On Tue 2021-06-15 23:49:50, Jia He wrote: > Previously, the specifier '%pD' is for printing dentry name of struct > file. It may not be perfect (by default it only prints one component.) > > As suggested by Linus at [1]: > A dentry has a parent, but at the same time, a dentry really does > inherently have "one name" (and given just the dentry pointers, you > can't show mount-related parenthood, so in many ways the "show just > one name" makes sense for "%pd" in ways it doesn't necessarily for > "%pD"). But while a dentry arguably has that "one primary component", > a _file_ is certainly not exclusively about that last component. > > Hence change the behavior of '%pD' to print full path of that file. > > Precision is never going to be used with %p (or any of its kernel > extensions) if -Wformat is turned on. > . > > [1] https://lore.kernel.org/lkml/CAHk-=wimsMqGdzik187YWLb-ru+iktb4MYbMQG1rnZ81dXYFVg@xxxxxxxxxxxxxx/ > > Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Jia He <justin.he@xxxxxxx> > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -920,13 +921,41 @@ char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_sp > } > > static noinline_for_stack > -char *file_dentry_name(char *buf, char *end, const struct file *f, > +char *file_d_path_name(char *buf, char *end, const struct file *f, > struct printf_spec spec, const char *fmt) > { > + const struct path *path; > + char *p; > + int prepend_len, reserved_size, dpath_len; > + > if (check_pointer(&buf, end, f, spec)) > return buf; > > - return dentry_name(buf, end, f->f_path.dentry, spec, fmt); > + path = &f->f_path; > + if (check_pointer(&buf, end, path, spec)) > + return buf; > + > + p = d_path_unsafe(path, buf, end - buf, &prepend_len); > + > + /* Calculate the full d_path length, ignoring the tail '\0' */ > + dpath_len = end - buf - prepend_len - 1; > + > + reserved_size = max_t(int, dpath_len, spec.field_width); "reserved_size" is kind of confusing. "dpath_widen_len" or just "widen_len" look much more obvious. The below comments are not bad. But they still made me thing about it more than I wanted ;-) I wonder if it following is better: > + /* case 1: no space at all, forward the buf with reserved size */ > + if (buf >= end) > + return buf + reserved_size; /* Case 1: Already started past the buffer. Just forward @buf. */ if (buf >= end) return buf + widen_len; > + > + /* > + * case 2: small scratch space for long d_path name. The space > + * [buf,end] has been filled with truncated string. Hence use the > + * full dpath_len for further string widening. > + */ > + if (prepend_len < 0) > + return widen_string(buf + dpath_len, dpath_len, end, spec); /* * Case 2: The entire remaining space of the buffer filled by * the truncated path. Still need to get moved right when * the filed width is greather than the full path length. */ if (prepend_len < 0) return widen_string(buf + dpath_len, dpath_len, end, spec); > + /* case3: space is big enough */ > + return string_nocheck(buf, end, p, spec); /* * Case 3: The full path is printed at the end of the buffer. * Print it at the right location in the same buffer. */ return string_nocheck(buf, end, p, spec); > } > #ifdef CONFIG_BLOCK > static noinline_for_stack In each case, I am happy that it was possible to simplify the logic. I got lost several times in the previous version. Best Regards, Petr
