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Subject[PATCH 4/7] 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 | 34 +++++++++++++++++++++++++++-------
include/linux/fs.h | 2 ++
2 files changed, 29 insertions(+), 7 deletions(-)

diff --git a/fs/read_write.c b/fs/read_write.c
index 8e8aab3..3d55cc6 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -51,14 +51,14 @@ static loff_t lseek_execute(struct file *file, struct inode *inode, loff_t offse
}

/**
- * generic_file_llseek - generic llseek implementation for regular files
+ * 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
+ * @size: max size of file system
*
- * This is a generic implemenation of ->llseek useable for all normal local
- * filesystems. It just updates the file offset to the value specified by
- * @offset and @origin under i_mutex.
+ * Variant of generic_file_llseek that allows passing in a custom
+ * file size.
*
* Synchronization:
* SEEK_SET is unsynchronized (but atomic on 64bit platforms)
@@ -67,7 +67,8 @@ static loff_t lseek_execute(struct file *file, struct inode *inode, loff_t offse
* SEEK_END
*/
loff_t
-generic_file_llseek(struct file *file, loff_t offset, int origin)
+generic_file_llseek_size(struct file *file, loff_t offset, int origin,
+ loff_t maxsize)
{
struct inode *inode = file->f_mapping->host;

@@ -91,7 +92,7 @@ generic_file_llseek(struct file *file, loff_t offset, int origin)
*/
spin_lock(&file->f_lock);
offset = lseek_execute(file, inode, file->f_pos + offset,
- inode->i_sb->s_maxbytes);
+ maxsize);
spin_unlock(&file->f_lock);
return offset;
case SEEK_DATA:
@@ -113,7 +114,26 @@ generic_file_llseek(struct file *file, loff_t offset, int origin)
break;
}

- return lseek_execute(file, inode, offset, inode->i_sb->s_maxbytes);
+ return lseek_execute(file, inode, offset, maxsize);
+}
+EXPORT_SYMBOL(generic_file_llseek_size);
+
+/**
+ * generic_file_llseek - generic llseek implementation for regular files
+ * @file: file structure to seek on
+ * @offset: file offset to seek to
+ * @origin: type of seek
+ *
+ * This is a generic implemenation of ->llseek useable for all normal local
+ * filesystems. It just updates the file offset to the value specified by
+ * @offset and @origin under i_mutex.
+ */
+loff_t generic_file_llseek(struct file *file, loff_t offset, int origin)
+{
+ struct inode *inode = file->f_mapping->host;
+
+ return generic_file_llseek_size(file, offset, origin,
+ inode->i_sb->s_maxbytes);
}
EXPORT_SYMBOL(generic_file_llseek);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 3417259..d64b601 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2395,6 +2395,8 @@ 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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