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Mon, 18 Feb 2019 06:37:50 -0800 (PST) Received: from box ([146.247.46.6]) by smtp.gmail.com with ESMTPSA id y22sm5293249wmj.6.2019.02.18.06.37.49 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 18 Feb 2019 06:37:50 -0800 (PST) Date: Mon, 18 Feb 2019 16:37:47 +0200 From: Slavomir Kaslev To: Steven Rostedt Cc: linux-trace-devel@vger.kernel.org, slavomir.kaslev@gmail.com Subject: Re: [RFC PATCH v6 07/11] trace-cmd: Add `trace-cmd setup-guest` command Message-ID: <20190218143746.GD11734@box> References: <20190214141335.28144-1-kaslevs@vmware.com> <20190214141335.28144-8-kaslevs@vmware.com> <20190214154132.43082ece@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190214154132.43082ece@gandalf.local.home> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-trace-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-trace-devel@vger.kernel.org On Thu, Feb 14, 2019 at 03:41:32PM -0500, Steven Rostedt wrote: > On Thu, 14 Feb 2019 16:13:31 +0200 > Slavomir Kaslev wrote: > > > Add `trace-cmd setup-guest` command that creates the necessary FIFOs for tracing > > a guest over FIFOs instead of vsockets. > > > > Signed-off-by: Slavomir Kaslev > > --- > > tracecmd/Makefile | 1 + > > tracecmd/include/trace-local.h | 6 ++ > > tracecmd/trace-cmd.c | 1 + > > tracecmd/trace-setup-guest.c | 186 +++++++++++++++++++++++++++++++++ > > tracecmd/trace-usage.c | 8 ++ > > 5 files changed, 202 insertions(+) > > create mode 100644 tracecmd/trace-setup-guest.c > > > > diff --git a/tracecmd/Makefile b/tracecmd/Makefile > > index 865b1c6..d3e3080 100644 > > --- a/tracecmd/Makefile > > +++ b/tracecmd/Makefile > > @@ -35,6 +35,7 @@ TRACE_CMD_OBJS += trace-msg.o > > > > ifeq ($(VSOCK_DEFINED), 1) > > TRACE_CMD_OBJS += trace-agent.o > > +TRACE_CMD_OBJS += trace-setup-guest.o > > endif > > > > ALL_OBJS := $(TRACE_CMD_OBJS:%.o=$(bdir)/%.o) > > diff --git a/tracecmd/include/trace-local.h b/tracecmd/include/trace-local.h > > index 823d323..b23130e 100644 > > --- a/tracecmd/include/trace-local.h > > +++ b/tracecmd/include/trace-local.h > > @@ -14,6 +14,10 @@ > > > > #define TRACE_AGENT_DEFAULT_PORT 823 > > > > +#define GUEST_PIPE_NAME "trace-pipe-cpu" > > +#define GUEST_DIR_FMT "/var/lib/trace-cmd/virt/%s" > > +#define GUEST_FIFO_FMT GUEST_DIR_FMT "/" GUEST_PIPE_NAME "%d" > > + > > extern int debug; > > extern int quiet; > > > > @@ -68,6 +72,8 @@ void trace_listen(int argc, char **argv); > > > > void trace_agent(int argc, char **argv); > > > > +void trace_setup_guest(int argc, char **argv); > > + > > void trace_restore(int argc, char **argv); > > > > void trace_clear(int argc, char **argv); > > diff --git a/tracecmd/trace-cmd.c b/tracecmd/trace-cmd.c > > index 3ae5e2e..4da82b4 100644 > > --- a/tracecmd/trace-cmd.c > > +++ b/tracecmd/trace-cmd.c > > @@ -85,6 +85,7 @@ struct command commands[] = { > > {"listen", trace_listen}, > > #ifdef VSOCK > > {"agent", trace_agent}, > > + {"setup-guest", trace_setup_guest}, > > #endif > > {"split", trace_split}, > > {"restore", trace_restore}, > > diff --git a/tracecmd/trace-setup-guest.c b/tracecmd/trace-setup-guest.c > > new file mode 100644 > > index 0000000..875ac0e > > --- /dev/null > > +++ b/tracecmd/trace-setup-guest.c > > @@ -0,0 +1,186 @@ > > +// SPDX-License-Identifier: GPL-2.0 > > +/* > > + * Copyright (C) 2019 VMware Inc, Slavomir Kaslev > > + * > > + */ > > + > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > + > > +#include "trace-local.h" > > +#include "trace-msg.h" > > + > > +static int make_dir(const char *path, mode_t mode) > > +{ > > + char *buf, *end, *p; > > + int ret = 0; > > + > > + buf = strdup(path); > > + end = buf + strlen(buf); > > + > > + for (p = buf; p < end; p++) { > > + for (; p < end && *p == '/'; p++); > > + for (; p < end && *p != '/'; p++); > > Why not: > for (p = buf; p && *p; p++) { > > for (; *p == '/'; p++); > p = index(p, '/'); > if (p) > *p = '\0'; > > > > + > > + *p = '\0'; > > + ret = mkdir(buf, mode); > > + if (ret < 0) { > > + if (errno != EEXIST) { > > + ret = -errno; > > + break; > > + } > > + ret = 0; > > + } > > if (p) > *p = '/'; > > ? > > No need for "end". > > -- Steve > > > + *p = '/'; > > + } > > + > > + free(buf); > > + return ret; > > +} > > + > This won't work as proposed: `p` will be NULL on the last iteration but will still get incremented from the outer for-loop and the check (p && *p) won't get triggered (p == 0x01 in this case). A fixed version might look like this: static int make_dir(const char *path, mode_t mode) { char buf[PATH_MAX+1], *p; int ret = 0; strncpy(buf, path, sizeof(buf)); for (p = buf; *p; p++) { for (; *p == '/'; p++); p = strchr(p, '/'); if (p) *p = '\0'; ret = mkdir(buf, mode); if (ret < 0) { if (errno != EEXIST) { ret = -errno; break; } ret = 0; } if (!p) break; *p = '/'; } return ret; } OTOH I find the original version much more readable: static int make_dir(const char *path, mode_t mode) { char buf[PATH_MAX+1], *end, *p; int ret = 0; end = stpncpy(buf, path, sizeof(buf)); for (p = buf; p < end; p++) { for (; p < end && *p == '/'; p++); for (; p < end && *p != '/'; p++); *p = '\0'; ret = mkdir(buf, mode); if (ret < 0) { if (errno != EEXIST) { ret = -errno; break; } ret = 0; } *p = '/'; } return ret; } The intent behind `*p = '\0'; ... *p = '/';` is more clearly expressed in this version without getting bogged down by strchr() edge case handling. Since this is not on a performance critical path how about sticking to the more readable of the two? -Slavi