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Date: Wed, 23 Jan 2019 15:19:18 +0100
From: Jann Horn <jannh@...gle.com>
To: Al Viro <viro@...iv.linux.org.uk>,
Miklos Szeredi <miklos@...redi.hu>,
Jens Axboe <axboe@...nel.dk>, Jens Axboe <axboe@...com>,
jannh@...gle.com
Cc: Eric Biggers <ebiggers@...nel.org>, linux-kernel@...r.kernel.org,
linux-fsdevel@...r.kernel.org, Kees Cook <keescook@...omium.org>
Subject: [PATCH v2 2/2] pipe: stop using ->can_merge
Al Viro pointed out that since there is only one pipe buffer type to which
new data can be appended, it isn't necessary to have a ->can_merge field in
struct pipe_buf_operations, we can just check for a magic type.
Suggested-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Jann Horn <jannh@...gle.com>
---
fs/pipe.c | 20 ++++++++++++++++----
fs/splice.c | 4 ----
include/linux/pipe_fs_i.h | 7 -------
kernel/relay.c | 1 -
kernel/trace/trace.c | 2 --
net/smc/smc_rx.c | 1 -
6 files changed, 16 insertions(+), 19 deletions(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index c51750ed4011..0ff09b490ddf 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -226,8 +226,8 @@ void generic_pipe_buf_release(struct pipe_inode_info *pipe,
}
EXPORT_SYMBOL(generic_pipe_buf_release);
+/* New data written to a pipe may be appended to a buffer with this type. */
static const struct pipe_buf_operations anon_pipe_buf_ops = {
- .can_merge = 1,
.confirm = generic_pipe_buf_confirm,
.release = anon_pipe_buf_release,
.steal = anon_pipe_buf_steal,
@@ -235,7 +235,6 @@ static const struct pipe_buf_operations anon_pipe_buf_ops = {
};
static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = anon_pipe_buf_release,
.steal = anon_pipe_buf_steal,
@@ -243,19 +242,32 @@ static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
};
static const struct pipe_buf_operations packet_pipe_buf_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = anon_pipe_buf_release,
.steal = anon_pipe_buf_steal,
.get = generic_pipe_buf_get,
};
+/**
+ * pipe_buf_mark_unmergeable - mark a &struct pipe_buffer as unmergeable
+ * @buf: the buffer to mark
+ *
+ * Description:
+ * This function ensures that no future writes will be merged into the
+ * given &struct pipe_buffer. This is necessary when multiple pipe buffers
+ * share the same backing page.
+ */
void pipe_buf_mark_unmergeable(struct pipe_buffer *buf)
{
if (buf->ops == &anon_pipe_buf_ops)
buf->ops = &anon_pipe_buf_nomerge_ops;
}
+static bool pipe_buf_can_merge(struct pipe_buffer *buf)
+{
+ return buf->ops == &anon_pipe_buf_ops;
+}
+
static ssize_t
pipe_read(struct kiocb *iocb, struct iov_iter *to)
{
@@ -393,7 +405,7 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
struct pipe_buffer *buf = pipe->bufs + lastbuf;
int offset = buf->offset + buf->len;
- if (buf->ops->can_merge && offset + chars <= PAGE_SIZE) {
+ if (pipe_buf_can_merge(buf) && offset + chars <= PAGE_SIZE) {
ret = pipe_buf_confirm(pipe, buf);
if (ret)
goto out;
diff --git a/fs/splice.c b/fs/splice.c
index 90c29675d573..fc71e9733f7a 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -138,7 +138,6 @@ static int page_cache_pipe_buf_confirm(struct pipe_inode_info *pipe,
}
const struct pipe_buf_operations page_cache_pipe_buf_ops = {
- .can_merge = 0,
.confirm = page_cache_pipe_buf_confirm,
.release = page_cache_pipe_buf_release,
.steal = page_cache_pipe_buf_steal,
@@ -156,7 +155,6 @@ static int user_page_pipe_buf_steal(struct pipe_inode_info *pipe,
}
static const struct pipe_buf_operations user_page_pipe_buf_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = page_cache_pipe_buf_release,
.steal = user_page_pipe_buf_steal,
@@ -326,7 +324,6 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
EXPORT_SYMBOL(generic_file_splice_read);
const struct pipe_buf_operations default_pipe_buf_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = generic_pipe_buf_release,
.steal = generic_pipe_buf_steal,
@@ -341,7 +338,6 @@ static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe,
/* Pipe buffer operations for a socket and similar. */
const struct pipe_buf_operations nosteal_pipe_buf_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = generic_pipe_buf_release,
.steal = generic_pipe_buf_nosteal,
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 3ecd7ea212ae..787d224ff43e 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -73,13 +73,6 @@ struct pipe_inode_info {
* in fs/pipe.c for the pipe and generic variants of these hooks.
*/
struct pipe_buf_operations {
- /*
- * This is set to 1, if the generic pipe read/write may coalesce
- * data into an existing buffer. If this is set to 0, a new pipe
- * page segment is always used for new data.
- */
- int can_merge;
-
/*
* ->confirm() verifies that the data in the pipe buffer is there
* and that the contents are good. If the pages in the pipe belong
diff --git a/kernel/relay.c b/kernel/relay.c
index 04f248644e06..db3e419c25a6 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -1175,7 +1175,6 @@ static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
}
static const struct pipe_buf_operations relay_pipe_buf_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = relay_pipe_buf_release,
.steal = generic_pipe_buf_steal,
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c521b7347482..f380139e972c 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -5823,7 +5823,6 @@ static void tracing_spd_release_pipe(struct splice_pipe_desc *spd,
}
static const struct pipe_buf_operations tracing_pipe_buf_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = generic_pipe_buf_release,
.steal = generic_pipe_buf_steal,
@@ -6843,7 +6842,6 @@ static void buffer_pipe_buf_get(struct pipe_inode_info *pipe,
/* Pipe buffer operations for a buffer. */
static const struct pipe_buf_operations buffer_pipe_buf_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = buffer_pipe_buf_release,
.steal = generic_pipe_buf_steal,
diff --git a/net/smc/smc_rx.c b/net/smc/smc_rx.c
index bbcf0fe4ae10..413a6abf227e 100644
--- a/net/smc/smc_rx.c
+++ b/net/smc/smc_rx.c
@@ -136,7 +136,6 @@ static int smc_rx_pipe_buf_nosteal(struct pipe_inode_info *pipe,
}
static const struct pipe_buf_operations smc_pipe_ops = {
- .can_merge = 0,
.confirm = generic_pipe_buf_confirm,
.release = smc_rx_pipe_buf_release,
.steal = smc_rx_pipe_buf_nosteal,
--
2.20.1.321.g9e740568ce-goog
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