selftests/efivarfs: add concurrent update tests

The delete on last close functionality can now only be tested properly
by using multiple threads to hold open the variable files and testing
what happens as they complete.

Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>

tools/testing/selftests/efivarfs/efivarfs.sh

@@ -227,6 +227,136 @@ test_no_set_size()
 	exit $ret
 }
 
+setup_test_multiple()
+{
+       ##
+       # we're going to do multi-threaded tests, so create a set of
+       # pipes for synchronization.  We use pipes 1..3 to start the
+       # stalled shell job and pipes 4..6 as indicators that the job
+       # has started.  If you need more than 3 jobs the two +3's below
+       # need increasing
+       ##
+
+       declare -ag p
+
+       # empty is because arrays number from 0 but jobs number from 1
+       p[0]=""
+
+       for f in 1 2 3 4 5 6; do
+               p[$f]=/tmp/efivarfs_pipe${f}
+               mknod ${p[$f]} p
+       done
+
+       declare -g var=$efivarfs_mount/test_multiple-$test_guid
+
+       cleanup() {
+               for f in ${p[@]}; do
+                       rm -f ${f}
+               done
+               if [ -e $var ]; then
+                       file_cleanup $var
+               fi
+       }
+       trap cleanup exit
+
+       waitstart() {
+               cat ${p[$[$1+3]]} > /dev/null
+       }
+
+       waitpipe() {
+               echo 1 > ${p[$[$1+3]]}
+               cat ${p[$1]} > /dev/null
+       }
+
+       endjob() {
+               echo 1 > ${p[$1]}
+               wait -n %$1
+       }
+}
+
+test_multiple_zero_size()
+{
+       ##
+       # check for remove on last close, set up three threads all
+       # holding the variable (one write and two reads) and then
+       # close them sequentially (waiting for completion) and check
+       # the state of the variable
+       ##
+
+       { waitpipe 1; echo 1; } > $var 2> /dev/null &
+       waitstart 1
+       # zero length file should exist
+       [ -e $var ] || exit 1
+       # second and third delayed close
+       { waitpipe 2; } < $var &
+       waitstart 2
+       { waitpipe 3; } < $var &
+       waitstart 3
+       # close first fd
+       endjob 1
+       # var should only be deleted on last close
+       [ -e $var ] || exit 1
+       # close second fd
+       endjob 2
+       [ -e $var ] || exit 1
+       # file should go on last close
+       endjob 3
+       [ ! -e $var ] || exit 1
+}
+
+test_multiple_create()
+{
+       ##
+       # set multiple threads to access the variable but delay
+       # the final write to check the close of 2 and 3.  The
+       # final write should succeed in creating the variable
+       ##
+       { waitpipe 1; printf '\x07\x00\x00\x00\x54'; } > $var &
+       waitstart 1
+       [ -e $var -a ! -s $var ] || exit 1
+       { waitpipe 2; } < $var &
+       waitstart 2
+       { waitpipe 3; } < $var &
+       waitstart 3
+       # close second and third fds
+       endjob 2
+       # var should only be created (have size) on last close
+       [ -e $var -a ! -s $var ] || exit 1
+       endjob 3
+       [ -e $var -a ! -s $var ] || exit 1
+       # close first fd
+       endjob 1
+       # variable should still exist
+       [ -s $var ] || exit 1
+       file_cleanup $var
+}
+
+test_multiple_delete_on_write() {
+       ##
+       # delete the variable on final write; seqencing similar
+       # to test_multiple_create()
+       ##
+       printf '\x07\x00\x00\x00\x54' > $var
+       chattr -i $var
+       { waitpipe 1; printf '\x07\x00\x00\x00'; } > $var &
+       waitstart 1
+       [ -e $var -a -s $var ] || exit 1
+       { waitpipe 2; } < $var &
+       waitstart 2
+       { waitpipe 3; } < $var &
+       waitstart 3
+       # close first fd; write should set variable size to zero
+       endjob 1
+       # var should only be deleted on last close
+       [ -e $var -a ! -s $var ] || exit 1
+       endjob 2
+       [ -e $var ] || exit 1
+       # close last fd
+       endjob 3
+       # variable should now be removed
+       [ ! -e $var ] || exit 1
+}
+
 check_prereqs
 
 rc=0
@@ -240,5 +370,9 @@ run_test test_open_unlink
 run_test test_valid_filenames
 run_test test_invalid_filenames
 run_test test_no_set_size
+setup_test_multiple
+run_test test_multiple_zero_size
+run_test test_multiple_create
+run_test test_multiple_delete_on_write
 
 exit $rc