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SubjectRe: [PATCH 2/7] lib/vsprintf: add %*pg format specifier
On Mon 13-04-15 16:31:35, Dmitry Monakhov wrote:
> This allow to directly print block_device name.
> Currently one should use bdevname() with temporal char buffer.
> This is very ineffective because bloat stack usage for deep IO call-traces
>
> Example:
> %pg -> sda, sda1 or loop0p1
>
> Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
I like this. Seeing how many places use bdevname() it seems as a
worthwhile simplification. %pg is somewhat arbitrary but I don't know about
a better free letter either... You can add:
Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> Documentation/printk-formats.txt | 6 ++++++
> lib/vsprintf.c | 28 ++++++++++++++++++++++++++++
> 2 files changed, 34 insertions(+), 0 deletions(-)
>
> diff --git a/Documentation/printk-formats.txt b/Documentation/printk-formats.txt
> index 5a615c1..de2f18f 100644
> --- a/Documentation/printk-formats.txt
> +++ b/Documentation/printk-formats.txt
> @@ -216,6 +216,12 @@ dentry names:
> 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.
>
> +block_device names:
> +
> + %pg sda, sda1 or loop0p1
> +
> + For printing name of block_device pointers.
> +
> struct va_format:
>
> %pV
> diff --git a/lib/vsprintf.c b/lib/vsprintf.c
> index b235c96..57f6fa9 100644
> --- a/lib/vsprintf.c
> +++ b/lib/vsprintf.c
> @@ -29,6 +29,9 @@
> #include <linux/dcache.h>
> #include <linux/cred.h>
> #include <net/addrconf.h>
> +#ifdef CONFIG_BLOCK
> +#include <linux/blkdev.h>
> +#endif
>
> #include <asm/page.h> /* for PAGE_SIZE */
> #include <asm/sections.h> /* for dereference_function_descriptor() */
> @@ -610,6 +613,23 @@ char *dentry_name(char *buf, char *end, const struct dentry *d, struct printf_sp
> return buf;
> }
>
> +#ifdef CONFIG_BLOCK
> +static noinline_for_stack
> +char *bdev_name(char *buf, char *end, struct block_device *bdev,
> + struct printf_spec spec, const char *fmt)
> +{
> + struct gendisk *hd = bdev->bd_disk;
> +
> + buf = string(buf, end, hd->disk_name, spec);
> + if (bdev->bd_part->partno) {
> + if (isdigit(hd->disk_name[strlen(hd->disk_name)-1]) && buf < end)
> + *buf++ = 'p';
> + buf = number(buf, end, bdev->bd_part->partno, spec);
> + }
> + return buf;
> +}
> +#endif
> +
> static noinline_for_stack
> char *symbol_string(char *buf, char *end, void *ptr,
> struct printf_spec spec, const char *fmt)
> @@ -1404,6 +1424,8 @@ int kptr_restrict __read_mostly;
> * (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
> + * - 'g' For block_device name (gendisk + partition number)
> +
> *
> * Note: The difference between 'S' and 'F' is that on ia64 and ppc64
> * function pointers are really function descriptors, which contain a
> @@ -1552,6 +1574,11 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
> return dentry_name(buf, end,
> ((const struct file *)ptr)->f_path.dentry,
> spec, fmt);
> +#ifdef CONFIG_BLOCK
> + case 'g':
> + return bdev_name(buf, end, ptr, spec, fmt);
> +#endif
> +
> }
> spec.flags |= SMALL;
> if (spec.field_width == -1) {
> @@ -1779,6 +1806,7 @@ qualifier:
> * %pF output the name of a function pointer with its offset
> * %pf output the name of a function pointer without its offset
> * %pB output the name of a backtrace symbol with its offset
> + * %pg output the name of a block_device
> * %pR output the address range in a struct resource with decoded flags
> * %pr output the address range in a struct resource with raw flags
> * %pb output the bitmap with field width as the number of bits
> --
> 1.7.1
>
> --
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--
Jan Kara <jack@suse.cz>
SUSE Labs, CR


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