git: 51ac5ee0d57f - main - unix/stream: refactor sendfile(2) logic to work without M_BLOCKER flag

[Gleb Smirnoff]

The branch main has been updated by glebius:

URL: 
https://cgit.FreeBSD.org/src/commit/?id=51ac5ee0d57f178882af4b40d36089e2069704e4

commit 51ac5ee0d57f178882af4b40d36089e2069704e4
Author:     Gleb Smirnoff <gleb...@freebsd.org>
AuthorDate: 2025-05-23 21:55:56 +0000
Commit:     Gleb Smirnoff <gleb...@freebsd.org>
CommitDate: 2025-05-23 22:04:39 +0000

    unix/stream: refactor sendfile(2) logic to work without M_BLOCKER flag
    
    This flag was initially an INVARIANT thing back in 2014, but we got
    stuck with it until today.  A bug with sendfile(2) headers/trailers
    fixed as a side effect of refactoring.
---
 sys/kern/uipc_usrreq.c | 34 +++++++++++++++++++---------------
 1 file changed, 19 insertions(+), 15 deletions(-)

diff --git a/sys/kern/uipc_usrreq.c b/sys/kern/uipc_usrreq.c
index 0f730cf9424b..5b1b8443f8e6 100644
--- a/sys/kern/uipc_usrreq.c
+++ b/sys/kern/uipc_usrreq.c
@@ -1008,10 +1008,10 @@ uipc_stream_sbcheck(struct sockbuf *sb)
 
        dacc = dccc = dctl = dmbcnt = 0;
        STAILQ_FOREACH(d, &sb->uxst_mbq, m_stailq) {
-               if (d == sb->uxst_fnrdy)
+               if (d == sb->uxst_fnrdy) {
+                       MPASS(d->m_flags & M_NOTREADY);
                        notready = true;
-               if (notready)
-                       MPASS(d->m_flags & (M_NOTREADY|M_BLOCKED));
+               }
                if (d->m_type == MT_CONTROL)
                        dctl += d->m_len;
                else if (d->m_type == MT_DATA) {
@@ -2471,15 +2471,21 @@ uipc_sendfile(struct socket *so, int flags, struct mbuf 
*m,
        sb->sb_mbcnt += mc.mc_mlen;
        if (sb->uxst_fnrdy == NULL) {
                if (notready) {
-                       sb->uxst_fnrdy = STAILQ_FIRST(&mc.mc_q);
                        wakeup = false;
+                       STAILQ_FOREACH(m, &mc.mc_q, m_stailq) {
+                               if (m->m_flags & M_NOTREADY) {
+                                       sb->uxst_fnrdy = m;
+                                       break;
+                               } else {
+                                       sb->sb_acc += m->m_len;
+                                       wakeup = true;
+                               }
+                       }
                } else {
-                       sb->sb_acc += mc.mc_len;
                        wakeup = true;
+                       sb->sb_acc += mc.mc_len;
                }
        } else {
-               STAILQ_FOREACH(m, &mc.mc_q, m_stailq)
-                       m->m_flags |= M_BLOCKED;
                wakeup = false;
        }
        STAILQ_CONCAT(&sb->uxst_mbq, &mc.mc_q);
@@ -2504,24 +2510,22 @@ out:
 static int
 uipc_sbready(struct sockbuf *sb, struct mbuf *m, int count)
 {
-       u_int blocker;
+       bool blocker;
 
        /* assert locked */
 
-       blocker = (sb->uxst_fnrdy == m) ? M_BLOCKED : 0;
+       blocker = (sb->uxst_fnrdy == m);
        STAILQ_FOREACH_FROM(m, &sb->uxst_mbq, m_stailq) {
                if (count > 0) {
                        MPASS(m->m_flags & M_NOTREADY);
-                       m->m_flags &= ~(M_NOTREADY | blocker);
+                       m->m_flags &= ~M_NOTREADY;
                        if (blocker)
                                sb->sb_acc += m->m_len;
                        count--;
-               } else if (blocker && !(m->m_flags & M_NOTREADY)) {
-                       MPASS(m->m_flags & M_BLOCKED);
-                       m->m_flags &= ~M_BLOCKED;
-                       sb->sb_acc += m->m_len;
-               } else
+               } else if (m->m_flags & M_NOTREADY)
                        break;
+               else if (blocker)
+                       sb->sb_acc += m->m_len;
        }
        if (blocker) {
                sb->uxst_fnrdy = m;