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Index: share/man/man9/sbuf.9
===================================================================
--- share/man/man9/sbuf.9
+++ share/man/man9/sbuf.9
@@ -25,7 +25,7 @@
.\"
.\" $FreeBSD$
.\"
-.Dd May 7, 2019
+.Dd July 21, 2019
.Dt SBUF 9
.Os
.Sh NAME
@@ -43,7 +43,7 @@
.Nm sbuf_bcpy ,
.Nm sbuf_cat ,
.Nm sbuf_copyin ,
-.Nm sbuf_cpy ,
+.Nm sbuf_cpy 21
.Nm sbuf_printf ,
.Nm sbuf_vprintf ,
.Nm sbuf_putc ,
@@ -288,6 +288,11 @@
and therefore cannot be drained without being split, an error of
.Er EDEADLK
is set.
+.It Dv SBUF_NOWAIT
+Indicates that attempts to extend the storage buffer should fail in low memory
+conditions, like
+.Xr malloc 9
+.Dv M_NOWAIT .
.El
.Pp
Note that if
Index: sys/kern/subr_sbuf.c
===================================================================
--- sys/kern/subr_sbuf.c
+++ sys/kern/subr_sbuf.c
@@ -56,11 +56,11 @@
#ifdef _KERNEL
static MALLOC_DEFINE(M_SBUF, "sbuf", "string buffers");
-#define SBMALLOC(size) malloc(size, M_SBUF, M_WAITOK|M_ZERO)
+#define SBMALLOC(size, flags) malloc(size, M_SBUF, (flags) | M_ZERO)
#define SBFREE(buf) free(buf, M_SBUF)
#else /* _KERNEL */
#define KASSERT(e, m)
-#define SBMALLOC(size) calloc(1, size)
+#define SBMALLOC(size, flags) calloc(1, size)
#define SBFREE(buf) free(buf)
#endif /* _KERNEL */
@@ -77,6 +77,8 @@
#define SBUF_NULINCLUDED(s) ((s)->s_flags & SBUF_INCLUDENUL)
#define SBUF_ISDRAINTOEOR(s) ((s)->s_flags & SBUF_DRAINTOEOR)
#define SBUF_DODRAINTOEOR(s) (SBUF_ISSECTION(s) && SBUF_ISDRAINTOEOR(s))
+#define SBUF_MALLOCFLAG(s) \
+ (((s)->s_flags & SBUF_NOWAIT) ? M_NOWAIT : M_WAITOK)
/*
* Set / clear flags
@@ -171,7 +173,7 @@
if (!SBUF_CANEXTEND(s))
return (-1);
newsize = sbuf_extendsize(s->s_size + addlen);
- newbuf = SBMALLOC(newsize);
+ newbuf = SBMALLOC(newsize, SBUF_MALLOCFLAG(s));
if (newbuf == NULL)
return (-1);
memcpy(newbuf, s->s_buf, s->s_size);
@@ -210,7 +212,7 @@
if ((flags & SBUF_AUTOEXTEND) != 0)
s->s_size = sbuf_extendsize(s->s_size);
- s->s_buf = SBMALLOC(s->s_size);
+ s->s_buf = SBMALLOC(s->s_size, M_WAITOK);
if (s->s_buf == NULL)
return (NULL);
SBUF_SETFLAG(s, SBUF_DYNAMIC);
@@ -235,7 +237,7 @@
if (s != NULL)
return (sbuf_newbuf(s, buf, length, flags));
- s = SBMALLOC(sizeof(*s));
+ s = SBMALLOC(sizeof(*s), M_WAITOK);
if (s == NULL)
return (NULL);
if (sbuf_newbuf(s, buf, length, flags) == NULL) {
Index: sys/sys/sbuf.h
===================================================================
--- sys/sys/sbuf.h
+++ sys/sys/sbuf.h
@@ -52,6 +52,7 @@
#define SBUF_AUTOEXTEND 0x00000001 /* automatically extend buffer */
#define SBUF_INCLUDENUL 0x00000002 /* nulterm byte is counted in len */
#define SBUF_DRAINTOEOR 0x00000004 /* use section 0 as drain EOR marker */
+#define SBUF_NOWAIT 0x00000008 /* Extend with non-blocking malloc */
#define SBUF_USRFLAGMSK 0x0000ffff /* mask of flags the user may specify */
#define SBUF_DYNAMIC 0x00010000 /* s_buf must be freed */
#define SBUF_FINISHED 0x00020000 /* set by sbuf_finish() */

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