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Commit f868089b authored by Trond Myklebust's avatar Trond Myklebust
Browse files

NFS: Fix a potential busy wait in nfs_page_group_lock 



We cannot allow nfs_page_group_lock to use TASK_KILLABLE here, since
the loop would cause a busy wait if somebody kills the task.

Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
parent c1109558

fs/nfs/pagelist.c

+9 −10
Original line number Diff line number Diff line
@@ -138,6 +138,12 @@ nfs_iocounter_wait(struct nfs_io_counter *c) 
	return __nfs_iocounter_wait(c);

}



static int nfs_wait_bit_uninterruptible(void *word)

{

	io_schedule();

	return 0;

}



/*

 * nfs_page_group_lock - lock the head of the page group

 * @req - request in group that is to be locked
@@ -148,13 +154,12 @@ void 
nfs_page_group_lock(struct nfs_page *req)

{

	struct nfs_page *head = req->wb_head;

	int err = -EAGAIN;



	WARN_ON_ONCE(head != head->wb_head);



	while (err)

		err = wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,

			nfs_wait_bit_killable, TASK_KILLABLE);

	wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,

			nfs_wait_bit_uninterruptible,

			TASK_UNINTERRUPTIBLE);

}



/*
@@ -410,12 +415,6 @@ void nfs_release_request(struct nfs_page *req) 
	kref_put(&req->wb_kref, nfs_page_group_destroy);

}



static int nfs_wait_bit_uninterruptible(void *word)

{

	io_schedule();

	return 0;

}



/**

 * nfs_wait_on_request - Wait for a request to complete.

 * @req: request to wait upon.