reads to dax-mode files fail.
Fixes: 8780356ef630 ("x86/asm/memcpy_mcsafe: Define copy_to_iter_mcsafe()")
Cc: Al Viro <[email protected]>
Cc: Andrew Morton <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Luck <[email protected]>
Reported-by: Ross Zwisler <[email protected]>
Signed-off-by: Dan Williams <[email protected]>
---
Hi Ingo,
I'm submitting this fix back through the tip tree since the regression
originated through tip/x86/dax.
lib/iov_iter.c | 37 +++++++++++++++++++++++++++++++++----
1 file changed, 33 insertions(+), 4 deletions(-)
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 7e43cd54c84c..d4c5de8d6fba 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -596,15 +596,44 @@ static unsigned long memcpy_mcsafe_to_page(struct page
*page, size_t offset,
return ret;
}
+static size_t copy_pipe_to_iter_mcsafe(const void *addr, size_t bytes,
+ struct iov_iter *i)
+{
+ struct pipe_inode_info *pipe = i->pipe;
+ size_t n, off, xfer = 0;
+ int idx;
+
+ if (!sanity(i))
+ return 0;
+
+ bytes = n = push_pipe(i, bytes, &idx, &off);
+ if (unlikely(!n))
+ return 0;
+ for ( ; n; idx = next_idx(idx, pipe), off = 0) {
+ size_t chunk = min_t(size_t, n, PAGE_SIZE - off);
+ unsigned long rem;
+
+ rem = memcpy_mcsafe_to_page(pipe->bufs[idx].page, off, addr,
+ chunk);
+ i->idx = idx;
+ i->iov_offset = off + chunk - rem;
+ xfer += chunk - rem;
+ if (rem)
+ break;
+ n -= chunk;
+ addr += chunk;
+ }
+ i->count -= xfer;
+ return xfer;
+}
+
size_t _copy_to_iter_mcsafe(const void *addr, size_t bytes, struct iov_iter *i)
{
const char *from = addr;
unsigned long rem, curr_addr, s_addr = (unsigned long) addr;
- if (unlikely(i->type & ITER_PIPE)) {
- WARN_ON(1);
- return 0;
- }
+ if (unlikely(i->type & ITER_PIPE))
+ return copy_pipe_to_iter_mcsafe(addr, bytes, i);
if (iter_is_iovec(i))
might_fault();
iterate_and_advance(i, bytes, v,
