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Commit 1f33c41c authored by Joe Perches's avatar Joe Perches Committed by Steven Rostedt
Browse files

seq_file: Rename seq_overflow() to seq_has_overflowed() and make public 

The return values of seq_printf/puts/putc are frequently misused.

Start down a path to remove all the return value uses of these
functions.

Move the seq_overflow() to a global inlined function called
seq_has_overflowed() that can be used by the users of seq_file() calls.

Update the documentation to not show return types for seq_printf
et al.  Add a description of seq_has_overflowed().

Link: http://lkml.kernel.org/p/848ac7e3d1c31cddf638a8526fa3c59fa6fdeb8a.1412031505.git.joe@perches.com



Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarJoe Perches <joe@perches.com>
[ Reworked the original patch from Joe ]
Signed-off-by: default avatarSteven Rostedt <rostedt@goodmis.org>
parent f114040e

Documentation/filesystems/seq_file.txt

+13 −9
Original line number Diff line number Diff line
@@ -180,23 +180,19 @@ output must be passed to the seq_file code. Some utility functions have 
been defined which make this task easy.



Most code will simply use seq_printf(), which works pretty much like

printk(), but which requires the seq_file pointer as an argument. It is

common to ignore the return value from seq_printf(), but a function

producing complicated output may want to check that value and quit if

something non-zero is returned; an error return means that the seq_file

buffer has been filled and further output will be discarded.

printk(), but which requires the seq_file pointer as an argument.



For straight character output, the following functions may be used:



	int seq_putc(struct seq_file *m, char c);

	int seq_puts(struct seq_file *m, const char *s);

	int seq_escape(struct seq_file *m, const char *s, const char *esc);

	seq_putc(struct seq_file *m, char c);

	seq_puts(struct seq_file *m, const char *s);

	seq_escape(struct seq_file *m, const char *s, const char *esc);



The first two output a single character and a string, just like one would

expect. seq_escape() is like seq_puts(), except that any character in s

which is in the string esc will be represented in octal form in the output.



There is also a pair of functions for printing filenames:

There are also a pair of functions for printing filenames:



	int seq_path(struct seq_file *m, struct path *path, char *esc);

	int seq_path_root(struct seq_file *m, struct path *path,
@@ -209,6 +205,14 @@ root is desired, it can be used with seq_path_root(). Note that, if it 
turns out that path cannot be reached from root, the value of root will be

changed in seq_file_root() to a root which *does* work.



A function producing complicated output may want to check

	bool seq_has_overflowed(struct seq_file *m);

and avoid further seq_<output> calls if true is returned.



A true return from seq_has_overflowed means that the seq_file buffer will

be discarded and the seq_show function will attempt to allocate a larger

buffer and retry printing.





Making it all work

fs/seq_file.c

+2 −13
Original line number Diff line number Diff line
@@ -16,17 +16,6 @@ 
#include <asm/uaccess.h>

#include <asm/page.h>





/*

 * seq_files have a buffer which can may overflow. When this happens a larger

 * buffer is reallocated and all the data will be printed again.

 * The overflow state is true when m->count == m->size.

 */

static bool seq_overflow(struct seq_file *m)

{

	return m->count == m->size;

}



static void seq_set_overflow(struct seq_file *m)

{

	m->count = m->size;
@@ -124,7 +113,7 @@ static int traverse(struct seq_file *m, loff_t offset) 
			error = 0;

			m->count = 0;

		}

		if (seq_overflow(m))

		if (seq_has_overflowed(m))

			goto Eoverflow;

		if (pos + m->count > offset) {

			m->from = offset - pos;
@@ -267,7 +256,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) 
			break;

		}

		err = m->op->show(m, p);

		if (seq_overflow(m) || err) {

		if (seq_has_overflowed(m) || err) {

			m->count = offs;

			if (likely(err <= 0))

				break;

include/linux/seq_file.h

+15 −0
Original line number Diff line number Diff line
@@ -42,6 +42,21 @@ struct seq_operations { 


#define SEQ_SKIP 1



/**

 * seq_has_overflowed - check if the buffer has overflowed

 * @m: the seq_file handle

 *

 * seq_files have a buffer which may overflow. When this happens a larger

 * buffer is reallocated and all the data will be printed again.

 * The overflow state is true when m->count == m->size.

 *

 * Returns true if the buffer received more than it can hold.

 */

static inline bool seq_has_overflowed(struct seq_file *m)

{

	return m->count == m->size;

}



/**

 * seq_get_buf - get buffer to write arbitrary data to

 * @m: the seq_file handle