On Wed, Mar 20, 2024 at 11:46:50AM -0400, Josef Bacik wrote: > Btrfs had a deadlock that you could trigger by mmap'ing a large file and > using that as the buffer for fiemap. This test adds a c program to do > this, and the fstest creates a large enough file and then runs the > reproducer on the file. Without the fix btrfs deadlocks, with the fix > we pass fine. > > Signed-off-by: Josef Bacik <josef@xxxxxxxxxxxxxx> > --- > v3->v4: > - Rework this to use punch-alternating to generate a fragmented file. > - Rework the _require's to reflect the new mode of fragmenting a file. Thanks, this version is good to me. Reviewed-by: Zorro Lang <zlang@xxxxxxxxxx> > > .gitignore | 1 + > src/Makefile | 2 +- > src/fiemap-fault.c | 74 +++++++++++++++++++++++++++++++++++++++++++ > tests/generic/808 | 51 +++++++++++++++++++++++++++++ > tests/generic/808.out | 2 ++ > 5 files changed, 129 insertions(+), 1 deletion(-) > create mode 100644 src/fiemap-fault.c > create mode 100755 tests/generic/808 > create mode 100644 tests/generic/808.out > > diff --git a/.gitignore b/.gitignore > index 3b160209..f0fb72bd 100644 > --- a/.gitignore > +++ b/.gitignore > @@ -205,6 +205,7 @@ tags > /src/vfs/mount-idmapped > /src/log-writes/replay-log > /src/perf/*.pyc > +/src/filemap-fault > > # Symlinked files > /tests/generic/035.out > diff --git a/src/Makefile b/src/Makefile > index e7442487..ab98a06f 100644 > --- a/src/Makefile > +++ b/src/Makefile > @@ -34,7 +34,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \ > attr_replace_test swapon mkswap t_attr_corruption t_open_tmpfiles \ > fscrypt-crypt-util bulkstat_null_ocount splice-test chprojid_fail \ > detached_mounts_propagation ext4_resize t_readdir_3 splice2pipe \ > - uuid_ioctl t_snapshot_deleted_subvolume > + uuid_ioctl t_snapshot_deleted_subvolume fiemap-fault > > EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \ > btrfs_crc32c_forged_name.py popdir.pl popattr.py \ > diff --git a/src/fiemap-fault.c b/src/fiemap-fault.c > new file mode 100644 > index 00000000..73260068 > --- /dev/null > +++ b/src/fiemap-fault.c > @@ -0,0 +1,74 @@ > +// SPDX-License-Identifier: GPL-2.0 > +/* > + * Copyright (c) 2024 Meta Platforms, Inc. All Rights Reserved. > + */ > + > +#include <sys/ioctl.h> > +#include <sys/mman.h> > +#include <sys/types.h> > +#include <sys/stat.h> > +#include <linux/fs.h> > +#include <linux/types.h> > +#include <linux/fiemap.h> > +#include <err.h> > +#include <errno.h> > +#include <fcntl.h> > +#include <stdio.h> > +#include <string.h> > +#include <unistd.h> > + > +int prep_mmap_buffer(int fd, void **addr) > +{ > + struct stat st; > + int ret; > + > + ret = fstat(fd, &st); > + if (ret) > + err(1, "failed to stat %d", fd); > + > + *addr = mmap(NULL, st.st_size, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); > + if (*addr == MAP_FAILED) > + err(1, "failed to mmap %d", fd); > + > + return st.st_size; > +} > + > +int main(int argc, char *argv[]) > +{ > + struct fiemap *fiemap; > + size_t sz, last = 0; > + void *buf = NULL; > + int ret, fd; > + > + if (argc != 2) > + errx(1, "no in and out file name arguments given"); > + > + fd = open(argv[1], O_RDWR, 0666); > + if (fd == -1) > + err(1, "failed to open %s", argv[1]); > + > + sz = prep_mmap_buffer(fd, &buf); > + > + fiemap = (struct fiemap *)buf; > + fiemap->fm_flags = 0; > + fiemap->fm_extent_count = (sz - sizeof(struct fiemap)) / > + sizeof(struct fiemap_extent); > + > + while (last < sz) { > + int i; > + > + fiemap->fm_start = last; > + fiemap->fm_length = sz - last; > + > + ret = ioctl(fd, FS_IOC_FIEMAP, (unsigned long)fiemap); > + if (ret < 0) > + err(1, "fiemap failed %d", errno); > + for (i = 0; i < fiemap->fm_mapped_extents; i++) > + last = fiemap->fm_extents[i].fe_logical + > + fiemap->fm_extents[i].fe_length; > + } > + > + munmap(buf, sz); > + close(fd); > + return 0; > +} > diff --git a/tests/generic/808 b/tests/generic/808 > new file mode 100755 > index 00000000..a3570076 > --- /dev/null > +++ b/tests/generic/808 > @@ -0,0 +1,51 @@ > +#! /bin/bash > +# SPDX-License-Identifier: GPL-2.0 > +# Copyright (c) 2024 Meta Platforms, Inc. All Rights Reserved. > +# > +# FS QA Test 808 > +# > +# Test fiemap into an mmaped buffer of the same file > +# > +# Create a reasonably large file, then run a program which mmaps it and uses > +# that as a buffer for an fiemap call. This is a regression test for btrfs > +# where we used to hold a lock for the duration of the fiemap call which would > +# result in a deadlock if we page faulted. > +# > +. ./common/preamble > +_begin_fstest quick auto fiemap > +[ $FSTYP == "btrfs" ] && \ > + _fixed_by_kernel_commit b0ad381fa769 \ > + "btrfs: fix deadlock with fiemap and extent locking" > + > +_cleanup() > +{ > + rm -f $dst > + cd / > + rm -r -f $tmp.* > +} > + > +# real QA test starts here > +_supported_fs generic > +_require_test > +_require_test_program "fiemap-fault" > +_require_test_program "punch-alternating" > +_require_xfs_io_command "fpunch" > + > +dst=$TEST_DIR/$seq/fiemap-fault > + > +mkdir -p $TEST_DIR/$seq > + > +echo "Silence is golden" > + > +# Generate a file with lots of extents > +blksz=$(_get_file_block_size $TEST_DIR) > +$XFS_IO_PROG -f -c "pwrite -q 0 $((blksz * 10000))" $dst > +$here/src/punch-alternating $dst > + > +# Now run the reproducer > +$here/src/fiemap-fault $dst > + > +# success, all done > +status=$? > +exit > + > diff --git a/tests/generic/808.out b/tests/generic/808.out > new file mode 100644 > index 00000000..88253428 > --- /dev/null > +++ b/tests/generic/808.out > @@ -0,0 +1,2 @@ > +QA output created by 808 > +Silence is golden > -- > 2.43.0 > >