[PATCH v3 2/2] iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc()
From: David Howells <dhowells@redhat.com>
Date: 2023-08-16 12:09:37
Also in:
linux-fsdevel, linux-mm, lkml
Subsystem:
library code, the rest, userspace copyin/copyout (uiovec) · Maintainers:
Andrew Morton, Linus Torvalds, Alexander Viro
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(), --- lib/iov_iter.c | 39 +++++++++++++++++++++++++++------------ 1 file changed, 27 insertions(+), 12 deletions(-)
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 378da0cb3069..33febccadd9d 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c@@ -450,14 +450,33 @@ 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) +{ + size_t progress; + + if (unlikely(i->count < bytes)) + bytes = i->count; + if (unlikely(!bytes)) + return 0; + progress = iterate_bvec(i, bytes, addr, NULL, memcpy_from_iter_mc); + i->count -= progress; + return progress; +} + +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)
@@ -467,9 +486,7 @@ 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);
@@ -690,9 +707,7 @@ 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); + __copy_from_iter(p, n, i); kunmap_atomic(p); copied += n; offset += n;