On Fri, Aug 18, 2017 at 03:35:02PM -0500, Eric Sandeen wrote: > From: Zheng Liu <wenqing.lz@xxxxxxxxxx> > > In this commit a new test case is added to test that i_size races don't > occur under dio reads/writes. We add a program in /src dir, which > has a writer to issue some append dio writes. Meanwhile it has a reader > in this test to do some dio reads. As we expect, reader should read > nothing or data with 'a'. But it might read some data with '0'. > > The bug can be reproduced by this test case [1]. > > 1. http://patchwork.ozlabs.org/patch/311761/ > > This ostensibly tests commit: > 9fe55eea7 Fix race when checking i_size on direct i/o read > > Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx> > Cc: Rich Johnston <rjohnston@xxxxxxx> > Cc: Dave Chinner <david@xxxxxxxxxxxxx> > Signed-off-by: Zheng Liu <wenqing.lz@xxxxxxxxxx> > [sandeen: update to recent xfstests, update commitlog] > Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> > --- > > This test was originally titled: > > xfstests: add a new test case to test i_size updated properly under dio > > but I think the issue is more of when and how it's tested, not how > it's updated. > > Note, this passes on xfs on 4.10, but fails on 4.12. > ext4 on 4.10 passes as well but is very slow. > > iomap dio maybe? Not sure yet. My test with 4.10 kernel suggested that test still failed there. And I digged into this test a bit, and found that it was commit d531d91d6990 ("xfs: always use unwritten extents for direct I/O writes") introduced this failure, which is in v3.14 kernel. This is because we start allocating unwritten extents for direct writes that can extend i_size, but in xfs_dio_write_end_io() we update in-core i_size before converting unwritten extents to real allocations. So a racing direct read could find the not-yet converted unwritten extents and read zeros instead of actual data. But I'm not sure what's the best way to fix it. I think taking exclusive iolock instead of shared lock for direct writes that can extend i_size could fix the non-aio dio write case, but aio-dio write still fails, because in the aio-dio write case we defer end_io to a workqueue, which doesn't take any iolock at all.. ext4 has no such problem because ext4 converts unwritten extents before updating i_size, and ext4 doesn't support appending aio dio writes. (Keep the rest of patch untrimmed for reference, as I added linux-xfs to cc list.) Thanks, Eryu > > changelog v3: > * rebase against latest xfstests/master branch > * update commit log > > changelog v2: > * add '-lpthread' into LLDLIBS > > diff --git a/configure.ac b/configure.ac > index 57092f1..4663004 100644 > --- a/configure.ac > +++ b/configure.ac > @@ -59,6 +59,7 @@ AC_PACKAGE_NEED_GETXATTR_LIBATTR > AC_PACKAGE_NEED_SYS_ACL_H > AC_PACKAGE_NEED_ACL_LIBACL_H > AC_PACKAGE_NEED_ACLINIT_LIBACL > +AC_PACKAGE_NEED_PTHREADMUTEXINIT > > AC_PACKAGE_WANT_GDBM > AC_PACKAGE_WANT_AIO > diff --git a/include/builddefs.in b/include/builddefs.in > index cb52b99..fcc8b90 100644 > --- a/include/builddefs.in > +++ b/include/builddefs.in > @@ -25,6 +25,7 @@ LIBGDBM = @libgdbm@ > LIBUUID = @libuuid@ > LIBHANDLE = @libhdl@ > LIBDM = @libdm@ > +LIBPTHREAD = @libpthread@ > LIBTEST = $(TOPDIR)/lib/libtest.la > prefix = @prefix@ > > diff --git a/src/Makefile b/src/Makefile > index b8aff49..e9419bd 100644 > --- a/src/Makefile > +++ b/src/Makefile > @@ -23,7 +23,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \ > seek_copy_test t_readdir_1 t_readdir_2 fsync-tester nsexec cloner \ > renameat2 t_getcwd e4compact test-nextquota punch-alternating \ > attr-list-by-handle-cursor-test listxattr dio-interleaved t_dir_type \ > - dio-invalidate-cache stat_test t_encrypted_d_revalidate > + dio-invalidate-cache stat_test t_encrypted_d_revalidate diotest > > SUBDIRS = > > diff --git a/src/diotest.c b/src/diotest.c > new file mode 100644 > index 0000000..7d2378f > --- /dev/null > +++ b/src/diotest.c > @@ -0,0 +1,166 @@ > +/* > + * Copyright (c) 2013 Alibaba Group. > + * All Rights Reserved. > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License as > + * published by the Free Software Foundation. > + * > + * This program is distributed in the hope that it would be useful, > + * but WITHOUT ANY WARRANTY; without even the implied warranty of > + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > + * GNU General Public License for more details. > + * > + * You should have received a copy of the GNU General Public License > + * along with this program; if not, write the Free Software Foundation, > + * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA > + */ > + > +/* > + * This is a normal case that we do some append dio writes and meanwhile > + * we do some dio reads. Currently in vfs we don't ensure that i_size > + * is updated properly. Hence the reader will read some data with '0'. > + * But we expect that the reader should read nothing or data with 'a'. > + */ > + > +#include <stdio.h> > +#include <stdlib.h> > +#include <string.h> > + > +#include <unistd.h> > +#include <sys/types.h> > +#include <sys/stat.h> > +#include <fcntl.h> > +#include <errno.h> > + > +#include <pthread.h> > + > +static char *prog; > + > +struct writer_data { > + int fd; > + size_t blksize; > + char *buf; > +}; > + > +static void usage(void) > +{ > + fprintf(stderr, "usage: %s [FILE]\n", prog); > +} > + > +static void *writer(void *arg) > +{ > + struct writer_data *data = (struct writer_data *)arg; > + int ret; > + > + ret = write(data->fd, data->buf, data->blksize); > + if (ret < 0) > + fprintf(stderr, "write file failed: %s\n", strerror(errno)); > + > + return NULL; > +} > + > +int main(int argc, char *argv[]) > +{ > + pthread_t tid; > + struct writer_data wdata; > + size_t max_blocks = 128; /* 128 */ > + size_t blksize = 1 * 1024 * 1024; /* 1M */ > + char *rbuf = NULL, *wbuf = NULL; > + int rfd = 0, wfd = 0; > + int i, j; > + int ret = 0; > + > + prog = basename(argv[0]); > + > + if (argc != 2) { > + usage(); > + exit(1); > + } > + > + wfd = open(argv[1], O_CREAT|O_DIRECT|O_WRONLY|O_APPEND|O_TRUNC, S_IRWXU); > + if (wfd < 0) { > + fprintf(stderr, "failed to open write file: %s\n", > + strerror(errno)); > + exit(1); > + } > + > + rfd = open(argv[1], O_DIRECT|O_RDONLY, S_IRWXU); > + if (wfd < 0) { > + fprintf(stderr, "failed to open read file: %s\n", > + strerror(errno)); > + ret = 1; > + goto err; > + } > + > + /* > + * We set 1024 as an alignment size for write buf. Feel free to change > + * it with 4096. But the problem is also hitted. > + */ > + if (posix_memalign((void **)&wbuf, 1024, blksize)) { > + fprintf(stderr, "failed to alloc memory: %s\n", strerror(errno)); > + ret = 1; > + goto err; > + } > + > + if (posix_memalign((void **)&rbuf, 4096, blksize)) { > + fprintf(stderr, "failed to alloc memory: %s\n", strerror(errno)); > + ret = 1; > + goto err; > + } > + > + memset(wbuf, 'a', blksize); > + wdata.fd = wfd; > + wdata.blksize = blksize; > + wdata.buf = wbuf; > + > + for (i = 0; i < max_blocks; i++) { > + void *retval; > + > + if (pthread_create(&tid, NULL, writer, &wdata)) { > + fprintf(stderr, "create thread failed: %s\n", > + strerror(errno)); > + ret = 1; > + goto err; > + } > + > + memset(rbuf, 'b', blksize); > + do { > + ret = pread(rfd, rbuf, blksize, i * blksize); > + if (ret < 0) > + fprintf(stderr, "read file failed: %s\n", > + strerror(errno)); > + } while (ret <= 0); > + > + if (pthread_join(tid, &retval)) { > + fprintf(stderr, " pthread join failed: %s\n", > + strerror(errno)); > + ret = 1; > + goto err; > + } > + > + if (ret >= 0) { > + for (j = 0; j < ret; j ++) { > + if (rbuf[j] != 'a') { > + fprintf(stderr, "encounter an error: " > + "offset %d content %c\n", > + i, rbuf[j]); > + ret = 1; > + goto err; > + } > + } > + } > + } > + > +err: > + if (rfd) > + close(rfd); > + if (wfd) > + close(wfd); > + if (rbuf) > + free(rbuf); > + if (wbuf) > + free(wbuf); > + > + return ret; > +} > diff --git a/tests/generic/450 b/tests/generic/450 > new file mode 100755 > index 0000000..cfb424c > --- /dev/null > +++ b/tests/generic/450 > @@ -0,0 +1,56 @@ > +#! /bin/bash > +# FS QA Test No. 450 > +# > +# Test i_size is updated properly under dio read/write > +# > +#----------------------------------------------------------------------- > +# Copyright (c) 2013 Alibaba Group. All Rights Reserved. > +# > +# This program is free software; you can redistribute it and/or > +# modify it under the terms of the GNU General Public License as > +# published by the Free Software Foundation. > +# > +# This program is distributed in the hope that it would be useful, > +# but WITHOUT ANY WARRANTY; without even the implied warranty of > +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the > +# GNU General Public License for more details. > +# > +# You should have received a copy of the GNU General Public License > +# along with this program; if not, write the Free Software Foundation, > +# Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA > +#----------------------------------------------------------------------- > +# > + > +seq=`basename $0` > +seqres=$RESULT_DIR/$seq > +echo "QA output created by $seq" > + > +here=`pwd` > +tmp=/tmp/$$ > +status=1 # failure is the default! > +trap "_cleanup; exit \$status" 0 1 2 3 15 > + > +_cleanup() > +{ > + cd / > + rm -f $tmp.* $testfile > +} > + > +# get standard environment, filters and checks > +. ./common/rc > +. ./common/filter > + > +# real QA test starts here > +_supported_fs generic > +_supported_os Linux > + > +testfile=$TEST_DIR/$seq.$$ > + > +[ -x $here/src/diotest ] || _notrun "diotest not built" > + > +$here/src/diotest $testfile # > $seqres.full 2>&1 || > + # _fail "i_size isn't update properly!" > + > +# success, all done > +status=0 > +exit > diff --git a/tests/generic/450.out b/tests/generic/450.out > new file mode 100644 > index 0000000..734761a > --- /dev/null > +++ b/tests/generic/450.out > @@ -0,0 +1 @@ > +QA output created by 450 > diff --git a/tests/generic/group b/tests/generic/group > index b9cd0e8..a555fa0 100644 > --- a/tests/generic/group > +++ b/tests/generic/group > @@ -452,3 +452,4 @@ > 447 auto quick clone > 448 auto quick rw > 449 auto quick acl enospc > +450 auto rw quick > > -- > To unsubscribe from this list: send the line "unsubscribe fstests" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-xfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
