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SubjectRe: [PATCH 04/12] perf inject: Add facility to do in place update
Em Thu, Apr 29, 2021 at 03:58:46PM +0300, Adrian Hunter escreveu:
> When there is a need to modify only timestamps, it is much simpler and
> quicker to do it to the existing file rather than re-write all the
> contents.
>
> In preparation for that, add the ability to modify the input file in place.
> In practice that just means making the file descriptor and mmaps writable.

Clever, and you took care of checking that the constraints are met, and
I see this paves the way for the actual 'perf inject' option that uses
this new 'perf inject' mode.

- Arnaldo

> Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
> ---
> tools/perf/builtin-inject.c | 30 ++++++++++++++++++++++++++----
> tools/perf/util/data.c | 3 ++-
> tools/perf/util/data.h | 1 +
> tools/perf/util/header.c | 5 +++++
> tools/perf/util/session.c | 6 +++++-
> 5 files changed, 39 insertions(+), 6 deletions(-)
>
> diff --git a/tools/perf/builtin-inject.c b/tools/perf/builtin-inject.c
> index ddccc0eb7390..ddfdeb85c586 100644
> --- a/tools/perf/builtin-inject.c
> +++ b/tools/perf/builtin-inject.c
> @@ -43,6 +43,8 @@ struct perf_inject {
> bool have_auxtrace;
> bool strip;
> bool jit_mode;
> + bool in_place_update;
> + bool in_place_update_dry_run;
> const char *input_name;
> struct perf_data output;
> u64 bytes_written;
> @@ -701,7 +703,7 @@ static int __cmd_inject(struct perf_inject *inject)
> int ret = -EINVAL;
> struct perf_session *session = inject->session;
> struct perf_data *data_out = &inject->output;
> - int fd = perf_data__fd(data_out);
> + int fd = inject->in_place_update ? -1 : perf_data__fd(data_out);
> u64 output_data_offset;
>
> signal(SIGINT, sig_handler);
> @@ -759,14 +761,14 @@ static int __cmd_inject(struct perf_inject *inject)
> if (!inject->itrace_synth_opts.set)
> auxtrace_index__free(&session->auxtrace_index);
>
> - if (!data_out->is_pipe)
> + if (!data_out->is_pipe && !inject->in_place_update)
> lseek(fd, output_data_offset, SEEK_SET);
>
> ret = perf_session__process_events(session);
> if (ret)
> return ret;
>
> - if (!data_out->is_pipe) {
> + if (!data_out->is_pipe && !inject->in_place_update) {
> if (inject->build_ids)
> perf_header__set_feat(&session->header,
> HEADER_BUILD_ID);
> @@ -900,7 +902,27 @@ int cmd_inject(int argc, const char **argv)
> return -1;
> }
>
> - if (perf_data__open(&inject.output)) {
> + if (inject.in_place_update) {
> + if (!strcmp(inject.input_name, "-")) {
> + pr_err("Input file name required for in-place updating\n");
> + return -1;
> + }
> + if (strcmp(inject.output.path, "-")) {
> + pr_err("Output file name must not be specified for in-place updating\n");
> + return -1;
> + }
> + if (!data.force && !inject.in_place_update_dry_run) {
> + char reply[10];
> +
> + printf("The input file will be updated in place. OK? (y/n) ");
> + if (!fgets(reply, sizeof(reply), stdin) || strcmp(reply, "y\n")) {
> + pr_err("Aborted\n");
> + return -1;
> + }
> + }
> + if (!inject.in_place_update_dry_run)
> + data.in_place_update = true;
> + } else if (perf_data__open(&inject.output)) {
> perror("failed to create output file");
> return -1;
> }
> diff --git a/tools/perf/util/data.c b/tools/perf/util/data.c
> index f29af4fc3d09..209fe63d4e49 100644
> --- a/tools/perf/util/data.c
> +++ b/tools/perf/util/data.c
> @@ -239,11 +239,12 @@ static bool is_dir(struct perf_data *data)
>
> static int open_file_read(struct perf_data *data)
> {
> + int flags = data->in_place_update ? O_RDWR : O_RDONLY;
> struct stat st;
> int fd;
> char sbuf[STRERR_BUFSIZE];
>
> - fd = open(data->file.path, O_RDONLY);
> + fd = open(data->file.path, flags);
> if (fd < 0) {
> int err = errno;
>
> diff --git a/tools/perf/util/data.h b/tools/perf/util/data.h
> index 62a3e66fbee8..c9de82af5584 100644
> --- a/tools/perf/util/data.h
> +++ b/tools/perf/util/data.h
> @@ -31,6 +31,7 @@ struct perf_data {
> bool is_dir;
> bool force;
> bool use_stdio;
> + bool in_place_update;
> enum perf_data_mode mode;
>
> struct {
> diff --git a/tools/perf/util/header.c b/tools/perf/util/header.c
> index aa1e42518d37..02b13c7a23be 100644
> --- a/tools/perf/util/header.c
> +++ b/tools/perf/util/header.c
> @@ -3814,6 +3814,11 @@ int perf_session__read_header(struct perf_session *session)
> if (perf_file_header__read(&f_header, header, fd) < 0)
> return -EINVAL;
>
> + if (header->needs_swap && data->in_place_update) {
> + pr_err("In-place update not supported when byte-swapping is required\n");
> + return -EINVAL;
> + }
> +
> /*
> * Sanity check that perf.data was written cleanly; data size is
> * initialized to 0 and updated only if the on_exit function is run.
> diff --git a/tools/perf/util/session.c b/tools/perf/util/session.c
> index eba3769be3f1..edd068ea8a6c 100644
> --- a/tools/perf/util/session.c
> +++ b/tools/perf/util/session.c
> @@ -2131,6 +2131,7 @@ struct reader {
> u64 data_size;
> u64 data_offset;
> reader_cb_t process;
> + bool in_place_update;
> };
>
> static int
> @@ -2164,7 +2165,9 @@ reader__process_events(struct reader *rd, struct perf_session *session,
> mmap_prot = PROT_READ;
> mmap_flags = MAP_SHARED;
>
> - if (session->header.needs_swap) {
> + if (rd->in_place_update) {
> + mmap_prot |= PROT_WRITE;
> + } else if (session->header.needs_swap) {
> mmap_prot |= PROT_WRITE;
> mmap_flags = MAP_PRIVATE;
> }
> @@ -2250,6 +2253,7 @@ static int __perf_session__process_events(struct perf_session *session)
> .data_size = session->header.data_size,
> .data_offset = session->header.data_offset,
> .process = process_simple,
> + .in_place_update = session->data->in_place_update,
> };
> struct ordered_events *oe = &session->ordered_events;
> struct perf_tool *tool = session->tool;
> --
> 2.17.1
>

--

- Arnaldo

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