On Sun, Oct 13, 2019 at 10:37:00PM +0800, Pingfan Liu wrote:
> When using fadump (fireware assist dump) mode on powerpc, a mismatch
> between grub xfs driver and kernel xfs driver has been obsevered. Note:
> fadump boots up in the following sequence: fireware -> grub reads kernel
> and initramfs -> kernel boots.
>
> The process to reproduce this mismatch:
> - On powerpc, boot kernel with fadump=on and edit /etc/kdump.conf.
> - Replacing "path /var/crash" with "path /var/crashnew", then, "kdumpctl
> restart" to rebuild the initramfs. Detail about the rebuilding looks
> like: mkdumprd /boot/initramfs-`uname -r`.img.tmp;
> mv /boot/initramfs-`uname -r`.img.tmp /boot/initramfs-`uname -r`.img
> sync
> - "echo c >/proc/sysrq-trigger".
>
> The result:
> The dump image will not be saved under /var/crashnew/* as expected, but
> still saved under /var/crash.
>
> The root cause:
> As Eric pointed out that on xfs, 'sync' ensures the consistency by writing
> back metadata to xlog, but not necessary to fsblock. This raises issue if
> grub can not replay the xlog before accessing the xfs files. Since the
> above dir entry of initramfs should be saved as inline data with xfs_inode,
> so xfs_fs_sync_fs() does not guarantee it written to fsblock.
>
> umount can be used to write metadata fsblock, but the filesystem can not be
> umounted if still in use.
>
> There are two ways to fix this mismatch, either grub or xfs. It may be
> easier to do this in xfs side by introducing an interface to flush metadata
> to fsblock explicitly.
>
> With this patch, metadata can be written to fsblock by:
> # update AIL
> sync
> # new introduced interface to flush metadata to fsblock
> mount -o remount,metasync mountpoint
I think this ought to be an ioctl or some sort of generic call since the
jbd2 filesystems (ext3, ext4, ocfs2) suffer from the same "$BOOTLOADER
is too dumb to recover logs but still wants to write to the fs"
checkpointing problem.
(Or maybe we should just put all that stuff in a vfat filesystem, I
don't know...)
--D
> Signed-off-by: Pingfan Liu <kernelfans@xxxxxxxxx>
> Cc: "Darrick J. Wong" <darrick.wong@xxxxxxxxxx>
> Cc: Dave Chinner <dchinner@xxxxxxxxxx>
> Cc: Eric Sandeen <esandeen@xxxxxxxxxx>
> Cc: Hari Bathini <hbathini@xxxxxxxxxxxxx>
> Cc: linuxppc-dev@xxxxxxxxxxxxxxxx
> To: linux-xfs@xxxxxxxxxxxxxxx
> ---
> fs/xfs/xfs_mount.h | 1 +
> fs/xfs/xfs_super.c | 15 ++++++++++++++-
> fs/xfs/xfs_trans.h | 2 ++
> fs/xfs/xfs_trans_ail.c | 26 +++++++++++++++++++++++++-
> fs/xfs/xfs_trans_priv.h | 1 +
> 5 files changed, 43 insertions(+), 2 deletions(-)
>
> diff --git a/fs/xfs/xfs_mount.h b/fs/xfs/xfs_mount.h
> index fdb60e0..85f32e6 100644
> --- a/fs/xfs/xfs_mount.h
> +++ b/fs/xfs/xfs_mount.h
> @@ -243,6 +243,7 @@ typedef struct xfs_mount {
> #define XFS_MOUNT_FILESTREAMS (1ULL << 24) /* enable the filestreams
> allocator */
> #define XFS_MOUNT_NOATTR2 (1ULL << 25) /* disable use of attr2 format */
> +#define XFS_MOUNT_METASYNC (1ull << 26) /* write meta to fsblock */
>
> #define XFS_MOUNT_DAX (1ULL << 62) /* TEST ONLY! */
>
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 8d1df9f..41df810 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -59,7 +59,7 @@ enum {
> Opt_filestreams, Opt_quota, Opt_noquota, Opt_usrquota, Opt_grpquota,
> Opt_prjquota, Opt_uquota, Opt_gquota, Opt_pquota,
> Opt_uqnoenforce, Opt_gqnoenforce, Opt_pqnoenforce, Opt_qnoenforce,
> - Opt_discard, Opt_nodiscard, Opt_dax, Opt_err,
> + Opt_discard, Opt_nodiscard, Opt_dax, Opt_metasync, Opt_err
> };
>
> static const match_table_t tokens = {
> @@ -106,6 +106,7 @@ static const match_table_t tokens = {
> {Opt_discard, "discard"}, /* Discard unused blocks */
> {Opt_nodiscard, "nodiscard"}, /* Do not discard unused blocks */
> {Opt_dax, "dax"}, /* Enable direct access to bdev pages */
> + {Opt_metasync, "metasync"}, /* one shot to write meta to fsblock */
> {Opt_err, NULL},
> };
>
> @@ -338,6 +339,9 @@ xfs_parseargs(
> mp->m_flags |= XFS_MOUNT_DAX;
> break;
> #endif
> + case Opt_metasync:
> + mp->m_flags |= XFS_MOUNT_METASYNC;
> + break;
> default:
> xfs_warn(mp, "unknown mount option [%s].", p);
> return -EINVAL;
> @@ -1259,6 +1263,9 @@ xfs_fs_remount(
> mp->m_flags |= XFS_MOUNT_SMALL_INUMS;
> mp->m_maxagi = xfs_set_inode_alloc(mp, sbp->sb_agcount);
> break;
> + case Opt_metasync:
> + mp->m_flags |= XFS_MOUNT_METASYNC;
> + break;
> default:
> /*
> * Logically we would return an error here to prevent
> @@ -1286,6 +1293,12 @@ xfs_fs_remount(
> }
> }
>
> + if (mp->m_flags & XFS_MOUNT_METASYNC) {
> + xfs_ail_push_sync(mp->m_ail);
> + /* one shot flag */
> + mp->m_flags &= ~XFS_MOUNT_METASYNC;
Wait, so the mount flag magically disables itself?
This really sounds like a system call, not the kinds of long term
behavioral modifications that mount options are for.
> + }
> +
> /* ro -> rw */
> if ((mp->m_flags & XFS_MOUNT_RDONLY) && !(*flags & SB_RDONLY)) {
> if (mp->m_flags & XFS_MOUNT_NORECOVERY) {
> diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h
> index 64d7f17..fcdb902 100644
> --- a/fs/xfs/xfs_trans.h
> +++ b/fs/xfs/xfs_trans.h
> @@ -242,6 +242,8 @@ void xfs_trans_buf_set_type(struct xfs_trans *, struct xfs_buf *,
> void xfs_trans_buf_copy_type(struct xfs_buf *dst_bp,
> struct xfs_buf *src_bp);
>
> +void xfs_ail_push_sync(struct xfs_ail *ailp);
> +
> extern kmem_zone_t *xfs_trans_zone;
>
> #endif /* __XFS_TRANS_H__ */
> diff --git a/fs/xfs/xfs_trans_ail.c b/fs/xfs/xfs_trans_ail.c
> index 6ccfd75..b8d8df1 100644
> --- a/fs/xfs/xfs_trans_ail.c
> +++ b/fs/xfs/xfs_trans_ail.c
> @@ -488,7 +488,11 @@ xfsaild_push(
> xfs_trans_ail_cursor_done(&cur);
> spin_unlock(&ailp->ail_lock);
>
> - if (xfs_buf_delwri_submit_nowait(&ailp->ail_buf_list))
> + if (unlikely(mp->m_flags & XFS_MOUNT_METASYNC)) {
> + xfs_buf_delwri_submit(&ailp->ail_buf_list);
I guess this never fails, because write IO is 100% successful?
--D
> + ailp->ail_log_flush++;
> + wake_up_all(&ailp->pushed_que);
> + } else if (xfs_buf_delwri_submit_nowait(&ailp->ail_buf_list))
> ailp->ail_log_flush++;
>
> if (!count || XFS_LSN_CMP(lsn, target) >= 0) {
> @@ -641,6 +645,25 @@ xfs_ail_push(
> wake_up_process(ailp->ail_task);
> }
>
> +void
> +xfs_ail_push_sync(
> + struct xfs_ail *ailp)
> +{
> + xfs_lsn_t sync_lsn;
> + DEFINE_WAIT(wait);
> +
> + sync_lsn = xfs_ail_max_lsn(ailp);
> + for (;;) {
> + xfs_ail_push(ailp, sync_lsn);
> + prepare_to_wait(&ailp->pushed_que, &wait, TASK_INTERRUPTIBLE);
> + if (XFS_LSN_CMP(READ_ONCE(ailp->ail_target_prev),
> + sync_lsn) >= 0)
> + break;
> + schedule();
> + }
> + finish_wait(&ailp->pushed_que, &wait);
> +}
> +
> /*
> * Push out all items in the AIL immediately
> */
> @@ -834,6 +857,7 @@ xfs_trans_ail_init(
> spin_lock_init(&ailp->ail_lock);
> INIT_LIST_HEAD(&ailp->ail_buf_list);
> init_waitqueue_head(&ailp->ail_empty);
> + init_waitqueue_head(&ailp->pushed_que);
>
> ailp->ail_task = kthread_run(xfsaild, ailp, "xfsaild/%s",
> ailp->ail_mount->m_fsname);
> diff --git a/fs/xfs/xfs_trans_priv.h b/fs/xfs/xfs_trans_priv.h
> index 2e073c1..9fe3cc6 100644
> --- a/fs/xfs/xfs_trans_priv.h
> +++ b/fs/xfs/xfs_trans_priv.h
> @@ -61,6 +61,7 @@ struct xfs_ail {
> int ail_log_flush;
> struct list_head ail_buf_list;
> wait_queue_head_t ail_empty;
> + wait_queue_head_t pushed_que;
> };
>
> /*
> --
> 2.7.5
>
