[PATCH 2/3] btrfs: add missing inode updates on each iteration when replacing extents

[fdmanana@kernel.org]

From: Filipe Manana <fdmanana@suse.com>

When replacing file extents, called during fallocate, hole punching,
clone and deduplication, we may not be able to replace/drop all the
target file extent items with a single transaction handle. We may get
-ENOSPC while doing it, in which case we release the transaction handle,
balance the dirty pages of the btree inode, flush delayed items and get
a new transaction handle to operate on what's left of the target range.

By dropping and replacing file extent items we have effectively modified
the inode, so we should bump its iversion and update its mtime/ctime
before we update the inode item. This is because if the transaction
we used for partially modifying the inode gets committed by someone after
we release it and before we finish the rest of the range, a power failure
happens, then after mounting the filesystem our inode has an outdated
iversion and mtime/ctime, corresponding to the values it had before we
changed it.

So add the missing iversion and mtime/ctime updates.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
 fs/btrfs/ctree.h   |  2 ++
 fs/btrfs/file.c    | 19 +++++++++++++++++++
 fs/btrfs/inode.c   |  1 +
 fs/btrfs/reflink.c |  1 +
 4 files changed, 23 insertions(+)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 55dee1564e90..737cd59d16b6 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -1330,6 +1330,8 @@ struct btrfs_replace_extent_info {
 	 * existing extent into a file range.
 	 */
 	bool is_new_extent;
+	/* Indicate if we should update the inode's mtime and ctime. */
+	bool update_times;
 	/* Meaningful only if is_new_extent is true. */
 	int qgroup_reserved;
 	/*
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 1fd827b99c1b..29de433b7804 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2803,6 +2803,25 @@ int btrfs_replace_file_extents(struct btrfs_inode *inode,
 			extent_info->file_offset += replace_len;
 		}
 
+		/*
+		 * We are releasing our handle on the transaction, balance the
+		 * dirty pages of the btree inode and flush delayed items, and
+		 * then get a new transaction handle, which may now point to a
+		 * new transaction in case someone else may have committed the
+		 * transaction we used to replace/drop file extent items. So
+		 * bump the inode's iversion and update mtime and ctime except
+		 * if we are called from a dedupe context. This is because a
+		 * power failure/crash may happen after the transaction is
+		 * committed and before we finish replacing/dropping all the
+		 * file extent items we need.
+		 */
+		inode_inc_iversion(&inode->vfs_inode);
+
+		if (!extent_info || extent_info->update_times) {
+			inode->vfs_inode.i_mtime = current_time(&inode->vfs_inode);
+			inode->vfs_inode.i_ctime = inode->vfs_inode.i_mtime;
+		}
+
 		ret = btrfs_update_inode(trans, root, inode);
 		if (ret)
 			break;
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 3ede3e873c2a..ab4ebcb7878c 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -9907,6 +9907,7 @@ static struct btrfs_trans_handle *insert_prealloc_file_extent(
 	extent_info.file_offset = file_offset;
 	extent_info.extent_buf = (char *)&stack_fi;
 	extent_info.is_new_extent = true;
+	extent_info.update_times = true;
 	extent_info.qgroup_reserved = qgroup_released;
 	extent_info.insertions = 0;
 
diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
index 7e3b0aa318c1..977e0d218d79 100644
--- a/fs/btrfs/reflink.c
+++ b/fs/btrfs/reflink.c
@@ -497,6 +497,7 @@ static int btrfs_clone(struct inode *src, struct inode *inode,
 			clone_info.file_offset = new_key.offset;
 			clone_info.extent_buf = buf;
 			clone_info.is_new_extent = false;
+			clone_info.update_times = !no_time_update;
 			ret = btrfs_replace_file_extents(BTRFS_I(inode), path,
 					drop_start, new_key.offset + datal - 1,
 					&clone_info, &trans);
-- 
2.35.1