seq_file: Rename seq_overflow() to seq_has_overflowed() and make public

The return values of seq_printf/puts/putc are frequently misused.

Start down a path to remove all the return value uses of these
functions.

Move the seq_overflow() to a global inlined function called
seq_has_overflowed() that can be used by the users of seq_file() calls.

Update the documentation to not show return types for seq_printf
et al.  Add a description of seq_has_overflowed().

Link: http://lkml.kernel.org/p/848ac7e3d1c31cddf638a8526fa3c59fa6fdeb8a.1412031505.git.joe@perches.com

Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Joe Perches <joe@perches.com>
[ Reworked the original patch from Joe ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
vfs: make first argument of dir_context.actor typed

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
new helper: is_root_inode()

replace open-coded instances

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
move d_rcu from overlapping d_child to overlapping d_alias

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
lustre: switch ll_intent_file_open() to struct dentry *

... because fake struct file is wrong.

ll_prep_inode() in there is an atrocity - despite passing a pointer to
inode by address, it actually only uses the value when that value is
non-NULL, as it will be here.

Oh, and ->d_parent of anything is never NULL.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
ll_setxattr(): get rid of struct file on stack

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
lustre: opened file can't have negative dentry

... and ll_md_close() gets inode already equal to file_inode(file),
along with ll_file_release()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
lustre: use %p[dD]

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
lustre: use file_inode()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
lustre: switch ll_release_openhandle() to struct inode *

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
kill ll_mknod_generic()

just fold into ll_mknod()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
kill ll_mkdir_generic()

fold into ll_mkdir()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
kill ll_symlink_generic()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
ll_new_inode(): don't bother with name - it's always &dentry->d_name

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
kill ll_rmdir_generic()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
kill ll_unlink_generic()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
kill ll_rename_generic()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
ll_get_child_fid(): callers already have the child

no need to bother with d_lookup()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
kill ll_link_generic()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
lustre: get rid of duplicate mountpoint checks

VFS has already done them

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>