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

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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: Joe Perches <joe@perches.com>
[ Reworked the original patch from Joe ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
This commit is contained in:
Joe Perches 2014-09-29 16:08:21 -07:00 committed by Steven Rostedt
parent f114040e3e
commit 1f33c41c03
3 changed files with 30 additions and 22 deletions
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22
Documentation/filesystems/seq_file.txt
View file

@ -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

15
fs/seq_file.c
View file

@ -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;

15
include/linux/seq_file.h
View file

@ -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