From 734550921e9b7ab924a43aa3d0bd4239dac4fbf1 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 14 Jul 2008 21:22:20 -0400 Subject: [PATCH] beginning of sysctl cleanup - ctl_table_set New object: set of sysctls [currently - root and per-net-ns]. Contains: pointer to parent set, list of tables and "should I see this set?" method (->is_seen(set)). Current lists of tables are subsumed by that; net-ns contains such a beast. ->lookup() for ctl_table_root returns pointer to ctl_table_set instead of that to ->list of that ctl_table_set. [folded compile fixes by rdd for configs without sysctl] Signed-off-by: Al Viro --- include/linux/sysctl.h | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-) (limited to 'include/linux/sysctl.h') diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 24141b4d1a11..c1e0cf408af9 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -947,6 +947,16 @@ struct ctl_table; struct nsproxy; struct ctl_table_root; +struct ctl_table_set { + struct list_head list; + struct ctl_table_set *parent; + int (*is_seen)(struct ctl_table_set *); +}; + +extern void setup_sysctl_set(struct ctl_table_set *p, + struct ctl_table_set *parent, + int (*is_seen)(struct ctl_table_set *)); + extern struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev); extern struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces, struct ctl_table_header *prev); @@ -1049,8 +1059,8 @@ struct ctl_table struct ctl_table_root { struct list_head root_list; - struct list_head header_list; - struct list_head *(*lookup)(struct ctl_table_root *root, + struct ctl_table_set default_set; + struct ctl_table_set *(*lookup)(struct ctl_table_root *root, struct nsproxy *namespaces); int (*permissions)(struct ctl_table_root *root, struct nsproxy *namespaces, struct ctl_table *table); @@ -1066,6 +1076,7 @@ struct ctl_table_header struct completion *unregistering; struct ctl_table *ctl_table_arg; struct ctl_table_root *root; + struct ctl_table_set *set; }; /* struct ctl_path describes where in the hierarchy a table is added */ -- cgit v1.2.3 From f7e6ced4061da509f737541ca4dbd44d83a6e82f Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 15 Jul 2008 01:44:23 -0400 Subject: [PATCH] allow delayed freeing of ctl_table_header Refcount the sucker; instead of freeing it by the end of unregistration just drop the refcount and free only when it hits zero. Make sure that we _always_ make ->unregistering non-NULL in start_unregistering(). That allows anybody to get a reference to such puppy, preventing its freeing and reuse. It does *not* block unregistration. Anybody who holds such a reference can * try to grab a "use" reference (ctl_head_grab()); that will succeeds if and only if it hadn't entered unregistration yet. If it succeeds, we can use it in all normal ways until we release the "use" reference (with ctl_head_finish()). Note that this relies on having ->unregistering become non-NULL in all cases when one starts to unregister the sucker. * keep pointers to ctl_table entries; they *can* be freed if the entire thing is unregistered. However, if ctl_head_grab() succeeds, we know that unregistration had not happened (and will not happen until ctl_head_finish()) and such pointers can be used safely. IOW, now we can have inodes under /proc/sys keep references to ctl_table entries, protecting them with references to ctl_table_header and grabbing the latter for the duration of operations that require access to ctl_table. That won't cause deadlocks, since unregistration will not be stopped by mere keeping a reference to ctl_table_header. Signed-off-by: Al Viro --- include/linux/sysctl.h | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'include/linux/sysctl.h') diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index c1e0cf408af9..956264d09ba0 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -957,6 +957,11 @@ extern void setup_sysctl_set(struct ctl_table_set *p, struct ctl_table_set *parent, int (*is_seen)(struct ctl_table_set *)); +struct ctl_table_header; + +extern void sysctl_head_get(struct ctl_table_header *); +extern void sysctl_head_put(struct ctl_table_header *); +extern struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *); extern struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev); extern struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces, struct ctl_table_header *prev); @@ -1073,6 +1078,7 @@ struct ctl_table_header struct ctl_table *ctl_table; struct list_head ctl_entry; int used; + int count; struct completion *unregistering; struct ctl_table *ctl_table_arg; struct ctl_table_root *root; -- cgit v1.2.3 From ae7edecc9b8810770a8e5cb9a466ea4bdcfa8401 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 15 Jul 2008 06:33:31 -0400 Subject: [PATCH] sysctl: keep track of tree relationships In a sense, that's the heart of the series. It's based on the following property of the trees we are actually asked to add: they can be split into stem that is already covered by registered trees and crown that is entirely new. IOW, if a/b and a/c/d are introduced by our tree, then a/c is also introduced by it. That allows to associate tree and table entry with each node in the union; while directory nodes might be covered by many trees, only one will cover the node by its crown. And that will allow much saner logics for /proc/sys in the next patches. This patch introduces the data structures needed to keep track of that. When adding a sysctl table, we find a "parent" one. Which is to say, find the deepest node on its stem that already is present in one of the tables from our table set or its ancestor sets. That table will be our parent and that node in it - attachment point. Add our table to list anchored in parent, have it refer the parent and contents of attachment point. Also remember where its crown lives. Signed-off-by: Al Viro --- include/linux/sysctl.h | 3 +++ 1 file changed, 3 insertions(+) (limited to 'include/linux/sysctl.h') diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 956264d09ba0..3f6599aeb0db 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -1083,6 +1083,9 @@ struct ctl_table_header struct ctl_table *ctl_table_arg; struct ctl_table_root *root; struct ctl_table_set *set; + struct ctl_table *attached_by; + struct ctl_table *attached_to; + struct ctl_table_header *parent; }; /* struct ctl_path describes where in the hierarchy a table is added */ -- cgit v1.2.3 From 9043476f726802f4b00c96d0c4f418dde48d1304 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Tue, 15 Jul 2008 08:54:06 -0400 Subject: [PATCH] sanitize proc_sysctl * keep references to ctl_table_head and ctl_table in /proc/sys inodes * grab the former during operations, use the latter for access to entry if that succeeds * have ->d_compare() check if table should be seen for one who does lookup; that allows us to avoid flipping inodes - if we have the same name resolve to different things, we'll just keep several dentries and ->d_compare() will reject the wrong ones. * have ->lookup() and ->readdir() scan the table of our inode first, then walk all ctl_table_header and scan ->attached_by for those that are attached to our directory. * implement ->getattr(). * get rid of insane amounts of tree-walking * get rid of the need to know dentry in ->permission() and of the contortions induced by that. Signed-off-by: Al Viro --- include/linux/sysctl.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include/linux/sysctl.h') diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h index 3f6599aeb0db..d0437f36921f 100644 --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -961,6 +961,7 @@ struct ctl_table_header; extern void sysctl_head_get(struct ctl_table_header *); extern void sysctl_head_put(struct ctl_table_header *); +extern int sysctl_is_seen(struct ctl_table_header *); extern struct ctl_table_header *sysctl_head_grab(struct ctl_table_header *); extern struct ctl_table_header *sysctl_head_next(struct ctl_table_header *prev); extern struct ctl_table_header *__sysctl_head_next(struct nsproxy *namespaces, -- cgit v1.2.3