[PATCH 3/5] VFS: Add generic_file_llseek_size

[Andi Kleen <andi@xxxxxxxxxxxxxx>]

From: Andi Kleen <ak@xxxxxxxxxxxxxxx>

Add a generic_file_llseek variant to the VFS that allows passing in
the current file size, instead of always using inode->i_size.
This can be used to eliminate some cut'n'paste seek code in ext4.

Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
---
 fs/read_write.c    |   20 ++++++++++++++++++++
 include/linux/fs.h |    2 ++
 2 files changed, 22 insertions(+), 0 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 0b1d4ca..4924602 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -99,6 +99,26 @@ generic_file_llseek(struct file *file, loff_t offset, int origin)
 EXPORT_SYMBOL(generic_file_llseek);
 
 /**
+ * generic_file_llseek_size - generic llseek implementation for regular files
+ * @file:	file structure to seek on
+ * @offset:	file offset to seek to
+ * @origin:	type of seek
+ * 
+ * Variant of generic_file_llseek_size that allows passing in a custom
+ * file size.
+ */
+loff_t generic_file_llseek_size(struct file *file, loff_t offset, int origin, 
+				loff_t size)
+{
+	struct inode *inode = file->f_mapping->host;
+
+	if (origin == SEEK_END)
+		return lseek_execute(file, inode, offset + size);
+	return generic_file_llseek(file, offset, origin);
+}
+EXPORT_SYMBOL(generic_file_llseek_size);
+
+/**
  * noop_llseek - No Operation Performed llseek implementation
  * @file:	file structure to seek on
  * @offset:	file offset to seek to
diff --git a/include/linux/fs.h b/include/linux/fs.h
index a19d164..0642821 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2336,6 +2336,8 @@ file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
 extern loff_t noop_llseek(struct file *file, loff_t offset, int origin);
 extern loff_t no_llseek(struct file *file, loff_t offset, int origin);
 extern loff_t generic_file_llseek(struct file *file, loff_t offset, int origin);
+extern loff_t generic_file_llseek_size(struct file *file, loff_t offset, int origin, 
+				       loff_t size);
 extern int generic_file_open(struct inode * inode, struct file * filp);
 extern int nonseekable_open(struct inode * inode, struct file * filp);
 
-- 
1.7.4.4

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