vserver 2.0 rc7

[linux-2.6.git] / fs / seq_file.c

diff --git a/fs/seq_file.c b/fs/seq_file.c
index 5a73e08..38ef913 100644 (file)
--- a/fs/seq_file.c
+++ b/fs/seq_file.c
@@ -36,6 +36,13 @@ int seq_open(struct file *file, struct seq_operations *op)
        p->op = op;
        file->private_data = p;
 
+       /*
+        * Wrappers around seq_open(e.g. swaps_open) need to be
+        * aware of this. If they set f_version themselves, they
+        * should call seq_open first and then set f_version.
+        */
+       file->f_version = 0;
+
        /* SEQ files support lseek, but not pread/pwrite */
        file->f_mode &= ~(FMODE_PREAD | FMODE_PWRITE);
        return 0;
@@ -44,7 +51,10 @@ EXPORT_SYMBOL(seq_open);
 
 /**
  *     seq_read -      ->read() method for sequential files.
- *     @file, @buf, @size, @ppos: see file_operations method
+ *     @file: the file to read from
+ *     @buf: the buffer to read to
+ *     @size: the maximum number of bytes to read
+ *     @ppos: the current position in the file
  *
  *     Ready-made ->f_op->read()
  */
@@ -58,6 +68,18 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
        int err = 0;
 
        down(&m->sem);
+       /*
+        * seq_file->op->..m_start/m_stop/m_next may do special actions
+        * or optimisations based on the file->f_version, so we want to
+        * pass the file->f_version to those methods.
+        *
+        * seq_file->version is just copy of f_version, and seq_file
+        * methods can treat it simply as file version.
+        * It is copied in first and copied out after all operations.
+        * It is convenient to have it as  part of structure to avoid the
+        * need of passing another argument to all the seq_file methods.
+        */
+       m->version = file->f_version;
        /* grab buffer if we didn't have one */
        if (!m->buf) {
                m->buf = kmalloc(m->size = PAGE_SIZE, GFP_KERNEL);
@@ -98,6 +120,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos)
                if (!m->buf)
                        goto Enomem;
                m->count = 0;
+               m->version = 0;
        }
        m->op->stop(m, p);
        m->count = 0;
@@ -136,6 +159,7 @@ Done:
                copied = err;
        else
                *ppos += copied;
+       file->f_version = m->version;
        up(&m->sem);
        return copied;
 Enomem:
@@ -153,6 +177,7 @@ static int traverse(struct seq_file *m, loff_t offset)
        int error = 0;
        void *p;
 
+       m->version = 0;
        m->index = 0;
        m->count = m->from = 0;
        if (!offset)
@@ -197,7 +222,9 @@ Eoverflow:
 
 /**
  *     seq_lseek -     ->llseek() method for sequential files.
- *     @file, @offset, @origin: see file_operations method
+ *     @file: the file in question
+ *     @offset: new position
+ *     @origin: 0 for absolute, 1 for relative position
  *
  *     Ready-made ->f_op->llseek()
  */
@@ -207,6 +234,7 @@ loff_t seq_lseek(struct file *file, loff_t offset, int origin)
        long long retval = -EINVAL;
 
        down(&m->sem);
+       m->version = file->f_version;
        switch (origin) {
                case 1:
                        offset += file->f_pos;
@@ -220,6 +248,7 @@ loff_t seq_lseek(struct file *file, loff_t offset, int origin)
                                if (retval) {
                                        /* with extreme prejudice... */
                                        file->f_pos = 0;
+                                       m->version = 0;
                                        m->index = 0;
                                        m->count = 0;
                                } else {
@@ -228,6 +257,7 @@ loff_t seq_lseek(struct file *file, loff_t offset, int origin)
                        }
        }
        up(&m->sem);
+       file->f_version = m->version;
        return retval;
 }
 EXPORT_SYMBOL(seq_lseek);