vfs: export lseek_execute() to modules

For those file systems(btrfs/ext4/ocfs2/tmpfs) that support
SEEK_DATA/SEEK_HOLE functions, we end up handling the similar
matter in lseek_execute() to update the current file offset
to the desired offset if it is valid, ceph also does the
simliar things at ceph_llseek().

To reduce the duplications, this patch make lseek_execute()
public accessible so that we can call it directly from the
underlying file systems.

Thanks Dave Chinner for this suggestion.

[AV: call it vfs_setpos(), don't bring the removed 'inode' argument back]

v2->v1:
- Add kernel-doc comments for lseek_execute()
- Call lseek_execute() in ceph->llseek()

Signed-off-by: Jie Liu <jeff.liu@oracle.com>
Cc: Dave Chinner <dchinner@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Chris Mason <chris.mason@fusionio.com>
Cc: Josef Bacik <jbacik@fusionio.com>
Cc: Ben Myers <bpm@sgi.com>
Cc: Ted Tso <tytso@mit.edu>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mark Fasheh <mfasheh@suse.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Sage Weil <sage@inktank.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 16 insertions, 3 deletions

diff --git a/fs/read_write.c b/fs/read_write.c
index 37d16e82b575..122a3846d9e1 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -41,7 +41,19 @@ static inline int unsigned_offsets(struct file *file)
 	return file->f_mode & FMODE_UNSIGNED_OFFSET;
 }
 
-static loff_t lseek_execute(struct file *file, loff_t offset, loff_t maxsize)
+/**
+ * vfs_setpos - update the file offset for lseek
+ * @file:	file structure in question
+ * @offset:	file offset to seek to
+ * @maxsize:	maximum file size
+ *
+ * This is a low-level filesystem helper for updating the file offset to
+ * the value specified by @offset if the given offset is valid and it is
+ * not equal to the current file offset.
+ *
+ * Return the specified offset on success and -EINVAL on invalid offset.
+ */
+loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize)
 {
 	if (offset < 0 && !unsigned_offsets(file))
 		return -EINVAL;
@@ -54,6 +66,7 @@ static loff_t lseek_execute(struct file *file, loff_t offset, loff_t maxsize)
 	}
 	return offset;
 }
+EXPORT_SYMBOL(vfs_setpos);
 
 /**
  * generic_file_llseek_size - generic llseek implementation for regular files
@@ -94,7 +107,7 @@ generic_file_llseek_size(struct file *file, loff_t offset, int whence,
 		 * like SEEK_SET.
 		 */
 		spin_lock(&file->f_lock);
-		offset = lseek_execute(file, file->f_pos + offset, maxsize);
+		offset = vfs_setpos(file, file->f_pos + offset, maxsize);
 		spin_unlock(&file->f_lock);
 		return offset;
 	case SEEK_DATA:
@@ -116,7 +129,7 @@ generic_file_llseek_size(struct file *file, loff_t offset, int whence,
 		break;
 	}
 
-	return lseek_execute(file, offset, maxsize);
+	return vfs_setpos(file, offset, maxsize);
 }
 EXPORT_SYMBOL(generic_file_llseek_size);