[LTP] lib: Use backoff polling to wait for loop device nodes

[linuxtestproject.agent@gmail.com]

Hi Wake,

On Fri, 7 Aug 2026, Wake Liu wrote:
> lib: Use backoff polling to wait for loop device nodes

> +				path_set = TST_RETRY_FN_EXP_BACKOFF(
> +					set_dev_loop_path(rc, path, path_len),
> +					TST_RETVAL_EQ0, 1);

Could the backoff arithmetic be made overflow-safe before these two new
uses?

LTP_TIMEOUT_MUL=3000 is accepted by parse_mul(), which makes
tst_max_delay_ 3,000,000,000. The unsigned int tst_delay_ reaches
2,147,483,648, still compares less than tst_max_delay_, and then doubles
to zero. If the device node does not appear, both new paths then retry
forever instead of honoring the multiplied timeout.

Verdict - Needs revision

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