Messages in this thread Patch in this message | | | Date | Thu, 17 Sep 2009 15:10:16 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | [PATCH 2/3][mmotm] showing size of kcore v2 |
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On Thu, 17 Sep 2009 14:02:39 +0800 Américo Wang <xiyou.wangcong@gmail.com> wrote: > > @@ -124,6 +126,7 @@ static void __kcore_update_ram(struct li > > write_unlock(&kclist_lock); > > > > free_kclist_ents(&garbage); > > + proc_root_kcore->size = get_kcore_size(&nphdr, &size); > > > This makes me to think if we will have some race condition here? > Two processes can open kcore at the same time... > Finally, == static void __kcore_update_ram(struct list_head *list) { write_lock(&kclist_lock); if (kcore_need_update) { list_for_each_entry_safe(pos, tmp, &kclist_head, list) { if (pos->type == KCORE_RAM || pos->type == KCORE_VMEMMAP) list_move(&pos->list, &garbage); } list_splice_tail(list, &kclist_head); } else list_splice(list, &garbage); kcore_need_update = 0; write_unlock(&kclist_lock); }
kclist itself is double checked under write_lock. And, once updated, get_kcore_size()'s return vaule is static. So, I think there are no race. But..Hmm...is this clearer ?
== From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Now, size of /proc/kcore which can be read by 'ls -l' is 0. But it's not correct value.
This is a patch for showing size of /proc/kcore as following.
On x86-64, ls -l shows ... root root 140737486266368 2009-09-17 10:29 /proc/kcore Then, 7FFFFFFE02000. This comes from vmalloc area's size. This shows "core" size, not memory size.
This patch shows the size by updating "size" field in struct proc_dir_entry. Later, lookup routine will create inode and fill inode->i_size based on this value. Then, this has a problem.
- Once inode is cached, inode->i_size will never be updated.
Then, this patch is not memory-hotplug-aware.
To update inode->i_size, we have to know dentry or inode. But there is no way to lookup them by inside kernel. Hmmm.... Next patch will try it.
Changelog: -moved upadting ->size under lock.
Cc: WANG Cong <xiyou.wangcong@gmail.com> Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> --- fs/proc/kcore.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
Index: mmotm-2.6.31-Sep14/fs/proc/kcore.c =================================================================== --- mmotm-2.6.31-Sep14.orig/fs/proc/kcore.c +++ mmotm-2.6.31-Sep14/fs/proc/kcore.c @@ -107,6 +107,8 @@ static void free_kclist_ents(struct list */ static void __kcore_update_ram(struct list_head *list) { + int nphdr; + size_t size; struct kcore_list *tmp, *pos; LIST_HEAD(garbage); @@ -121,6 +123,7 @@ static void __kcore_update_ram(struct li } else list_splice(list, &garbage); kcore_need_update = 0; + proc_root_kcore->size = get_kcore_size(&nphdr, &size); write_unlock(&kclist_lock); free_kclist_ents(&garbage); @@ -429,7 +432,8 @@ read_kcore(struct file *file, char __use unsigned long start; read_lock(&kclist_lock); - proc_root_kcore->size = size = get_kcore_size(&nphdr, &elf_buflen); + size = get_kcore_size(&nphdr, &elf_buflen); + if (buflen == 0 || *fpos >= size) { read_unlock(&kclist_lock); return 0;
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