We have '%pD' for printing a filename. 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 "file_dentry_name()" simply shouldn't use "dentry_name()" at all. Despite that shared code origin, and despite that similar letter choice (lower-vs-upper case), a dentry and a file really are very different from a name standpoint. [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> --- Documentation/core-api/printk-formats.rst | 5 +++-- lib/vsprintf.c | 12 ++++++++++-- 2 files changed, 13 insertions(+), 4 deletions(-) diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst index f063a384c7c8..6770130d32c8 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 does the same thing for struct file and prints full +file path together with mount-related parenthood. Passed by reference. diff --git a/lib/vsprintf.c b/lib/vsprintf.c index f0c35d9b65bf..8220ab1411c5 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> #include <linux/kallsyms.h> #include <linux/math64.h> #include <linux/uaccess.h> @@ -923,10 +924,17 @@ static noinline_for_stack char *file_dentry_name(char *buf, char *end, const struct file *f, struct printf_spec spec, const char *fmt) { + const struct path *path = &f->f_path; + char *p; + char tmp[128]; + if (check_pointer(&buf, end, f, spec)) return buf; - return dentry_name(buf, end, f->f_path.dentry, spec, fmt); + p = d_path_fast(path, (char *)tmp, 128); + buf = string(buf, end, p, spec); + + return buf; } #ifdef CONFIG_BLOCK static noinline_for_stack @@ -2296,7 +2304,7 @@ 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' Same as 'd' but for 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 -- 2.17.1
