Author: cem Date: Wed Aug 7 19:23:07 2019 New Revision: 350691 URL: https://svnweb.freebsd.org/changeset/base/350691
Log: sbuf(9): Add NOWAIT dynamic buffer extension mode The goal is to avoid some kinds of low-memory deadlock when formatting heap-allocated buffers. Reviewed by: vangyzen Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D21015 Modified: head/share/man/man9/sbuf.9 head/sys/kern/subr_sbuf.c head/sys/sys/sbuf.h Modified: head/share/man/man9/sbuf.9 ============================================================================== --- head/share/man/man9/sbuf.9 Wed Aug 7 19:18:32 2019 (r350690) +++ head/share/man/man9/sbuf.9 Wed Aug 7 19:23:07 2019 (r350691) @@ -25,7 +25,7 @@ .\" .\" $FreeBSD$ .\" -.Dd May 7, 2019 +.Dd August 7, 2019 .Dt SBUF 9 .Os .Sh NAME @@ -288,6 +288,11 @@ If a record grows sufficiently large such that it fill 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 Modified: head/sys/kern/subr_sbuf.c ============================================================================== --- head/sys/kern/subr_sbuf.c Wed Aug 7 19:18:32 2019 (r350690) +++ head/sys/kern/subr_sbuf.c Wed Aug 7 19:23:07 2019 (r350691) @@ -56,11 +56,11 @@ __FBSDID("$FreeBSD$"); #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 @@ static MALLOC_DEFINE(M_SBUF, "sbuf", "string buffers") #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 @@ sbuf_extend(struct sbuf *s, int addlen) 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); @@ -198,7 +200,7 @@ sbuf_newbuf(struct sbuf *s, char *buf, int length, int s->s_size = length; s->s_buf = buf; - if ((s->s_flags & SBUF_AUTOEXTEND) == 0) { + if (!SBUF_CANEXTEND(s)) { KASSERT(s->s_size >= SBUF_MINSIZE, ("attempt to create an sbuf smaller than %d bytes", SBUF_MINSIZE)); @@ -207,10 +209,10 @@ sbuf_newbuf(struct sbuf *s, char *buf, int length, int if (s->s_buf != NULL) return (s); - if ((flags & SBUF_AUTOEXTEND) != 0) + if (SBUF_CANEXTEND(s)) s->s_size = sbuf_extendsize(s->s_size); - s->s_buf = SBMALLOC(s->s_size); + s->s_buf = SBMALLOC(s->s_size, SBUF_MALLOCFLAG(s)); if (s->s_buf == NULL) return (NULL); SBUF_SETFLAG(s, SBUF_DYNAMIC); @@ -235,7 +237,7 @@ sbuf_new(struct sbuf *s, char *buf, int length, int fl if (s != NULL) return (sbuf_newbuf(s, buf, length, flags)); - s = SBMALLOC(sizeof(*s)); + s = SBMALLOC(sizeof(*s), (flags & SBUF_NOWAIT) ? M_NOWAIT : M_WAITOK); if (s == NULL) return (NULL); if (sbuf_newbuf(s, buf, length, flags) == NULL) { Modified: head/sys/sys/sbuf.h ============================================================================== --- head/sys/sys/sbuf.h Wed Aug 7 19:18:32 2019 (r350690) +++ head/sys/sys/sbuf.h Wed Aug 7 19:23:07 2019 (r350691) @@ -52,6 +52,7 @@ struct sbuf { #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() */ _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
