Re: [PATCH 1/1] generic: test fsnotify filesystem error reporting

Zorro Lang
2026-03-13T18:01:14Z

On Mon, Mar 09, 2026 at 08:50:08PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
>
> Test the fsnotify filesystem error reporting.
>
> Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
> ---
> common/rc | 25 ++++++
> doc/group-names.txt | 1
> src/Makefile | 2
> src/fs-monitor.c | 153 ++++++++++++++++++++++++++++++++++

I'll add "src/fs-monitor" into .gitignore file when I merge this patch.
Others look good to me.

Reviewed-by: Zorro Lang <zlang@redhat.com>

> tests/generic/1838 | 214 ++++++++++++++++++++++++++++++++++++++++++++++++
> tests/generic/1838.out | 20 ++++
> 6 files changed, 414 insertions(+), 1 deletion(-)
> create mode 100644 src/fs-monitor.c
> create mode 100755 tests/generic/1838
> create mode 100644 tests/generic/1838.out
>
>
> diff --git a/common/rc b/common/rc
> index fd4ca9641822cf..ccb78baf5bd41a 100644
> --- a/common/rc
> +++ b/common/rc
> @@ -3013,6 +3013,11 @@ _require_xfs_io_command()
> echo $testio | grep -q "Inappropriate ioctl" && \
> _notrun "xfs_io $command support is missing"
> ;;
> + "healthmon")
> + test -z "$param" && param="-p"
> + testio=`$XFS_IO_PROG -c "healthmon $param" $TEST_DIR 2>&1`
> + param_checked="$param"
> + ;;
> "label")
> testio=`$XFS_IO_PROG -c "label" $TEST_DIR 2>&1`
> ;;
> @@ -6149,6 +6154,26 @@ _require_max_file_range_blocks()
> esac
> }
>
> +_require_fanotify_ioerrors()
> +{
> + local x
> +
> + case "$FSTYP" in
> + xfs)
> + # added as a part of xfs health monitoring
> + _require_xfs_io_command healthmon
> + return 0
> + ;;
> + ext4)
> + # added at the same time as err_report_sec
> + x="$(_get_fs_sysfs_attr $TEST_DEV err_report_sec)"
> + test -n "$x" && return 0
> + ;;
> + esac
> +
> + _notrun "$FSTYP does not support fanotify ioerrors"
> +}
> +
> ################################################################################
> # make sure this script returns success
> /bin/true
> diff --git a/doc/group-names.txt b/doc/group-names.txt
> index 10b49e50517797..158f84d36d3154 100644
> --- a/doc/group-names.txt
> +++ b/doc/group-names.txt
> @@ -117,6 +117,7 @@ samefs overlayfs when all layers are on the same fs
> scrub filesystem metadata scrubbers
> seed btrfs seeded filesystems
> seek llseek functionality
> +selfhealing self healing filesystem code
> selftest tests with fixed results, used to validate testing setup
> send btrfs send/receive
> shrinkfs decreasing the size of a filesystem
> diff --git a/src/Makefile b/src/Makefile
> index 577d816ae859b6..1c761da0ccff20 100644
> --- a/src/Makefile
> +++ b/src/Makefile
> @@ -36,7 +36,7 @@ LINUX_TARGETS = xfsctl bstat t_mtab getdevicesize preallo_rw_pattern_reader \
> 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 fiemap-fault min_dio_alignment \
> - rw_hint
> + rw_hint fs-monitor
>
> EXTRA_EXECS = dmerror fill2attr fill2fs fill2fs_check scaleread.sh \
> btrfs_crc32c_forged_name.py popdir.pl popattr.py \
> diff --git a/src/fs-monitor.c b/src/fs-monitor.c
> new file mode 100644
> index 00000000000000..0cf09677a3efda
> --- /dev/null
> +++ b/src/fs-monitor.c
> @@ -0,0 +1,153 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2021, Collabora Ltd.
> + * Copied from https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/samples/fanotify/fs-monitor.c
> + */
> +
> +#include <errno.h>
> +#include <err.h>
> +#include <stdlib.h>
> +#include <stdio.h>
> +#include <fcntl.h>
> +#include <sys/fanotify.h>
> +#include <sys/types.h>
> +#include <unistd.h>
> +
> +#ifndef FAN_FS_ERROR
> +#define FAN_FS_ERROR 0x00008000
> +#define FAN_EVENT_INFO_TYPE_ERROR 5
> +
> +struct fanotify_event_info_error {
> + struct fanotify_event_info_header hdr;
> + __s32 error;
> + __u32 error_count;
> +};
> +#endif
> +
> +#ifndef FILEID_INO32_GEN
> +#define FILEID_INO32_GEN 1
> +#endif
> +
> +#ifndef FILEID_INVALID
> +#define FILEID_INVALID 0xff
> +#endif
> +
> +static void print_fh(struct file_handle *fh)
> +{
> + int i;
> + uint32_t *h = (uint32_t *) fh->f_handle;
> +
> + printf("\tfh: ");
> + for (i = 0; i < fh->handle_bytes; i++)
> + printf("%hhx", fh->f_handle[i]);
> + printf("\n");
> +
> + printf("\tdecoded fh: ");
> + if (fh->handle_type == FILEID_INO32_GEN)
> + printf("inode=%u gen=%u\n", h[0], h[1]);
> + else if (fh->handle_type == FILEID_INVALID && !fh->handle_bytes)
> + printf("Type %d (Superblock error)\n", fh->handle_type);
> + else
> + printf("Type %d (Unknown)\n", fh->handle_type);
> +
> +}
> +
> +static void handle_notifications(char *buffer, int len)
> +{
> + struct fanotify_event_metadata *event =
> + (struct fanotify_event_metadata *) buffer;
> + struct fanotify_event_info_header *info;
> + struct fanotify_event_info_error *err;
> + struct fanotify_event_info_fid *fid;
> + int off;
> +
> + for (; FAN_EVENT_OK(event, len); event = FAN_EVENT_NEXT(event, len)) {
> +
> + if (event->mask != FAN_FS_ERROR) {
> + printf("unexpected FAN MARK: %llx\n",
> + (unsigned long long)event->mask);
> + goto next_event;
> + }
> +
> + if (event->fd != FAN_NOFD) {
> + printf("Unexpected fd (!= FAN_NOFD)\n");
> + goto next_event;
> + }
> +
> + printf("FAN_FS_ERROR (len=%d)\n", event->event_len);
> +
> + for (off = sizeof(*event) ; off < event->event_len;
> + off += info->len) {
> + info = (struct fanotify_event_info_header *)
> + ((char *) event + off);
> +
> + switch (info->info_type) {
> + case FAN_EVENT_INFO_TYPE_ERROR:
> + err = (struct fanotify_event_info_error *) info;
> +
> + printf("\tGeneric Error Record: len=%d\n",
> + err->hdr.len);
> + printf("\terror: %d\n", err->error);
> + printf("\terror_count: %d\n", err->error_count);
> + break;
> +
> + case FAN_EVENT_INFO_TYPE_FID:
> + fid = (struct fanotify_event_info_fid *) info;
> +
> + printf("\tfsid: %x%x\n",
> +#if defined(__GLIBC__)
> + fid->fsid.val[0], fid->fsid.val[1]);
> +#else
> + fid->fsid.__val[0], fid->fsid.__val[1]);
> +#endif
> + print_fh((struct file_handle *) &fid->handle);
> + break;
> +
> + default:
> + printf("\tUnknown info type=%d len=%d:\n",
> + info->info_type, info->len);
> + }
> + }
> +next_event:
> + printf("---\n\n");
> + fflush(stdout);
> + }
> +}
> +
> +int main(int argc, char **argv)
> +{
> + int fd;
> +
> + char buffer[BUFSIZ];
> +
> + if (argc < 2) {
> + printf("Missing path argument\n");
> + return 1;
> + }
> +
> + fd = fanotify_init(FAN_CLASS_NOTIF|FAN_REPORT_FID, O_RDONLY);
> + if (fd < 0) {
> + perror("fanotify_init");
> + errx(1, "fanotify_init");
> + }
> +
> + if (fanotify_mark(fd, FAN_MARK_ADD|FAN_MARK_FILESYSTEM,
> + FAN_FS_ERROR, AT_FDCWD, argv[1])) {
> + perror("fanotify_mark");
> + errx(1, "fanotify_mark");
> + }
> +
> + printf("fanotify active\n");
> + fflush(stdout);
> +
> + while (1) {
> + int n = read(fd, buffer, BUFSIZ);
> +
> + if (n < 0)
> + errx(1, "read");
> +
> + handle_notifications(buffer, n);
> + }
> +
> + return 0;
> +}
> diff --git a/tests/generic/1838 b/tests/generic/1838
> new file mode 100755
> index 00000000000000..940811baae3a6e
> --- /dev/null
> +++ b/tests/generic/1838
> @@ -0,0 +1,214 @@
> +#! /bin/bash
> +# SPDX-License-Identifier: GPL-2.0-or-later
> +# Copyright (c) 2024-2026 Oracle. All Rights Reserved.
> +#
> +# FS QA Test No. 1838
> +#
> +# Check that fsnotify can report file IO errors.
> +
> +. ./common/preamble
> +_begin_fstest auto quick eio selfhealing
> +
> +# Override the default cleanup function.
> +_cleanup()
> +{
> + cd /
> + test -n "$fsmonitor_pid" && kill -TERM $fsmonitor_pid
> + rm -f $tmp.*
> + _dmerror_cleanup
> +}
> +
> +# Import common functions.
> +. ./common/fuzzy
> +. ./common/filter
> +. ./common/dmerror
> +. ./common/systemd
> +
> +_require_scratch
> +_require_dm_target error
> +_require_test_program fs-monitor
> +_require_xfs_io_command "fiemap"
> +_require_odirect
> +_require_fanotify_ioerrors
> +
> +# no out of place writes
> +test "$FSTYP" = "xfs" && _require_no_xfs_always_cow
> +
> +# fsnotify only gives us a file handle, the error number, and the number of
> +# times it was seen in between event deliveries. The handle is mostly useless
> +# since we have no generic way to map that to a file path. Therefore we can
> +# only coalesce all the I/O errors into one report.
> +filter_fsnotify_errors() {
> + _filter_scratch | \
> + grep -E '(FAN_FS_ERROR|Generic Error Record|error: 5)' | \
> + sed -e "s/len=[0-9]*/len=XXX/g" | \
> + sort | \
> + uniq
> +}
> +
> +_scratch_mkfs >> $seqres.full
> +
> +#
> +# The dm-error map added by this test doesn't work on zoned devices because
> +# table sizes need to be aligned to the zone size, and even for zoned on
> +# conventional this test will get confused because of the internal RT device.
> +#
> +# That check requires a mounted file system, so do a dummy mount before setting
> +# up DM.
> +#
> +_scratch_mount
> +test $FSTYP = xfs && _require_xfs_scratch_non_zoned
> +_scratch_unmount
> +
> +_dmerror_init
> +_dmerror_mount >> $seqres.full 2>&1
> +
> +test $FSTYP = xfs && _xfs_force_bdev data $SCRATCH_MNT
> +
> +# Write a file with 4 file blocks worth of data, figure out the LBA to target
> +victim=$SCRATCH_MNT/a
> +file_blksz=$(_get_file_block_size $SCRATCH_MNT)
> +$XFS_IO_PROG -f -c "pwrite -S 0x58 0 $((4 * file_blksz))" -c "fsync" $victim >> $seqres.full
> +
> +awk_len_prog='{print $4}'
> +bmap_str="$($XFS_IO_PROG -c "fiemap -v" $victim | grep "^[[:space:]]*0:")"
> +echo "$bmap_str" >> $seqres.full
> +
> +phys="$(echo "$bmap_str" | $AWK_PROG '{print $3}')"
> +len="$(echo "$bmap_str" | $AWK_PROG "$awk_len_prog")"
> +
> +fs_blksz=$(_get_block_size $SCRATCH_MNT)
> +echo "file_blksz:$file_blksz:fs_blksz:$fs_blksz" >> $seqres.full
> +kernel_sectors_per_fs_block=$((fs_blksz / 512))
> +
> +# Did we get at least 4 fs blocks worth of extent?
> +min_len_sectors=$(( 4 * kernel_sectors_per_fs_block ))
> +test "$len" -lt $min_len_sectors && \
> + _fail "could not format a long enough extent on an empty fs??"
> +
> +phys_start=$(echo "$phys" | sed -e 's/\.\..*//g')
> +
> +echo "$phys:$len:$fs_blksz:$phys_start" >> $seqres.full
> +echo "victim file:" >> $seqres.full
> +od -tx1 -Ad -c $victim >> $seqres.full
> +
> +# Set the dmerror table so that all IO will pass through.
> +_dmerror_reset_table
> +
> +cat >> $seqres.full << ENDL
> +dmerror before:
> +$DMERROR_TABLE
> +$DMERROR_RTTABLE
> +<end table>
> +ENDL
> +
> +# All sector numbers that we feed to the kernel must be in units of 512b, but
> +# they also must be aligned to the device's logical block size.
> +logical_block_size=`$here/src/min_dio_alignment $SCRATCH_MNT $SCRATCH_DEV`
> +kernel_sectors_per_device_lba=$((logical_block_size / 512))
> +
> +# Mark as bad one of the device LBAs in the middle of the extent. Target the
> +# second LBA of the third block of the four-block file extent that we allocated
> +# earlier, but without overflowing into the fourth file block.
> +bad_sector=$(( phys_start + (2 * kernel_sectors_per_fs_block) ))
> +bad_len=$kernel_sectors_per_device_lba
> +if (( kernel_sectors_per_device_lba < kernel_sectors_per_fs_block )); then
> + bad_sector=$((bad_sector + kernel_sectors_per_device_lba))
> +fi
> +if (( (bad_sector % kernel_sectors_per_device_lba) != 0)); then
> + echo "bad_sector $bad_sector not congruent with device logical block size $logical_block_size"
> +fi
> +
> +# Remount to flush the page cache, start fsnotify, and make the LBA bad
> +_dmerror_unmount
> +_dmerror_mount
> +
> +$here/src/fs-monitor $SCRATCH_MNT > $tmp.fsmonitor &
> +fsmonitor_pid=$!
> +sleep 1
> +
> +_dmerror_mark_range_bad $bad_sector $bad_len
> +
> +cat >> $seqres.full << ENDL
> +dmerror after marking bad:
> +$DMERROR_TABLE
> +$DMERROR_RTTABLE
> +<end table>
> +ENDL
> +
> +_dmerror_load_error_table
> +
> +# See if buffered reads pick it up
> +echo "Try buffered read"
> +$XFS_IO_PROG -c "pread 0 $((4 * file_blksz))" $victim >> $seqres.full
> +
> +# See if directio reads pick it up
> +echo "Try directio read"
> +$XFS_IO_PROG -d -c "pread 0 $((4 * file_blksz))" $victim >> $seqres.full
> +
> +# See if directio writes pick it up
> +echo "Try directio write"
> +$XFS_IO_PROG -d -c "pwrite -S 0x58 0 $((4 * file_blksz))" -c fsync $victim >> $seqres.full
> +
> +# See if buffered writes pick it up
> +echo "Try buffered write"
> +$XFS_IO_PROG -c "pwrite -S 0x58 0 $((4 * file_blksz))" -c fsync $victim >> $seqres.full
> +
> +# Now mark the bad range good so that unmount won't fail due to IO errors.
> +echo "Fix device"
> +_dmerror_mark_range_good $bad_sector $bad_len
> +_dmerror_load_error_table
> +
> +cat >> $seqres.full << ENDL
> +dmerror after marking good:
> +$DMERROR_TABLE
> +$DMERROR_RTTABLE
> +<end table>
> +ENDL
> +
> +# Unmount filesystem to start fresh
> +echo "Kill fsnotify"
> +_dmerror_unmount
> +sleep 1
> +kill -TERM $fsmonitor_pid
> +unset fsmonitor_pid
> +echo fsnotify log >> $seqres.full
> +cat $tmp.fsmonitor >> $seqres.full
> +cat $tmp.fsmonitor | filter_fsnotify_errors
> +
> +# Start fsnotify again so that can verify that the errors don't persist after
> +# we flip back to the good dm table.
> +echo "Remount and restart fsnotify"
> +_dmerror_mount
> +$here/src/fs-monitor $SCRATCH_MNT > $tmp.fsmonitor &
> +fsmonitor_pid=$!
> +sleep 1
> +
> +# See if buffered reads pick it up
> +echo "Try buffered read again"
> +$XFS_IO_PROG -c "pread 0 $((4 * file_blksz))" $victim >> $seqres.full
> +
> +# See if directio reads pick it up
> +echo "Try directio read again"
> +$XFS_IO_PROG -d -c "pread 0 $((4 * file_blksz))" $victim >> $seqres.full
> +
> +# See if directio writes pick it up
> +echo "Try directio write again"
> +$XFS_IO_PROG -d -c "pwrite -S 0x58 0 $((4 * file_blksz))" -c fsync $victim >> $seqres.full
> +
> +# See if buffered writes pick it up
> +echo "Try buffered write again"
> +$XFS_IO_PROG -c "pwrite -S 0x58 0 $((4 * file_blksz))" -c fsync $victim >> $seqres.full
> +
> +# Unmount fs and kill fsnotify, then wait for it to finish
> +echo "Kill fsnotify again"
> +_dmerror_unmount
> +sleep 1
> +kill -TERM $fsmonitor_pid
> +unset fsmonitor_pid
> +cat $tmp.fsmonitor >> $seqres.full
> +cat $tmp.fsmonitor | filter_fsnotify_errors
> +
> +# success, all done
> +status=0
> +exit
> diff --git a/tests/generic/1838.out b/tests/generic/1838.out
> new file mode 100644
> index 00000000000000..adae590fe0b2ea
> --- /dev/null
> +++ b/tests/generic/1838.out
> @@ -0,0 +1,20 @@
> +QA output created by 1838
> +Try buffered read
> +pread: Input/output error
> +Try directio read
> +pread: Input/output error
> +Try directio write
> +pwrite: Input/output error
> +Try buffered write
> +fsync: Input/output error
> +Fix device
> +Kill fsnotify
> + Generic Error Record: len=XXX
> + error: 5
> +FAN_FS_ERROR (len=XXX)
> +Remount and restart fsnotify
> +Try buffered read again
> +Try directio read again
> +Try directio write again
> +Try buffered write again
> +Kill fsnotify again
>