[PATCH][makedumpfile -R] Promptly return error on truncated regular file.

[Aureau, Georges (Kernel Tools ERT)]

Hello,

Forget about this PATCH, it is missing some option as to control the behavior.
What I'm really after is to promptly detect truncated flatten files without the 10-minute timeout.
This would be assuming stdin is not a file in the process of being created (where eof is a moving target).
Maybe something like "makedumpfile -R --some-option", where some-option would cause returning an
immediate error in premature EOF:
-                       if (TIMEOUT_STDIN < (tm - last_time)) {
+                       if (some_option || TIMEOUT_STDIN < (tm - last_time)) {

Thanks,
Georges

I 
|-----Original Message-----
|From: Aureau, Georges (Kernel Tools ERT)
|Sent: Friday, October 31, 2025 9:41 PM
|To: kexec at lists.infradead.org
|Cc: yamazaki-msmt at nec.com; HAGIO KAZUHITO(萩尾　一仁) <k-hagio-
|ab at nec.com>
|Subject: [PATCH][makedumpfile -R] Promptly return error on truncated regular
|file.
|
|[PATCH][makedumpfile -R] Promptly return error on truncated regular file.
|
|When reaching the end-of-file on a truncated input regular file,
|makedumpfile -R is looping for 10 minutes before producing an error.
|This is confusing for users. When stdin is a regular file, an improved
|behavior is to promptly return an EOF error.
|
|Signed-off-by: Georges Aureau <georges.aureau at hpe.com>
|--
|diff --git a/makedumpfile.c b/makedumpfile.c
|index 12fb0d8..295b3cc 100644
|--- a/makedumpfile.c
|+++ b/makedumpfile.c
|@@ -5135,6 +5135,21 @@ write_cache_zero(struct cache_data *cd, size_t size)
|        return write_cache_bufsz(cd);
| }
|
|+int
|+is_stdin_regular_file(void)
|+{
|+       struct stat st;
|+       static int regular_file = -1;
|+       if (regular_file == -1) {
|+               if (fstat(STDIN_FILENO, &st) == -1) {
|+                       regular_file = FALSE;
|+               } else {
|+                       regular_file = S_ISREG(st.st_mode) ? TRUE : FALSE;
|+               }
|+       }
|+       return regular_file;
|+}
|+
| int
| read_buf_from_stdin(void *buf, int buf_size)
| {
|@@ -5154,11 +5169,12 @@ read_buf_from_stdin(void *buf, int buf_size)
|
|                } else if (0 == tmp_read_size) {
|                        /*
|-                        * If it cannot get any data from a standard input
|+                        * If we reach end-of-file on regular file, or
|+                        * if we cannot get any data from a standard input
|                         * for a long time, break this loop.
|                         */
|                        tm = time(NULL);
|-                       if (TIMEOUT_STDIN < (tm - last_time)) {
|+                       if (is_stdin_regular_file() || TIMEOUT_STDIN < (tm - last_time)) {
|                                ERRMSG("Can't get any data from STDIN.\n");
|                                return FALSE;
|                        }
|
|