coredump: always chunk writes

Right now dump_emit() is the only coredump helper that writes buffers
larger than a page in one call. For elf notes that can easily blow past
PAGE_SIZE. That's annoying because neither pipes nor af_unix sockets
take such writes in one piece.

If a signal arrives while the writer is waiting they drop a short write.
With the coredump records work coming up that means header and its data
are desynchronized. A write that fits in one pipe buffer or one skb
doesn't suffer from this.

So split all writes up, including elf notes, and cap every write at a
page. The coredump socket already raises sk_sndbuf far enough for a page
to fit a single skb and pipes always work that way.

That means dump_interrupted() is now checked once per page. So a large
coredump stops earlier (good). An empty write no longer issues a
zero-length write. The rlimit core check stays where it was. It
continues refusing whole writes.

Link: https://patch.msgid.link/20260820-work-coredump-sparse-v2-11-ba32dd718c51@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

0 files changed, 0 insertions, 0 deletions