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sendfile: retire M_BLOCKED

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Follow unix(4) commit 51ac5ee0d5 and retire M_BLOCKED for TCP sockets as
well.  The M_BLOCKED flag was introduced back 2016 together with non-
blocking sendfile(2).  It marked mbufs in a sending socket buffer that
could be ready to sent, but are sitting behind an M_NOTREADY mbuf(s), that
blocks them.

You may consider this flag as an INVARIANT flag that helped to ensure
socket buffer consistency.  Or maybe the socket code was so convoluted
back then, that it was unclear if sbfree() may be called on an mbuf that
is in the middle of the buffer, and I decided to introduce the flag to
protect against that.  With today state of socket buffer code it became
clear that the latter cannot happen.  And this commit adds an assertion
proving that.

Reviewed by:		markj
Differential Revision:	https://reviews.freebsd.org/D50728
This commit is contained in:
Gleb Smirnoff 2025-07-25 13:06:28 -07:00
parent f2c2ed7df3
commit b93e930ca2
6 changed files with 22 additions and 36 deletions
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6
sys/dev/cxgbe/tom/t4_cpl_io.c
View file

@ -703,7 +703,7 @@ t4_push_frames(struct adapter *sc, struct toepcb *toep, int drop)
for (m = sndptr; m != NULL; m = m->m_next) {
int n;
if ((m->m_flags & M_NOTAVAIL) != 0)
if ((m->m_flags & M_NOTREADY) != 0)
break;
if (m->m_flags & M_EXTPG) {
#ifdef KERN_TLS
@ -787,7 +787,7 @@ t4_push_frames(struct adapter *sc, struct toepcb *toep, int drop)
/* nothing to send */
if (plen == 0) {
KASSERT(m == NULL || (m->m_flags & M_NOTAVAIL) != 0,
KASSERT(m == NULL || (m->m_flags & M_NOTREADY) != 0,
("%s: nothing to send, but m != NULL is ready",
__func__));
break;
@ -880,7 +880,7 @@ t4_push_frames(struct adapter *sc, struct toepcb *toep, int drop)
toep->txsd_avail--;
t4_l2t_send(sc, wr, toep->l2te);
} while (m != NULL && (m->m_flags & M_NOTAVAIL) == 0);
} while (m != NULL && (m->m_flags & M_NOTREADY) == 0);
/* Send a FIN if requested, but only if there's no more data to send */
if (m == NULL && toep->flags & TPF_SEND_FIN)

4
sys/dev/cxgbe/tom/t4_tls.c
View file

@ -563,7 +563,7 @@ t4_push_ktls(struct adapter *sc, struct toepcb *toep, int drop)
* If there is no ready data to send, wait until more
* data arrives.
*/
if (m == NULL || (m->m_flags & M_NOTAVAIL) != 0) {
if (m == NULL || (m->m_flags & M_NOTREADY) != 0) {
if (sowwakeup)
sowwakeup_locked(so);
else
@ -614,7 +614,7 @@ t4_push_ktls(struct adapter *sc, struct toepcb *toep, int drop)
/* Shove if there is no additional data pending. */
shove = ((m->m_next == NULL ||
(m->m_next->m_flags & M_NOTAVAIL) != 0)) &&
(m->m_next->m_flags & M_NOTREADY) != 0)) &&
(tp->t_flags & TF_MORETOCOME) == 0;
if (sb->sb_flags & SB_AUTOSIZE &&

2
sys/kern/uipc_ktls.c
View file

@ -1207,7 +1207,7 @@ sb_mark_notready(struct sockbuf *sb)
for (; m != NULL; m = m->m_next) {
KASSERT(m->m_nextpkt == NULL, ("%s: m_nextpkt != NULL",
__func__));
KASSERT((m->m_flags & M_NOTAVAIL) == 0, ("%s: mbuf not avail",
KASSERT((m->m_flags & M_NOTREADY) == 0, ("%s: mbuf not ready",
__func__));
KASSERT(sb->sb_acc >= m->m_len, ("%s: sb_acc < m->m_len",
__func__));

42
sys/kern/uipc_sockbuf.c
View file

@ -195,14 +195,14 @@ int
sbready(struct sockbuf *sb, struct mbuf *m0, int count)
{
struct mbuf *m;
u_int blocker;
bool blocker;
SOCKBUF_LOCK_ASSERT(sb);
KASSERT(sb->sb_fnrdy != NULL, ("%s: sb %p NULL fnrdy", __func__, sb));
KASSERT(count > 0, ("%s: invalid count %d", __func__, count));
m = m0;
blocker = (sb->sb_fnrdy == m) ? M_BLOCKED : 0;
blocker = (sb->sb_fnrdy == m);
while (count > 0) {
KASSERT(m->m_flags & M_NOTREADY,
@ -217,8 +217,7 @@ sbready(struct sockbuf *sb, struct mbuf *m0, int count)
m->m_epg_nrdy = 0;
} else
count--;
m->m_flags &= ~(M_NOTREADY | blocker);
m->m_flags &= ~M_NOTREADY;
if (blocker)
sb->sb_acc += m->m_len;
m = m->m_next;
@ -240,12 +239,8 @@ sbready(struct sockbuf *sb, struct mbuf *m0, int count)
}
/* This one was blocking all the queue. */
for (; m && (m->m_flags & M_NOTREADY) == 0; m = m->m_next) {
KASSERT(m->m_flags & M_BLOCKED,
("%s: m %p !M_BLOCKED", __func__, m));
m->m_flags &= ~M_BLOCKED;
for (; m && (m->m_flags & M_NOTREADY) == 0; m = m->m_next)
sb->sb_acc += m->m_len;
}
sb->sb_fnrdy = m;
sbready_compress(sb, m0, m);
@ -269,8 +264,7 @@ sballoc(struct sockbuf *sb, struct mbuf *m)
sb->sb_fnrdy = m;
else
sb->sb_acc += m->m_len;
} else
m->m_flags |= M_BLOCKED;
}
if (m->m_type != MT_DATA && m->m_type != MT_OOBDATA)
sb->sb_ctl += m->m_len;
@ -287,29 +281,29 @@ sballoc(struct sockbuf *sb, struct mbuf *m)
void
sbfree(struct sockbuf *sb, struct mbuf *m)
{
struct mbuf *n;
#if 0 /* XXX: not yet: soclose() call path comes here w/o lock. */
SOCKBUF_LOCK_ASSERT(sb);
#endif
sb->sb_ccc -= m->m_len;
if (!(m->m_flags & M_NOTAVAIL))
sb->sb_acc -= m->m_len;
if (m == sb->sb_fnrdy) {
struct mbuf *n;
KASSERT(m->m_flags & M_NOTREADY,
("%s: m %p !M_NOTREADY", __func__, m));
n = m->m_next;
while (n != NULL && !(n->m_flags & M_NOTREADY)) {
n->m_flags &= ~M_BLOCKED;
sb->sb_acc += n->m_len;
n = n->m_next;
}
sb->sb_fnrdy = n;
} else {
/* Assert that mbuf is not behind sb_fnrdy. */
for (n = sb->sb_fnrdy; n != NULL; n = n->m_next)
KASSERT(n != m, ("%s: sb %p freeing %p behind sb_fnrdy",
__func__, sb, m));
sb->sb_acc -= m->m_len;
}
if (m->m_type != MT_DATA && m->m_type != MT_OOBDATA)
@ -1129,13 +1123,7 @@ sbcheck(struct sockbuf *sb, const char *file, int line)
}
fnrdy = m;
}
if (fnrdy) {
if (!(m->m_flags & M_NOTAVAIL)) {
printf("sb %p: fnrdy %p, m %p is avail\n",
sb, sb->sb_fnrdy, m);
goto fail;
}
} else
if (fnrdy == NULL)
acc += m->m_len;
ccc += m->m_len;
mbcnt += MSIZE;
@ -1602,8 +1590,8 @@ sbcut_internal(struct sockbuf *sb, int len)
next = m->m_nextpkt;
}
if (m->m_len > len) {
KASSERT(!(m->m_flags & M_NOTAVAIL),
("%s: m %p M_NOTAVAIL", __func__, m));
KASSERT(!(m->m_flags & M_NOTREADY),
("%s: m %p M_NOTREADY", __func__, m));
m->m_len -= len;
m->m_data += len;
sb->sb_ccc -= len;

2
sys/kern/uipc_socket.c
View file

@ -3342,7 +3342,7 @@ deliver:
for (m = sb->sb_mb;
m != NULL && m->m_len <= len;
m = m->m_next) {
KASSERT(!(m->m_flags & M_NOTAVAIL),
KASSERT(!(m->m_flags & M_NOTREADY),
("%s: m %p not available", __func__, m));
len -= m->m_len;
uio->uio_resid -= m->m_len;

2
sys/sys/sockbuf.h
View file

@ -210,8 +210,6 @@ typedef enum { SO_RCV, SO_SND } sb_which;
* Socket buffer private mbuf(9) flags.
*/
#define M_NOTREADY M_PROTO1 /* m_data not populated yet */
#define M_BLOCKED M_PROTO2 /* M_NOTREADY in front of m */
#define M_NOTAVAIL (M_NOTREADY | M_BLOCKED)
void sbappend(struct sockbuf *sb, struct mbuf *m, int flags);
void sbappend_locked(struct sockbuf *sb, struct mbuf *m, int flags);