[PATCH v6 00/13] iov_iter: Convert the iterator macros into inline funcs

[PATCH v6 00/13] iov_iter: Convert the iterator macros into inline funcs

[David Howells]

Hi Jens,

Could you take these patches into the block tree?  The patches convert the
iov_iter iteration macros to be inline functions.

 (1) Remove last_offset from iov_iter as it was only used by ITER_PIPE.

 (2) Add a __user tag on copy_mc_to_user()'s dst argument on x86 to match
     that on powerpc and get rid of a sparse warning.

 (3) Convert iter->user_backed to user_backed_iter() in the sound PCM
     driver.

 (4) Convert iter->user_backed to user_backed_iter() in a couple of
     infiniband drivers.

 (5) Renumber the type enum so that the ITER_* constants match the order in
     iterate_and_advance*().

 (6) Since the preceding patch puts UBUF and IOVEC at 0 and 1, change
     user_backed_iter() to just use the type value and get rid of the extra
     flag.

 (7) Convert the iov_iter iteration macros to always-inline functions to
     make the code easier to follow.  It uses function pointers, but they
     get optimised away.  The priv2 argument likewise gets optimised away
     if unused.

     The functions are placed into a header file so that bespoke iterators
     can be created elsewhere.  For instance, rbd has an optimisation that
     requires it to scan to the buffer it is given to see if it is all
     zeros.  It would be nice if this could use iterate_and_advance() - but
     that's currently buried inside lib/iov_iter.c.

     Whilst we could provide a generic iteration function that takes a pair
     of function pointers instead, it does add around 16% overhead in the
     framework, presumably from the combination of function pointers and
     various mitigations.

     Further, if it is known that just a particular iterator-type is in
     play, just that iteration function can be used.

 (8) Move the check for ->copy_mc to _copy_from_iter() and
     copy_page_from_iter_atomic() rather than in memcpy_from_iter_mc()
     where it gets repeated for every segment.  Instead, we check once and
     invoke a side function that can use iterate_bvec() rather than
     iterate_and_advance() and supply a different step function.

 (9) Provide a cut-down iteration function that only handles kernel-backed
     iterators (ie. BVEC, KVEC, XARRAY and DISCARD) for situations where we
     know that we won't see UBUF/IOVEC.  This crops up in a number of
     filesystems where we decant a UBUF/IOVEC iter into a series of BVEC
     iters.

(10) Move the copy-and-csum code to net/ where it can be in proximity with
     the code that uses it.  This eliminates the code if CONFIG_NET=n and
     allows for the slim possibility of it being inlined.

(11) Fold memcpy_and_csum() in to its two users.

(12) Move csum_and_copy_from_iter_full() out of line and merge in
     csum_and_copy_from_iter() since the former is the only caller of the
     latter.

(13) Move hash_and_copy_to_iter() to net/ where it can be with its only
     caller.

Anyway, the changes in compiled function size either side of patches
(5)+(6) on x86_64 look like:

	__copy_from_iter_mc                      new 0xe8
	_copy_from_iter                          inc 0x360 -> 0x3a7 +0x47
	_copy_from_iter_flushcache               inc 0x34c -> 0x38e +0x42
	_copy_from_iter_nocache                  inc 0x354 -> 0x378 +0x24
	_copy_mc_to_iter                         inc 0x396 -> 0x3f1 +0x5b
	_copy_to_iter                            inc 0x33b -> 0x385 +0x4a
	copy_page_from_iter_atomic.part.0        inc 0x393 -> 0x3e0 +0x4d
	copy_page_to_iter_nofault.part.0         inc 0x3de -> 0x3eb +0xd
	copyin                                   del 0x30
	copyout                                  del 0x2d
	copyout_mc                               del 0x2b
	csum_and_copy_from_iter                  inc 0x3db -> 0x41d +0x42
	csum_and_copy_to_iter                    inc 0x45d -> 0x48d +0x30
	iov_iter_zero                            inc 0x34a -> 0x36a +0x20
	memcpy_from_iter.isra.0                  del 0x1f

Note that there's a noticeable expansion on some of the main functions
because a number of the helpers get inlined instead of being called.

In terms of benchmarking patch (5)+(6), three runs without them:

	iov_kunit_benchmark_ubuf: avg 3955 uS, stddev 169 uS
	iov_kunit_benchmark_ubuf: avg 4122 uS, stddev 1292 uS
	iov_kunit_benchmark_ubuf: avg 4451 uS, stddev 1362 uS
	iov_kunit_benchmark_iovec: avg 6607 uS, stddev 22 uS
	iov_kunit_benchmark_iovec: avg 6608 uS, stddev 19 uS
	iov_kunit_benchmark_iovec: avg 6609 uS, stddev 24 uS
	iov_kunit_benchmark_bvec: avg 3166 uS, stddev 11 uS
	iov_kunit_benchmark_bvec: avg 3167 uS, stddev 13 uS
	iov_kunit_benchmark_bvec: avg 3170 uS, stddev 16 uS
	iov_kunit_benchmark_bvec_split: avg 3394 uS, stddev 12 uS
	iov_kunit_benchmark_bvec_split: avg 3394 uS, stddev 20 uS
	iov_kunit_benchmark_bvec_split: avg 3395 uS, stddev 19 uS
	iov_kunit_benchmark_kvec: avg 2672 uS, stddev 12 uS
	iov_kunit_benchmark_kvec: avg 2672 uS, stddev 12 uS
	iov_kunit_benchmark_kvec: avg 2672 uS, stddev 9 uS
	iov_kunit_benchmark_xarray: avg 3719 uS, stddev 9 uS
	iov_kunit_benchmark_xarray: avg 3719 uS, stddev 9 uS
	iov_kunit_benchmark_xarray: avg 3721 uS, stddev 24 uS

and three runs with them:

	iov_kunit_benchmark_ubuf: avg 4110 uS, stddev 1254 uS
	iov_kunit_benchmark_ubuf: avg 4141 uS, stddev 1411 uS
	iov_kunit_benchmark_ubuf: avg 4572 uS, stddev 1889 uS
	iov_kunit_benchmark_iovec: avg 6582 uS, stddev 27 uS
	iov_kunit_benchmark_iovec: avg 6585 uS, stddev 25 uS
	iov_kunit_benchmark_iovec: avg 6586 uS, stddev 48 uS
	iov_kunit_benchmark_bvec: avg 3175 uS, stddev 13 uS
	iov_kunit_benchmark_bvec: avg 3177 uS, stddev 12 uS
	iov_kunit_benchmark_bvec: avg 3178 uS, stddev 12 uS
	iov_kunit_benchmark_bvec_split: avg 3380 uS, stddev 20 uS
	iov_kunit_benchmark_bvec_split: avg 3384 uS, stddev 15 uS
	iov_kunit_benchmark_bvec_split: avg 3386 uS, stddev 25 uS
	iov_kunit_benchmark_kvec: avg 2671 uS, stddev 11 uS
	iov_kunit_benchmark_kvec: avg 2672 uS, stddev 12 uS
	iov_kunit_benchmark_kvec: avg 2677 uS, stddev 20 uS
	iov_kunit_benchmark_xarray: avg 3599 uS, stddev 20 uS
	iov_kunit_benchmark_xarray: avg 3603 uS, stddev 8 uS
	iov_kunit_benchmark_xarray: avg 3610 uS, stddev 16 uS

I've pushed the patches here also:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-cleanup

David

Changes
=======
ver #6)
 - Rebase on v6.6-rc2 rather than on my iov-kunit branch.
 - Add a patch to remove last_offset from iov_iter.
 - Add a patch to tag copy_mc_to_user() with __user on x86.
 - Document the priv2 arg of iterate_and_advance_kernel().

ver #5)
 - Moved kunit test patches out to a separate set.
 - Moved "iter->count - progress" into individual iteration subfunctions.
 - Fix iterate_iovec() and to update iter->__iovec after subtracting it to
   calculate iter->nr_segs.
 - Merged the function inlining patch and the move-to-header patch.
 - Rearranged the patch order slightly to put the patches to move
   networking stuff to net/ last.
 - Went back to a simpler patch to special-case ->copy_mc in
   _copy_from_iter() and copy_page_from_iter_atomic() before we get to call
   iterate_and_advance() so as to reduce the number of checks for this.

ver #4)
 - Fix iterate_bvec() and iterate_kvec() to update iter->bvec and
   iter->kvec after subtracting it to calculate iter->nr_segs.
 - Change iterate_xarray() to use start+progress rather than increasing
   start to reduce code size.
 - Added patches to move some iteration functions over to net/ as the files
   there can #include the iterator framework.
 - Added a patch to benchmark the iteration.
 - Tried an experimental patch to make copy_from_iter() and similar always
   catch MCE.

ver #3)
 - Use min_t(size_t,) not min() to avoid a warning on Hexagon.
 - Inline all the step functions.
 - Added a patch to better handle copy_mc.

ver #2)
 - Rebased on top of Willy's changes in linux-next.
 - Change the checksum argument to the iteration functions to be a general
   void* and use it to pass iter->copy_mc flag to memcpy_from_iter_mc() to
   avoid using a function pointer.
 - Arrange the end of the iterate_*() functions to look the same to give
   the optimiser the best chance.
 - Make iterate_and_advance() a wrapper around iterate_and_advance2().
 - Adjust iterate_and_advance2() to use if-else-if-else-if-else rather than
   switch(), to put ITER_BVEC before KVEC and to mark UBUF and IOVEC as
   likely().
 - Move "iter->count += progress" into iterate_and_advance2() from the
   iterate functions.
 - Mark a number of the iterator helpers with __always_inline.
 - Fix _copy_from_iter_flushcache() to use memcpy_from_iter_flushcache()
   not memcpy_from_iter().

Link: https://lore.kernel.org/r/3710261.1691764329@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/855.1692047347@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/20230816120741.534415-1-dhowells@redhat.com/ # v3
Link: https://lore.kernel.org/r/20230913165648.2570623-1-dhowells@redhat.com/ # v4
Link: https://lore.kernel.org/r/20230920222231.686275-1-dhowells@redhat.com/ # v5

David Howells (13):
  iov_iter: Remove last_offset from iov_iter as it was for ITER_PIPE
  iov_iter: Be consistent about the __user tag on copy_mc_to_user()
  sound: Fix snd_pcm_readv()/writev() to use iov access functions
  infiniband: Use user_backed_iter() to see if iterator is UBUF/IOVEC
  iov_iter: Renumber ITER_* constants
  iov_iter: Derive user-backedness from the iterator type
  iov_iter: Convert iterate*() to inline funcs
  iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc()
  iov_iter: Add a kernel-type iterator-only iteration function
  iov_iter, net: Move csum_and_copy_to/from_iter() to net/
  iov_iter, net: Fold in csum_and_memcpy()
  iov_iter, net: Merge csum_and_copy_from_iter{,_full}() together
  iov_iter, net: Move hash_and_copy_to_iter() to net/

 arch/x86/include/asm/uaccess.h           |   2 +-
 arch/x86/lib/copy_mc.c                   |   8 +-
 drivers/infiniband/hw/hfi1/file_ops.c    |   2 +-
 drivers/infiniband/hw/qib/qib_file_ops.c |   2 +-
 include/linux/iov_iter.h                 | 306 ++++++++++++++++
 include/linux/skbuff.h                   |   3 +
 include/linux/uio.h                      |  34 +-
 lib/iov_iter.c                           | 441 +++++++----------------
 net/core/datagram.c                      |  75 +++-
 net/core/skbuff.c                        |  40 ++
 sound/core/pcm_native.c                  |   4 +-
 11 files changed, 576 insertions(+), 341 deletions(-)
 create mode 100644 include/linux/iov_iter.h

[PATCH v6 01/13] iov_iter: Remove last_offset from iov_iter as it was for ITER_PIPE

[David Howells]

Now that ITER_PIPE has been removed, iov_iter::last_offset is no longer
used, so remove it.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---
 include/linux/uio.h | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 42bce38a8e87..2000e42a6586 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -44,10 +44,7 @@ struct iov_iter {
 	bool nofault;
 	bool data_source;
 	bool user_backed;
-	union {
-		size_t iov_offset;
-		int last_offset;
-	};
+	size_t iov_offset;
 	/*
 	 * Hack alert: overlay ubuf_iovec with iovec + count, so
 	 * that the members resolve correctly regardless of the type

[PATCH v6 02/13] iov_iter: Be consistent about the __user tag on copy_mc_to_user()

[David Howells]

copy_mc_to_user() has the destination marked __user on powerpc, but not on
x86; the latter results in a sparse warning in lib/iov_iter.c.

Fix this by applying the tag on x86 too.

Fixes: ec6347bb4339 ("x86, powerpc: Rename memcpy_mcsafe() to copy_mc_to_{user, kernel}()")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Dan Williams <dan.j.williams@intel.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---
 arch/x86/include/asm/uaccess.h | 2 +-
 arch/x86/lib/copy_mc.c         | 8 ++++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/uaccess.h b/arch/x86/include/asm/uaccess.h
index 8bae40a66282..5c367c1290c3 100644
--- a/arch/x86/include/asm/uaccess.h
+++ b/arch/x86/include/asm/uaccess.h
@@ -496,7 +496,7 @@ copy_mc_to_kernel(void *to, const void *from, unsigned len);
 #define copy_mc_to_kernel copy_mc_to_kernel
 
 unsigned long __must_check
-copy_mc_to_user(void *to, const void *from, unsigned len);
+copy_mc_to_user(void __user *to, const void *from, unsigned len);
 #endif
 
 /*
diff --git a/arch/x86/lib/copy_mc.c b/arch/x86/lib/copy_mc.c
index 80efd45a7761..6e8b7e600def 100644
--- a/arch/x86/lib/copy_mc.c
+++ b/arch/x86/lib/copy_mc.c
@@ -70,23 +70,23 @@ unsigned long __must_check copy_mc_to_kernel(void *dst, const void *src, unsigne
 }
 EXPORT_SYMBOL_GPL(copy_mc_to_kernel);
 
-unsigned long __must_check copy_mc_to_user(void *dst, const void *src, unsigned len)
+unsigned long __must_check copy_mc_to_user(void __user *dst, const void *src, unsigned len)
 {
 	unsigned long ret;
 
 	if (copy_mc_fragile_enabled) {
 		__uaccess_begin();
-		ret = copy_mc_fragile(dst, src, len);
+		ret = copy_mc_fragile((__force void *)dst, src, len);
 		__uaccess_end();
 		return ret;
 	}
 
 	if (static_cpu_has(X86_FEATURE_ERMS)) {
 		__uaccess_begin();
-		ret = copy_mc_enhanced_fast_string(dst, src, len);
+		ret = copy_mc_enhanced_fast_string((__force void *)dst, src, len);
 		__uaccess_end();
 		return ret;
 	}
 
-	return copy_user_generic(dst, src, len);
+	return copy_user_generic((__force void *)dst, src, len);
 }

[PATCH v6 03/13] sound: Fix snd_pcm_readv()/writev() to use iov access functions

[David Howells]

Fix snd_pcm_readv()/writev() to use iov access functions rather than poking
at the iov_iter internals directly.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Reviewed-by: Takashi Iwai <tiwai@suse.de>
cc: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
cc: Jens Axboe <axboe@kernel.dk>
cc: Suren Baghdasaryan <surenb@google.com>
cc: Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>
cc: alsa-devel@alsa-project.org
---
 sound/core/pcm_native.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index bd9ddf412b46..9a69236fa207 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -3527,7 +3527,7 @@ static ssize_t snd_pcm_readv(struct kiocb *iocb, struct iov_iter *to)
 	if (runtime->state == SNDRV_PCM_STATE_OPEN ||
 	    runtime->state == SNDRV_PCM_STATE_DISCONNECTED)
 		return -EBADFD;
-	if (!to->user_backed)
+	if (!user_backed_iter(to))
 		return -EINVAL;
 	if (to->nr_segs > 1024 || to->nr_segs != runtime->channels)
 		return -EINVAL;
@@ -3567,7 +3567,7 @@ static ssize_t snd_pcm_writev(struct kiocb *iocb, struct iov_iter *from)
 	if (runtime->state == SNDRV_PCM_STATE_OPEN ||
 	    runtime->state == SNDRV_PCM_STATE_DISCONNECTED)
 		return -EBADFD;
-	if (!from->user_backed)
+	if (!user_backed_iter(from))
 		return -EINVAL;
 	if (from->nr_segs > 128 || from->nr_segs != runtime->channels ||
 	    !frame_aligned(runtime, iov->iov_len))

[PATCH v6 04/13] infiniband: Use user_backed_iter() to see if iterator is UBUF/IOVEC

[David Howells]

Use user_backed_iter() to see if iterator is UBUF/IOVEC rather than poking
inside the iterator.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
cc: Jason Gunthorpe <jgg@ziepe.ca>
cc: Leon Romanovsky <leon@kernel.org>
cc: linux-rdma@vger.kernel.org
---
 drivers/infiniband/hw/hfi1/file_ops.c    | 2 +-
 drivers/infiniband/hw/qib/qib_file_ops.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/infiniband/hw/hfi1/file_ops.c b/drivers/infiniband/hw/hfi1/file_ops.c
index a5ab22cedd41..788fc249234f 100644
--- a/drivers/infiniband/hw/hfi1/file_ops.c
+++ b/drivers/infiniband/hw/hfi1/file_ops.c
@@ -267,7 +267,7 @@ static ssize_t hfi1_write_iter(struct kiocb *kiocb, struct iov_iter *from)
 
 	if (!HFI1_CAP_IS_KSET(SDMA))
 		return -EINVAL;
-	if (!from->user_backed)
+	if (!user_backed_iter(from))
 		return -EINVAL;
 	idx = srcu_read_lock(&fd->pq_srcu);
 	pq = srcu_dereference(fd->pq, &fd->pq_srcu);
diff --git a/drivers/infiniband/hw/qib/qib_file_ops.c b/drivers/infiniband/hw/qib/qib_file_ops.c
index 152952127f13..29e4c59aa23b 100644
--- a/drivers/infiniband/hw/qib/qib_file_ops.c
+++ b/drivers/infiniband/hw/qib/qib_file_ops.c
@@ -2244,7 +2244,7 @@ static ssize_t qib_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	struct qib_ctxtdata *rcd = ctxt_fp(iocb->ki_filp);
 	struct qib_user_sdma_queue *pq = fp->pq;
 
-	if (!from->user_backed || !from->nr_segs || !pq)
+	if (!user_backed_iter(from) || !from->nr_segs || !pq)
 		return -EINVAL;
 
 	return qib_user_sdma_writev(rcd, pq, iter_iov(from), from->nr_segs);

[PATCH v6 05/13] iov_iter: Renumber ITER_* constants

[David Howells]

Renumber the ITER_* iterator-type constants to put things in the same order
as in the iteration functions and to group user-backed iterators at the
bottom.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---
 include/linux/uio.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 2000e42a6586..bef8e56aa45c 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -21,12 +21,12 @@ struct kvec {
 
 enum iter_type {
 	/* iter types */
+	ITER_UBUF,
 	ITER_IOVEC,
-	ITER_KVEC,
 	ITER_BVEC,
+	ITER_KVEC,
 	ITER_XARRAY,
 	ITER_DISCARD,
-	ITER_UBUF,
 };
 
 #define ITER_SOURCE	1	// == WRITE

[PATCH v6 06/13] iov_iter: Derive user-backedness from the iterator type

[David Howells]

Use the iterator type to determine whether an iterator is user-backed or
not rather than using a special flag for it.  Now that ITER_UBUF and
ITER_IOVEC are 0 and 1, they can be checked with a single comparison.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---
 include/linux/uio.h | 4 +---
 lib/iov_iter.c      | 1 -
 2 files changed, 1 insertion(+), 4 deletions(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index bef8e56aa45c..65d9143f83c8 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -43,7 +43,6 @@ struct iov_iter {
 	bool copy_mc;
 	bool nofault;
 	bool data_source;
-	bool user_backed;
 	size_t iov_offset;
 	/*
 	 * Hack alert: overlay ubuf_iovec with iovec + count, so
@@ -140,7 +139,7 @@ static inline unsigned char iov_iter_rw(const struct iov_iter *i)
 
 static inline bool user_backed_iter(const struct iov_iter *i)
 {
-	return i->user_backed;
+	return iter_is_ubuf(i) || iter_is_iovec(i);
 }
 
 /*
@@ -380,7 +379,6 @@ static inline void iov_iter_ubuf(struct iov_iter *i, unsigned int direction,
 	*i = (struct iov_iter) {
 		.iter_type = ITER_UBUF,
 		.copy_mc = false,
-		.user_backed = true,
 		.data_source = direction,
 		.ubuf = buf,
 		.count = count,
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 27234a820eeb..227c9f536b94 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -290,7 +290,6 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
 		.iter_type = ITER_IOVEC,
 		.copy_mc = false,
 		.nofault = false,
-		.user_backed = true,
 		.data_source = direction,
 		.__iov = iov,
 		.nr_segs = nr_segs,

[PATCH v6 07/13] iov_iter: Convert iterate*() to inline funcs

[David Howells]

Convert the iov_iter iteration macros to inline functions to make the code
easier to follow.

The functions are marked __always_inline as we don't want to end up with
indirect calls in the code.  This, however, leaves dealing with ->copy_mc
in an awkard situation since the step function (memcpy_from_iter_mc())
needs to test the flag in the iterator, but isn't passed the iterator.
This will be dealt with in a follow-up patch.

The variable names in the per-type iterator functions have been harmonised
as much as possible and made clearer as to the variable purpose.

The iterator functions are also moved to a header file so that other
operations that need to scan over an iterator can be added.  For instance,
the rbd driver could use this to scan a buffer to see if it is all zeros
and libceph could use this to generate a crc.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
Link: https://lore.kernel.org/r/3710261.1691764329@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/855.1692047347@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/20230816120741.534415-1-dhowells@redhat.com/ # v3
---

Notes:
    Changes
    =======
    ver #5)
     - Merge in patch to move iteration framework to a header file.
     - Move "iter->count - progress" into individual iteration subfunctions.

 include/linux/iov_iter.h | 274 ++++++++++++++++++++++++++
 lib/iov_iter.c           | 416 ++++++++++++++++-----------------------
 2 files changed, 449 insertions(+), 241 deletions(-)
 create mode 100644 include/linux/iov_iter.h

diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h
new file mode 100644
index 000000000000..270454a6703d
--- /dev/null
+++ b/include/linux/iov_iter.h
@@ -0,0 +1,274 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/* I/O iterator iteration building functions.
+ *
+ * Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#ifndef _LINUX_IOV_ITER_H
+#define _LINUX_IOV_ITER_H
+
+#include <linux/uio.h>
+#include <linux/bvec.h>
+
+typedef size_t (*iov_step_f)(void *iter_base, size_t progress, size_t len,
+			     void *priv, void *priv2);
+typedef size_t (*iov_ustep_f)(void __user *iter_base, size_t progress, size_t len,
+			      void *priv, void *priv2);
+
+/*
+ * Handle ITER_UBUF.
+ */
+static __always_inline
+size_t iterate_ubuf(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		    iov_ustep_f step)
+{
+	void __user *base = iter->ubuf;
+	size_t progress = 0, remain;
+
+	remain = step(base + iter->iov_offset, 0, len, priv, priv2);
+	progress = len - remain;
+	iter->iov_offset += progress;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_IOVEC.
+ */
+static __always_inline
+size_t iterate_iovec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		     iov_ustep_f step)
+{
+	const struct iovec *p = iter->__iov;
+	size_t progress = 0, skip = iter->iov_offset;
+
+	do {
+		size_t remain, consumed;
+		size_t part = min(len, p->iov_len - skip);
+
+		if (likely(part)) {
+			remain = step(p->iov_base + skip, progress, part, priv, priv2);
+			consumed = part - remain;
+			progress += consumed;
+			skip += consumed;
+			len -= consumed;
+			if (skip < p->iov_len)
+				break;
+		}
+		p++;
+		skip = 0;
+	} while (len);
+
+	iter->nr_segs -= p - iter->__iov;
+	iter->__iov = p;
+	iter->iov_offset = skip;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_KVEC.
+ */
+static __always_inline
+size_t iterate_kvec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		    iov_step_f step)
+{
+	const struct kvec *p = iter->kvec;
+	size_t progress = 0, skip = iter->iov_offset;
+
+	do {
+		size_t remain, consumed;
+		size_t part = min(len, p->iov_len - skip);
+
+		if (likely(part)) {
+			remain = step(p->iov_base + skip, progress, part, priv, priv2);
+			consumed = part - remain;
+			progress += consumed;
+			skip += consumed;
+			len -= consumed;
+			if (skip < p->iov_len)
+				break;
+		}
+		p++;
+		skip = 0;
+	} while (len);
+
+	iter->nr_segs -= p - iter->kvec;
+	iter->kvec = p;
+	iter->iov_offset = skip;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_BVEC.
+ */
+static __always_inline
+size_t iterate_bvec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		    iov_step_f step)
+{
+	const struct bio_vec *p = iter->bvec;
+	size_t progress = 0, skip = iter->iov_offset;
+
+	do {
+		size_t remain, consumed;
+		size_t offset = p->bv_offset + skip, part;
+		void *kaddr = kmap_local_page(p->bv_page + offset / PAGE_SIZE);
+
+		part = min3(len,
+			   (size_t)(p->bv_len - skip),
+			   (size_t)(PAGE_SIZE - offset % PAGE_SIZE));
+		remain = step(kaddr + offset % PAGE_SIZE, progress, part, priv, priv2);
+		kunmap_local(kaddr);
+		consumed = part - remain;
+		len -= consumed;
+		progress += consumed;
+		skip += consumed;
+		if (skip >= p->bv_len) {
+			skip = 0;
+			p++;
+		}
+		if (remain)
+			break;
+	} while (len);
+
+	iter->nr_segs -= p - iter->bvec;
+	iter->bvec = p;
+	iter->iov_offset = skip;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_XARRAY.
+ */
+static __always_inline
+size_t iterate_xarray(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		      iov_step_f step)
+{
+	struct folio *folio;
+	size_t progress = 0;
+	loff_t start = iter->xarray_start + iter->iov_offset;
+	pgoff_t index = start / PAGE_SIZE;
+	XA_STATE(xas, iter->xarray, index);
+
+	rcu_read_lock();
+	xas_for_each(&xas, folio, ULONG_MAX) {
+		size_t remain, consumed, offset, part, flen;
+
+		if (xas_retry(&xas, folio))
+			continue;
+		if (WARN_ON(xa_is_value(folio)))
+			break;
+		if (WARN_ON(folio_test_hugetlb(folio)))
+			break;
+
+		offset = offset_in_folio(folio, start + progress);
+		flen = min(folio_size(folio) - offset, len);
+
+		while (flen) {
+			void *base = kmap_local_folio(folio, offset);
+
+			part = min_t(size_t, flen,
+				     PAGE_SIZE - offset_in_page(offset));
+			remain = step(base, progress, part, priv, priv2);
+			kunmap_local(base);
+
+			consumed = part - remain;
+			progress += consumed;
+			len -= consumed;
+
+			if (remain || len == 0)
+				goto out;
+			flen -= consumed;
+			offset += consumed;
+		}
+	}
+
+out:
+	rcu_read_unlock();
+	iter->iov_offset += progress;
+	iter->count -= progress;
+	return progress;
+}
+
+/*
+ * Handle ITER_DISCARD.
+ */
+static __always_inline
+size_t iterate_discard(struct iov_iter *iter, size_t len, void *priv, void *priv2,
+		      iov_step_f step)
+{
+	size_t progress = len;
+
+	iter->count -= progress;
+	return progress;
+}
+
+/**
+ * iterate_and_advance2 - Iterate over an iterator
+ * @iter: The iterator to iterate over.
+ * @len: The amount to iterate over.
+ * @priv: Data for the step functions.
+ * @priv2: More data for the step functions.
+ * @ustep: Function for UBUF/IOVEC iterators; given __user addresses.
+ * @step: Function for other iterators; given kernel addresses.
+ *
+ * Iterate over the next part of an iterator, up to the specified length.  The
+ * buffer is presented in segments, which for kernel iteration are broken up by
+ * physical pages and mapped, with the mapped address being presented.
+ *
+ * Two step functions, @step and @ustep, must be provided, one for handling
+ * mapped kernel addresses and the other is given user addresses which have the
+ * potential to fault since no pinning is performed.
+ *
+ * The step functions are passed the address and length of the segment, @priv,
+ * @priv2 and the amount of data so far iterated over (which can, for example,
+ * be added to @priv to point to the right part of a second buffer).  The step
+ * functions should return the amount of the segment they didn't process (ie. 0
+ * indicates complete processsing).
+ *
+ * This function returns the amount of data processed (ie. 0 means nothing was
+ * processed and the value of @len means processes to completion).
+ */
+static __always_inline
+size_t iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv,
+			    void *priv2, iov_ustep_f ustep, iov_step_f step)
+{
+	if (unlikely(iter->count < len))
+		len = iter->count;
+	if (unlikely(!len))
+		return 0;
+
+	if (likely(iter_is_ubuf(iter)))
+		return iterate_ubuf(iter, len, priv, priv2, ustep);
+	if (likely(iter_is_iovec(iter)))
+		return iterate_iovec(iter, len, priv, priv2, ustep);
+	if (iov_iter_is_bvec(iter))
+		return iterate_bvec(iter, len, priv, priv2, step);
+	if (iov_iter_is_kvec(iter))
+		return iterate_kvec(iter, len, priv, priv2, step);
+	if (iov_iter_is_xarray(iter))
+		return iterate_xarray(iter, len, priv, priv2, step);
+	return iterate_discard(iter, len, priv, priv2, step);
+}
+
+/**
+ * iterate_and_advance - Iterate over an iterator
+ * @iter: The iterator to iterate over.
+ * @len: The amount to iterate over.
+ * @priv: Data for the step functions.
+ * @ustep: Function for UBUF/IOVEC iterators; given __user addresses.
+ * @step: Function for other iterators; given kernel addresses.
+ *
+ * As iterate_and_advance2(), but priv2 is always NULL.
+ */
+static __always_inline
+size_t iterate_and_advance(struct iov_iter *iter, size_t len, void *priv,
+			   iov_ustep_f ustep, iov_step_f step)
+{
+	return iterate_and_advance2(iter, len, priv, NULL, ustep, step);
+}
+
+#endif /* _LINUX_IOV_ITER_H */
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 227c9f536b94..65374ee91ecd 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -13,189 +13,69 @@
 #include <net/checksum.h>
 #include <linux/scatterlist.h>
 #include <linux/instrumented.h>
+#include <linux/iov_iter.h>
 
-/* covers ubuf and kbuf alike */
-#define iterate_buf(i, n, base, len, off, __p, STEP) {		\
-	size_t __maybe_unused off = 0;				\
-	len = n;						\
-	base = __p + i->iov_offset;				\
-	len -= (STEP);						\
-	i->iov_offset += len;					\
-	n = len;						\
-}
-
-/* covers iovec and kvec alike */
-#define iterate_iovec(i, n, base, len, off, __p, STEP) {	\
-	size_t off = 0;						\
-	size_t skip = i->iov_offset;				\
-	do {							\
-		len = min(n, __p->iov_len - skip);		\
-		if (likely(len)) {				\
-			base = __p->iov_base + skip;		\
-			len -= (STEP);				\
-			off += len;				\
-			skip += len;				\
-			n -= len;				\
-			if (skip < __p->iov_len)		\
-				break;				\
-		}						\
-		__p++;						\
-		skip = 0;					\
-	} while (n);						\
-	i->iov_offset = skip;					\
-	n = off;						\
-}
-
-#define iterate_bvec(i, n, base, len, off, p, STEP) {		\
-	size_t off = 0;						\
-	unsigned skip = i->iov_offset;				\
-	while (n) {						\
-		unsigned offset = p->bv_offset + skip;		\
-		unsigned left;					\
-		void *kaddr = kmap_local_page(p->bv_page +	\
-					offset / PAGE_SIZE);	\
-		base = kaddr + offset % PAGE_SIZE;		\
-		len = min(min(n, (size_t)(p->bv_len - skip)),	\
-		     (size_t)(PAGE_SIZE - offset % PAGE_SIZE));	\
-		left = (STEP);					\
-		kunmap_local(kaddr);				\
-		len -= left;					\
-		off += len;					\
-		skip += len;					\
-		if (skip == p->bv_len) {			\
-			skip = 0;				\
-			p++;					\
-		}						\
-		n -= len;					\
-		if (left)					\
-			break;					\
-	}							\
-	i->iov_offset = skip;					\
-	n = off;						\
-}
-
-#define iterate_xarray(i, n, base, len, __off, STEP) {		\
-	__label__ __out;					\
-	size_t __off = 0;					\
-	struct folio *folio;					\
-	loff_t start = i->xarray_start + i->iov_offset;		\
-	pgoff_t index = start / PAGE_SIZE;			\
-	XA_STATE(xas, i->xarray, index);			\
-								\
-	len = PAGE_SIZE - offset_in_page(start);		\
-	rcu_read_lock();					\
-	xas_for_each(&xas, folio, ULONG_MAX) {			\
-		unsigned left;					\
-		size_t offset;					\
-		if (xas_retry(&xas, folio))			\
-			continue;				\
-		if (WARN_ON(xa_is_value(folio)))		\
-			break;					\
-		if (WARN_ON(folio_test_hugetlb(folio)))		\
-			break;					\
-		offset = offset_in_folio(folio, start + __off);	\
-		while (offset < folio_size(folio)) {		\
-			base = kmap_local_folio(folio, offset);	\
-			len = min(n, len);			\
-			left = (STEP);				\
-			kunmap_local(base);			\
-			len -= left;				\
-			__off += len;				\
-			n -= len;				\
-			if (left || n == 0)			\
-				goto __out;			\
-			offset += len;				\
-			len = PAGE_SIZE;			\
-		}						\
-	}							\
-__out:								\
-	rcu_read_unlock();					\
-	i->iov_offset += __off;					\
-	n = __off;						\
-}
-
-#define __iterate_and_advance(i, n, base, len, off, I, K) {	\
-	if (unlikely(i->count < n))				\
-		n = i->count;					\
-	if (likely(n)) {					\
-		if (likely(iter_is_ubuf(i))) {			\
-			void __user *base;			\
-			size_t len;				\
-			iterate_buf(i, n, base, len, off,	\
-						i->ubuf, (I)) 	\
-		} else if (likely(iter_is_iovec(i))) {		\
-			const struct iovec *iov = iter_iov(i);	\
-			void __user *base;			\
-			size_t len;				\
-			iterate_iovec(i, n, base, len, off,	\
-						iov, (I))	\
-			i->nr_segs -= iov - iter_iov(i);	\
-			i->__iov = iov;				\
-		} else if (iov_iter_is_bvec(i)) {		\
-			const struct bio_vec *bvec = i->bvec;	\
-			void *base;				\
-			size_t len;				\
-			iterate_bvec(i, n, base, len, off,	\
-						bvec, (K))	\
-			i->nr_segs -= bvec - i->bvec;		\
-			i->bvec = bvec;				\
-		} else if (iov_iter_is_kvec(i)) {		\
-			const struct kvec *kvec = i->kvec;	\
-			void *base;				\
-			size_t len;				\
-			iterate_iovec(i, n, base, len, off,	\
-						kvec, (K))	\
-			i->nr_segs -= kvec - i->kvec;		\
-			i->kvec = kvec;				\
-		} else if (iov_iter_is_xarray(i)) {		\
-			void *base;				\
-			size_t len;				\
-			iterate_xarray(i, n, base, len, off,	\
-							(K))	\
-		}						\
-		i->count -= n;					\
-	}							\
-}
-#define iterate_and_advance(i, n, base, len, off, I, K) \
-	__iterate_and_advance(i, n, base, len, off, I, ((void)(K),0))
-
-static int copyout(void __user *to, const void *from, size_t n)
+static __always_inline
+size_t copy_to_user_iter(void __user *iter_to, size_t progress,
+			 size_t len, void *from, void *priv2)
 {
 	if (should_fail_usercopy())
-		return n;
-	if (access_ok(to, n)) {
-		instrument_copy_to_user(to, from, n);
-		n = raw_copy_to_user(to, from, n);
+		return len;
+	if (access_ok(iter_to, len)) {
+		from += progress;
+		instrument_copy_to_user(iter_to, from, len);
+		len = raw_copy_to_user(iter_to, from, len);
 	}
-	return n;
+	return len;
 }
 
-static int copyout_nofault(void __user *to, const void *from, size_t n)
+static __always_inline
+size_t copy_to_user_iter_nofault(void __user *iter_to, size_t progress,
+				 size_t len, void *from, void *priv2)
 {
-	long res;
+	ssize_t res;
 
 	if (should_fail_usercopy())
-		return n;
-
-	res = copy_to_user_nofault(to, from, n);
+		return len;
 
-	return res < 0 ? n : res;
+	from += progress;
+	res = copy_to_user_nofault(iter_to, from, len);
+	return res < 0 ? len : res;
 }
 
-static int copyin(void *to, const void __user *from, size_t n)
+static __always_inline
+size_t copy_from_user_iter(void __user *iter_from, size_t progress,
+			   size_t len, void *to, void *priv2)
 {
-	size_t res = n;
+	size_t res = len;
 
 	if (should_fail_usercopy())
-		return n;
-	if (access_ok(from, n)) {
-		instrument_copy_from_user_before(to, from, n);
-		res = raw_copy_from_user(to, from, n);
-		instrument_copy_from_user_after(to, from, n, res);
+		return len;
+	if (access_ok(iter_from, len)) {
+		to += progress;
+		instrument_copy_from_user_before(to, iter_from, len);
+		res = raw_copy_from_user(to, iter_from, len);
+		instrument_copy_from_user_after(to, iter_from, len, res);
 	}
 	return res;
 }
 
+static __always_inline
+size_t memcpy_to_iter(void *iter_to, size_t progress,
+		      size_t len, void *from, void *priv2)
+{
+	memcpy(iter_to, from + progress, len);
+	return 0;
+}
+
+static __always_inline
+size_t memcpy_from_iter(void *iter_from, size_t progress,
+			size_t len, void *to, void *priv2)
+{
+	memcpy(to + progress, iter_from, len);
+	return 0;
+}
+
 /*
  * fault_in_iov_iter_readable - fault in iov iterator for reading
  * @i: iterator
@@ -312,23 +192,29 @@ size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 		return 0;
 	if (user_backed_iter(i))
 		might_fault();
-	iterate_and_advance(i, bytes, base, len, off,
-		copyout(base, addr + off, len),
-		memcpy(base, addr + off, len)
-	)
-
-	return bytes;
+	return iterate_and_advance(i, bytes, (void *)addr,
+				   copy_to_user_iter, memcpy_to_iter);
 }
 EXPORT_SYMBOL(_copy_to_iter);
 
 #ifdef CONFIG_ARCH_HAS_COPY_MC
-static int copyout_mc(void __user *to, const void *from, size_t n)
-{
-	if (access_ok(to, n)) {
-		instrument_copy_to_user(to, from, n);
-		n = copy_mc_to_user((__force void *) to, from, n);
+static __always_inline
+size_t copy_to_user_iter_mc(void __user *iter_to, size_t progress,
+			    size_t len, void *from, void *priv2)
+{
+	if (access_ok(iter_to, len)) {
+		from += progress;
+		instrument_copy_to_user(iter_to, from, len);
+		len = copy_mc_to_user(iter_to, from, len);
 	}
-	return n;
+	return len;
+}
+
+static __always_inline
+size_t memcpy_to_iter_mc(void *iter_to, size_t progress,
+			 size_t len, void *from, void *priv2)
+{
+	return copy_mc_to_kernel(iter_to, from + progress, len);
 }
 
 /**
@@ -361,22 +247,20 @@ size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 		return 0;
 	if (user_backed_iter(i))
 		might_fault();
-	__iterate_and_advance(i, bytes, base, len, off,
-		copyout_mc(base, addr + off, len),
-		copy_mc_to_kernel(base, addr + off, len)
-	)
-
-	return bytes;
+	return iterate_and_advance(i, bytes, (void *)addr,
+				   copy_to_user_iter_mc, memcpy_to_iter_mc);
 }
 EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
 #endif /* CONFIG_ARCH_HAS_COPY_MC */
 
-static void *memcpy_from_iter(struct iov_iter *i, void *to, const void *from,
-				 size_t size)
+static size_t memcpy_from_iter_mc(void *iter_from, size_t progress,
+				  size_t len, void *to, void *priv2)
 {
-	if (iov_iter_is_copy_mc(i))
-		return (void *)copy_mc_to_kernel(to, from, size);
-	return memcpy(to, from, size);
+	struct iov_iter *iter = priv2;
+
+	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);
 }
 
 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
@@ -386,30 +270,46 @@ size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
 
 	if (user_backed_iter(i))
 		might_fault();
-	iterate_and_advance(i, bytes, base, len, off,
-		copyin(addr + off, base, len),
-		memcpy_from_iter(i, addr + off, base, len)
-	)
-
-	return bytes;
+	return iterate_and_advance2(i, bytes, addr, i,
+				    copy_from_user_iter,
+				    memcpy_from_iter_mc);
 }
 EXPORT_SYMBOL(_copy_from_iter);
 
+static __always_inline
+size_t copy_from_user_iter_nocache(void __user *iter_from, size_t progress,
+				   size_t len, void *to, void *priv2)
+{
+	return __copy_from_user_inatomic_nocache(to + progress, iter_from, len);
+}
+
 size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
 {
 	if (WARN_ON_ONCE(!i->data_source))
 		return 0;
 
-	iterate_and_advance(i, bytes, base, len, off,
-		__copy_from_user_inatomic_nocache(addr + off, base, len),
-		memcpy(addr + off, base, len)
-	)
-
-	return bytes;
+	return iterate_and_advance(i, bytes, addr,
+				   copy_from_user_iter_nocache,
+				   memcpy_from_iter);
 }
 EXPORT_SYMBOL(_copy_from_iter_nocache);
 
 #ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
+static __always_inline
+size_t copy_from_user_iter_flushcache(void __user *iter_from, size_t progress,
+				      size_t len, void *to, void *priv2)
+{
+	return __copy_from_user_flushcache(to + progress, iter_from, len);
+}
+
+static __always_inline
+size_t memcpy_from_iter_flushcache(void *iter_from, size_t progress,
+				   size_t len, void *to, void *priv2)
+{
+	memcpy_flushcache(to + progress, iter_from, len);
+	return 0;
+}
+
 /**
  * _copy_from_iter_flushcache - write destination through cpu cache
  * @addr: destination kernel address
@@ -431,12 +331,9 @@ size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
 	if (WARN_ON_ONCE(!i->data_source))
 		return 0;
 
-	iterate_and_advance(i, bytes, base, len, off,
-		__copy_from_user_flushcache(addr + off, base, len),
-		memcpy_flushcache(addr + off, base, len)
-	)
-
-	return bytes;
+	return iterate_and_advance(i, bytes, addr,
+				   copy_from_user_iter_flushcache,
+				   memcpy_from_iter_flushcache);
 }
 EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
 #endif
@@ -508,10 +405,9 @@ size_t copy_page_to_iter_nofault(struct page *page, unsigned offset, size_t byte
 		void *kaddr = kmap_local_page(page);
 		size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
 
-		iterate_and_advance(i, n, base, len, off,
-			copyout_nofault(base, kaddr + offset + off, len),
-			memcpy(base, kaddr + offset + off, len)
-		)
+		n = iterate_and_advance(i, bytes, kaddr,
+					copy_to_user_iter_nofault,
+					memcpy_to_iter);
 		kunmap_local(kaddr);
 		res += n;
 		bytes -= n;
@@ -554,14 +450,25 @@ size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 }
 EXPORT_SYMBOL(copy_page_from_iter);
 
-size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
+static __always_inline
+size_t zero_to_user_iter(void __user *iter_to, size_t progress,
+			 size_t len, void *priv, void *priv2)
 {
-	iterate_and_advance(i, bytes, base, len, count,
-		clear_user(base, len),
-		memset(base, 0, len)
-	)
+	return clear_user(iter_to, len);
+}
 
-	return bytes;
+static __always_inline
+size_t zero_to_iter(void *iter_to, size_t progress,
+		    size_t len, void *priv, void *priv2)
+{
+	memset(iter_to, 0, len);
+	return 0;
+}
+
+size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
+{
+	return iterate_and_advance(i, bytes, NULL,
+				   zero_to_user_iter, zero_to_iter);
 }
 EXPORT_SYMBOL(iov_iter_zero);
 
@@ -586,10 +493,9 @@ size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
 		}
 
 		p = kmap_atomic(page) + offset;
-		iterate_and_advance(i, n, base, len, off,
-			copyin(p + off, base, len),
-			memcpy_from_iter(i, p + off, base, len)
-		)
+		n = iterate_and_advance2(i, n, p, i,
+					 copy_from_user_iter,
+					 memcpy_from_iter_mc);
 		kunmap_atomic(p);
 		copied += n;
 		offset += n;
@@ -1180,32 +1086,64 @@ ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
 }
 EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
 
+static __always_inline
+size_t copy_from_user_iter_csum(void __user *iter_from, size_t progress,
+				size_t len, void *to, void *priv2)
+{
+	__wsum next, *csum = priv2;
+
+	next = csum_and_copy_from_user(iter_from, to + progress, len);
+	*csum = csum_block_add(*csum, next, progress);
+	return next ? 0 : len;
+}
+
+static __always_inline
+size_t memcpy_from_iter_csum(void *iter_from, size_t progress,
+			     size_t len, void *to, void *priv2)
+{
+	__wsum *csum = priv2;
+
+	*csum = csum_and_memcpy(to + progress, iter_from, len, *csum, progress);
+	return 0;
+}
+
 size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
 			       struct iov_iter *i)
 {
-	__wsum sum, next;
-	sum = *csum;
 	if (WARN_ON_ONCE(!i->data_source))
 		return 0;
-
-	iterate_and_advance(i, bytes, base, len, off, ({
-		next = csum_and_copy_from_user(base, addr + off, len);
-		sum = csum_block_add(sum, next, off);
-		next ? 0 : len;
-	}), ({
-		sum = csum_and_memcpy(addr + off, base, len, sum, off);
-	})
-	)
-	*csum = sum;
-	return bytes;
+	return iterate_and_advance2(i, bytes, addr, csum,
+				    copy_from_user_iter_csum,
+				    memcpy_from_iter_csum);
 }
 EXPORT_SYMBOL(csum_and_copy_from_iter);
 
+static __always_inline
+size_t copy_to_user_iter_csum(void __user *iter_to, size_t progress,
+			      size_t len, void *from, void *priv2)
+{
+	__wsum next, *csum = priv2;
+
+	next = csum_and_copy_to_user(from + progress, iter_to, len);
+	*csum = csum_block_add(*csum, next, progress);
+	return next ? 0 : len;
+}
+
+static __always_inline
+size_t memcpy_to_iter_csum(void *iter_to, size_t progress,
+			   size_t len, void *from, void *priv2)
+{
+	__wsum *csum = priv2;
+
+	*csum = csum_and_memcpy(iter_to, from + progress, len, *csum, progress);
+	return 0;
+}
+
 size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
 			     struct iov_iter *i)
 {
 	struct csum_state *csstate = _csstate;
-	__wsum sum, next;
+	__wsum sum;
 
 	if (WARN_ON_ONCE(i->data_source))
 		return 0;
@@ -1219,14 +1157,10 @@ size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
 	}
 
 	sum = csum_shift(csstate->csum, csstate->off);
-	iterate_and_advance(i, bytes, base, len, off, ({
-		next = csum_and_copy_to_user(addr + off, base, len);
-		sum = csum_block_add(sum, next, off);
-		next ? 0 : len;
-	}), ({
-		sum = csum_and_memcpy(base, addr + off, len, sum, off);
-	})
-	)
+	
+	bytes = iterate_and_advance2(i, bytes, (void *)addr, &sum,
+				     copy_to_user_iter_csum,
+				     memcpy_to_iter_csum);
 	csstate->csum = csum_shift(sum, csstate->off);
 	csstate->off += bytes;
 	return bytes;

[PATCH v6 08/13] iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc()

[David Howells]

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 65374ee91ecd..943aa3cfd7b3 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -253,14 +253,33 @@ 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)
+{
+	return copy_mc_to_kernel(to + progress, iter_from, len);
+}
+
+static size_t __copy_from_iter_mc(void *addr, size_t bytes, struct iov_iter *i)
 {
-	struct iov_iter *iter = priv2;
+	size_t progress;
 
-	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);
+	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)
@@ -270,9 +289,7 @@ 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 +510,7 @@ 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;

[PATCH v6 09/13] iov_iter: Add a kernel-type iterator-only iteration function

[David Howells]

Add an iteration function that can only iterate over kernel internal-type
iterators (ie. BVEC, KVEC, XARRAY) and not user-backed iterators (ie. UBUF
and IOVEC).  This allows for smaller iterators to be built when it is known
the caller won't have a user-backed iterator.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---

Notes:
    Changes
    =======
    ver #6)
     - Document the priv2 arg of iterate_and_advance_kernel().

 include/linux/iov_iter.h | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h
index 270454a6703d..d8733dc22b54 100644
--- a/include/linux/iov_iter.h
+++ b/include/linux/iov_iter.h
@@ -271,4 +271,36 @@ size_t iterate_and_advance(struct iov_iter *iter, size_t len, void *priv,
 	return iterate_and_advance2(iter, len, priv, NULL, ustep, step);
 }
 
+/**
+ * iterate_and_advance_kernel - Iterate over a kernel iterator
+ * @iter: The iterator to iterate over.
+ * @len: The amount to iterate over.
+ * @priv: Data for the step functions.
+ * @priv2: More data for the step functions.
+ * @step: Processing function; given kernel addresses.
+ *
+ * Like iterate_and_advance2(), but rejected UBUF and IOVEC iterators and does
+ * not take a user-step function.
+ */
+static __always_inline
+size_t iterate_and_advance_kernel(struct iov_iter *iter, size_t len, void *priv,
+				  void *priv2, iov_step_f step)
+{
+	if (unlikely(iter->count < len))
+		len = iter->count;
+	if (unlikely(!len))
+		return 0;
+
+	if (iov_iter_is_bvec(iter))
+		return iterate_bvec(iter, len, priv, priv2, step);
+	if (iov_iter_is_kvec(iter))
+		return iterate_kvec(iter, len, priv, priv2, step);
+	if (iov_iter_is_xarray(iter))
+		return iterate_xarray(iter, len, priv, priv2, step);
+	if (iov_iter_is_discard(iter))
+		return iterate_discard(iter, len, priv, priv2, step);
+	WARN_ON_ONCE(1);
+	return 0;
+}
+
 #endif /* _LINUX_IOV_ITER_H */

[PATCH v6 10/13] iov_iter, net: Move csum_and_copy_to/from_iter() to net/

[David Howells]

Move csum_and_copy_to/from_iter() to net code now that the iteration
framework can be #included.

Signed-off-by: David Howells <dhowells@redhat.com>
---
 include/linux/skbuff.h | 25 ++++++++++++
 include/linux/uio.h    | 18 ---------
 lib/iov_iter.c         | 89 ------------------------------------------
 net/core/datagram.c    | 50 +++++++++++++++++++++++-
 net/core/skbuff.c      | 33 ++++++++++++++++
 5 files changed, 107 insertions(+), 108 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 4174c4b82d13..d0656cc11c16 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3679,6 +3679,31 @@ static inline int __must_check skb_put_padto(struct sk_buff *skb, unsigned int l
 	return __skb_put_padto(skb, len, true);
 }
 
+static inline __wsum csum_and_memcpy(void *to, const void *from, size_t len,
+				     __wsum sum, size_t off)
+{
+	__wsum next = csum_partial_copy_nocheck(from, to, len);
+	return csum_block_add(sum, next, off);
+}
+
+struct csum_state {
+	__wsum csum;
+	size_t off;
+};
+
+size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
+
+static __always_inline __must_check
+bool csum_and_copy_from_iter_full(void *addr, size_t bytes,
+				  __wsum *csum, struct iov_iter *i)
+{
+	size_t copied = csum_and_copy_from_iter(addr, bytes, csum, i);
+	if (likely(copied == bytes))
+		return true;
+	iov_iter_revert(i, copied);
+	return false;
+}
+
 static inline int skb_add_data(struct sk_buff *skb,
 			       struct iov_iter *from, int copy)
 {
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 65d9143f83c8..0a5426c97e02 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -338,24 +338,6 @@ iov_iter_npages_cap(struct iov_iter *i, int maxpages, size_t max_bytes)
 	return npages;
 }
 
-struct csum_state {
-	__wsum csum;
-	size_t off;
-};
-
-size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *csstate, struct iov_iter *i);
-size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
-
-static __always_inline __must_check
-bool csum_and_copy_from_iter_full(void *addr, size_t bytes,
-				  __wsum *csum, struct iov_iter *i)
-{
-	size_t copied = csum_and_copy_from_iter(addr, bytes, csum, i);
-	if (likely(copied == bytes))
-		return true;
-	iov_iter_revert(i, copied);
-	return false;
-}
 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
 		struct iov_iter *i);
 
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 943aa3cfd7b3..fef934a8745d 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -10,7 +10,6 @@
 #include <linux/vmalloc.h>
 #include <linux/splice.h>
 #include <linux/compat.h>
-#include <net/checksum.h>
 #include <linux/scatterlist.h>
 #include <linux/instrumented.h>
 #include <linux/iov_iter.h>
@@ -179,13 +178,6 @@ void iov_iter_init(struct iov_iter *i, unsigned int direction,
 }
 EXPORT_SYMBOL(iov_iter_init);
 
-static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
-			      __wsum sum, size_t off)
-{
-	__wsum next = csum_partial_copy_nocheck(from, to, len);
-	return csum_block_add(sum, next, off);
-}
-
 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
 {
 	if (WARN_ON_ONCE(i->data_source))
@@ -1101,87 +1093,6 @@ ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
 }
 EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
 
-static __always_inline
-size_t copy_from_user_iter_csum(void __user *iter_from, size_t progress,
-				size_t len, void *to, void *priv2)
-{
-	__wsum next, *csum = priv2;
-
-	next = csum_and_copy_from_user(iter_from, to + progress, len);
-	*csum = csum_block_add(*csum, next, progress);
-	return next ? 0 : len;
-}
-
-static __always_inline
-size_t memcpy_from_iter_csum(void *iter_from, size_t progress,
-			     size_t len, void *to, void *priv2)
-{
-	__wsum *csum = priv2;
-
-	*csum = csum_and_memcpy(to + progress, iter_from, len, *csum, progress);
-	return 0;
-}
-
-size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
-			       struct iov_iter *i)
-{
-	if (WARN_ON_ONCE(!i->data_source))
-		return 0;
-	return iterate_and_advance2(i, bytes, addr, csum,
-				    copy_from_user_iter_csum,
-				    memcpy_from_iter_csum);
-}
-EXPORT_SYMBOL(csum_and_copy_from_iter);
-
-static __always_inline
-size_t copy_to_user_iter_csum(void __user *iter_to, size_t progress,
-			      size_t len, void *from, void *priv2)
-{
-	__wsum next, *csum = priv2;
-
-	next = csum_and_copy_to_user(from + progress, iter_to, len);
-	*csum = csum_block_add(*csum, next, progress);
-	return next ? 0 : len;
-}
-
-static __always_inline
-size_t memcpy_to_iter_csum(void *iter_to, size_t progress,
-			   size_t len, void *from, void *priv2)
-{
-	__wsum *csum = priv2;
-
-	*csum = csum_and_memcpy(iter_to, from + progress, len, *csum, progress);
-	return 0;
-}
-
-size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
-			     struct iov_iter *i)
-{
-	struct csum_state *csstate = _csstate;
-	__wsum sum;
-
-	if (WARN_ON_ONCE(i->data_source))
-		return 0;
-	if (unlikely(iov_iter_is_discard(i))) {
-		// can't use csum_memcpy() for that one - data is not copied
-		csstate->csum = csum_block_add(csstate->csum,
-					       csum_partial(addr, bytes, 0),
-					       csstate->off);
-		csstate->off += bytes;
-		return bytes;
-	}
-
-	sum = csum_shift(csstate->csum, csstate->off);
-	
-	bytes = iterate_and_advance2(i, bytes, (void *)addr, &sum,
-				     copy_to_user_iter_csum,
-				     memcpy_to_iter_csum);
-	csstate->csum = csum_shift(sum, csstate->off);
-	csstate->off += bytes;
-	return bytes;
-}
-EXPORT_SYMBOL(csum_and_copy_to_iter);
-
 size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
 		struct iov_iter *i)
 {
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 176eb5834746..37c89d0933b7 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -50,7 +50,7 @@
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 #include <linux/pagemap.h>
-#include <linux/uio.h>
+#include <linux/iov_iter.h>
 #include <linux/indirect_call_wrapper.h>
 
 #include <net/protocol.h>
@@ -716,6 +716,54 @@ int zerocopy_sg_from_iter(struct sk_buff *skb, struct iov_iter *from)
 }
 EXPORT_SYMBOL(zerocopy_sg_from_iter);
 
+static __always_inline
+size_t copy_to_user_iter_csum(void __user *iter_to, size_t progress,
+			      size_t len, void *from, void *priv2)
+{
+	__wsum next, *csum = priv2;
+
+	next = csum_and_copy_to_user(from + progress, iter_to, len);
+	*csum = csum_block_add(*csum, next, progress);
+	return next ? 0 : len;
+}
+
+static __always_inline
+size_t memcpy_to_iter_csum(void *iter_to, size_t progress,
+			   size_t len, void *from, void *priv2)
+{
+	__wsum *csum = priv2;
+
+	*csum = csum_and_memcpy(iter_to, from + progress, len, *csum, progress);
+	return 0;
+}
+
+static size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
+				    struct iov_iter *i)
+{
+	struct csum_state *csstate = _csstate;
+	__wsum sum;
+
+	if (WARN_ON_ONCE(i->data_source))
+		return 0;
+	if (unlikely(iov_iter_is_discard(i))) {
+		// can't use csum_memcpy() for that one - data is not copied
+		csstate->csum = csum_block_add(csstate->csum,
+					       csum_partial(addr, bytes, 0),
+					       csstate->off);
+		csstate->off += bytes;
+		return bytes;
+	}
+
+	sum = csum_shift(csstate->csum, csstate->off);
+
+	bytes = iterate_and_advance2(i, bytes, (void *)addr, &sum,
+				     copy_to_user_iter_csum,
+				     memcpy_to_iter_csum);
+	csstate->csum = csum_shift(sum, csstate->off);
+	csstate->off += bytes;
+	return bytes;
+}
+
 /**
  *	skb_copy_and_csum_datagram - Copy datagram to an iovec iterator
  *          and update a checksum.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 4eaf7ed0d1f4..5dbdfce2d05f 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -62,6 +62,7 @@
 #include <linux/if_vlan.h>
 #include <linux/mpls.h>
 #include <linux/kcov.h>
+#include <linux/iov_iter.h>
 
 #include <net/protocol.h>
 #include <net/dst.h>
@@ -6931,3 +6932,35 @@ ssize_t skb_splice_from_iter(struct sk_buff *skb, struct iov_iter *iter,
 	return spliced ?: ret;
 }
 EXPORT_SYMBOL(skb_splice_from_iter);
+
+static __always_inline
+size_t memcpy_from_iter_csum(void *iter_from, size_t progress,
+			     size_t len, void *to, void *priv2)
+{
+	__wsum *csum = priv2;
+
+	*csum = csum_and_memcpy(to + progress, iter_from, len, *csum, progress);
+	return 0;
+}
+
+static __always_inline
+size_t copy_from_user_iter_csum(void __user *iter_from, size_t progress,
+				size_t len, void *to, void *priv2)
+{
+	__wsum next, *csum = priv2;
+
+	next = csum_and_copy_from_user(iter_from, to + progress, len);
+	*csum = csum_block_add(*csum, next, progress);
+	return next ? 0 : len;
+}
+
+size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
+			       struct iov_iter *i)
+{
+	if (WARN_ON_ONCE(!i->data_source))
+		return 0;
+	return iterate_and_advance2(i, bytes, addr, csum,
+				    copy_from_user_iter_csum,
+				    memcpy_from_iter_csum);
+}
+EXPORT_SYMBOL(csum_and_copy_from_iter);

[PATCH v6 11/13] iov_iter, net: Fold in csum_and_memcpy()

[David Howells]

Fold csum_and_memcpy() in to its callers.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
cc: netdev@vger.kernel.org
---
 include/linux/skbuff.h | 7 -------
 net/core/datagram.c    | 3 ++-
 net/core/skbuff.c      | 3 ++-
 3 files changed, 4 insertions(+), 9 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index d0656cc11c16..c81ef5d76953 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3679,13 +3679,6 @@ static inline int __must_check skb_put_padto(struct sk_buff *skb, unsigned int l
 	return __skb_put_padto(skb, len, true);
 }
 
-static inline __wsum csum_and_memcpy(void *to, const void *from, size_t len,
-				     __wsum sum, size_t off)
-{
-	__wsum next = csum_partial_copy_nocheck(from, to, len);
-	return csum_block_add(sum, next, off);
-}
-
 struct csum_state {
 	__wsum csum;
 	size_t off;
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 37c89d0933b7..452620dd41e4 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -732,8 +732,9 @@ size_t memcpy_to_iter_csum(void *iter_to, size_t progress,
 			   size_t len, void *from, void *priv2)
 {
 	__wsum *csum = priv2;
+	__wsum next = csum_partial_copy_nocheck(from, iter_to, len);
 
-	*csum = csum_and_memcpy(iter_to, from + progress, len, *csum, progress);
+	*csum = csum_block_add(*csum, next, progress);
 	return 0;
 }
 
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 5dbdfce2d05f..3efed86321db 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -6938,8 +6938,9 @@ size_t memcpy_from_iter_csum(void *iter_from, size_t progress,
 			     size_t len, void *to, void *priv2)
 {
 	__wsum *csum = priv2;
+	__wsum next = csum_partial_copy_nocheck(iter_from, to + progress, len);
 
-	*csum = csum_and_memcpy(to + progress, iter_from, len, *csum, progress);
+	*csum = csum_block_add(*csum, next, progress);
 	return 0;
 }
 

[PATCH v6 12/13] iov_iter, net: Merge csum_and_copy_from_iter{,_full}() together

[David Howells]

Move csum_and_copy_from_iter_full() out of line and then merge
csum_and_copy_from_iter() into its only caller.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
cc: netdev@vger.kernel.org
---
 include/linux/skbuff.h | 19 ++-----------------
 net/core/datagram.c    |  5 +++++
 net/core/skbuff.c      | 20 +++++++++++++-------
 3 files changed, 20 insertions(+), 24 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c81ef5d76953..be402f55f6d6 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -3679,23 +3679,8 @@ static inline int __must_check skb_put_padto(struct sk_buff *skb, unsigned int l
 	return __skb_put_padto(skb, len, true);
 }
 
-struct csum_state {
-	__wsum csum;
-	size_t off;
-};
-
-size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i);
-
-static __always_inline __must_check
-bool csum_and_copy_from_iter_full(void *addr, size_t bytes,
-				  __wsum *csum, struct iov_iter *i)
-{
-	size_t copied = csum_and_copy_from_iter(addr, bytes, csum, i);
-	if (likely(copied == bytes))
-		return true;
-	iov_iter_revert(i, copied);
-	return false;
-}
+bool csum_and_copy_from_iter_full(void *addr, size_t bytes, __wsum *csum, struct iov_iter *i)
+	__must_check;
 
 static inline int skb_add_data(struct sk_buff *skb,
 			       struct iov_iter *from, int copy)
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 452620dd41e4..722311eeee18 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -738,6 +738,11 @@ size_t memcpy_to_iter_csum(void *iter_to, size_t progress,
 	return 0;
 }
 
+struct csum_state {
+	__wsum csum;
+	size_t off;
+};
+
 static size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
 				    struct iov_iter *i)
 {
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 3efed86321db..2bfa6a7ba244 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -6955,13 +6955,19 @@ size_t copy_from_user_iter_csum(void __user *iter_from, size_t progress,
 	return next ? 0 : len;
 }
 
-size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
-			       struct iov_iter *i)
+bool csum_and_copy_from_iter_full(void *addr, size_t bytes,
+				  __wsum *csum, struct iov_iter *i)
 {
+	size_t copied;
+
 	if (WARN_ON_ONCE(!i->data_source))
-		return 0;
-	return iterate_and_advance2(i, bytes, addr, csum,
-				    copy_from_user_iter_csum,
-				    memcpy_from_iter_csum);
+		return false;
+	copied = iterate_and_advance2(i, bytes, addr, csum,
+				      copy_from_user_iter_csum,
+				      memcpy_from_iter_csum);
+	if (likely(copied == bytes))
+		return true;
+	iov_iter_revert(i, copied);
+	return false;
 }
-EXPORT_SYMBOL(csum_and_copy_from_iter);
+EXPORT_SYMBOL(csum_and_copy_from_iter_full);

[PATCH v6 13/13] iov_iter, net: Move hash_and_copy_to_iter() to net/

[David Howells]

Move hash_and_copy_to_iter() to be with its only caller in networking code.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: "David S. Miller" <davem@davemloft.net>
cc: Eric Dumazet <edumazet@google.com>
cc: Jakub Kicinski <kuba@kernel.org>
cc: Paolo Abeni <pabeni@redhat.com>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
cc: netdev@vger.kernel.org
---
 include/linux/uio.h |  3 ---
 lib/iov_iter.c      | 20 --------------------
 net/core/datagram.c | 19 +++++++++++++++++++
 3 files changed, 19 insertions(+), 23 deletions(-)

diff --git a/include/linux/uio.h b/include/linux/uio.h
index 0a5426c97e02..b6214cbf2a43 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -338,9 +338,6 @@ iov_iter_npages_cap(struct iov_iter *i, int maxpages, size_t max_bytes)
 	return npages;
 }
 
-size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
-		struct iov_iter *i);
-
 struct iovec *iovec_from_user(const struct iovec __user *uvector,
 		unsigned long nr_segs, unsigned long fast_segs,
 		struct iovec *fast_iov, bool compat);
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index fef934a8745d..2547c96d56c7 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1,5 +1,4 @@
 // SPDX-License-Identifier: GPL-2.0-only
-#include <crypto/hash.h>
 #include <linux/export.h>
 #include <linux/bvec.h>
 #include <linux/fault-inject-usercopy.h>
@@ -1093,25 +1092,6 @@ ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
 }
 EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
 
-size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
-		struct iov_iter *i)
-{
-#ifdef CONFIG_CRYPTO_HASH
-	struct ahash_request *hash = hashp;
-	struct scatterlist sg;
-	size_t copied;
-
-	copied = copy_to_iter(addr, bytes, i);
-	sg_init_one(&sg, addr, copied);
-	ahash_request_set_crypt(hash, &sg, NULL, copied);
-	crypto_ahash_update(hash);
-	return copied;
-#else
-	return 0;
-#endif
-}
-EXPORT_SYMBOL(hash_and_copy_to_iter);
-
 static int iov_npages(const struct iov_iter *i, int maxpages)
 {
 	size_t skip = i->iov_offset, size = i->count;
diff --git a/net/core/datagram.c b/net/core/datagram.c
index 722311eeee18..103d46fa0eeb 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -61,6 +61,7 @@
 #include <net/tcp_states.h>
 #include <trace/events/skb.h>
 #include <net/busy_poll.h>
+#include <crypto/hash.h>
 
 /*
  *	Is a socket 'connection oriented' ?
@@ -489,6 +490,24 @@ static int __skb_datagram_iter(const struct sk_buff *skb, int offset,
 	return 0;
 }
 
+static size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
+				    struct iov_iter *i)
+{
+#ifdef CONFIG_CRYPTO_HASH
+	struct ahash_request *hash = hashp;
+	struct scatterlist sg;
+	size_t copied;
+
+	copied = copy_to_iter(addr, bytes, i);
+	sg_init_one(&sg, addr, copied);
+	ahash_request_set_crypt(hash, &sg, NULL, copied);
+	crypto_ahash_update(hash);
+	return copied;
+#else
+	return 0;
+#endif
+}
+
 /**
  *	skb_copy_and_hash_datagram_iter - Copy datagram to an iovec iterator
  *          and update a hash.

Re: [PATCH v6 08/13] iov_iter: Don't deal with iter->copy_mc in memcpy_from_iter_mc()

[Linus Torvalds]

On Fri, 22 Sept 2023 at 05:02, David Howells <dhowells@redhat.com> wrote:
>
> 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(),

This looks fine now, but is missing your sign-off...

             Linus

Re: [PATCH v6 09/13] iov_iter: Add a kernel-type iterator-only iteration function

[Linus Torvalds]

On Fri, 22 Sept 2023 at 05:03, David Howells <dhowells@redhat.com> wrote:
>
> Add an iteration function that can only iterate over kernel internal-type
> iterators (ie. BVEC, KVEC, XARRAY) and not user-backed iterators (ie. UBUF
> and IOVEC).  This allows for smaller iterators to be built when it is known
> the caller won't have a user-backed iterator.

This one is pretty ugly, and has no actual users.

Without even explaining why we'd care about this abomination, NAK.

If we actyually have some static knowledge of "this will only use
iterators X/Y/Z", then we should probably pass that in as a constant
bitmask to the thing, instead of this kind of "kernel only" special
case.

But even then, we'd want to have actual explicit use-cases, not a
hypothetical "if you have this situation here's this function".

                 Linus