The branch stable/12 has been updated by imp: URL: https://cgit.FreeBSD.org/src/commit/?id=81999965113107eb9cecc217a4f496dd78c1ca3a
commit 81999965113107eb9cecc217a4f496dd78c1ca3a Author: Conrad Meyer <[email protected]> AuthorDate: 2019-08-07 19:23:07 +0000 Commit: Warner Losh <[email protected]> CommitDate: 2021-07-16 17:43:55 +0000 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 (cherry picked from commit 71db411eb627601a5f9a3464f88d75741927ce60) --- share/man/man9/sbuf.9 | 11 +++++++++-- sys/kern/subr_sbuf.c | 16 +++++++++------- sys/sys/sbuf.h | 1 + 3 files changed, 19 insertions(+), 9 deletions(-) diff --git a/share/man/man9/sbuf.9 b/share/man/man9/sbuf.9 index 519e801e4868..4184f77631a7 100644 --- a/share/man/man9/sbuf.9 +++ b/share/man/man9/sbuf.9 @@ -25,7 +25,7 @@ .\" .\" $FreeBSD$ .\" -.Dd August 26, 2020 +.Dd July 12, 2021 .Dt SBUF 9 .Os .Sh NAME @@ -278,7 +278,14 @@ as a record boundary marker that will be used during drain operations to avoid records being split. If a record grows sufficiently large such that it fills the .Fa sbuf -and therefore cannot be drained without being split, an error of EDEADLK is set. +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 diff --git a/sys/kern/subr_sbuf.c b/sys/kern/subr_sbuf.c index 03f7b1e94c51..4a046cc41787 100644 --- a/sys/kern/subr_sbuf.c +++ b/sys/kern/subr_sbuf.c @@ -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 flags) 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 flags) 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 flags) 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) { diff --git a/sys/sys/sbuf.h b/sys/sys/sbuf.h index 1927996c8f38..9ef9bad7d9be 100644 --- a/sys/sys/sbuf.h +++ b/sys/sys/sbuf.h @@ -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() */ _______________________________________________ [email protected] mailing list https://lists.freebsd.org/mailman/listinfo/dev-commits-src-all To unsubscribe, send any mail to "[email protected]"
