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Diffstat (limited to 'fs')
-rw-r--r--fs/open.c18
-rw-r--r--fs/read_write.c5
2 files changed, 21 insertions, 2 deletions
diff --git a/fs/open.c b/fs/open.c
index f1c2f855fd43..a00350018a47 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -1215,3 +1215,21 @@ int nonseekable_open(struct inode *inode, struct file *filp)
}
EXPORT_SYMBOL(nonseekable_open);
+
+/*
+ * stream_open is used by subsystems that want stream-like file descriptors.
+ * Such file descriptors are not seekable and don't have notion of position
+ * (file.f_pos is always 0). Contrary to file descriptors of other regular
+ * files, .read() and .write() can run simultaneously.
+ *
+ * stream_open never fails and is marked to return int so that it could be
+ * directly used as file_operations.open .
+ */
+int stream_open(struct inode *inode, struct file *filp)
+{
+ filp->f_mode &= ~(FMODE_LSEEK | FMODE_PREAD | FMODE_PWRITE | FMODE_ATOMIC_POS);
+ filp->f_mode |= FMODE_STREAM;
+ return 0;
+}
+
+EXPORT_SYMBOL(stream_open);
diff --git a/fs/read_write.c b/fs/read_write.c
index 177ccc3d405a..61b43ad7608e 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -560,12 +560,13 @@ ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_
static inline loff_t file_pos_read(struct file *file)
{
- return file->f_pos;
+ return file->f_mode & FMODE_STREAM ? 0 : file->f_pos;
}
static inline void file_pos_write(struct file *file, loff_t pos)
{
- file->f_pos = pos;
+ if ((file->f_mode & FMODE_STREAM) == 0)
+ file->f_pos = pos;
}
ssize_t ksys_read(unsigned int fd, char __user *buf, size_t count)