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pipe: merge anon_pipe_buf*_ops

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All the op vectors are exactly the same, they are just used to encode
packet or nomerge behavior.  There already is a flag for the packet
behavior, so just add a new one to allow for merging.  Inverting it vs
the previous nomerge special casing actually allows for much nicer code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Christoph Hellwig 2020-05-20 17:58:12 +02:00 committed by Al Viro
parent 00c285d0d0
commit f6dd975583
3 changed files with 11 additions and 48 deletions
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45
fs/pipe.c
View File

@ -231,7 +231,6 @@ 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 = {
.confirm = generic_pipe_buf_confirm,
.release = anon_pipe_buf_release,
@ -239,40 +238,6 @@ static const struct pipe_buf_operations anon_pipe_buf_ops = {
.get = generic_pipe_buf_get,
};
static const struct pipe_buf_operations anon_pipe_buf_nomerge_ops = {
.confirm = generic_pipe_buf_confirm,
.release = anon_pipe_buf_release,
.steal = anon_pipe_buf_steal,
.get = generic_pipe_buf_get,
};
static const struct pipe_buf_operations packet_pipe_buf_ops = {
.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;
}
/* Done while waiting without holding the pipe lock - thus the READ_ONCE() */
static inline bool pipe_readable(const struct pipe_inode_info *pipe)
{
@ -478,7 +443,8 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
struct pipe_buffer *buf = &pipe->bufs[(head - 1) & mask];
int offset = buf->offset + buf->len;
if (pipe_buf_can_merge(buf) && offset + chars <= PAGE_SIZE) {
if ((buf->flags & PIPE_BUF_FLAG_CAN_MERGE) &&
offset + chars <= PAGE_SIZE) {
ret = pipe_buf_confirm(pipe, buf);
if (ret)
goto out;
@ -541,11 +507,10 @@ pipe_write(struct kiocb *iocb, struct iov_iter *from)
buf->ops = &anon_pipe_buf_ops;
buf->offset = 0;
buf->len = 0;
buf->flags = 0;
if (is_packetized(filp)) {
buf->ops = &packet_pipe_buf_ops;
if (is_packetized(filp))
buf->flags = PIPE_BUF_FLAG_PACKET;
}
else
buf->flags = PIPE_BUF_FLAG_CAN_MERGE;
pipe->tmp_page = NULL;
copied = copy_page_from_iter(page, 0, PAGE_SIZE, from);

12
fs/splice.c
View File

@ -1624,12 +1624,11 @@ retry:
*obuf = *ibuf;
/*
* Don't inherit the gift flag, we need to
* Don't inherit the gift and merge flags, we need to
* prevent multiple steals of this page.
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
pipe_buf_mark_unmergeable(obuf);
obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
obuf->len = len;
ibuf->offset += len;
@ -1717,12 +1716,11 @@ static int link_pipe(struct pipe_inode_info *ipipe,
*obuf = *ibuf;
/*
* Don't inherit the gift flag, we need to
* prevent multiple steals of this page.
* Don't inherit the gift and merge flag, we need to prevent
* multiple steals of this page.
*/
obuf->flags &= ~PIPE_BUF_FLAG_GIFT;
pipe_buf_mark_unmergeable(obuf);
obuf->flags &= ~PIPE_BUF_FLAG_CAN_MERGE;
if (obuf->len > len)
obuf->len = len;

2
include/linux/pipe_fs_i.h
View File

@ -8,6 +8,7 @@
#define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */
#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */
#define PIPE_BUF_FLAG_PACKET 0x08 /* read() as a packet */
#define PIPE_BUF_FLAG_CAN_MERGE 0x10 /* can merge buffers */
/**
* struct pipe_buffer - a linux kernel pipe buffer
@ -233,7 +234,6 @@ int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *);
int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *);
int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *);
void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *);
void pipe_buf_mark_unmergeable(struct pipe_buffer *buf);
extern const struct pipe_buf_operations nosteal_pipe_buf_ops;