On 10/25/19 8:18 AM, Ajay Kaher wrote: > On 17/10/19, 9:58 PM, "Ajay Kaher" <akaher@xxxxxxxxxx> wrote: > >> > This seems to have the same issue as the 4.9 stable version [1], in not >> > touching the arch-specific gup.c variants. >> > >> > [1] >> > https://lore.kernel.org/lkml/6650323f-dbc9-f069-000b-f6b0f941a065@xxxxxxx/ >> >> Thanks Vlastimil for highlighting this here. >> >> Yes, arch-specific gup.c variants also need to handle not only for 4.4.y, >> however it should be handled till 4.19.y. I believe it's better to start >> from 4.19.y and then backport those changes till 4.4.y. >> >> Affected areas of gup.c (where page->count have been used) are: >> #1: get_page() used in these files and this is safe as >> it's defined in mm.h (here it's already taken care of) >> #2: get_head_page_multiple() has following: >> VM_BUG_ON_PAGE(page_count(page) == 0, page); >> Need to change this to: >> VM_BUG_ON_PAGE(page_ref_zero_or_close_to_overflow(page), page); >> #3: Some of the files have used page_cache_get_speculative(), >> page_cache_add_speculative() with combination of compound_head(), >> this scenario needs to be handled as it was handled here: >> https://lore.kernel.org/stable/1570581863-12090-7-git-send-email-akaher@xxxxxxxxxx/ >> >> Please share with me any suggestions or patches if you have already >> worked on this. >> >> Could we handle arch-specific gup.c in different patch sets and >> let these patches to merge to 4.4.y? > > Vlastimil, please suggest if it's fine to merge these patches to 4.4.y I'm not sure if it makes much sense to merge them without the arch-specific gup support, when we're aware that it's missing. > and handle arch-specific gup.c in different patch sets starts from 4.19.y, Actually arch-specific gup.c were removed in 4.13, so it's enough to start from 4.9.y, which I'm going to finally look into. > then backport all the way to 4.4.y. > > Greg, any suggestion from your side. > >> - Ajay > > > >
