On 2016/04/26 20:56, Michal Hocko wrote: > Not only this is easier to understand and maintain because there are > much less problematic contexts than specific allocation requests, this > also helps code paths where FS layer interacts with other layers (e.g. > crypto, security modules, MM etc...) and there is no easy way to convey > the allocation context between the layers. > You arrived at what I wished at http://lkml.kernel.org/r/201503172305.DIH52162.FOFMFOVJHLOtQS@xxxxxxxxxxxxxxxxxxx (i.e. not CONFIG_DEBUG_* but always enabled). > Introduce PF_MEMALLOC_NOFS task specific flag and memalloc_nofs_{save,restore} > API to control the scope. This is basically copying > memalloc_noio_{save,restore} API we have for other restricted allocation > context GFP_NOIO. > > Xfs has already had a similar functionality as PF_FSTRANS so let's just > give it a more generic name and make it usable for others as well and > move the GFP_NOFS context tracking to the page allocator. Xfs has its > own accessor functions but let's keep them for now to reduce this patch > as minimum. > > This patch shouldn't introduce any functional changes. Xfs code paths > preserve their semantic. kmem_flags_convert() doesn't need to evaluate > the flag anymore because it is the page allocator to care about the > flag. memalloc_noio_flags is renamed to current_gfp_context because it > now cares about both PF_MEMALLOC_NOFS and PF_MEMALLOC_NOIO contexts. > > Let's hope that filesystems will drop direct GFP_NOFS (resp. ~__GFP_FS) > usage as much and possible and only use a properly documented > memalloc_nofs_{save,restore} checkpoints where they are appropriate. Is the story simple enough to monotonically replace GFP_NOFS/GFP_NOIO with GFP_KERNEL after memalloc_no{fs,io}_{save,restore} are inserted? We sometimes delegate some operations to somebody else. Don't we need to convey PF_MEMALLOC_NOFS/PF_MEMALLOC_NOIO flags to APIs which interact with other threads? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>