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    Subject[v2.6.34-stable 040/213] tcp: tcp_sendpages() should call tcp_push() once
    Date
    From: Eric Dumazet <eric.dumazet@gmail.com>

    -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
    -------------------

    commit 35f9c09fe9c72eb8ca2b8e89a593e1c151f28fc2 upstream.

    commit 2f533844242 (tcp: allow splice() to build full TSO packets) added
    a regression for splice() calls using SPLICE_F_MORE.

    We need to call tcp_flush() at the end of the last page processed in
    tcp_sendpages(), or else transmits can be deferred and future sends
    stall.

    Add a new internal flag, MSG_SENDPAGE_NOTLAST, acting like MSG_MORE, but
    with different semantic.

    For all sendpage() providers, its a transparent change. Only
    sock_sendpage() and tcp_sendpages() can differentiate the two different
    flags provided by pipe_to_sendpage()

    Reported-by: Tom Herbert <therbert@google.com>
    Cc: Nandita Dukkipati <nanditad@google.com>
    Cc: Neal Cardwell <ncardwell@google.com>
    Cc: Tom Herbert <therbert@google.com>
    Cc: Yuchung Cheng <ycheng@google.com>
    Cc: H.K. Jerry Chu <hkchu@google.com>
    Cc: Maciej Żenczykowski <maze@google.com>
    Cc: Mahesh Bandewar <maheshb@google.com>
    Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
    Signed-off-by: Eric Dumazet <eric.dumazet@gmail>com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    ---
    fs/splice.c | 5 ++++-
    include/linux/socket.h | 2 +-
    net/ipv4/tcp.c | 2 +-
    net/socket.c | 6 +++---
    4 files changed, 9 insertions(+), 6 deletions(-)

    diff --git a/fs/splice.c b/fs/splice.c
    index cc617b09e4c2..3bec7c63be64 100644
    --- a/fs/splice.c
    +++ b/fs/splice.c
    @@ -31,6 +31,7 @@
    #include <linux/uio.h>
    #include <linux/security.h>
    #include <linux/gfp.h>
    +#include <linux/socket.h>

    /*
    * Attempt to steal a page from a pipe buffer. This should perhaps go into
    @@ -638,7 +639,9 @@ static int pipe_to_sendpage(struct pipe_inode_info *pipe,

    ret = buf->ops->confirm(pipe, buf);
    if (!ret) {
    - more = (sd->flags & SPLICE_F_MORE) || sd->len < sd->total_len;
    + more = (sd->flags & SPLICE_F_MORE) ? MSG_MORE : 0;
    + if (sd->len < sd->total_len)
    + more |= MSG_SENDPAGE_NOTLAST;
    if (file->f_op && file->f_op->sendpage)
    ret = file->f_op->sendpage(file, buf->page, buf->offset,
    sd->len, &pos, more);
    diff --git a/include/linux/socket.h b/include/linux/socket.h
    index 354cc5617f8b..7cfb4f881644 100644
    --- a/include/linux/socket.h
    +++ b/include/linux/socket.h
    @@ -256,7 +256,7 @@ struct ucred {
    #define MSG_NOSIGNAL 0x4000 /* Do not generate SIGPIPE */
    #define MSG_MORE 0x8000 /* Sender will send more */
    #define MSG_WAITFORONE 0x10000 /* recvmmsg(): block until 1+ packets avail */
    -
    +#define MSG_SENDPAGE_NOTLAST 0x20000 /* sendpage() internal : not the last page */
    #define MSG_EOF MSG_FIN

    #define MSG_CMSG_CLOEXEC 0x40000000 /* Set close_on_exit for file
    diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
    index cea0a9223c5d..df671c76f196 100644
    --- a/net/ipv4/tcp.c
    +++ b/net/ipv4/tcp.c
    @@ -849,7 +849,7 @@ wait_for_memory:
    }

    out:
    - if (copied && !(flags & MSG_MORE))
    + if (copied && !(flags & MSG_SENDPAGE_NOTLAST))
    tcp_push(sk, flags, mss_now, tp->nonagle);
    return copied;

    diff --git a/net/socket.c b/net/socket.c
    index c63ebf4e31b5..c802797e3a4a 100644
    --- a/net/socket.c
    +++ b/net/socket.c
    @@ -746,9 +746,9 @@ static ssize_t sock_sendpage(struct file *file, struct page *page,

    sock = file->private_data;

    - flags = !(file->f_flags & O_NONBLOCK) ? 0 : MSG_DONTWAIT;
    - if (more)
    - flags |= MSG_MORE;
    + flags = (file->f_flags & O_NONBLOCK) ? MSG_DONTWAIT : 0;
    + /* more is a combination of MSG_MORE and MSG_SENDPAGE_NOTLAST */
    + flags |= more;

    return kernel_sendpage(sock, page, offset, size, flags);
    }
    --
    1.8.5.2
    --
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