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Subject: [PATCH v2 04/18] ext4: Add ext4_break_layouts() to the inode
 eviction path
From:   Dan Williams <dan.j.williams@intel.com>
To:     akpm@linux-foundation.org
Cc:     Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
        "Darrick J. Wong" <djwong@kernel.org>,
        Jason Gunthorpe <jgg@nvidia.com>,
        Christoph Hellwig <hch@lst.de>,
        John Hubbard <jhubbard@nvidia.com>,
        linux-fsdevel@vger.kernel.org, nvdimm@lists.linux.dev,
        linux-xfs@vger.kernel.org, linux-mm@kvack.org,
        linux-ext4@vger.kernel.org
Date:   Thu, 15 Sep 2022 20:35:33 -0700
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References: <166329930818.2786261.6086109734008025807.stgit@dwillia2-xfh.jf.intel.com>
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In preparation for moving DAX pages to be 0-based rather than 1-based
for the idle refcount, the fsdax core wants to have all mappings in a
"zapped" state before truncate. For typical pages this happens naturally
via unmap_mapping_range(), for DAX pages some help is needed to record
this state in the 'struct address_space' of the inode(s) where the page
is mapped.

That "zapped" state is recorded in DAX entries as a side effect of
ext4_break_layouts(). Arrange for it to be called before all truncation
events which already happens for truncate() and PUNCH_HOLE, but not
truncate_inode_pages_final(). Arrange for ext4_break_layouts() before
truncate_inode_pages_final().

Cc: Matthew Wilcox <willy@infradead.org>
Cc: Jan Kara <jack@suse.cz>
Cc: "Darrick J. Wong" <djwong@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: John Hubbard <jhubbard@nvidia.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
---
 fs/ext4/inode.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 478ec6bc0935..326269ad3961 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -207,7 +207,11 @@ void ext4_evict_inode(struct inode *inode)
 			jbd2_complete_transaction(journal, commit_tid);
 			filemap_write_and_wait(&inode->i_data);
 		}
+
+		filemap_invalidate_lock(inode->i_mapping);
+		ext4_break_layouts(inode);
 		truncate_inode_pages_final(&inode->i_data);
+		filemap_invalidate_unlock(inode->i_mapping);
 
 		goto no_delete;
 	}
@@ -218,7 +222,11 @@ void ext4_evict_inode(struct inode *inode)
 
 	if (ext4_should_order_data(inode))
 		ext4_begin_ordered_truncate(inode, 0);
+
+	filemap_invalidate_lock(inode->i_mapping);
+	ext4_break_layouts(inode);
 	truncate_inode_pages_final(&inode->i_data);
+	filemap_invalidate_unlock(inode->i_mapping);
 
 	/*
 	 * For inodes with journalled data, transaction commit could have