On Wed, May 19, 2021 at 02:00:45PM +0800, Shiyang Ruan wrote:
> Introduce xfs_mmaplock_two_inodes_and_break_dax_layout() for dax files
> who are going to be deduped. After that, call compare range function
> only when files are both DAX or not.
>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
> ---
> fs/xfs/xfs_file.c | 2 +-
> fs/xfs/xfs_inode.c | 57 ++++++++++++++++++++++++++++++++++++++++++++
> fs/xfs/xfs_inode.h | 1 +
> fs/xfs/xfs_reflink.c | 4 ++--
> 4 files changed, 61 insertions(+), 3 deletions(-)
>
> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
> index 38d8eca05aee..bd5002d38df4 100644
> --- a/fs/xfs/xfs_file.c
> +++ b/fs/xfs/xfs_file.c
> @@ -823,7 +823,7 @@ xfs_wait_dax_page(
> xfs_ilock(ip, XFS_MMAPLOCK_EXCL);
> }
>
> -static int
> +int
> xfs_break_dax_layouts(
> struct inode *inode,
> bool *retry)
> diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
> index 0369eb22c1bb..d5e2791969ba 100644
> --- a/fs/xfs/xfs_inode.c
> +++ b/fs/xfs/xfs_inode.c
> @@ -3711,6 +3711,59 @@ xfs_iolock_two_inodes_and_break_layout(
> return 0;
> }
>
> +static int
> +xfs_mmaplock_two_inodes_and_break_dax_layout(
> + struct xfs_inode *ip1,
> + struct xfs_inode *ip2)
> +{
> + int error, attempts = 0;
> + bool retry;
> + struct page *page;
> + struct xfs_log_item *lp;
> +
> + if (ip1->i_ino > ip2->i_ino)
> + swap(ip1, ip2);
If Jan Kara [added to cc] succeeds in hoisting the MMAPLOCK to struct
address space then this is going to have to change to:
if (VFS_I(ip1)->i_mapping > VFS_I(ip2)->i_mapping)
swap(ip1, ip2);
For now this is ok.
> +
> +again:
> + retry = false;
> + /* Lock the first inode */
> + xfs_ilock(ip1, XFS_MMAPLOCK_EXCL);
> + error = xfs_break_dax_layouts(VFS_I(ip1), &retry);
> + if (error || retry) {
> + xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
> + goto again;
> + }
> +
> + if (ip1 == ip2)
> + return 0;
> +
> + /* Nested lock the second inode */
> + lp = &ip1->i_itemp->ili_item;
> + if (lp && test_bit(XFS_LI_IN_AIL, &lp->li_flags)) {
> + if (!xfs_ilock_nowait(ip2,
> + xfs_lock_inumorder(XFS_MMAPLOCK_EXCL, 1))) {
> + xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
> + if ((++attempts % 5) == 0)
> + delay(1); /* Don't just spin the CPU */
> + goto again;
> + }
> + } else
> + xfs_ilock(ip2, xfs_lock_inumorder(XFS_MMAPLOCK_EXCL, 1));
I wonder if this chunk is really necessary considering that the AIL
never touches the MMAPLOCK/i_mapping invalidation lock? I guess it
doesn't really hurt anything since that's what the code does now.
Reviewed-by: Darrick J. Wong <djwong@xxxxxxxxxx>
--D
> + /*
> + * We cannot use xfs_break_dax_layouts() directly here because it may
> + * need to unlock & lock the XFS_MMAPLOCK_EXCL which is not suitable
> + * for this nested lock case.
> + */
> + page = dax_layout_busy_page(VFS_I(ip2)->i_mapping);
> + if (page && page_ref_count(page) != 1) {
> + xfs_iunlock(ip2, XFS_MMAPLOCK_EXCL);
> + xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
> + goto again;
> + }
> +
> + return 0;
> +}
> +
> /*
> * Lock two inodes so that userspace cannot initiate I/O via file syscalls or
> * mmap activity.
> @@ -3725,6 +3778,10 @@ xfs_ilock2_io_mmap(
> ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1), VFS_I(ip2));
> if (ret)
> return ret;
> +
> + if (IS_DAX(VFS_I(ip1)) && IS_DAX(VFS_I(ip2)))
> + return xfs_mmaplock_two_inodes_and_break_dax_layout(ip1, ip2);
> +
> if (ip1 == ip2)
> xfs_ilock(ip1, XFS_MMAPLOCK_EXCL);
> else
> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
> index ca826cfba91c..2d0b344fb100 100644
> --- a/fs/xfs/xfs_inode.h
> +++ b/fs/xfs/xfs_inode.h
> @@ -457,6 +457,7 @@ enum xfs_prealloc_flags {
>
> int xfs_update_prealloc_flags(struct xfs_inode *ip,
> enum xfs_prealloc_flags flags);
> +int xfs_break_dax_layouts(struct inode *inode, bool *retry);
> int xfs_break_layouts(struct inode *inode, uint *iolock,
> enum layout_break_reason reason);
>
> diff --git a/fs/xfs/xfs_reflink.c b/fs/xfs/xfs_reflink.c
> index 9a780948dbd0..ff308304c5cd 100644
> --- a/fs/xfs/xfs_reflink.c
> +++ b/fs/xfs/xfs_reflink.c
> @@ -1324,8 +1324,8 @@ xfs_reflink_remap_prep(
> if (XFS_IS_REALTIME_INODE(src) || XFS_IS_REALTIME_INODE(dest))
> goto out_unlock;
>
> - /* Don't share DAX file data for now. */
> - if (IS_DAX(inode_in) || IS_DAX(inode_out))
> + /* Don't share DAX file data with non-DAX file. */
> + if (IS_DAX(inode_in) != IS_DAX(inode_out))
> goto out_unlock;
>
> if (!IS_DAX(inode_in))
> --
> 2.31.1
>
>
>
