mm/vmalloc: support non-blocking GFP flags in alloc_vmap_area()

alloc_vmap_area() currently assumes that sleeping is allowed during
allocation.  This is not true for callers which pass non-blocking GFP
flags, such as GFP_ATOMIC or GFP_NOWAIT.

This patch adds logic to detect whether the given gfp_mask permits
blocking.  It avoids invoking might_sleep() or falling back to reclaim
path if blocking is not allowed.

This makes alloc_vmap_area() safer for use in non-sleeping contexts, where
previously it could hit unexpected sleeps, trigger warnings.

It is a preparation and adjustment step to later allow both GFP_ATOMIC and
GFP_NOWAIT allocations in this series.

Link: https://lkml.kernel.org/r/20251007122035.56347-4-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 798b2ed21e46059f341ed0d46c7fe56bbe357b22..d83c01caaabea88b15225576034b87e50e26dc20 100644 (file)
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2017,6 +2017,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
        unsigned long freed;
        unsigned long addr;
        unsigned int vn_id;
+       bool allow_block;
        int purged = 0;
        int ret;
 
@@ -2028,7 +2029,8 @@ static struct vmap_area *alloc_vmap_area(unsigned long size,
 
        /* Only reclaim behaviour flags are relevant. */
        gfp_mask = gfp_mask & GFP_RECLAIM_MASK;
-       might_sleep();
+       allow_block = gfpflags_allow_blocking(gfp_mask);
+       might_sleep_if(allow_block);
 
        /*
         * If a VA is obtained from a global heap(if it fails here)
@@ -2062,7 +2064,8 @@ retry:
                 * This is not a fast path.  Check if yielding is needed. This
                 * is the only reschedule point in the vmalloc() path.
                 */
-               cond_resched();
+               if (allow_block)
+                       cond_resched();
        }
 
        trace_alloc_vmap_area(addr, size, align, vstart, vend, IS_ERR_VALUE(addr));
@@ -2071,8 +2074,16 @@ retry:
         * If an allocation fails, the error value is
         * returned. Therefore trigger the overflow path.
         */
-       if (IS_ERR_VALUE(addr))
-               goto overflow;
+       if (IS_ERR_VALUE(addr)) {
+               if (allow_block)
+                       goto overflow;
+
+               /*
+                * We can not trigger any reclaim logic because
+                * sleeping is not allowed, thus fail an allocation.
+                */
+               goto out_free_va;
+       }
 
        va->va_start = addr;
        va->va_end = addr + size;
@@ -2122,6 +2133,7 @@ overflow:
                pr_warn("vmalloc_node_range for size %lu failed: Address range restricted to %#lx - %#lx\n",
                                size, vstart, vend);
 
+out_free_va:
        kmem_cache_free(vmap_area_cachep, va);
        return ERR_PTR(-EBUSY);
 }