From: Jeff Layton <jlayton@kernel.org>
To: Al Viro <viro@zeniv.linux.org.uk>, linux-fsdevel@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Jens Axboe <axboe@kernel.dk>, Christoph Hellwig <hch@lst.de>,
Matthew Wilcox <willy@infradead.org>,
David Howells <dhowells@redhat.com>,
Dominique Martinet <asmadeus@codewreck.org>,
Christian Brauner <brauner@kernel.org>
Subject: Re: [PATCH 12/44] fix short copy handling in copy_mc_pipe_to_iter()
Date: Mon, 27 Jun 2022 15:15:33 -0400 [thread overview]
Message-ID: <b036442de875b654c20299950352f08614aed3bb.camel@kernel.org> (raw)
In-Reply-To: <20220622041552.737754-12-viro@zeniv.linux.org.uk>
On Wed, 2022-06-22 at 05:15 +0100, Al Viro wrote:
> Unlike other copying operations on ITER_PIPE, copy_mc_to_iter() can
> result in a short copy. In that case we need to trim the unused
> buffers, as well as the length of partially filled one - it's not
> enough to set ->head, ->iov_offset and ->count to reflect how
> much had we copied. Not hard to fix, fortunately...
>
> I'd put a helper (pipe_discard_from(pipe, head)) into pipe_fs_i.h,
> rather than iov_iter.c - it has nothing to do with iov_iter and
> having it will allow us to avoid an ugly kludge in fs/splice.c.
> We could put it into lib/iov_iter.c for now and move it later,
> but I don't see the point going that way...
>
> Fixes: ca146f6f091e "lib/iov_iter: Fix pipe handling in _copy_to_iter_mcsafe()"
> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
> ---
> include/linux/pipe_fs_i.h | 9 +++++++++
> lib/iov_iter.c | 15 +++++++++++----
> 2 files changed, 20 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
> index cb0fd633a610..4ea496924106 100644
> --- a/include/linux/pipe_fs_i.h
> +++ b/include/linux/pipe_fs_i.h
> @@ -229,6 +229,15 @@ static inline bool pipe_buf_try_steal(struct pipe_inode_info *pipe,
> return buf->ops->try_steal(pipe, buf);
> }
>
> +static inline void pipe_discard_from(struct pipe_inode_info *pipe,
> + unsigned int old_head)
> +{
> + unsigned int mask = pipe->ring_size - 1;
> +
> + while (pipe->head > old_head)
> + pipe_buf_release(pipe, &pipe->bufs[--pipe->head & mask]);
> +}
> +
> /* Differs from PIPE_BUF in that PIPE_SIZE is the length of the actual
> memory allocation, whereas PIPE_BUF makes atomicity guarantees. */
> #define PIPE_SIZE PAGE_SIZE
> diff --git a/lib/iov_iter.c b/lib/iov_iter.c
> index 0b64695ab632..2bf20b48a04a 100644
> --- a/lib/iov_iter.c
> +++ b/lib/iov_iter.c
> @@ -689,6 +689,7 @@ static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
> struct pipe_inode_info *pipe = i->pipe;
> unsigned int p_mask = pipe->ring_size - 1;
> unsigned int i_head;
> + unsigned int valid = pipe->head;
> size_t n, off, xfer = 0;
>
> if (!sanity(i))
> @@ -702,11 +703,17 @@ static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
> rem = copy_mc_to_kernel(p + off, addr + xfer, chunk);
> chunk -= rem;
> kunmap_local(p);
> - i->head = i_head;
> - i->iov_offset = off + chunk;
> - xfer += chunk;
> - if (rem)
> + if (chunk) {
> + i->head = i_head;
> + i->iov_offset = off + chunk;
> + xfer += chunk;
> + valid = i_head + 1;
> + }
> + if (rem) {
> + pipe->bufs[i_head & p_mask].len -= rem;
> + pipe_discard_from(pipe, valid);
> break;
> + }
> n -= chunk;
> off = 0;
> i_head++;
Reviewed-by: Jeff Layton <jlayton@kernel.org>
next prev parent reply other threads:[~2022-06-27 19:15 UTC|newest]
Thread overview: 118+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-22 4:10 [RFC][CFT][PATCHSET] iov_iter stuff Al Viro
2022-06-22 4:15 ` [PATCH 01/44] 9p: handling Rerror without copy_from_iter_full() Al Viro
2022-06-22 4:15 ` [PATCH 02/44] No need of likely/unlikely on calls of check_copy_size() Al Viro
2022-06-22 4:15 ` [PATCH 03/44] teach iomap_dio_rw() to suppress dsync Al Viro
2022-06-22 4:15 ` [PATCH 04/44] btrfs: use IOMAP_DIO_NOSYNC Al Viro
2022-06-22 4:15 ` [PATCH 05/44] struct file: use anonymous union member for rcuhead and llist Al Viro
2022-06-22 4:15 ` [PATCH 06/44] iocb: delay evaluation of IS_SYNC(...) until we want to check IOCB_DSYNC Al Viro
2022-06-22 4:15 ` [PATCH 07/44] keep iocb_flags() result cached in struct file Al Viro
2022-06-22 4:15 ` [PATCH 08/44] copy_page_{to,from}_iter(): switch iovec variants to generic Al Viro
2022-06-27 18:31 ` Jeff Layton
2022-06-28 12:32 ` Christian Brauner
2022-06-28 18:36 ` Al Viro
2022-06-22 4:15 ` [PATCH 09/44] new iov_iter flavour - ITER_UBUF Al Viro
2022-06-27 18:47 ` Jeff Layton
2022-06-28 18:41 ` Al Viro
2022-06-28 12:38 ` Christian Brauner
2022-06-28 18:44 ` Al Viro
2022-07-28 9:55 ` [PATCH 9/44] " Alexander Gordeev
2022-07-29 17:21 ` Al Viro
2022-07-29 21:12 ` Alexander Gordeev
2022-07-30 0:03 ` Al Viro
2022-06-22 4:15 ` [PATCH 10/44] switch new_sync_{read,write}() to ITER_UBUF Al Viro
2022-06-22 4:15 ` [PATCH 11/44] iov_iter_bvec_advance(): don't bother with bvec_iter Al Viro
2022-06-27 18:48 ` Jeff Layton
2022-06-28 12:40 ` Christian Brauner
2022-06-22 4:15 ` [PATCH 12/44] fix short copy handling in copy_mc_pipe_to_iter() Al Viro
2022-06-27 19:15 ` Jeff Layton [this message]
2022-06-28 12:42 ` Christian Brauner
2022-06-22 4:15 ` [PATCH 13/44] splice: stop abusing iov_iter_advance() to flush a pipe Al Viro
2022-06-27 19:17 ` Jeff Layton
2022-06-28 12:43 ` Christian Brauner
2022-06-22 4:15 ` [PATCH 14/44] ITER_PIPE: helper for getting pipe buffer by index Al Viro
2022-06-28 10:38 ` Jeff Layton
2022-06-28 12:45 ` Christian Brauner
2022-06-22 4:15 ` [PATCH 15/44] ITER_PIPE: helpers for adding pipe buffers Al Viro
2022-06-28 11:32 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 16/44] ITER_PIPE: allocate buffers as we go in copy-to-pipe primitives Al Viro
2022-06-22 4:15 ` [PATCH 17/44] ITER_PIPE: fold push_pipe() into __pipe_get_pages() Al Viro
2022-06-22 4:15 ` [PATCH 18/44] ITER_PIPE: lose iter_head argument of __pipe_get_pages() Al Viro
2022-06-22 4:15 ` [PATCH 19/44] ITER_PIPE: clean pipe_advance() up Al Viro
2022-06-22 4:15 ` [PATCH 20/44] ITER_PIPE: clean iov_iter_revert() Al Viro
2022-06-22 4:15 ` [PATCH 21/44] ITER_PIPE: cache the type of last buffer Al Viro
2022-06-22 4:15 ` [PATCH 22/44] ITER_PIPE: fold data_start() and pipe_space_for_user() together Al Viro
2022-06-22 4:15 ` [PATCH 23/44] iov_iter_get_pages{,_alloc}(): cap the maxsize with MAX_RW_COUNT Al Viro
2022-06-28 11:41 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 24/44] iov_iter_get_pages_alloc(): lift freeing pages array on failure exits into wrapper Al Viro
2022-06-28 11:45 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 25/44] iov_iter_get_pages(): sanity-check arguments Al Viro
2022-06-28 11:47 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 26/44] unify pipe_get_pages() and pipe_get_pages_alloc() Al Viro
2022-06-28 11:49 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 27/44] unify xarray_get_pages() and xarray_get_pages_alloc() Al Viro
2022-06-28 11:50 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 28/44] unify the rest of iov_iter_get_pages()/iov_iter_get_pages_alloc() guts Al Viro
2022-06-28 11:54 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 29/44] ITER_XARRAY: don't open-code DIV_ROUND_UP() Al Viro
2022-06-28 11:54 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 30/44] iov_iter: lift dealing with maxpages out of first_{iovec,bvec}_segment() Al Viro
2022-06-28 11:56 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 31/44] iov_iter: first_{iovec,bvec}_segment() - simplify a bit Al Viro
2022-06-28 11:58 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 32/44] iov_iter: massage calling conventions for first_{iovec,bvec}_segment() Al Viro
2022-06-28 12:06 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 33/44] found_iovec_segment(): just return address Al Viro
2022-06-28 12:09 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 34/44] fold __pipe_get_pages() into pipe_get_pages() Al Viro
2022-06-28 12:11 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 35/44] iov_iter: saner helper for page array allocation Al Viro
2022-06-28 12:12 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 36/44] iov_iter: advancing variants of iov_iter_get_pages{,_alloc}() Al Viro
2022-06-28 12:13 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 37/44] block: convert to " Al Viro
2022-06-28 12:16 ` Jeff Layton
2022-06-30 22:11 ` [block.git conflicts] " Al Viro
2022-06-30 22:39 ` Al Viro
2022-07-01 2:07 ` Keith Busch
2022-07-01 17:40 ` Al Viro
2022-07-01 17:53 ` Keith Busch
2022-07-01 18:07 ` Al Viro
2022-07-01 18:12 ` Al Viro
2022-07-01 18:38 ` Keith Busch
2022-07-01 19:08 ` Al Viro
2022-07-01 19:28 ` Keith Busch
2022-07-01 19:43 ` Al Viro
2022-07-01 19:56 ` Keith Busch
2022-07-02 5:35 ` Al Viro
2022-07-02 21:02 ` Keith Busch
2022-07-01 19:05 ` Keith Busch
2022-07-01 21:30 ` Jens Axboe
2022-06-30 23:07 ` Jens Axboe
2022-07-10 18:04 ` Sedat Dilek
2022-06-22 4:15 ` [PATCH 38/44] iter_to_pipe(): switch to advancing variant of iov_iter_get_pages() Al Viro
2022-06-28 12:18 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 39/44] af_alg_make_sg(): " Al Viro
2022-06-28 12:18 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 40/44] 9p: convert to advancing variant of iov_iter_get_pages_alloc() Al Viro
2022-07-01 9:01 ` Dominique Martinet
2022-07-01 13:47 ` Christian Schoenebeck
2022-07-06 22:06 ` Christian Schoenebeck
2022-06-22 4:15 ` [PATCH 41/44] ceph: switch the last caller " Al Viro
2022-06-28 12:20 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 42/44] get rid of non-advancing variants Al Viro
2022-06-28 12:21 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 43/44] pipe_get_pages(): switch to append_pipe() Al Viro
2022-06-28 12:23 ` Jeff Layton
2022-06-22 4:15 ` [PATCH 44/44] expand those iov_iter_advance() Al Viro
2022-06-28 12:23 ` Jeff Layton
2022-07-01 6:21 ` [PATCH 01/44] 9p: handling Rerror without copy_from_iter_full() Dominique Martinet
2022-07-01 6:25 ` Dominique Martinet
2022-07-01 16:02 ` Christian Schoenebeck
2022-07-01 21:00 ` Dominique Martinet
2022-07-03 13:30 ` Christian Schoenebeck
2022-08-01 12:42 ` [PATCH 09/44] new iov_iter flavour - ITER_UBUF David Howells
2022-08-01 21:14 ` Al Viro
2022-08-01 22:54 ` David Howells
2022-06-23 15:21 ` [RFC][CFT][PATCHSET] iov_iter stuff David Howells
2022-06-23 20:32 ` Al Viro
2022-06-28 12:25 ` Jeff Layton
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