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Subject[PATCH 2/7] lib/vsprintf: add %*pg format specifier
Date
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

Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
---
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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