From c9eec08bac96898573c236af9cb0ccee765684fc Mon Sep 17 00:00:00 2001 From: David Howells Date: Mon, 25 Sep 2023 13:03:05 +0100 Subject: [PATCH] iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc() iter->copy_mc is only used with a bvec iterator and only by dump_emit_page() in fs/coredump.c so rather than handle this in memcpy_from_iter_mc() where it is checked repeatedly by _copy_from_iter() and copy_page_from_iter_atomic(), Signed-off-by: David Howells Link: https://lore.kernel.org/r/20230925120309.1731676-9-dhowells@redhat.com cc: Alexander Viro cc: Jens Axboe cc: Christoph Hellwig cc: Christian Brauner cc: Matthew Wilcox cc: Linus Torvalds cc: David Laight cc: linux-block@vger.kernel.org cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org Signed-off-by: Christian Brauner --- lib/iov_iter.c | 35 +++++++++++++++++++++++------------ 1 file changed, 23 insertions(+), 12 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 65374ee91ecd..0a7160aa4e31 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -253,14 +253,29 @@ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i) EXPORT_SYMBOL_GPL(_copy_mc_to_iter); #endif /* CONFIG_ARCH_HAS_COPY_MC */ -static size_t memcpy_from_iter_mc(void *iter_from, size_t progress, - size_t len, void *to, void *priv2) +static __always_inline +size_t memcpy_from_iter_mc(void *iter_from, size_t progress, + size_t len, void *to, void *priv2) { - struct iov_iter *iter = priv2; + return copy_mc_to_kernel(to + progress, iter_from, len); +} - if (iov_iter_is_copy_mc(iter)) - return copy_mc_to_kernel(to + progress, iter_from, len); - return memcpy_from_iter(iter_from, progress, len, to, priv2); +static size_t __copy_from_iter_mc(void *addr, size_t bytes, struct iov_iter *i) +{ + if (unlikely(i->count < bytes)) + bytes = i->count; + if (unlikely(!bytes)) + return 0; + return iterate_bvec(i, bytes, addr, NULL, memcpy_from_iter_mc); +} + +static __always_inline +size_t __copy_from_iter(void *addr, size_t bytes, struct iov_iter *i) +{ + if (unlikely(iov_iter_is_copy_mc(i))) + return __copy_from_iter_mc(addr, bytes, i); + return iterate_and_advance(i, bytes, addr, + copy_from_user_iter, memcpy_from_iter); } size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i) @@ -270,9 +285,7 @@ size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i) if (user_backed_iter(i)) might_fault(); - return iterate_and_advance2(i, bytes, addr, i, - copy_from_user_iter, - memcpy_from_iter_mc); + return __copy_from_iter(addr, bytes, i); } EXPORT_SYMBOL(_copy_from_iter); @@ -493,9 +506,7 @@ size_t copy_page_from_iter_atomic(struct page *page, size_t offset, } p = kmap_atomic(page) + offset; - n = iterate_and_advance2(i, n, p, i, - copy_from_user_iter, - memcpy_from_iter_mc); + n = __copy_from_iter(p, n, i); kunmap_atomic(p); copied += n; offset += n;