[patch 33/56] seq_file: move traverse so it can be used from seq_read

Greg KH
2009-02-11T00:39:38Z

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2.6.27-stable review patch. If anyone has any objections, please let us know.
------------------

From: Eric Biederman <ebiederm@xmission.com>

commit 33da8892a2f9e7d4b2d9a35fc80833ba2d2b1aa6 upstream.

In 2.6.25 some /proc files were converted to use the seq_file
infrastructure. But seq_files do not correctly support pread(), which
broke some usersapce applications.

To handle pread correctly we can't assume that f_pos is where we left it
in seq_read. So move traverse() so that we can eventually use it in
seq_read and do thus some day support pread().

Signed-off-by: Eric Biederman <ebiederm@xmission.com>
Cc: Paul Turner <pjt@google.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
fs/seq_file.c | 114 +++++++++++++++++++++++++++++-----------------------------
1 file changed, 57 insertions(+), 57 deletions(-)

--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -54,6 +54,63 @@ int seq_open(struct file *file, const st
}
EXPORT_SYMBOL(seq_open);

+static int traverse(struct seq_file *m, loff_t offset)
+{
+ loff_t pos = 0, index;
+ int error = 0;
+ void *p;
+
+ m->version = 0;
+ index = 0;
+ m->count = m->from = 0;
+ if (!offset) {
+ m->index = index;
+ return 0;
+ }
+ if (!m->buf) {
+ m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
+ if (!m->buf)
+ return -ENOMEM;
+ }
+ p = m->op->start(m, &index);
+ while (p) {
+ error = PTR_ERR(p);
+ if (IS_ERR(p))
+ break;
+ error = m->op->show(m, p);
+ if (error < 0)
+ break;
+ if (unlikely(error)) {
+ error = 0;
+ m->count = 0;
+ }
+ if (m->count == m->size)
+ goto Eoverflow;
+ if (pos + m->count > offset) {
+ m->from = offset - pos;
+ m->count -= m->from;
+ m->index = index;
+ break;
+ }
+ pos += m->count;
+ m->count = 0;
+ if (pos == offset) {
+ index++;
+ m->index = index;
+ break;
+ }
+ p = m->op->next(m, p, &index);
+ }
+ m->op->stop(m, p);
+ return error;
+
+Eoverflow:
+ m->op->stop(m, p);
+ kfree(m->buf);
+ m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
+ return !m->buf ? -ENOMEM : -EAGAIN;
+}
+
/**
* seq_read - ->read() method for sequential files.
* @file: the file to read from
@@ -186,63 +243,6 @@ Efault:
}
EXPORT_SYMBOL(seq_read);

-static int traverse(struct seq_file *m, loff_t offset)
-{
- loff_t pos = 0, index;
- int error = 0;
- void *p;
-
- m->version = 0;
- index = 0;
- m->count = m->from = 0;
- if (!offset) {
- m->index = index;
- return 0;
- }
- if (!m->buf) {
- m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
- if (!m->buf)
- return -ENOMEM;
- }
- p = m->op->start(m, &index);
- while (p) {
- error = PTR_ERR(p);
- if (IS_ERR(p))
- break;
- error = m->op->show(m, p);
- if (error < 0)
- break;
- if (unlikely(error)) {
- error = 0;
- m->count = 0;
- }
- if (m->count == m->size)
- goto Eoverflow;
- if (pos + m->count > offset) {
- m->from = offset - pos;
- m->count -= m->from;
- m->index = index;
- break;
- }
- pos += m->count;
- m->count = 0;
- if (pos == offset) {
- index++;
- m->index = index;
- break;
- }
- p = m->op->next(m, p, &index);
- }
- m->op->stop(m, p);
- return error;
-
-Eoverflow:
- m->op->stop(m, p);
- kfree(m->buf);
- m->buf = kmalloc(m->size <<= 1, GFP_KERNEL);
- return !m->buf ? -ENOMEM : -EAGAIN;
-}
-
/**
* seq_lseek - ->llseek() method for sequential files.
* @file: the file in question