On Tue, Jun 15, 2021 at 6:54 PM Jia He <justin.he@xxxxxxx> 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. print the full > > 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/ Put it as a Link: tag? > > Suggested-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> > Signed-off-by: Jia He <justin.he@xxxxxxx> > --- > Documentation/core-api/printk-formats.rst | 5 +-- > lib/vsprintf.c | 37 ++++++++++++++++++++--- > 2 files changed, 36 insertions(+), 6 deletions(-) > > diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst > index f063a384c7c8..95ba14dc529b 100644 > --- a/Documentation/core-api/printk-formats.rst > +++ b/Documentation/core-api/printk-formats.rst > @@ -408,12 +408,13 @@ dentry names > :: > > %pd{,2,3,4} > - %pD{,2,3,4} > + %pD > > For printing dentry name; if we race with :c:func:`d_move`, the name might > be a mix of old and new ones, but it won't oops. %pd dentry is a safer > equivalent of %s dentry->d_name.name we used to use, %pd<n> prints ``n`` > -last components. %pD does the same thing for struct file. > +last components. %pD prints full file path together with mount-related > +parenthood. > > Passed by reference. > > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index f0c35d9b65bf..9d3166332726 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -27,6 +27,7 @@ > #include <linux/string.h> > #include <linux/ctype.h> > #include <linux/kernel.h> > +#include <linux/dcache.h> I know that this is an arbitrary order, but can you keep it after ctype.h? > #include <linux/kallsyms.h> > #include <linux/math64.h> > #include <linux/uaccess.h> > @@ -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); > + > + /* case 1: no space at all, forward the buf with reserved size */ Case 1: > + if (buf >= end) > + return buf + reserved_size; > + > + /* > + * case 2: small scratch space for long d_path name. The space Case 2: > + * [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); > + > + /* case3: space is big enough */ Case 3: > + return string_nocheck(buf, end, p, spec); > } > #ifdef CONFIG_BLOCK > static noinline_for_stack > @@ -2296,7 +2325,7 @@ early_param("no_hash_pointers", no_hash_pointers_enable); > * - 'a[pd]' For address types [p] phys_addr_t, [d] dma_addr_t and derivatives > * (default assumed to be phys_addr_t, passed by reference) > * - 'd[234]' For a dentry name (optionally 2-4 last components) > - * - 'D[234]' Same as 'd' but for a struct file > + * - 'D' For full path name of a struct file > * - 'g' For block_device name (gendisk + partition number) > * - 't[RT][dt][r]' For time and date as represented by: > * R struct rtc_time > @@ -2395,7 +2424,7 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr, > case 'C': > return clock(buf, end, ptr, spec, fmt); > case 'D': > - return file_dentry_name(buf, end, ptr, spec, fmt); > + return file_d_path_name(buf, end, ptr, spec, fmt); > #ifdef CONFIG_BLOCK > case 'g': > return bdev_name(buf, end, ptr, spec, fmt); > -- > 2.17.1 > -- With Best Regards, Andy Shevchenko
