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Date: Wed, 15 Sep 2021 17:22:27 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: Shiyang Ruan <ruansy.fnst@...itsu.com>
Cc: hch@....de, linux-xfs@...r.kernel.org, dan.j.williams@...el.com,
david@...morbit.com, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, nvdimm@...ts.linux.dev,
rgoldwyn@...e.de, viro@...iv.linux.org.uk, willy@...radead.org
Subject: Re: [PATCH v9 7/8] xfs: support CoW in fsdax mode
On Wed, Sep 15, 2021 at 06:45:00PM +0800, Shiyang Ruan wrote:
> In fsdax mode, WRITE and ZERO on a shared extent need CoW performed.
> After that, new allocated extents needs to be remapped to the file.
> So, add a CoW identification in ->iomap_begin(), and implement
> ->iomap_end() to do the remapping work.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@...itsu.com>
> ---
> fs/xfs/xfs_bmap_util.c | 3 +--
> fs/xfs/xfs_file.c | 6 +++---
> fs/xfs/xfs_iomap.c | 38 +++++++++++++++++++++++++++++++++++++-
> fs/xfs/xfs_iomap.h | 30 ++++++++++++++++++++++++++++++
> fs/xfs/xfs_iops.c | 7 +++----
> fs/xfs/xfs_reflink.c | 3 +--
> 6 files changed, 75 insertions(+), 12 deletions(-)
>
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index 73a36b7be3bd..0681250e0a5d 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -1009,8 +1009,7 @@ xfs_free_file_space(
> return 0;
> if (offset + len > XFS_ISIZE(ip))
> len = XFS_ISIZE(ip) - offset;
> - error = iomap_zero_range(VFS_I(ip), offset, len, NULL,
> - &xfs_buffered_write_iomap_ops);
> + error = xfs_iomap_zero_range(ip, offset, len, NULL);
> if (error)
> return error;
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 7aa943edfc02..2ef1930374d2 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -704,7 +704,7 @@ xfs_file_dax_write(
> pos = iocb->ki_pos;
>
> trace_xfs_file_dax_write(iocb, from);
> - ret = dax_iomap_rw(iocb, from, &xfs_direct_write_iomap_ops);
> + ret = dax_iomap_rw(iocb, from, &xfs_dax_write_iomap_ops);
> if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
> i_size_write(inode, iocb->ki_pos);
> error = xfs_setfilesize(ip, pos, ret);
> @@ -1329,8 +1329,8 @@ __xfs_filemap_fault(
> xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL,
> (write_fault && !vmf->cow_page) ?
> - &xfs_direct_write_iomap_ops :
> - &xfs_read_iomap_ops);
> + &xfs_dax_write_iomap_ops :
> + &xfs_read_iomap_ops);
Hmm... I wonder if this should get hoisted to a "xfs_dax_iomap_fault"
wrapper like you did for xfs_iomap_zero_range?
> if (ret & VM_FAULT_NEEDDSYNC)
> ret = dax_finish_sync_fault(vmf, pe_size, pfn);
> xfs_iunlock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index 093758440ad5..6fa3b377cb81 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -761,7 +761,8 @@ xfs_direct_write_iomap_begin(
>
> /* may drop and re-acquire the ilock */
> error = xfs_reflink_allocate_cow(ip, &imap, &cmap, &shared,
> - &lockmode, flags & IOMAP_DIRECT);
> + &lockmode,
> + (flags & IOMAP_DIRECT) || IS_DAX(inode));
> if (error)
> goto out_unlock;
> if (shared)
> @@ -854,6 +855,41 @@ const struct iomap_ops xfs_direct_write_iomap_ops = {
> .iomap_begin = xfs_direct_write_iomap_begin,
> };
>
> +static int
> +xfs_dax_write_iomap_end(
> + struct inode *inode,
> + loff_t pos,
> + loff_t length,
> + ssize_t written,
> + unsigned flags,
> + struct iomap *iomap)
Whitespace nit: ^ space before a tab.
> +{
> + struct xfs_inode *ip = XFS_I(inode);
> + /*
> + * Usually we use @written to indicate whether the operation was
> + * successful. But it is always positive or zero. The CoW needs the
> + * actual error code from actor(). So, get it from
> + * iomap_iter->processed.
Hm. All six arguments are derived from the struct iomap_iter, so maybe
it makes more sense to pass that in? I'll poke around with this more
tomorrow.
> + */
> + const struct iomap_iter *iter =
> + container_of(iomap, typeof(*iter), iomap);
> +
> + if (!xfs_is_cow_inode(ip))
> + return 0;
> +
> + if (iter->processed <= 0) {
> + xfs_reflink_cancel_cow_range(ip, pos, length, true);
> + return 0;
> + }
> +
> + return xfs_reflink_end_cow(ip, pos, iter->processed);
> +}
> +
> +const struct iomap_ops xfs_dax_write_iomap_ops = {
> + .iomap_begin = xfs_direct_write_iomap_begin,
Space before tab ^
> + .iomap_end = xfs_dax_write_iomap_end,
> +};
> +
> static int
> xfs_buffered_write_iomap_begin(
Also, we have an related request to drop the EXPERIMENTAL tag for
non-DAX reflink. Whichever patch enables dax+reflink for xfs needs to
make it clear that reflink + any possibility of DAX emits an
EXPERIMENTAL warning.
--D
> struct inode *inode,
> diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
> index 7d3703556d0e..92679a0c3578 100644
> --- a/fs/xfs/xfs_iomap.h
> +++ b/fs/xfs/xfs_iomap.h
> @@ -45,5 +45,35 @@ extern const struct iomap_ops xfs_direct_write_iomap_ops;
> extern const struct iomap_ops xfs_read_iomap_ops;
> extern const struct iomap_ops xfs_seek_iomap_ops;
> extern const struct iomap_ops xfs_xattr_iomap_ops;
> +extern const struct iomap_ops xfs_dax_write_iomap_ops;
> +
> +static inline int
> +xfs_iomap_zero_range(
> + struct xfs_inode *ip,
> + loff_t pos,
> + loff_t len,
> + bool *did_zero)
> +{
> + struct inode *inode = VFS_I(ip);
> +
> + return iomap_zero_range(inode, pos, len, did_zero,
> + IS_DAX(inode) ?
> + &xfs_dax_write_iomap_ops :
> + &xfs_buffered_write_iomap_ops);
> +}
> +
> +static inline int
> +xfs_iomap_truncate_page(
> + struct xfs_inode *ip,
> + loff_t pos,
> + bool *did_zero)
> +{
> + struct inode *inode = VFS_I(ip);
> +
> + return iomap_truncate_page(inode, pos, did_zero,
> + IS_DAX(inode)?
> + &xfs_dax_write_iomap_ops :
> + &xfs_buffered_write_iomap_ops);
> +}
>
> #endif /* __XFS_IOMAP_H__*/
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index a607d6aca5c4..332e6208dffd 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -911,8 +911,8 @@ xfs_setattr_size(
> */
> if (newsize > oldsize) {
> trace_xfs_zero_eof(ip, oldsize, newsize - oldsize);
> - error = iomap_zero_range(inode, oldsize, newsize - oldsize,
> - &did_zeroing, &xfs_buffered_write_iomap_ops);
> + error = xfs_iomap_zero_range(ip, oldsize, newsize - oldsize,
> + &did_zeroing);
> } else {
> /*
> * iomap won't detect a dirty page over an unwritten block (or a
> @@ -924,8 +924,7 @@ xfs_setattr_size(
> newsize);
> if (error)
> return error;
> - error = iomap_truncate_page(inode, newsize, &did_zeroing,
> - &xfs_buffered_write_iomap_ops);
> + error = xfs_iomap_truncate_page(ip, newsize, &did_zeroing);
> }
>
> if (error)
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 7ecea0311e88..9d876e268734 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -1269,8 +1269,7 @@ xfs_reflink_zero_posteof(
> return 0;
>
> trace_xfs_zero_eof(ip, isize, pos - isize);
> - return iomap_zero_range(VFS_I(ip), isize, pos - isize, NULL,
> - &xfs_buffered_write_iomap_ops);
> + return xfs_iomap_zero_range(ip, isize, pos - isize, NULL);
> }
>
> /*
> --
> 2.33.0
>
>
>
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