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Subject[PATCH 3/5] VFS: Add generic_file_llseek_size
Date
From: Andi Kleen <ak@linux.intel.com>

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@linux.intel.com>
---
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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