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

Darrick J. Wong
2026-03-13T23:27:16Z

On Sat, Mar 14, 2026 at 02:01:02AM +0800, Zorro Lang wrote:
> 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.

Oops, thanks for fixing that for me!

--D

> 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
> >
>
>