Messages in this thread | | | Date | Wed, 1 Mar 2017 11:03:04 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] lockdep: Teach lockdep about memalloc_noio_save |
| |
On Wed, Mar 01, 2017 at 11:57:13AM +0200, Nikolay Borisov wrote: > > > On 1.03.2017 11:46, Peter Zijlstra wrote: > > On Wed, Mar 01, 2017 at 09:59:00AM +0200, Nikolay Borisov wrote: > >> Commit 21caf2fc1931 ("mm: teach mm by current context info to not do I/O > >> during memory allocation") added the memalloc_noio_(save|restore) functions > >> to enable people to modify the MM behavior by disbaling I/O during memory > >> allocation. This prevents allocation paths recursing back into the filesystem > >> without explicitly changing the flags for every allocation site. Yet, lockdep > >> not being aware of that is prone to showing false positives. Fix this > >> by teaching it that the presence of PF_MEMALLOC_NOIO flag mean we are not > >> going to issue any I/O > > > > I'm not up to date on the specific, but GFP_IO is separate from GFP_FS. > > > > And MEMALLOC_NOIO only clears GFP_IO but leaves GFP_FS set. > > static inline gfp_t memalloc_noio_flags(gfp_t flags) > { > if (unlikely(current->flags & PF_MEMALLOC_NOIO)) > flags &= ~(__GFP_IO | __GFP_FS); > return flags; > } >
Ah, so in the initial patch you referenced there was:
+static inline gfp_t memalloc_noio_flags(gfp_t flags) +{ + if (unlikely(current->flags & PF_MEMALLOC_NOIO)) + flags &= ~__GFP_IO; + return flags; +}
OK, so then this commit needs something like:
Fixes: 934f3072c17c ("mm: clear __GFP_FS when PF_MEMALLOC_NOIO is set")
| |