linux-kernel - Re: [syzbot] Re: [syzbot] [mm?] BUG: stack guard page was hit in v9fs_file_read

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Message-ID: <672c3db0.050a0220.350062.0286.GAE@google.com>
Date: Wed, 06 Nov 2024 20:10:24 -0800
From: syzbot <syzbot+1fc6f64c40a9d143cfb6@...kaller.appspotmail.com>
To: linux-kernel@...r.kernel.org
Subject: Re: [syzbot] Re: [syzbot] [mm?] BUG: stack guard page was hit in v9fs_file_read_iter

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Subject: Re: [syzbot] [mm?] BUG: stack guard page was hit in v9fs_file_read_iter
Author: lizhi.xu@...driver.com

add resched to avoid retry too frequently when rreq need to retry

#syz test

diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c
index b18c65ba5580..eb4fc1f62000 100644
--- a/fs/netfs/read_collect.c
+++ b/fs/netfs/read_collect.c
@@ -366,6 +366,7 @@ static void netfs_rreq_assess(struct netfs_io_request *rreq)
 	//netfs_rreq_is_still_valid(rreq);
 
 	if (test_and_clear_bit(NETFS_RREQ_NEED_RETRY, &rreq->flags)) {
+		cond_resched();
 		netfs_retry_reads(rreq);
 		return;
 	}
@@ -512,9 +513,15 @@ void netfs_read_subreq_terminated(struct netfs_io_subrequest *subreq,
 				__set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
 				__clear_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags);
 				set_bit(NETFS_RREQ_NEED_RETRY, &rreq->flags);
+				printk("async: %d, r: %p, %s\n", was_async, rreq, __func__);
+				if (!was_async)
+					cond_resched();
 			} else if (!__test_and_set_bit(NETFS_SREQ_NO_PROGRESS, &subreq->flags)) {
 				__set_bit(NETFS_SREQ_NEED_RETRY, &subreq->flags);
 				set_bit(NETFS_RREQ_NEED_RETRY, &rreq->flags);
+				printk("async: %d, r: %p, %s\n", was_async, rreq, __func__);
+				if (!was_async)
+					cond_resched();
 			} else {
 				__set_bit(NETFS_SREQ_FAILED, &subreq->flags);
 				error = -ENODATA;