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Date: Wed, 12 May 2021 01:26:30 +0000
From: "ruansy.fnst@...itsu.com" <ruansy.fnst@...itsu.com>
To: "Darrick J. Wong" <djwong@...nel.org>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-xfs@...r.kernel.org" <linux-xfs@...r.kernel.org>,
"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
"linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
"darrick.wong@...cle.com" <darrick.wong@...cle.com>,
"dan.j.williams@...el.com" <dan.j.williams@...el.com>,
"willy@...radead.org" <willy@...radead.org>,
"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
"david@...morbit.com" <david@...morbit.com>,
"hch@....de" <hch@....de>, "rgoldwyn@...e.de" <rgoldwyn@...e.de>
Subject: RE: [PATCH v5 7/7] fs/xfs: Add dax dedupe support
> -----Original Message-----
> From: Darrick J. Wong <djwong@...nel.org>
> Subject: Re: [PATCH v5 7/7] fs/xfs: Add dax dedupe support
>
> On Tue, May 11, 2021 at 11:09:33AM +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@...itsu.com>
> > ---
> > fs/xfs/xfs_file.c | 2 +-
> > fs/xfs/xfs_inode.c | 66
> +++++++++++++++++++++++++++++++++++++++++++-
> > fs/xfs/xfs_inode.h | 1 +
> > fs/xfs/xfs_reflink.c | 4 +--
> > 4 files changed, 69 insertions(+), 4 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..0774b6e2b940 100644
> > --- a/fs/xfs/xfs_inode.c
> > +++ b/fs/xfs/xfs_inode.c
> > @@ -3711,6 +3711,64 @@ xfs_iolock_two_inodes_and_break_layout(
> > return 0;
> > }
> >
> > +static int
> > +xfs_mmaplock_two_inodes_and_break_dax_layout(
> > + struct inode *src,
> > + struct inode *dest)
>
> MMAPLOCK is an xfs_inode lock, so please pass those in here.
>
> > +{
> > + int error, attempts = 0;
> > + bool retry;
> > + struct xfs_inode *ip0, *ip1;
> > + struct page *page;
> > + struct xfs_log_item *lp;
> > +
> > + if (src > dest)
> > + swap(src, dest);
>
> The MMAPLOCK (and ILOCK) locking order is increasing inode number, not the
> address of the incore object. This is different (and not consistent
> with) i_rwsem/XFS_IOLOCK, but those are the rules.
Yes, I misunderstood here.
>
> > + ip0 = XFS_I(src);
> > + ip1 = XFS_I(dest);
> > +
> > +again:
> > + retry = false;
> > + /* Lock the first inode */
> > + xfs_ilock(ip0, XFS_MMAPLOCK_EXCL);
> > + error = xfs_break_dax_layouts(src, &retry);
> > + if (error || retry) {
> > + xfs_iunlock(ip0, XFS_MMAPLOCK_EXCL);
> > + goto again;
> > + }
> > +
> > + if (src == dest)
> > + return 0;
> > +
> > + /* Nested lock the second inode */
> > + lp = &ip0->i_itemp->ili_item;
> > + if (lp && test_bit(XFS_LI_IN_AIL, &lp->li_flags)) {
> > + if (!xfs_ilock_nowait(ip1,
> > + xfs_lock_inumorder(XFS_MMAPLOCK_EXCL, 1))) {
> > + xfs_iunlock(ip0, XFS_MMAPLOCK_EXCL);
> > + if ((++attempts % 5) == 0)
> > + delay(1); /* Don't just spin the CPU */
> > + goto again;
> > + }
> > + } else
> > + xfs_ilock(ip1, xfs_lock_inumorder(XFS_MMAPLOCK_EXCL, 1));
> > + /*
> > + * 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(dest->i_mapping);
> > + if (page) {
> > + if (page_ref_count(page) != 1) {
>
> This could be flattened to:
>
> if (page && page_ref_count(page) != 1) {
> ...
> }
OK.
--
Thanks,
Ruan Shiyang.
>
> --D
>
> > + xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
> > + xfs_iunlock(ip0, XFS_MMAPLOCK_EXCL);
> > + goto again;
> > + }
> > + }
> > +
> > + return 0;
> > +}
> > +
> > /*
> > * Lock two inodes so that userspace cannot initiate I/O via file syscalls or
> > * mmap activity.
> > @@ -3721,10 +3779,16 @@ xfs_ilock2_io_mmap(
> > struct xfs_inode *ip2)
> > {
> > int ret;
> > + struct inode *ino1 = VFS_I(ip1);
> > + struct inode *ino2 = VFS_I(ip2);
> >
> > - ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1), VFS_I(ip2));
> > + ret = xfs_iolock_two_inodes_and_break_layout(ino1, ino2);
> > if (ret)
> > return ret;
> > +
> > + if (IS_DAX(ino1) && IS_DAX(ino2))
> > + return xfs_mmaplock_two_inodes_and_break_dax_layout(ino1, ino2);
> > +
> > 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
> >
> >
> >
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