On Thu, Oct 7, 2021 at 12:03 PM 'John Hubbard' via kernel-team <kernel-team@xxxxxxxxxxx> wrote: > > On 10/7/21 11:50, Suren Baghdasaryan wrote: > ... > >>>>>>>>>> I believe Pavel meant something as simple as > >>>>>>>>>> $ YOUR_FILE=$YOUR_IDS_DIR/my_string_name > >>>>>>>>>> $ touch $YOUR_FILE > >>>>>>>>>> $ stat -c %i $YOUR_FILE > >>>>>>> > >>>>>>> Ah, ok, now I understand the proposal. Thanks for the clarification! > >>>>>>> So, this would use filesystem as a directory for inode->name mappings. > >>>>>>> One rough edge for me is that the consumer would still need to parse > >>>>>>> /proc/$pid/maps and convert [anon:inode] into [anon:name] instead of > >>>>>>> just dumping the content for the user. Would it be acceptable if we > >>>>>>> require the ID provided by prctl() to always be a valid inode and > >>>>>>> show_map_vma() would do the inode-to-filename conversion when > >>>>>>> generating maps/smaps files? I know that inode->dentry is not > >>>>>>> one-to-one mapping but we can simply output the first dentry name. > >>>>>>> WDYT? > >>>>>> > >>>>>> No. You do not want to dictate any particular way of the mapping. The > >>>>>> above is just one way to do that without developing any actual mapping > >>>>>> yourself. You just use a filesystem for that. Kernel doesn't and > >>>>>> shouldn't understand the meaning of those numbers. It has no business in > >>>>>> that. > >>>>>> > >>>>>> In a way this would be pushing policy into the kernel. > >>>>> > >>>>> I can see your point. Any other ideas on how to prevent tools from > >>>>> doing this id-to-name conversion themselves? > >>>> > >>>> I really fail to understand why you really want to prevent them from that. > >>>> Really, the whole thing is just a cookie that kernel maintains for memory > >>>> mappings so that two parties can understand what the meaning of that > >>>> mapping is from a higher level. They both have to agree on the naming > >>>> but the kernel shouldn't dictate any specific convention because the > >>>> kernel _doesn't_ _care_. These things are not really anything actionable > >>>> for the kernel. It is just a metadata. > >>> > >>> The desire is for one of these two parties to be a human who can get > >>> the data and use it as is without additional conversions. > >>> /proc/$pid/maps could report FD numbers instead of pathnames, which > >>> could be converted to pathnames in userspace. However we do not do > >>> that because pathnames are more convenient for humans to identify a > >>> specific resource. Same logic applies here IMHO. > >> > >> Yes, please. It really seems like the folks that are interested in this > >> feature want strings. (I certainly do.) For those not interested in the > >> feature, it sounds like a CONFIG to keep it away would be sufficient. > >> Can we just move forward with that? > > > > Would love to if others are ok with this. > > > > If this doesn't get accepted, then another way forward would to continue > the ideas above to their logical conclusion, and create a new file system: > vma-fs. Like debug-fs and other special file systems, similar policy and > motivation. Also protected by a CONFIG option. TBH, I would prefer to have the current simple solution protected with a CONFIG option. > > Actually this seems at least as natural as the procfs approach, especially > given the nature of these strings, which feel more like dir+file names, than > simple strings. > > thanks, > -- > John Hubbard > NVIDIA > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@xxxxxxxxxxx. >
