NFSD: Protect against filesystem freezing

Flole observes this WARNING on occasion:

[1210423.486503] WARNING: CPU: 8 PID: 1524732 at fs/ext4/ext4_jbd2.c:75 ext4_journal_check_start+0x68/0xb0

Reported-by: <flole@flole.de>
Suggested-by: Jan Kara <jack@suse.cz>
Link: https://bugzilla.kernel.org/show_bug.cgi?id=217123
Fixes: 73da852e3831 ("nfsd: use vfs_iter_read/write")
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 21d5209..ba34a31 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1104,7 +1104,9 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct nfsd_file *nf,
        since = READ_ONCE(file->f_wb_err);
        if (verf)
                nfsd_copy_write_verifier(verf, nn);
+       file_start_write(file);
        host_err = vfs_iter_write(file, &iter, &pos, flags);
+       file_end_write(file);
        if (host_err < 0) {
                nfsd_reset_write_verifier(nn);
                trace_nfsd_writeverf_reset(nn, rqstp, host_err);