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SubjectRe: [PATCH v9 8/8] xfs: Add dax dedupe support
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On 2021/9/16 8:30, Darrick J. Wong wrote:
> On Wed, Sep 15, 2021 at 06:45:01PM +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@fujitsu.com>
>> Reviewed-by: Darrick J. Wong <djwong@kernel.org>
>> Reviewed-by: Christoph Hellwig <hch@lst.de>
>> ---
>> fs/xfs/xfs_file.c | 2 +-
>> fs/xfs/xfs_inode.c | 80 +++++++++++++++++++++++++++++++++++++++++---
>> fs/xfs/xfs_inode.h | 1 +
>> fs/xfs/xfs_reflink.c | 4 +--
>> 4 files changed, 80 insertions(+), 7 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
>> index 2ef1930374d2..c3061723613c 100644
>> --- a/fs/xfs/xfs_file.c
>> +++ b/fs/xfs/xfs_file.c
>> @@ -846,7 +846,7 @@ 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 a4f6f034fb81..bdc084cdbf46 100644
>> --- a/fs/xfs/xfs_inode.c
>> +++ b/fs/xfs/xfs_inode.c
>> @@ -3790,6 +3790,61 @@ 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);
>> +
>> +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);
>> + if (error == 0 && retry)
>> + goto again;
>> + return error;
>> + }
>> +
>> + 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;
>> + }
>
> I suspect we don't need this part for grabbing the MMAPLOCK^W pagecache
> invalidatelock. The AIL only grabs the ILOCK, never the IOLOCK or the
> MMAPLOCK.

Maybe I have misunderstood this part.

What I want is to lock the two inode nestedly. This code is copied from
xfs_lock_two_inodes(), which checks this AIL during locking two inode
with each of the three kinds of locks.

But I also found the recent merged function:
filemap_invalidate_lock_two() just locks two inode directly without
checking AIL. So, I am not if the AIL check is needed in this case.

>
>> + } else
>> + xfs_ilock(ip2, 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(VFS_I(ip2)->i_mapping);
>> + if (page && page_ref_count(page) != 1) {
>
> Do you think the patch "ext4/xfs: add page refcount helper" would be a
> good cleanup to head this series?
>
> https://lore.kernel.org/linux-xfs/20210913161604.31981-1-alex.sierra@amd.com/T/#m59cf7cd5c0d521ad487fa3a15d31c3865db88bdf

Got it.


--
Thanks,
Ruan

>
> The rest of the logic looks ok.
>
> --D
>
>> + 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.
>> @@ -3804,8 +3859,19 @@ xfs_ilock2_io_mmap(
>> ret = xfs_iolock_two_inodes_and_break_layout(VFS_I(ip1), VFS_I(ip2));
>> if (ret)
>> return ret;
>> - filemap_invalidate_lock_two(VFS_I(ip1)->i_mapping,
>> - VFS_I(ip2)->i_mapping);
>> +
>> + if (IS_DAX(VFS_I(ip1)) && IS_DAX(VFS_I(ip2))) {
>> + ret = xfs_mmaplock_two_inodes_and_break_dax_layout(ip1, ip2);
>> + if (ret) {
>> + inode_unlock(VFS_I(ip2));
>> + if (ip1 != ip2)
>> + inode_unlock(VFS_I(ip1));
>> + return ret;
>> + }
>> + } else
>> + filemap_invalidate_lock_two(VFS_I(ip1)->i_mapping,
>> + VFS_I(ip2)->i_mapping);
>> +
>> return 0;
>> }
>>
>> @@ -3815,8 +3881,14 @@ xfs_iunlock2_io_mmap(
>> struct xfs_inode *ip1,
>> struct xfs_inode *ip2)
>> {
>> - filemap_invalidate_unlock_two(VFS_I(ip1)->i_mapping,
>> - VFS_I(ip2)->i_mapping);
>> + if (IS_DAX(VFS_I(ip1)) && IS_DAX(VFS_I(ip2))) {
>> + xfs_iunlock(ip2, XFS_MMAPLOCK_EXCL);
>> + if (ip1 != ip2)
>> + xfs_iunlock(ip1, XFS_MMAPLOCK_EXCL);
>> + } else
>> + filemap_invalidate_unlock_two(VFS_I(ip1)->i_mapping,
>> + VFS_I(ip2)->i_mapping);
>> +
>> inode_unlock(VFS_I(ip2));
>> if (ip1 != ip2)
>> inode_unlock(VFS_I(ip1));
>> diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
>> index b21b177832d1..f7e26fe31a26 100644
>> --- a/fs/xfs/xfs_inode.h
>> +++ b/fs/xfs/xfs_inode.h
>> @@ -472,6 +472,7 @@ 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 9d876e268734..3b99c9dfcf0d 100644
>> --- a/fs/xfs/xfs_reflink.c
>> +++ b/fs/xfs/xfs_reflink.c
>> @@ -1327,8 +1327,8 @@ 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))
>> --
>> 2.33.0
>>
>>
>>


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