On Wed, Feb 19, 2020 at 05:42:06PM -0800, Darrick J. Wong wrote:
> From: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
>
> Add a new function that will ensure that everything we changed has
> landed on stable media, and report the results. Subsequent commits will
> teach the individual programs to report when things go wrong.
>
> Signed-off-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx>
> ---
> include/xfs_mount.h | 3 +++
> libxfs/init.c | 43 +++++++++++++++++++++++++++++++++++++++++++
> libxfs/libxfs_io.h | 2 ++
> libxfs/rdwr.c | 27 +++++++++++++++++++++++++--
> 4 files changed, 73 insertions(+), 2 deletions(-)
>
>
> diff --git a/include/xfs_mount.h b/include/xfs_mount.h
> index 29b3cc1b..c80aaf69 100644
> --- a/include/xfs_mount.h
> +++ b/include/xfs_mount.h
> @@ -187,4 +187,7 @@ extern xfs_mount_t *libxfs_mount (xfs_mount_t *, xfs_sb_t *,
> extern void libxfs_umount (xfs_mount_t *);
> extern void libxfs_rtmount_destroy (xfs_mount_t *);
>
> +void libxfs_flush_devices(struct xfs_mount *mp, int *datadev, int *logdev,
> + int *rtdev);
> +
> #endif /* __XFS_MOUNT_H__ */
> diff --git a/libxfs/init.c b/libxfs/init.c
> index a0d4b7f4..d1d3f4df 100644
> --- a/libxfs/init.c
> +++ b/libxfs/init.c
> @@ -569,6 +569,8 @@ libxfs_buftarg_alloc(
> }
> btp->bt_mount = mp;
> btp->dev = dev;
> + btp->lost_writes = false;
> +
> return btp;
> }
>
> @@ -791,6 +793,47 @@ libxfs_rtmount_destroy(xfs_mount_t *mp)
> mp->m_rsumip = mp->m_rbmip = NULL;
> }
>
> +static inline int
> +libxfs_flush_buftarg(
> + struct xfs_buftarg *btp)
> +{
> + if (btp->lost_writes)
> + return -ENOTRECOVERABLE;
> +
> + return libxfs_blkdev_issue_flush(btp);
> +}
> +
> +/*
> + * Purge the buffer cache to write all dirty buffers to disk and free all
> + * incore buffers. Buffers that cannot be written will cause the lost_writes
> + * flag to be set in the buftarg. If there were no lost writes, flush the
> + * device to make sure the writes made it to stable storage.
> + *
> + * For each device, the return code will be set to -ENOTRECOVERABLE if we
> + * couldn't write something to disk; or the results of the block device flush
> + * operation.
> + */
> +void
> +libxfs_flush_devices(
> + struct xfs_mount *mp,
> + int *datadev,
> + int *logdev,
> + int *rtdev)
> +{
> + *datadev = *logdev = *rtdev = 0;
> +
> + libxfs_bcache_purge();
> +
> + if (mp->m_ddev_targp)
> + *datadev = libxfs_flush_buftarg(mp->m_ddev_targp);
> +
> + if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp)
> + *logdev = libxfs_flush_buftarg(mp->m_logdev_targp);
> +
> + if (mp->m_rtdev_targp)
> + *rtdev = libxfs_flush_buftarg(mp->m_rtdev_targp);
> +}
So one of the things I'm trying to do is make this use similar code
to the kernel. basically this close process is equivalent of
xfs_wait_buftarg() which waits for all references to buffers to
got away, and if any buffer it tagged with WRITE_FAIL then it issues
and alert before it frees the buffer.
IOWs, any sort of delayed/async write failure that hasn't been
otherwise caught by the async/delwri code is caught by the device
close code....
Doing things like this (storing a "lost writes" flag on the buftarg)
I think is just going to make it harder to switch to kernel
equivalent code because it just introduces even more of an impedance
mismatch between userspace and kernel code...
Cheers,
Dave.
--
Dave Chinner
david@xxxxxxxxxxxxx
