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authorjan Blunck <jblunck@suse.de>2010-05-26 14:44:48 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2010-05-27 09:12:56 -0700
commitae6afc3f5cf53fb97bac2d0a209bb465952742e7 (patch)
tree541e3f4ed4f2600ffe239e2f23341055199329b1 /fs/read_write.c
parent09eeb1f5f4d9b52ab57820160dea6027bbea82a3 (diff)
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vfs: introduce noop_llseek()
This is an implementation of ->llseek useable for the rare special case when userspace expects the seek to succeed but the (device) file is actually not able to perform the seek. In this case you use noop_llseek() instead of falling back to the default implementation of ->llseek. Signed-off-by: Jan Blunck <jblunck@suse.de> Cc: Frederic Weisbecker <fweisbec@gmail.com> Cc: Christoph Hellwig <hch@lst.de> 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>
Diffstat (limited to 'fs/read_write.c')
-rw-r--r--fs/read_write.c17
1 files changed, 17 insertions, 0 deletions
diff --git a/fs/read_write.c b/fs/read_write.c
index 113386d6fd2..9c0485236e6 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -97,6 +97,23 @@ loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
}
EXPORT_SYMBOL(generic_file_llseek);
+/**
+ * noop_llseek - No Operation Performed llseek implementation
+ * @file: file structure to seek on
+ * @offset: file offset to seek to
+ * @origin: type of seek
+ *
+ * This is an implementation of ->llseek useable for the rare special case when
+ * userspace expects the seek to succeed but the (device) file is actually not
+ * able to perform the seek. In this case you use noop_llseek() instead of
+ * falling back to the default implementation of ->llseek.
+ */
+loff_t noop_llseek(struct file *file, loff_t offset, int origin)
+{
+ return file->f_pos;
+}
+EXPORT_SYMBOL(noop_llseek);
+
loff_t no_llseek(struct file *file, loff_t offset, int origin)
{
return -ESPIPE;