Re: [patch 1/9] procfs: Move /proc/pid/fd[info] handling code to fd.[ch]

On Sat, Aug 25, 2012 at 06:16:05PM +0100, Al Viro wrote:

On Thu, Aug 23, 2012 at 02:43:24PM +0400, Cyrill Gorcunov wrote:

quoted

This patch prepares the ground for further extension of
/proc/pid/fd[info] handling code by moving fdinfo handling
code into fs/proc/fd.c.

I think such move makes both fs/proc/base.c and fs/proc/fd.c
easier to read.

BTW, looking at the other stuff in fs/proc/base.c, why the hell is
struct file * grabbed in proc_map_files_readdir()?  All we do with
it is passing it to proc_fill_cache(), which passes it to
proc_map_files_instantiate(), which looks at two sodding bits
in file->f_mode.  Then we go and fput() all those struct file
references we'd been putting into the array...  What for?

Another thing:
			f_flags = fd_file->f_flags & ~O_CLOEXEC;
in there is really wrong; we shouldn't leak that bit into ->f_flags
at all (which is properly fixed in fs/open.c).  Close-on-exec is
a property of descriptor, not of file...

tid_fd_revalidate(): these dances with get_files_struct()/put_files_struct()
are pointless.  We really only need "is it opened" + f_mode if it is.
Extracting that information is cheap enough to have it done right under
task_lock() (see what get_files_struct() is doing); no need to mess with
files_struct refcount, etc.

proc_fd_link() and seq_fd_open(): ditto.

As the matter of fact, the only place in there where get_files_struct() is
warranted is proc_readfd_common().

intantiate callback: sodding atrocity; as the absolute minimum it should
lose its "dir" argument.  dentry->d_parent->d_inode is stable (we are
holding ->i_mutex on parent in all callers) and it's equal to dir in all
cases.