[PATCH 6/6] NFSv4/flexfiles: allocate the per-mirror stripe array with kvzalloc_objs

[Benjamin Coddington <ben.coddington@hammerspace.com>]

Each mirror's stripe array is a single contiguous allocation of
dss_count * sizeof(struct nfs4_ff_layout_ds_stripe) -- roughly 300
bytes per stripe.  With the LAYOUTGET reply buffer no longer capped at
a single page, a wide striped layout can push this well past the
high-order allocation comfort zone (a 2048-stripe mirror is a ~600KB
contiguous allocation) where it can fail under memory fragmentation.

Use kvzalloc_objs() so wide stripe arrays fall back to vmalloc.  Note
the vmalloc fallback is unavailable when the pageio path allocates
under memalloc_noio (swap over pNFS); that case simply behaves as
before.

Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Benjamin Coddington <bcodding@hammerspace.com>
---
 fs/nfs/flexfilelayout/flexfilelayout.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index c4aa995026f6..d96d73d04f01 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -285,8 +285,8 @@ static struct nfs4_ff_layout_mirror *ff_layout_alloc_mirror(u32 dss_count,
 
 	mirror->dss_count = dss_count;
 	mirror->dss =
-		kzalloc_objs(struct nfs4_ff_layout_ds_stripe, dss_count,
-			     gfp_flags);
+		kvzalloc_objs(struct nfs4_ff_layout_ds_stripe, dss_count,
+			      gfp_flags);
 	if (mirror->dss == NULL) {
 		kfree(mirror);
 		return NULL;
@@ -315,7 +315,7 @@ static void ff_layout_free_mirror(struct nfs4_ff_layout_mirror *mirror)
 		nfs4_ff_layout_put_deviceid(mirror->dss[dss_id].mirror_ds);
 	}
 
-	kfree(mirror->dss);
+	kvfree(mirror->dss);
 	kfree(mirror);
 }
 
-- 
2.53.0