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Message-ID: <20141029202756.70cb1f27@gandalf.local.home>
Date: Wed, 29 Oct 2014 20:27:56 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Joe Perches <joe@...ches.com>
Cc: linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Al Viro <viro@...iv.linux.org.uk>
Subject: Re: [RFA][PATCH 1/8] seq_file: Rename seq_overflow() to
seq_has_overflowed() and make public
On Wed, 29 Oct 2014 20:20:45 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:
> I'll change the comment about that.
How's this?
-- Steve
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@...iv.linux.org.uk>
Signed-off-by: Joe Perches <joe@...ches.com>
[ Reworked the original patch from Joe ]
Signed-off-by: Steven Rostedt <rostedt@...dmis.org>
---
Documentation/filesystems/seq_file.txt | 22 +++++++++++++---------
fs/seq_file.c | 15 ++-------------
include/linux/seq_file.h | 15 +++++++++++++++
3 files changed, 30 insertions(+), 22 deletions(-)
diff --git a/Documentation/filesystems/seq_file.txt b/Documentation/filesystems/seq_file.txt
index 8ea3e90ace07..b797ed38de46 100644
--- a/Documentation/filesystems/seq_file.txt
+++ b/Documentation/filesystems/seq_file.txt
@@ -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
diff --git a/fs/seq_file.c b/fs/seq_file.c
index 3857b720cb1b..353948ba1c5b 100644
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -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 @@ Fill:
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;
diff --git a/include/linux/seq_file.h b/include/linux/seq_file.h
index 52e0097f61f0..cf6a9daaaf6d 100644
--- a/include/linux/seq_file.h
+++ b/include/linux/seq_file.h
@@ -43,6 +43,21 @@ 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
* @bufp: the beginning of the buffer is stored here
--
1.8.1.4
--
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