ALSA: memalloc: Add fallback SG-buffer allocations for x86
The recent change for memory allocator replaced the SG-buffer handling helper for x86 with the standard non-contiguous page handler. This works for most cases, but there is a corner case I obviously overlooked, namely, the fallback of non-contiguous handler without IOMMU. When the system runs without IOMMU, the core handler tries to use the continuous pages with a single SGL entry. It works nicely for most cases, but when the system memory gets fragmented, the large allocation may fail frequently. Ideally the non-contig handler could deal with the proper SG pages, it's cumbersome to extend for now. As a workaround, here we add new types for (minimalistic) SG allocations, instead, so that the allocator falls back to those types automatically when the allocation with the standard API failed. BTW, one better (but pretty minor) improvement from the previous SG-buffer code is that this provides the proper mmap support without the PCM's page fault handling. Fixes: 2c95b92e ("ALSA: memalloc: Unify x86 SG-buffer handling (take#3)") BugLink: https://gitlab.freedesktop.org/pipewire/pipewire/-/issues/2272 BugLink: https://bugzilla.suse.com/show_bug.cgi?id=1198248 Cc: <stable@vger.kernel.org> Link: https://lore.kernel.org/r/20220413054808.7547-1-tiwai@suse.de Signed-off-by:Takashi Iwai <tiwai@suse.de>
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