Lucian thanks for the review.

Lucian Adrian Grijincu [off-list ref] writes:

On Fri, Jan 27, 2012 at 6:51 AM, Eric W. Biederman
[off-list ref] wrote:

quoted

Every other directory has a .child member and we look at the .child
for our entries.  Do the same for the root_table.

Signed-off-by: Eric W. Biederman <redacted>
---
 fs/proc/proc_sysctl.c |   15 +++++++++++----
 1 files changed, 11 insertions(+), 4 deletions(-)

diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
index 7e96a26..88d1b06 100644
--- a/fs/proc/proc_sysctl.c
+++ b/fs/proc/proc_sysctl.c

@@ -25,7 +25,14 @@ void proc_sys_poll_notify(struct ctl_table_poll *poll)

       wake_up_interruptible(&poll->wait);
 }

-static struct ctl_table root_table[1];
+static struct ctl_table root_table[] = {
+       {
+               .procname = "",
+               .mode = S_IRUGO|S_IXUGO,

Why not: .mode = S_IFDIR|S_IRUGO|S_IXUGO ?

You change it later and add IFDIR in patch 22/29 because of this
change (from 22/29):
-	if (!table->child) {
+	if (!S_ISDIR(table->mode)) {

but if might as well be done here.

Actually doing not adding S_IFDIR here is important for keeping the
notion of changing one logical thing at a time.

I see normalizing this table early as deliberately emphasizing that we
started using S_IFDIR later.

quoted

+               .child = &root_table[1],
+       },
+       { }
+};
 static struct ctl_table_root sysctl_table_root;
 static struct ctl_table_header root_table_header = {
       {{.count = 1,

@@ -319,7 +326,7 @@ static struct dentry *proc_sys_lookup(struct inode *dir, struct dentry *dentry,

               goto out;
       }

Somewhere above we have
  struct ctl_table *table = PROC_I(inode)->sysctl_entry;
and sysctl_entry can take two values:
   - NULL: fs/proc/inode.c:proc_alloc_inode()
   - a non-NULL table in: proc_sys_make_inode()

The only inode that can be passed to proc_sys_lookup that can have
table=NULL is the root inode.
In that case head will be &root_table_header.


So head->ctl_table[1] == root_table_header.ctl_table[1] == root_table[1].

Yes.

quoted

-       table = table ? table->child : head->ctl_table;
+       table = table ? table->child : &head->ctl_table[1];

I think this could be improved to something like this:
/* table == NULL only for the procfs root directory */
table = table ? table->child : &root_table[1];


It's not that important, as this code will go away in a few patches.

Good catch.  I had to ask myself after I read this why the code wasn't
pointing at root_table already.  The answer as it turns out was because
it was static in kernel/sysctl.c until my earlier patches and I simply
missed the opportunity.

quoted

       p = find_in_table(table, name);
       if (!p) {

@@ -510,7 +517,7 @@ static int proc_sys_readdir(struct file *filp, void *dirent, filldir_t filldir)

               goto out;
       }

-       table = table ? table->child : head->ctl_table;
+       table = table ? table->child : &head->ctl_table[1];

Similar.

Agreed.  At this point in the game since this code does go away I don't
think it is worth making the change now. But I will keep it in mind
and I you have definitely spotted an opportunity missed in this
patchset.

Eric
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