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Date: Mon, 13 Apr 2020 09:12:40 -0700
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: ira.weiny@...el.com
Cc: linux-kernel@...r.kernel.org,
Dan Williams <dan.j.williams@...el.com>,
Dave Chinner <david@...morbit.com>,
Christoph Hellwig <hch@....de>,
"Theodore Y. Ts'o" <tytso@....edu>, Jan Kara <jack@...e.cz>,
Jeff Moyer <jmoyer@...hat.com>, linux-ext4@...r.kernel.org,
linux-xfs@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH V7 8/9] fs/xfs: Change xfs_ioctl_setattr_dax_invalidate()
On Sun, Apr 12, 2020 at 10:40:45PM -0700, ira.weiny@...el.com wrote:
> From: Ira Weiny <ira.weiny@...el.com>
>
> We only support changing FS_XFLAG_DAX on directories. Files get their
> flag from the parent directory on creation only. So no data
> invalidation needs to happen.
>
> Alter the xfs_ioctl_setattr_dax_invalidate() to be
> xfs_ioctl_setattr_dax_validate(). xfs_ioctl_setattr_dax_validate() now
> validates that any FS_XFLAG_DAX change is ok.
>
> This also allows use to remove the join_flags logic.
>
> Signed-off-by: Ira Weiny <ira.weiny@...el.com>
>
> ---
> Changes from v6:
> Fix completely broken implementation and update commit message.
> Use the new VFS layer I_DONTCACHE to facilitate inode eviction
> and S_DAX changing on drop_caches
>
> Changes from v5:
> New patch
> ---
> fs/xfs/xfs_ioctl.c | 102 +++++++--------------------------------------
> 1 file changed, 16 insertions(+), 86 deletions(-)
>
> diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c
> index c6cd92ef4a05..ba42a5fb5b05 100644
> --- a/fs/xfs/xfs_ioctl.c
> +++ b/fs/xfs/xfs_ioctl.c
> @@ -1145,63 +1145,23 @@ xfs_ioctl_setattr_xflags(
> }
>
> /*
> - * If we are changing DAX flags, we have to ensure the file is clean and any
> - * cached objects in the address space are invalidated and removed. This
> - * requires us to lock out other IO and page faults similar to a truncate
> - * operation. The locks need to be held until the transaction has been committed
> - * so that the cache invalidation is atomic with respect to the DAX flag
> - * manipulation.
> + * Mark inodes with a changing FS_XFLAG_DAX, I_DONTCACHE
> */
> -static int
> +static void
> xfs_ioctl_setattr_dax_invalidate(
> struct xfs_inode *ip,
> - struct fsxattr *fa,
> - int *join_flags)
> + struct fsxattr *fa)
> {
> - struct inode *inode = VFS_I(ip);
> - struct super_block *sb = inode->i_sb;
> - int error;
> -
> - *join_flags = 0;
> -
> - /*
> - * It is only valid to set the DAX flag on regular files and
> - * directories on filesystems where the block size is equal to the page
> - * size. On directories it serves as an inherited hint so we don't
> - * have to check the device for dax support or flush pagecache.
> - */
> - if (fa->fsx_xflags & FS_XFLAG_DAX) {
> - struct xfs_buftarg *target = xfs_inode_buftarg(ip);
> -
> - if (!bdev_dax_supported(target->bt_bdev, sb->s_blocksize))
> - return -EINVAL;
> - }
> -
> - /* If the DAX state is not changing, we have nothing to do here. */
> - if ((fa->fsx_xflags & FS_XFLAG_DAX) && IS_DAX(inode))
> - return 0;
> - if (!(fa->fsx_xflags & FS_XFLAG_DAX) && !IS_DAX(inode))
> - return 0;
> + struct inode *inode = VFS_I(ip);
>
> if (S_ISDIR(inode->i_mode))
> - return 0;
> -
> - /* lock, flush and invalidate mapping in preparation for flag change */
> - xfs_ilock(ip, XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL);
> - error = filemap_write_and_wait(inode->i_mapping);
> - if (error)
> - goto out_unlock;
> - error = invalidate_inode_pages2(inode->i_mapping);
> - if (error)
> - goto out_unlock;
> -
> - *join_flags = XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL;
> - return 0;
> -
> -out_unlock:
> - xfs_iunlock(ip, XFS_MMAPLOCK_EXCL | XFS_IOLOCK_EXCL);
> - return error;
> + return;
We also need a check up here to skip the I_DONTCACHE setting if the
admin has set a mount option to override the inode flag.
The rest looks good to me.
--D
> + if (((fa->fsx_xflags & FS_XFLAG_DAX) &&
> + !(ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)) ||
> + (!(fa->fsx_xflags & FS_XFLAG_DAX) &&
> + (ip->i_d.di_flags2 & XFS_DIFLAG2_DAX)))
> + inode->i_state |= I_DONTCACHE;
> }
>
> /*
> @@ -1209,17 +1169,10 @@ xfs_ioctl_setattr_dax_invalidate(
> * have permission to do so. On success, return a clean transaction and the
> * inode locked exclusively ready for further operation specific checks. On
> * failure, return an error without modifying or locking the inode.
> - *
> - * The inode might already be IO locked on call. If this is the case, it is
> - * indicated in @join_flags and we take full responsibility for ensuring they
> - * are unlocked from now on. Hence if we have an error here, we still have to
> - * unlock them. Otherwise, once they are joined to the transaction, they will
> - * be unlocked on commit/cancel.
> */
> static struct xfs_trans *
> xfs_ioctl_setattr_get_trans(
> - struct xfs_inode *ip,
> - int join_flags)
> + struct xfs_inode *ip)
> {
> struct xfs_mount *mp = ip->i_mount;
> struct xfs_trans *tp;
> @@ -1236,8 +1189,7 @@ xfs_ioctl_setattr_get_trans(
> goto out_unlock;
>
> xfs_ilock(ip, XFS_ILOCK_EXCL);
> - xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL | join_flags);
> - join_flags = 0;
> + xfs_trans_ijoin(tp, ip, XFS_ILOCK_EXCL);
>
> /*
> * CAP_FOWNER overrides the following restrictions:
> @@ -1258,8 +1210,6 @@ xfs_ioctl_setattr_get_trans(
> out_cancel:
> xfs_trans_cancel(tp);
> out_unlock:
> - if (join_flags)
> - xfs_iunlock(ip, join_flags);
> return ERR_PTR(error);
> }
>
> @@ -1386,7 +1336,6 @@ xfs_ioctl_setattr(
> struct xfs_dquot *pdqp = NULL;
> struct xfs_dquot *olddquot = NULL;
> int code;
> - int join_flags = 0;
>
> trace_xfs_ioctl_setattr(ip);
>
> @@ -1410,18 +1359,9 @@ xfs_ioctl_setattr(
> return code;
> }
>
> - /*
> - * Changing DAX config may require inode locking for mapping
> - * invalidation. These need to be held all the way to transaction commit
> - * or cancel time, so need to be passed through to
> - * xfs_ioctl_setattr_get_trans() so it can apply them to the join call
> - * appropriately.
> - */
> - code = xfs_ioctl_setattr_dax_invalidate(ip, fa, &join_flags);
> - if (code)
> - goto error_free_dquots;
> + xfs_ioctl_setattr_dax_invalidate(ip, fa);
>
> - tp = xfs_ioctl_setattr_get_trans(ip, join_flags);
> + tp = xfs_ioctl_setattr_get_trans(ip);
> if (IS_ERR(tp)) {
> code = PTR_ERR(tp);
> goto error_free_dquots;
> @@ -1552,7 +1492,6 @@ xfs_ioc_setxflags(
> struct fsxattr fa;
> struct fsxattr old_fa;
> unsigned int flags;
> - int join_flags = 0;
> int error;
>
> if (copy_from_user(&flags, arg, sizeof(flags)))
> @@ -1569,18 +1508,9 @@ xfs_ioc_setxflags(
> if (error)
> return error;
>
> - /*
> - * Changing DAX config may require inode locking for mapping
> - * invalidation. These need to be held all the way to transaction commit
> - * or cancel time, so need to be passed through to
> - * xfs_ioctl_setattr_get_trans() so it can apply them to the join call
> - * appropriately.
> - */
> - error = xfs_ioctl_setattr_dax_invalidate(ip, &fa, &join_flags);
> - if (error)
> - goto out_drop_write;
> + xfs_ioctl_setattr_dax_invalidate(ip, &fa);
>
> - tp = xfs_ioctl_setattr_get_trans(ip, join_flags);
> + tp = xfs_ioctl_setattr_get_trans(ip);
> if (IS_ERR(tp)) {
> error = PTR_ERR(tp);
> goto out_drop_write;
> --
> 2.25.1
>
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