Re: [PATCH v4 6/7] fs/xfs: Handle CoW for fsdax write() path

From: Darrick J. Wong
Date: Thu Apr 08 2021 - 18:40:11 EST

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In reply to: Shiyang Ruan: "[PATCH v4 6/7] fs/xfs: Handle CoW for fsdax write() path"
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On Thu, Apr 08, 2021 at 08:04:31PM +0800, Shiyang Ruan wrote:
> In fsdax mode, WRITE and ZERO on a shared extent need CoW performed. After
> CoW, new allocated extents needs to be remapped to the file. So, add an
> iomap_end for dax write ops to do the remapping work.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
> ---
> fs/xfs/xfs_bmap_util.c | 3 +--
> fs/xfs/xfs_file.c | 9 +++----
> fs/xfs/xfs_iomap.c | 58 +++++++++++++++++++++++++++++++++++++++++-
> fs/xfs/xfs_iomap.h | 4 +++
> fs/xfs/xfs_iops.c | 7 +++--
> fs/xfs/xfs_reflink.c | 3 +--
> 6 files changed, 69 insertions(+), 15 deletions(-)
>
> diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c
> index e7d68318e6a5..9fcea33dd2c9 100644
> --- a/fs/xfs/xfs_bmap_util.c
> +++ b/fs/xfs/xfs_bmap_util.c
> @@ -954,8 +954,7 @@ 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(VFS_I(ip), offset, len, NULL);
> if (error)
> return error;
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index a007ca0711d9..5795d5d6f869 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -684,11 +684,8 @@ 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);
> - if (ret > 0 && iocb->ki_pos > i_size_read(inode)) {
> - i_size_write(inode, iocb->ki_pos);
> - error = xfs_setfilesize(ip, pos, ret);
> - }
> + ret = dax_iomap_rw(iocb, from, &xfs_dax_write_iomap_ops);
> +
> out:
> if (iolock)
> xfs_iunlock(ip, iolock);
> @@ -1309,7 +1306,7 @@ __xfs_filemap_fault(
>
> ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL,
> (write_fault && !vmf->cow_page) ?
> - &xfs_direct_write_iomap_ops :
> + &xfs_dax_write_iomap_ops :
> &xfs_read_iomap_ops);
> if (ret & VM_FAULT_NEEDDSYNC)
> ret = dax_finish_sync_fault(vmf, pe_size, pfn);
> diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c
> index e17ab7f42928..f818f989687b 100644
> --- a/fs/xfs/xfs_iomap.c
> +++ b/fs/xfs/xfs_iomap.c
> @@ -760,7 +760,8 @@ 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));

Parentheses, please:
(flags & IOMAP_DIRECT) || IS_DAX(inode));

> if (error)
> goto out_unlock;
> if (shared)
> @@ -853,6 +854,38 @@ 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 int flags,
> + struct iomap *iomap)
> +{
> + int error = 0;
> + xfs_inode_t *ip = XFS_I(inode);

Please don't use typedefs:

struct xfs_inode *ip = XFS_I(inode);

> + bool cow = xfs_is_cow_inode(ip);
> +
> + if (pos + written > i_size_read(inode)) {

What if we wrote zero bytes? Usually that means error, right?

> + i_size_write(inode, pos + written);
> + error = xfs_setfilesize(ip, pos, written);
> + if (error && cow) {
> + xfs_reflink_cancel_cow_range(ip, pos, written, true);
> + return error;
> + }
> + }
> + if (cow)
> + error = xfs_reflink_end_cow(ip, pos, written);
> +
> + return error;
> +}
> +
> +const struct iomap_ops xfs_dax_write_iomap_ops = {
> + .iomap_begin = xfs_direct_write_iomap_begin,
> + .iomap_end = xfs_dax_write_iomap_end,
> +};
> +
> static int
> xfs_buffered_write_iomap_begin(
> struct inode *inode,
> @@ -1314,3 +1347,26 @@ xfs_xattr_iomap_begin(
> const struct iomap_ops xfs_xattr_iomap_ops = {
> .iomap_begin = xfs_xattr_iomap_begin,
> };
> +
> +int
> +xfs_iomap_zero_range(
> + struct inode *inode,

Might as well pass the xfs_inode pointers directly into these two functions.

--D

> + loff_t offset,
> + loff_t len,
> + bool *did_zero)
> +{
> + return iomap_zero_range(inode, offset, len, did_zero,
> + IS_DAX(inode) ? &xfs_dax_write_iomap_ops :
> + &xfs_buffered_write_iomap_ops);
> +}
> +
> +int
> +xfs_iomap_truncate_page(
> + struct inode *inode,
> + loff_t pos,
> + bool *did_zero)
> +{
> + return iomap_truncate_page(inode, pos, did_zero,
> + IS_DAX(inode) ? &xfs_dax_write_iomap_ops :
> + &xfs_buffered_write_iomap_ops);
> +}
> diff --git a/fs/xfs/xfs_iomap.h b/fs/xfs/xfs_iomap.h
> index 7d3703556d0e..8adb2bf78a5a 100644
> --- a/fs/xfs/xfs_iomap.h
> +++ b/fs/xfs/xfs_iomap.h
> @@ -14,6 +14,9 @@ struct xfs_bmbt_irec;
> int xfs_iomap_write_direct(struct xfs_inode *ip, xfs_fileoff_t offset_fsb,
> xfs_fileoff_t count_fsb, struct xfs_bmbt_irec *imap);
> int xfs_iomap_write_unwritten(struct xfs_inode *, xfs_off_t, xfs_off_t, bool);
> +int xfs_iomap_zero_range(struct inode *inode, loff_t offset, loff_t len,
> + bool *did_zero);
> +int xfs_iomap_truncate_page(struct inode *inode, loff_t pos, bool *did_zero);
> xfs_fileoff_t xfs_iomap_eof_align_last_fsb(struct xfs_inode *ip,
> xfs_fileoff_t end_fsb);
>
> @@ -42,6 +45,7 @@ xfs_aligned_fsb_count(
>
> extern const struct iomap_ops xfs_buffered_write_iomap_ops;
> extern const struct iomap_ops xfs_direct_write_iomap_ops;
> +extern const struct iomap_ops xfs_dax_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;
> diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
> index 66ebccb5a6ff..db8eeaa8a773 100644
> --- a/fs/xfs/xfs_iops.c
> +++ b/fs/xfs/xfs_iops.c
> @@ -879,8 +879,8 @@ 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(inode, oldsize, newsize - oldsize,
> + &did_zeroing);
> } else {
> /*
> * iomap won't detect a dirty page over an unwritten block (or a
> @@ -892,8 +892,7 @@ 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(inode, newsize, &did_zeroing);
> }
>
> if (error)
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 9ef9f98725a2..a4cd6e8a7aa0 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -1266,8 +1266,7 @@ 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(VFS_I(ip), isize, pos - isize, NULL);
> }
>
> /*
> --
> 2.31.0
>
>
>

Next message: Frank Rowand: "Re: [PATCH v4 1/1] of: unittest: overlay: ensure proper alignment of copied FDT"
Previous message: Frederic Weisbecker: "[PATCH 5/5] srcu: Early test SRCU polling start"
In reply to: Shiyang Ruan: "[PATCH v4 6/7] fs/xfs: Handle CoW for fsdax write() path"
Next in thread: Shiyang Ruan: "[PATCH v4 7/7] fs/xfs: Add dedupe support for fsdax"
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