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Commit 17dfeb91 authored by Trond Myklebust's avatar Trond Myklebust
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NFS: Fix races in nfs_revalidate_mapping 



Commit d529ef83 (NFS: fix the handling
of NFS_INO_INVALID_DATA flag in nfs_revalidate_mapping) introduces
a potential race, since it doesn't test the value of nfsi->cache_validity
and set the bitlock in nfsi->flags atomically.

Signed-off-by: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
Cc: Jeff Layton <jlayton@redhat.com>
parent 0ea9de0e

fs/nfs/inode.c

+14 −14
Original line number Diff line number Diff line
@@ -1038,23 +1038,23 @@ int nfs_revalidate_mapping(struct inode *inode, struct address_space *mapping) 
				  nfs_wait_bit_killable, TASK_KILLABLE);

		if (ret)

			goto out;

		if (!(nfsi->cache_validity & NFS_INO_INVALID_DATA))

			goto out;

		if (!test_and_set_bit_lock(NFS_INO_INVALIDATING, bitlock))

		spin_lock(&inode->i_lock);

		if (test_bit(NFS_INO_INVALIDATING, bitlock)) {

			spin_unlock(&inode->i_lock);

			continue;

		}

		if (nfsi->cache_validity & NFS_INO_INVALID_DATA)

			break;

		spin_unlock(&inode->i_lock);

		goto out;

	}



	spin_lock(&inode->i_lock);

	if (nfsi->cache_validity & NFS_INO_INVALID_DATA) {

	set_bit(NFS_INO_INVALIDATING, bitlock);

	nfsi->cache_validity &= ~NFS_INO_INVALID_DATA;

	spin_unlock(&inode->i_lock);

	trace_nfs_invalidate_mapping_enter(inode);

	ret = nfs_invalidate_mapping(inode, mapping);

	trace_nfs_invalidate_mapping_exit(inode, ret);

	} else {

		/* something raced in and cleared the flag */

		spin_unlock(&inode->i_lock);

	}



	clear_bit_unlock(NFS_INO_INVALIDATING, bitlock);

	smp_mb__after_clear_bit();