Messages in this thread | | | Date | Mon, 5 Mar 2012 21:05:56 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [PATCH 0/1] turn mm->exe_file into mm->exe_path |
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On Mon, Mar 05, 2012 at 04:28:26PM +0100, Oleg Nesterov wrote: > I think the patch is simple and self-explanatory, it simply > does s/mm->exe_file/mm->exe_path/. > > Why do we need mm->exe_file? IIUC, there are 2 reasons: > > 1. we do not want O(n) proc/pid/exe looking for the 1st > VM_EXECUTABLE vma. > > 2. we do not want to rely on vma->vm_file->f_path, > bprm->file->f_op->mmap can change ->vm_file. > > Unless there was another subtle reason, "struct path *exe_path" > can equally work but it looks more clear. > > And can't we also remove added_exe_file_vma/removed_exe_file_vma? > Why do we need mm->num_exe_file_vmas? Afaics it is only needed to > "free" mm->exe_file if the application unmaps all these vmas. Say, > to allow to unmount fs. > > Can't we simply add PR_CLEAR_MM_EXE_PATH instead? Of course it is > not enough if ->vm_file still has a reference. But c/r people want > PR_SET_MM_EXE_FILE anyway, see http://marc.info/?t=133052865500016 > So perhaps we can add PR_SET_MM_EXE_PATH which accepts NULL as well > and kill this counter? >
So, if I understand you correctly, if there is exe_path, I would simply put() it and get() and assign new one. Looks cool for me.
Not sure where we may use PR_SET_MM_EXE_PATH with NULL to kill num_exe_file_vmas from user space though (or to kill this exe_path in case if num_exe_file_vmas is removed from code).
Cyrill
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