According to the investigation performed by Jacob Shivers at Red Hat,
cifs_lookup and cifs_readdir leak EAGAIN when the user session is
deleted on the server. Fix this issue by implementing a retry with
limits, as is implemented in cifs_revalidate_dentry_attr.
Reproducer based on the work by Jacob Shivers:
~~~
$ cat readdir-cifs-test.sh
#!/bin/bash
# Install and configure powershell and sshd on the windows
# server as descibed in
# https://docs.microsoft.com/en-us/windows-server/administration/openssh/openssh_overview
# This script uses expect(1)
USER=dude
SERVER=192.168.0.2
RPATH=root
PASS='password'
function debug_funcs {
for line in $@ ; do
echo "func $line +p" > /sys/kernel/debug/dynamic_debug/control
done
}
function setup {
echo 1 > /proc/fs/cifs/cifsFYI
debug_funcs wait_for_compound_request \
smb2_query_dir_first cifs_readdir \
compound_send_recv cifs_reconnect_tcon \
generic_ip_connect cifs_reconnect \
smb2_reconnect_server smb2_reconnect \
cifs_readv_from_socket cifs_readv_receive
tcpdump -i eth0 -w cifs.pcap host 192.168.2.182 & sleep 5
dmesg -C
}
function test_call {
if [[ $1 == 1 ]] ; then
tracer="strace -tt -f -s 4096 -o trace-$(date -Iseconds).txt"
fi
# Change the command here to anything appropriate
$tracer ls $2 > /dev/null
res=$?
if [[ $1 == 1 ]] ; then
if [[ $res == 0 ]] ; then
1>&2 echo success
else
1>&2 echo "failure ($res)"
fi
fi
}
mountpoint /mnt > /dev/null || mount -t cifs -o username=$USER,pass=$PASS //$SERVER/$RPATH /mnt
test_call 0 /mnt/
/usr/bin/expect << EOF
set timeout 60
spawn ssh $USER@$SERVER
expect "yes/no" {
send "yes\r"
expect "*?assword" { send "$PASS\r" }
} "*?assword" { send "$PASS\r" }
expect ">" { send "powershell close-smbsession -force\r" }
expect ">" { send "exit\r" }
expect eof
EOF
sysctl -w vm.drop_caches=2 > /dev/null
sysctl -w vm.drop_caches=2 > /dev/null
setup
test_call 1 /mnt/
~~~
Signed-off-by: Thiago Rafael Becker <trbecker@gmail.com>
Acked-by: Ronnie Sahlberg <lsahlber@redhat.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
6efa994e35