On Wed, Mar 20, 2024 at 03:07:38PM -0400, Kent Overstreet wrote: > On Wed, Mar 20, 2024 at 06:55:36PM +0000, Matthew Wilcox wrote: > > GFP_NOFAIL should still fail for allocations larger than KMALLOC_MAX_SIZE. > > Or should we interpret that as "die now"? Or "go into an unkillable > > sleep"? If the caller really has taken the opportunity to remove their > > error handling path, returning NULL will lead to a crash and a lot of > > beard stroking trying to understand why a GFP_NOFAIL allocation has > > returned NULL. May as well BUG_ON(size > KMALLOC_MAX_SIZE) and give > > the developer a clear indication of what they did wrong. > > Why do we even need KMALLOC_MAX_SIZE...? > > Given that kmalloc internally switches to the page allocator when > needed, I would think that that's something we can do away with. ... maybe check what I said before replying? /* * SLUB directly allocates requests fitting in to an order-1 page * (PAGE_SIZE*2). Larger requests are passed to the page allocator. */ #define KMALLOC_SHIFT_MAX (MAX_PAGE_ORDER + PAGE_SHIFT) You caan't allocate larger than that without going to CMA or some other custom allocator. So. The caller has requested NOFAIL, and requested a size larger than we can allocate. Do we panic, go into an uninterruptible sleep, or return NULL?
