On Tue, Aug 08, 2023 at 09:15:54AM -0700, Christoph Hellwig wrote:
> blkdev_put must not be called under sb->s_umount to avoid a lock order
> reversal with disk->open_mutex. Move closing the buftargs into ->kill_sb
> to archive that. Note that the flushing of the disk caches needs to be
> kept in ->put_super as the main block device is closed in
> kill_block_super already.
>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> ---
> fs/xfs/xfs_buf.c | 1 -
> fs/xfs/xfs_super.c | 27 +++++++++++++++++++--------
> 2 files changed, 19 insertions(+), 9 deletions(-)
>
> diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
> index c57e6e03dfa80c..3b903f6bce98d8 100644
> --- a/fs/xfs/xfs_buf.c
> +++ b/fs/xfs/xfs_buf.c
> @@ -1945,7 +1945,6 @@ xfs_free_buftarg(
> percpu_counter_destroy(&btp->bt_io_count);
> list_lru_destroy(&btp->bt_lru);
>
> - blkdev_issue_flush(btp->bt_bdev);
> fs_put_dax(btp->bt_daxdev, btp->bt_mount);
> /* the main block device is closed by kill_block_super */
> if (bdev != btp->bt_mount->m_super->s_bdev)
> diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c
> index 37b1b763a0bef0..67343364ac66e9 100644
> --- a/fs/xfs/xfs_super.c
> +++ b/fs/xfs/xfs_super.c
> @@ -396,14 +396,14 @@ xfs_blkdev_get(
> }
>
> STATIC void
> -xfs_close_devices(
> +xfs_flush_disk_caches(
> struct xfs_mount *mp)
> {
> if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
> - xfs_free_buftarg(mp->m_logdev_targp);
> + blkdev_issue_flush(mp->m_logdev_targp->bt_bdev);
> if (mp->m_rtdev_targp)
> - xfs_free_buftarg(mp->m_rtdev_targp);
> - xfs_free_buftarg(mp->m_ddev_targp);
> + blkdev_issue_flush(mp->m_rtdev_targp->bt_bdev);
> + blkdev_issue_flush(mp->m_ddev_targp->bt_bdev);
If I'm following this correctly, putting the superblock flushes the
bdevs (though it doesn't invalidate the bdev mapping!) and only later
when we free the xfs_mount do we actually put the buftargs?
That works, though I still think we need to invalidate the bdev
pagecache for the log and data bdevs.
--D
> }
>
> /*
> @@ -741,6 +741,17 @@ static void
> xfs_mount_free(
> struct xfs_mount *mp)
> {
> + /*
> + * Free the buftargs here because blkdev_put needs to be called outside
> + * of sb->s_umount, which is held around the call to ->put_super.
> + */
> + if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
> + xfs_free_buftarg(mp->m_logdev_targp);
> + if (mp->m_rtdev_targp)
> + xfs_free_buftarg(mp->m_rtdev_targp);
> + if (mp->m_ddev_targp)
> + xfs_free_buftarg(mp->m_ddev_targp);
> +
> kfree(mp->m_rtname);
> kfree(mp->m_logname);
> kmem_free(mp);
> @@ -1126,7 +1137,7 @@ xfs_fs_put_super(
> xfs_inodegc_free_percpu(mp);
> xfs_destroy_percpu_counters(mp);
> xfs_destroy_mount_workqueues(mp);
> - xfs_close_devices(mp);
> + xfs_flush_disk_caches(mp);
> }
>
> static long
> @@ -1499,7 +1510,7 @@ xfs_fs_fill_super(
>
> error = xfs_init_mount_workqueues(mp);
> if (error)
> - goto out_close_devices;
> + goto out_flush_caches;
>
> error = xfs_init_percpu_counters(mp);
> if (error)
> @@ -1713,8 +1724,8 @@ xfs_fs_fill_super(
> xfs_destroy_percpu_counters(mp);
> out_destroy_workqueues:
> xfs_destroy_mount_workqueues(mp);
> - out_close_devices:
> - xfs_close_devices(mp);
> + out_flush_caches:
> + xfs_flush_disk_caches(mp);
> return error;
>
> out_unmount:
> --
> 2.39.2
>
