From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
David Sterba <dsterba@suse.com>,
Miklos Szeredi <miklos@szeredi.hu>,
Anton Altaparmakov <anton@tuxera.com>,
David Howells <dhowells@redhat.com>,
Matthew Wilcox <willy@infradead.org>,
Pavel Begunkov <asml.silence@gmail.com>
Subject: [RFC PATCH 05/37] teach copy_page_to_iter() to handle compound pages
Date: Sun, 6 Jun 2021 19:10:19 +0000 [thread overview]
Message-ID: <20210606191051.1216821-5-viro@zeniv.linux.org.uk> (raw)
In-Reply-To: <20210606191051.1216821-1-viro@zeniv.linux.org.uk>
In situation when copy_page_to_iter() got a compound page the current
code would only work on systems with no CONFIG_HIGHMEM. It *is* the majority
of real-world setups, or we would've drown in bug reports by now. Still needs
fixing.
Current variant works for solitary page; rename that to
__copy_page_to_iter() and turn the handling of compound pages into a loop over
subpages.
Cc: stable@vger.kernel.org
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
lib/iov_iter.c | 28 +++++++++++++++++++++++++---
1 file changed, 25 insertions(+), 3 deletions(-)
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 8f5ce5b1ff91..12fb04b23143 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -957,11 +957,9 @@ static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
return false;
}
-size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
+static size_t __copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
- if (unlikely(!page_copy_sane(page, offset, bytes)))
- return 0;
if (i->type & (ITER_BVEC | ITER_KVEC | ITER_XARRAY)) {
void *kaddr = kmap_atomic(page);
size_t wanted = copy_to_iter(kaddr + offset, bytes, i);
@@ -974,6 +972,30 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
else
return copy_page_to_iter_pipe(page, offset, bytes, i);
}
+
+size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
+ struct iov_iter *i)
+{
+ size_t res = 0;
+ if (unlikely(!page_copy_sane(page, offset, bytes)))
+ return 0;
+ page += offset / PAGE_SIZE; // first subpage
+ offset %= PAGE_SIZE;
+ while (1) {
+ size_t n = __copy_page_to_iter(page, offset,
+ min(bytes, (size_t)PAGE_SIZE - offset), i);
+ res += n;
+ bytes -= n;
+ if (!bytes || !n)
+ break;
+ offset += n;
+ if (offset == PAGE_SIZE) {
+ page++;
+ offset = 0;
+ }
+ }
+ return res;
+}
EXPORT_SYMBOL(copy_page_to_iter);
size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
--
2.11.0
next prev parent reply other threads:[~2021-06-06 19:10 UTC|newest]
Thread overview: 57+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-06 19:07 [RFC][PATCHSET] iov_iter work Al Viro
2021-06-06 19:10 ` [RFC PATCH 01/37] ntfs_copy_from_user_iter(): don't bother with copying iov_iter Al Viro
2021-06-06 19:10 ` [RFC PATCH 02/37] generic_perform_write()/iomap_write_actor(): saner logics for short copy Al Viro
2021-06-06 19:10 ` [RFC PATCH 03/37] fuse_fill_write_pages(): don't bother with iov_iter_single_seg_count() Al Viro
2021-06-06 19:10 ` [RFC PATCH 04/37] iov_iter: Remove iov_iter_for_each_range() Al Viro
2021-06-06 19:10 ` Al Viro [this message]
2021-06-06 19:10 ` [RFC PATCH 06/37] copy_page_to_iter(): fix ITER_DISCARD case Al Viro
2021-06-06 19:10 ` [RFC PATCH 07/37] [xarray] iov_iter_fault_in_readable() should do nothing in xarray case Al Viro
2021-06-06 19:10 ` [RFC PATCH 08/37] iov_iter_advance(): use consistent semantics for move past the end Al Viro
2021-06-06 19:10 ` [RFC PATCH 09/37] iov_iter: switch ..._full() variants of primitives to use of iov_iter_revert() Al Viro
2021-06-06 19:10 ` [RFC PATCH 10/37] iov_iter: reorder handling of flavours in primitives Al Viro
2021-06-06 19:10 ` [RFC PATCH 11/37] iov_iter_advance(): don't modify ->iov_offset for ITER_DISCARD Al Viro
2021-06-06 19:10 ` [RFC PATCH 12/37] iov_iter: separate direction from flavour Al Viro
2021-06-06 19:10 ` [RFC PATCH 13/37] iov_iter: optimize iov_iter_advance() for iovec and kvec Al Viro
2021-06-06 19:10 ` [RFC PATCH 14/37] sanitize iov_iter_fault_in_readable() Al Viro
2021-06-06 19:10 ` [RFC PATCH 15/37] iov_iter_alignment(): don't bother with iterate_all_kinds() Al Viro
2021-06-06 19:10 ` [RFC PATCH 16/37] iov_iter_gap_alignment(): get rid of iterate_all_kinds() Al Viro
2021-06-09 13:01 ` Qian Cai
2021-06-09 18:06 ` Al Viro
2021-06-06 19:10 ` [RFC PATCH 17/37] get rid of iterate_all_kinds() in iov_iter_get_pages()/iov_iter_get_pages_alloc() Al Viro
2021-06-06 19:10 ` [RFC PATCH 18/37] iov_iter_npages(): don't bother with iterate_all_kinds() Al Viro
2021-06-06 19:10 ` [RFC PATCH 19/37] [xarray] iov_iter_npages(): just use DIV_ROUND_UP() Al Viro
2021-06-06 19:10 ` [RFC PATCH 20/37] iov_iter: replace iov_iter_copy_from_user_atomic() with iterator-advancing variant Al Viro
2021-06-06 19:10 ` [RFC PATCH 21/37] csum_and_copy_to_iter(): massage into form closer to csum_and_copy_from_iter() Al Viro
2021-06-06 19:10 ` [RFC PATCH 22/37] iterate_and_advance(): get rid of magic in case when n is 0 Al Viro
2021-06-06 19:10 ` [RFC PATCH 23/37] iov_iter: massage iterate_iovec and iterate_kvec to logics similar to iterate_bvec Al Viro
2021-06-06 19:10 ` [RFC PATCH 24/37] iov_iter: unify iterate_iovec and iterate_kvec Al Viro
2021-06-06 19:10 ` [RFC PATCH 25/37] iterate_bvec(): expand bvec.h macro forest, massage a bit Al Viro
2021-06-06 19:10 ` [RFC PATCH 26/37] iov_iter: teach iterate_{bvec,xarray}() about possible short copies Al Viro
2021-06-06 19:10 ` [RFC PATCH 27/37] iov_iter: get rid of separate bvec and xarray callbacks Al Viro
2021-06-06 19:10 ` [RFC PATCH 28/37] iov_iter: make the amount already copied available to iterator callbacks Al Viro
2021-06-06 19:10 ` [RFC PATCH 29/37] iov_iter: make iterator callbacks use base and len instead of iovec Al Viro
2021-06-06 19:10 ` [RFC PATCH 30/37] pull handling of ->iov_offset into iterate_{iovec,bvec,xarray} Al Viro
2021-06-06 19:10 ` [RFC PATCH 31/37] iterate_xarray(): only of the first iteration we might get offset != 0 Al Viro
2021-06-06 19:10 ` [RFC PATCH 32/37] copy_page_to_iter(): don't bother with kmap_atomic() for bvec/kvec cases Al Viro
2021-06-06 19:10 ` [RFC PATCH 33/37] copy_page_from_iter(): don't need kmap_atomic() for kvec/bvec cases Al Viro
2021-06-06 19:10 ` [RFC PATCH 34/37] iov_iter: clean csum_and_copy_...() primitives up a bit Al Viro
2021-06-06 19:10 ` [RFC PATCH 35/37] pipe_zero(): we don't need no stinkin' kmap_atomic() Al Viro
2021-06-06 19:10 ` [RFC PATCH 36/37] clean up copy_mc_pipe_to_iter() Al Viro
2021-06-06 19:10 ` [RFC PATCH 37/37] csum_and_copy_to_pipe_iter(): leave handling of csum_state to caller Al Viro
2021-06-06 22:05 ` [RFC][PATCHSET] iov_iter work Linus Torvalds
2021-06-06 22:46 ` Linus Torvalds
2021-06-07 9:28 ` Christoph Hellwig
2021-06-07 14:43 ` Al Viro
2021-06-07 15:59 ` Christoph Hellwig
2021-06-07 21:07 ` Al Viro
2021-06-07 22:01 ` Linus Torvalds
2021-06-07 23:35 ` Linus Torvalds
2021-06-08 5:25 ` Christoph Hellwig
2021-06-08 11:27 ` Al Viro
2021-06-06 23:29 ` Al Viro
2021-06-07 10:38 ` Pavel Begunkov
2021-06-08 14:43 ` David Laight
2021-06-10 14:29 ` Qian Cai
2021-06-10 15:35 ` Al Viro
2021-06-10 15:48 ` Al Viro
2021-06-10 19:08 ` Qian Cai
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