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>

fs/btrfs/file.c

@@ -2425,20 +2425,7 @@ static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int whence)
 		}
 	}
 
-	if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET)) {
-		offset = -EINVAL;
-		goto out;
-	}
-	if (offset > inode->i_sb->s_maxbytes) {
-		offset = -EINVAL;
-		goto out;
-	}
-
-	/* Special lock needed here? */
-	if (offset != file->f_pos) {
-		file->f_pos = offset;
-		file->f_version = 0;
-	}
+	offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
 out:
 	mutex_unlock(&inode->i_mutex);
 	return offset;

fs/ceph/file.c

@@ -866,16 +866,7 @@ static loff_t ceph_llseek(struct file *file, loff_t offset, int whence)
 		break;
 	}
 
-	if (offset < 0 || offset > inode->i_sb->s_maxbytes) {
-		offset = -EINVAL;
-		goto out;
-	}
-
-	/* Special lock needed here? */
-	if (offset != file->f_pos) {
-		file->f_pos = offset;
-		file->f_version = 0;
-	}
+	offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
 
 out:
 	mutex_unlock(&inode->i_mutex);

fs/ext4/file.c

@@ -494,17 +494,7 @@ static loff_t ext4_seek_data(struct file *file, loff_t offset, loff_t maxsize)
 	if (dataoff > isize)
 		return -ENXIO;
 
-	if (dataoff < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET))
-		return -EINVAL;
-	if (dataoff > maxsize)
-		return -EINVAL;
-
-	if (dataoff != file->f_pos) {
-		file->f_pos = dataoff;
-		file->f_version = 0;
-	}
-
-	return dataoff;
+	return vfs_setpos(file, dataoff, maxsize);
 }
 
 /*
@@ -580,17 +570,7 @@ static loff_t ext4_seek_hole(struct file *file, loff_t offset, loff_t maxsize)
 	if (holeoff > isize)
 		holeoff = isize;
 
-	if (holeoff < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET))
-		return -EINVAL;
-	if (holeoff > maxsize)
-		return -EINVAL;
-
-	if (holeoff != file->f_pos) {
-		file->f_pos = holeoff;
-		file->f_version = 0;
-	}
-
-	return holeoff;
+	return vfs_setpos(file, holeoff, maxsize);
 }
 
 /*

fs/ocfs2/file.c

@@ -2646,17 +2646,7 @@ static loff_t ocfs2_file_llseek(struct file *file, loff_t offset, int whence)
 		goto out;
 	}
 
-	if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET))
-		ret = -EINVAL;
-	if (!ret && offset > inode->i_sb->s_maxbytes)
-		ret = -EINVAL;
-	if (ret)
-		goto out;
-
-	if (offset != file->f_pos) {
-		file->f_pos = offset;
-		file->f_version = 0;
-	}
+	offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
 
 out:
 	mutex_unlock(&inode->i_mutex);

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);
 

fs/xfs/xfs_file.c

@@ -1268,8 +1268,7 @@ xfs_seek_data(
 	}
 
 out:
-	if (offset != file->f_pos)
-		file->f_pos = offset;
+	offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
 
 out_unlock:
 	xfs_iunlock_map_shared(ip, lock);
@@ -1377,8 +1376,7 @@ out:
 	 * situation in particular.
 	 */
 	offset = min_t(loff_t, offset, isize);
-	if (offset != file->f_pos)
-		file->f_pos = offset;
+	offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
 
 out_unlock:
 	xfs_iunlock_map_shared(ip, lock);

include/linux/fs.h

@@ -2426,6 +2426,7 @@ extern void
 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 whence);
 extern loff_t no_llseek(struct file *file, loff_t offset, int whence);
+extern loff_t vfs_setpos(struct file *file, loff_t offset, loff_t maxsize);
 extern loff_t generic_file_llseek(struct file *file, loff_t offset, int whence);
 extern loff_t generic_file_llseek_size(struct file *file, loff_t offset,
 		int whence, loff_t maxsize, loff_t eof);

mm/shmem.c

@@ -1798,10 +1798,7 @@ static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
 		}
 	}
 
-	if (offset >= 0 && offset != file->f_pos) {
-		file->f_pos = offset;
-		file->f_version = 0;
-	}
+	offset = vfs_setpos(file, offset, MAX_LFS_FILESIZE);
 	mutex_unlock(&inode->i_mutex);
 	return offset;
 }