On Mon, 17 Feb 2020 19:39:56 +0200
"Tzvetomir Stoyanov (VMware)" <tz.stoyanov@xxxxxxxxx> wrote:
> The existing tracefs_instance_file_write() API truncates the file before writing to it.
> The are use cases where the file must not be truncated. The new
> tracefs_instance_file_append()
> API appends to the end of the file.
>
> Signed-off-by: Tzvetomir Stoyanov (VMware) <tz.stoyanov@xxxxxxxxx>
> ---
> include/tracefs/tracefs.h | 2 ++
> lib/tracefs/tracefs-instance.c | 40 ++++++++++++++++++++++++++++++----
> 2 files changed, 38 insertions(+), 4 deletions(-)
>
> diff --git a/include/tracefs/tracefs.h b/include/tracefs/tracefs.h
> index bd3f732..16fcb66 100644
> --- a/include/tracefs/tracefs.h
> +++ b/include/tracefs/tracefs.h
> @@ -30,6 +30,8 @@ tracefs_instance_get_file(struct tracefs_instance *instance, const char *file);
> char *tracefs_instance_get_dir(struct tracefs_instance *instance);
> int tracefs_instance_file_write(struct tracefs_instance *instance,
> const char *file, const char *str);
> +int tracefs_instance_file_append(struct tracefs_instance *instance,
> + const char *file, const char *str);
> char *tracefs_instance_file_read(struct tracefs_instance *instance,
> char *file, int *psize);
>
> diff --git a/lib/tracefs/tracefs-instance.c b/lib/tracefs/tracefs-instance.c
> index b96ab61..e6b0a95 100644
> --- a/lib/tracefs/tracefs-instance.c
> +++ b/lib/tracefs/tracefs-instance.c
> @@ -176,12 +176,16 @@ char *tracefs_instance_get_name(struct tracefs_instance *instance)
> return NULL;
> }
>
> -static int write_file(const char *file, const char *str)
> +static int write_file(const char *file, const char *str, bool appned)
Typo, s/appned/append/
> {
> int ret;
> int fd;
>
> - fd = open(file, O_WRONLY | O_TRUNC);
> + if (appned)
> + fd = open(file, O_WRONLY | O_APPEND);
> + else
> + fd = open(file, O_WRONLY | O_TRUNC);
> +
> if (fd < 0) {
> warning("Failed to open '%s'", file);
> return -1;
> @@ -198,7 +202,9 @@ static int write_file(const char *file, const char *str)
> * @file: name of the file
> * @str: nul terminated string, that will be written in the file.
> *
> - * Returns the number of written bytes, or -1 in case of an error
> + * Returns the number of written bytes, or -1 in case of an error.
> + * The content of the file is replaced with the new one.
> + *
> */
> int tracefs_instance_file_write(struct tracefs_instance *instance,
> const char *file, const char *str)
> @@ -212,7 +218,33 @@ int tracefs_instance_file_write(struct tracefs_instance *instance,
> return -1;
> ret = stat(path, &st);
> if (ret == 0)
> - ret = write_file(path, str);
> + ret = write_file(path, str, false);
> + tracefs_put_tracing_file(path);
> +
> + return ret;
> +}
> +
> +/**
> + * tracefs_instance_file_append - Append to a trace file of specific instance.
> + * @instance: ftrace instance, can be NULL for the top instance
> + * @file: name of the file
> + * @str: nul terminated string, that will be written in the file.
> + *
> + * Returns the number of written bytes, or -1 in case of an error.
> + */
> +int tracefs_instance_file_append(struct tracefs_instance *instance,
> + const char *file, const char *str)
> +{
> + struct stat st;
> + char *path;
> + int ret;
> +
> + path = tracefs_instance_get_file(instance, file);
> + if (!path)
> + return -1;
> + ret = stat(path, &st);
> + if (ret == 0)
> + ret = write_file(path, str, true);
> tracefs_put_tracing_file(path);
>
> return ret;
I would actually make one more static helper as the above two functions
are identical except for the write file part.
static int instance_file_write(struct tracefs_instance *instance,
const char *file, const char *str,
bool append)
{
struct stat st;
char *path;
int ret;
path = tracefs_instance_get_file(instance, file);
if (!path)
return -1;
ret = stat(path, &st);
if (ret == 0)
ret = write_file(path, str, append);
tracefs_put_tracing_file(path);
return ret;
}
int tracefs_instance_file_write(struct tracefs_instance *instance,
const char *file, const char *str)
{
return instance_file_write(instance, file, str, false);
}
int tracefs_instance_file_append(struct tracefs_instance *instance,
const char *file, const char *str)
{
return instance_file_write(instance, file, str, true);
}
-- Steve
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