[PATCH] s390: debug feature changes

This patch changes the memory allocation method for the s390 debug feature.
Trace buffers had been allocated using the get_free_pages() function before.
Therefore it was not possible to get big memory areas in a running system due
to memory fragmentation.  Now the trace buffers are subdivided into several
subbuffers with pagesize.  Therefore it is now possible to allocate more
memory for the trace buffers and more trace records can be written.

In addition to that, dynamic specification of the size of the trace buffers is
implemented.  It is now possible to change the size of a trace buffer using a
new debugfs file instance.  When writing a number into this file, the trace
buffer size is changed to 'number * pagesize'.

In the past all the traces could be obtained from userspace by accessing files
in the "proc" filesystem.  Now with debugfs we have a new filesystem which
should be used for debugging purposes.  This patch moves the debug feature
from procfs to debugfs.

Since the interface of debug_register() changed, all device drivers, which use
the debug feature had to be adjusted.

Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 46 insertions, 33 deletions

diff --git a/Documentation/s390/s390dbf.txt b/Documentation/s390/s390dbf.txt
index 2d1cd939b4df..e24fdeada970 100644
--- a/Documentation/s390/s390dbf.txt
+++ b/Documentation/s390/s390dbf.txt
@@ -12,8 +12,8 @@ where log records can be stored efficiently in memory, where each component
 One purpose of this is to inspect the debug logs after a production system crash
 in order to analyze the reason for the crash.
 If the system still runs but only a subcomponent which uses dbf failes,
-it is possible to look at the debug logs on a live system via the Linux proc
-filesystem.
+it is possible to look at the debug logs on a live system via the Linux
+debugfs filesystem.
 The debug feature may also very useful for kernel and driver development.
 
 Design:
@@ -52,16 +52,18 @@ Each debug entry contains the following data:
 - Flag, if entry is an exception or not
 
 The debug logs can be inspected in a live system through entries in
-the proc-filesystem. Under the path /proc/s390dbf there is 
+the debugfs-filesystem. Under the toplevel directory "s390dbf" there is
 a directory for each registered component, which is named like the
-corresponding component.
+corresponding component. The debugfs normally should be mounted to
+/sys/kernel/debug therefore the debug feature can be accessed unter
+/sys/kernel/debug/s390dbf.
 
 The content of the directories are files which represent different views
 to the debug log. Each component can decide which views should be
 used through registering them with the function debug_register_view().
 Predefined views for hex/ascii, sprintf and raw binary data are provided.
 It is also possible to define other views. The content of
-a view can be inspected simply by reading the corresponding proc file.
+a view can be inspected simply by reading the corresponding debugfs file.
 
 All debug logs have an an actual debug level (range from 0 to 6).
 The default level is 3. Event and Exception functions have a 'level'
@@ -69,14 +71,14 @@ parameter. Only debug entries with a level that is lower or equal
 than the actual level are written to the log. This means, when
 writing events, high priority log entries should have a low level
 value whereas low priority entries should have a high one.
-The actual debug level can be changed with the help of the proc-filesystem 
-through writing a number string "x" to the 'level' proc file which is
+The actual debug level can be changed with the help of the debugfs-filesystem
+through writing a number string "x" to the 'level' debugfs file which is
 provided for every debug log. Debugging can be switched off completely
-by using "-" on the 'level' proc file.
+by using "-" on the 'level' debugfs file.
 
 Example:
 
-> echo "-" > /proc/s390dbf/dasd/level
+> echo "-" > /sys/kernel/debug/s390dbf/dasd/level
 
 It is also possible to deactivate the debug feature globally for every
 debug log. You can change the behavior using  2 sysctl parameters in
@@ -99,11 +101,11 @@ Kernel Interfaces:
 ------------------
 
 ----------------------------------------------------------------------------
-debug_info_t *debug_register(char *name, int pages_index, int nr_areas,
+debug_info_t *debug_register(char *name, int pages, int nr_areas,
                              int buf_size);
 
-Parameter:    name:        Name of debug log (e.g. used for proc entry) 
-              pages_index: 2^pages_index pages will be allocated per area
+Parameter:    name:        Name of debug log (e.g. used for debugfs entry)
+              pages:       number of pages, which will be allocated per area
               nr_areas:    number of debug areas
               buf_size:    size of data area in each debug entry
 
@@ -134,7 +136,7 @@ Return Value:  none
 Description:   Sets new actual debug level if new_level is valid. 
 
 ---------------------------------------------------------------------------
-+void debug_stop_all(void);
+void debug_stop_all(void);
 
 Parameter:     none
 
@@ -270,7 +272,7 @@ Parameter:     id:    handle for debug log
 Return Value:  0  : ok 
                < 0: Error 
 
-Description:   registers new debug view and creates proc dir entry 
+Description:   registers new debug view and creates debugfs dir entry
 
 ---------------------------------------------------------------------------
 int debug_unregister_view (debug_info_t * id, struct debug_view *view); 
@@ -281,7 +283,7 @@ Parameter:     id:    handle for debug log
 Return Value:  0  : ok 
                < 0: Error 
 
-Description:   unregisters debug view and removes proc dir entry 
+Description:   unregisters debug view and removes debugfs dir entry
 
 
 
@@ -308,7 +310,7 @@ static int init(void)
 {
     /* register 4 debug areas with one page each and 4 byte data field */
 
-    debug_info = debug_register ("test", 0, 4, 4 );
+    debug_info = debug_register ("test", 1, 4, 4 );
     debug_register_view(debug_info,&debug_hex_ascii_view);
     debug_register_view(debug_info,&debug_raw_view);
 
@@ -343,7 +345,7 @@ static int init(void)
     /* register 4 debug areas with one page each and data field for */
     /* format string pointer + 2 varargs (= 3 * sizeof(long))       */
 
-    debug_info = debug_register ("test", 0, 4, sizeof(long) * 3);
+    debug_info = debug_register ("test", 1, 4, sizeof(long) * 3);
     debug_register_view(debug_info,&debug_sprintf_view);
 
     debug_sprintf_event(debug_info, 2 , "first event in %s:%i\n",__FILE__,__LINE__);
@@ -362,16 +364,16 @@ module_exit(cleanup);
 
 
 
-ProcFS Interface
+Debugfs Interface
 ----------------
 Views to the debug logs can be investigated through reading the corresponding 
-proc-files:
+debugfs-files:
 
 Example:
 
-> ls /proc/s390dbf/dasd
-flush  hex_ascii  level      raw 
-> cat /proc/s390dbf/dasd/hex_ascii | sort +1
+> ls /sys/kernel/debug/s390dbf/dasd
+flush  hex_ascii  level pages raw
+> cat /sys/kernel/debug/s390dbf/dasd/hex_ascii | sort +1
 00 00974733272:680099 2 - 02 0006ad7e  07 ea 4a 90 | ....
 00 00974733272:682210 2 - 02 0006ade6  46 52 45 45 | FREE
 00 00974733272:682213 2 - 02 0006adf6  07 ea 4a 90 | ....
@@ -391,25 +393,36 @@ Changing the debug level
 Example:
 
 
-> cat /proc/s390dbf/dasd/level
+> cat /sys/kernel/debug/s390dbf/dasd/level
 3
-> echo "5" > /proc/s390dbf/dasd/level
-> cat /proc/s390dbf/dasd/level
+> echo "5" > /sys/kernel/debug/s390dbf/dasd/level
+> cat /sys/kernel/debug/s390dbf/dasd/level
 5
 
 Flushing debug areas
 --------------------
 Debug areas can be flushed with piping the number of the desired
-area (0...n) to the proc file "flush". When using "-" all debug areas
+area (0...n) to the debugfs file "flush". When using "-" all debug areas
 are flushed.
 
 Examples:
 
 1. Flush debug area 0:
-> echo "0" > /proc/s390dbf/dasd/flush  
+> echo "0" > /sys/kernel/debug/s390dbf/dasd/flush
 
 2. Flush all debug areas:
-> echo "-" > /proc/s390dbf/dasd/flush
+> echo "-" > /sys/kernel/debug/s390dbf/dasd/flush
+
+Changing the size of debug areas
+------------------------------------
+It is possible the change the size of debug areas through piping
+the number of pages to the debugfs file "pages". The resize request will
+also flush the debug areas.
+
+Example:
+
+Define 4 pages for the debug areas of debug feature "dasd":
+> echo "4" > /sys/kernel/debug/s390dbf/dasd/pages
 
 Stooping the debug feature
 --------------------------
@@ -491,7 +504,7 @@ Defining views
 --------------
 
 Views are specified with the 'debug_view' structure. There are defined
-callback functions which are used for reading and writing the proc files:
+callback functions which are used for reading and writing the debugfs files:
 
 struct debug_view {
         char name[DEBUG_MAX_PROCF_LEN];  
@@ -525,7 +538,7 @@ typedef int (debug_input_proc_t) (debug_info_t* id,
 The "private_data" member can be used as pointer to view specific data.
 It is not used by the debug feature itself.
 
-The output when reading a debug-proc file is structured like this:
+The output when reading a debugfs file is structured like this:
 
 "prolog_proc output"
 
@@ -534,13 +547,13 @@ The output when reading a debug-proc file is structured like this:
 "header_proc output 3"  "format_proc output 3"
 ...
 
-When a view is read from the proc fs, the Debug Feature calls the 
+When a view is read from the debugfs, the Debug Feature calls the
 'prolog_proc' once for writing the prolog.
 Then 'header_proc' and 'format_proc' are called for each 
 existing debug entry.
 
 The input_proc can be used to implement functionality when it is written to 
-the view (e.g. like with 'echo "0" > /proc/s390dbf/dasd/level).
+the view (e.g. like with 'echo "0" > /sys/kernel/debug/s390dbf/dasd/level).
 
 For header_proc there can be used the default function
 debug_dflt_header_fn() which is defined in in debug.h.
@@ -602,7 +615,7 @@ debug_info = debug_register ("test", 0, 4, 4 ));
 debug_register_view(debug_info, &debug_test_view);
 for(i = 0; i < 10; i ++) debug_int_event(debug_info, 1, i);
 
-> cat /proc/s390dbf/test/myview
+> cat /sys/kernel/debug/s390dbf/test/myview
 00 00964419734:611402 1 - 00 88042ca   This error...........
 00 00964419734:611405 1 - 00 88042ca   That error...........
 00 00964419734:611408 1 - 00 88042ca   Problem..............