On Thu, Nov 28, 2024 at 03:25:32PM +0100, Amir Goldstein wrote:
> Commit 2a010c412853 ("fs: don't block i_writecount during exec") removed
> the legacy behavior of getting ETXTBSY on attempt to open and executable
> file for write while it is being executed.
>
> This commit was reverted because an application that depends on this
> legacy behavior was broken by the change.
>
> We need to allow HSM writing into executable files while executed to
> fill their content on-the-fly.
>
> To that end, disable the ETXTBSY legacy behavior for files that are
> watched by pre-content events.
>
> This change is not expected to cause regressions with existing systems
> which do not have any pre-content event listeners.
>
> +
> +/*
> + * Do not prevent write to executable file when watched by pre-content events.
> + */
> +static inline int exe_file_deny_write_access(struct file *exe_file)
> +{
> + if (unlikely(FMODE_FSNOTIFY_HSM(exe_file->f_mode)))
> + return 0;
> + return deny_write_access(exe_file);
> +}
> +static inline void exe_file_allow_write_access(struct file *exe_file)
> +{
> + if (unlikely(FMODE_FSNOTIFY_HSM(exe_file->f_mode)))
> + return;
> + allow_write_access(exe_file);
> +}
> +
so this depends on FMODE_FSNOTIFY_HSM showing up on the file before any
of the above calls and staying there for its lifetime -- does that hold?
I think it would be less error prone down the road to maintain the
counters, except not return the error if HSM is on.
