From: Dave Chinner <david@fromorbit.com>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: linux-xfs@vger.kernel.org
Subject: Re: [PATCH 4/9] xfs: create shadow transaction reservations for computing minimum log size
Date: Wed, 27 Apr 2022 14:28:01 +1000 [thread overview]
Message-ID: <20220427042801.GG1098723@dread.disaster.area> (raw)
In-Reply-To: <165102073482.3922658.3874181264513799865.stgit@magnolia>
On Tue, Apr 26, 2022 at 05:52:14PM -0700, Darrick J. Wong wrote:
> From: Darrick J. Wong <djwong@kernel.org>
>
> Every time someone changes the transaction reservation sizes, they
> introduce potential compatibility problems if the changes affect the
> minimum log size that we validate at mount time. If the minimum log
> size gets larger (which should be avoided because doing so presents a
> serious risk of log livelock), filesystems created with old mkfs will
> not mount on a newer kernel; if the minimum size shrinks, filesystems
> created with newer mkfs will not mount on older kernels.
>
> Therefore, enable the creation of a shadow log reservation structure
> where we can "undo" the effects of tweaks when computing minimum log
> sizes. These shadow reservations should never be used in practice, but
> they insulate us from perturbations in minimum log size.
>
> Signed-off-by: Darrick J. Wong <djwong@kernel.org>
> ---
> fs/xfs/libxfs/xfs_log_rlimit.c | 15 +++++++++++----
> fs/xfs/xfs_trace.h | 12 ++++++++++--
> 2 files changed, 21 insertions(+), 6 deletions(-)
>
>
> diff --git a/fs/xfs/libxfs/xfs_log_rlimit.c b/fs/xfs/libxfs/xfs_log_rlimit.c
> index 67798ff5e14e..4d04568ab07e 100644
> --- a/fs/xfs/libxfs/xfs_log_rlimit.c
> +++ b/fs/xfs/libxfs/xfs_log_rlimit.c
> @@ -14,6 +14,7 @@
> #include "xfs_trans_space.h"
> #include "xfs_da_btree.h"
> #include "xfs_bmap_btree.h"
> +#include "xfs_trace.h"
>
> /*
> * Calculate the maximum length in bytes that would be required for a local
> @@ -46,19 +47,25 @@ xfs_log_get_max_trans_res(
> struct xfs_mount *mp,
> struct xfs_trans_res *max_resp)
> {
> + struct xfs_trans_resv resv;
> struct xfs_trans_res *resp;
> struct xfs_trans_res *end_resp;
> + unsigned int i;
> int log_space = 0;
> int attr_space;
>
> attr_space = xfs_log_calc_max_attrsetm_res(mp);
>
> - resp = (struct xfs_trans_res *)M_RES(mp);
> - end_resp = (struct xfs_trans_res *)(M_RES(mp) + 1);
> - for (; resp < end_resp; resp++) {
> + memcpy(&resv, M_RES(mp), sizeof(struct xfs_trans_resv));
Looks much nicer, but I had to read on further into the patchset
before it made sense. As it all ends up ok:
Reviewed-by: Dave Chinner <dchinner@redhat.com>
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2022-04-27 4:28 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-27 0:51 [PATCHSET v2 0/9] xfs: fix reflink inefficiencies Darrick J. Wong
2022-04-27 0:51 ` [PATCH 1/9] xfs: count EFIs when deciding to ask for a continuation of a refcount update Darrick J. Wong
2022-04-27 22:59 ` Darrick J. Wong
2022-04-28 12:46 ` Christoph Hellwig
2022-04-27 0:52 ` [PATCH 2/9] xfs: stop artificially limiting the length of bunmap calls Darrick J. Wong
2022-04-28 12:46 ` Christoph Hellwig
2022-04-27 0:52 ` [PATCH 3/9] xfs: remove a __xfs_bunmapi call from reflink Darrick J. Wong
2022-04-27 0:52 ` [PATCH 4/9] xfs: create shadow transaction reservations for computing minimum log size Darrick J. Wong
2022-04-27 4:28 ` Dave Chinner [this message]
2022-04-28 12:50 ` Christoph Hellwig
2022-04-27 0:52 ` [PATCH 5/9] xfs: report "max_resp" used for min log size computation Darrick J. Wong
2022-04-27 4:28 ` Dave Chinner
2022-04-28 12:51 ` Christoph Hellwig
2022-04-27 0:52 ` [PATCH 6/9] xfs: reduce the absurdly large log operation count Darrick J. Wong
2022-04-27 4:29 ` Dave Chinner
2022-04-28 12:54 ` Christoph Hellwig
2022-04-27 0:52 ` [PATCH 7/9] xfs: reduce transaction reservations with reflink Darrick J. Wong
2022-04-27 4:30 ` Dave Chinner
2022-04-28 12:55 ` Christoph Hellwig
2022-04-27 0:52 ` [PATCH 8/9] xfs: rewrite xfs_reflink_end_cow to use intents Darrick J. Wong
2022-04-28 12:56 ` Christoph Hellwig
2022-04-27 0:52 ` [PATCH 9/9] xfs: rename xfs_*alloc*_log_count to _block_count Darrick J. Wong
2022-04-27 4:32 ` Dave Chinner
2022-04-28 12:56 ` Christoph Hellwig
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