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From:   Kent Overstreet <kent.overstreet@linux.dev>
To:     linux-kernel@vger.kernel.org
Cc:     Kent Overstreet <kent.overstreet@linux.dev>,
        Thomas Graf <tgraf@suug.ch>,
        Herbert Xu <herbert@gondor.apana.org.au>
Subject: [PATCH] rhashtable: Better error message on allocation failure
Date:   Wed, 22 Nov 2023 18:32:16 -0500
Message-ID: <20231122233225.178910-1-kent.overstreet@linux.dev>
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Memory allocation failures print backtraces by default, but when we're
running out of a rhashtable worker the backtrace is useless - it doesn't
tell us which hashtable the allocation failure was for.

This adds a dedicated warning that prints out functions from the
rhashtable params, which will be a bit more useful.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>
Cc: Thomas Graf <tgraf@suug.ch>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
---
 lib/rhashtable.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/rhashtable.c b/lib/rhashtable.c
index 6ae2ba8e06a2..d3fce9c8989a 100644
--- a/lib/rhashtable.c
+++ b/lib/rhashtable.c
@@ -360,9 +360,14 @@ static int rhashtable_rehash_alloc(struct rhashtable *ht,
 
 	ASSERT_RHT_MUTEX(ht);
 
-	new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL);
-	if (new_tbl == NULL)
+	new_tbl = bucket_table_alloc(ht, size, GFP_KERNEL|__GFP_NOWARN);
+	if (new_tbl == NULL) {
+		WARN("rhashtable bucket table allocation failure for %ps",
+		     (void *) ht->p.hashfn ?:
+		     (void *) ht->p.obj_hashfn ?:
+		     (void *) ht->p.obj_cmpfn);
 		return -ENOMEM;
+	}
 
 	err = rhashtable_rehash_attach(ht, old_tbl, new_tbl);
 	if (err)
-- 
2.42.0