kernel/resource: Increment by align value in get_free_mem_region()

[ Upstream commit 659aa05 ]

Currently get_free_mem_region() searches for available capacity
in increments equal to the region size being requested. This can
cause the search to take giant steps through the resource leaving
needless gaps and missing available space.

Specifically 'cxl create-region' fails with ERANGE even though capacity
of the given size and CXL's expected 256M x InterleaveWays alignment can
be satisfied.

Replace the total-request-size increment with a next alignment increment
so that the next possible address is always examined for availability.

Fixes: 14b8058 ("resource: Introduce alloc_free_mem_region()")
Reported-by: Dmytro Adamenko <dmytro.adamenko@intel.com>
Reported-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Alison Schofield <alison.schofield@intel.com>
Reviewed-by: Dave Jiang <dave.jiang@intel.com>
Link: https://lore.kernel.org/r/20231113221324.1118092-1-alison.schofield@intel.com
Cc: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

kernel/resource.c

@@ -1847,8 +1847,8 @@ get_free_mem_region(struct device *dev, struct resource *base,
 
 	write_lock(&resource_lock);
 	for (addr = gfr_start(base, size, align, flags);
-	     gfr_continue(base, addr, size, flags);
-	     addr = gfr_next(addr, size, flags)) {
+	     gfr_continue(base, addr, align, flags);
+	     addr = gfr_next(addr, align, flags)) {
 		if (__region_intersects(base, addr, size, 0, IORES_DESC_NONE) !=
 		    REGION_DISJOINT)
 			continue;