From a47604de3ee0ecbf79ce9d3fd271562177777ec8 Mon Sep 17 00:00:00 2001
From: Su Yue <suy.fnst@cn.fujitsu.com>
Date: Tue, 29 Aug 2017 11:33:23 +0800
Subject: [PATCH] btrfs-progs: check: punch_extent_hole in lowmem

While checking file extents, there are two errors that may occur:

1) There is one hole between the last extent end and beginning of the
   current extent but no-holes is disabled.

2) No-holes is disabled, one file's nbytes equals 0 but isize is not 0.

Those both mean the file may have lost some extents.
To avoid btrfsck's error message, fix it by introducing function
'punch_extent_hole' to punch holes.

For case 1, punch a hole extent whose length is
  (current extent begin - last extent end)
while checking one extent.

For case 2, punch a hole extent whose length is
  (file isize - actual file size)
after traversing one entire file.

Then repair_inode_nbytes will set the nbytes to isize.

Signed-off-by: Su Yue <suy.fnst@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 cmds-check.c | 51 +++++++++++++++++++++++++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 6 deletions(-)

diff --git a/cmds-check.c b/cmds-check.c
index ffb3e0ca..edc2726c 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -5322,6 +5322,34 @@ out:
 	return err;
 }
 
+/*
+ * Wrapper function of btrfs_punch_hole.
+ *
+ * Returns 0 means success.
+ * Returns not 0 means error.
+ */
+static int punch_extent_hole(struct btrfs_root *root, u64 ino, u64 start,
+			     u64 len)
+{
+	struct btrfs_trans_handle *trans;
+	int ret = 0;
+
+	trans = btrfs_start_transaction(root, 1);
+	if (IS_ERR(trans))
+		return PTR_ERR(trans);
+
+	ret = btrfs_punch_hole(trans, root, ino, start, len);
+	if (ret)
+		error("failed to add hole [%llu, %llu] in inode [%llu]",
+		      start, len, ino);
+	else
+		printf("Add a hole [%llu, %llu] in inode [%llu]\n", start, len,
+		       ino);
+
+	btrfs_commit_transaction(trans, root);
+	return ret;
+}
+
 /*
  * Check file extent datasum/hole, update the size of the file extents,
  * check and update the last offset of the file extent.
@@ -5437,9 +5465,14 @@ static int check_file_extent(struct btrfs_root *root, struct btrfs_key *fkey,
 
 	/* Check EXTENT_DATA hole */
 	if (!no_holes && *end != fkey->offset) {
-		err |= FILE_EXTENT_ERROR;
-		error("root %llu EXTENT_DATA[%llu %llu] interrupt",
-		      root->objectid, fkey->objectid, fkey->offset);
+		if (repair)
+			ret = punch_extent_hole(root, fkey->objectid,
+						*end, fkey->offset - *end);
+		if (!repair || ret) {
+			err |= FILE_EXTENT_ERROR;
+			error("root %llu EXTENT_DATA[%llu %llu] interrupt",
+			      root->objectid, fkey->objectid, fkey->offset);
+		}
 	}
 
 	*end += extent_num_bytes;
@@ -5879,9 +5912,15 @@ out:
 		}
 
 		if (!nbytes && !no_holes && extent_end < isize) {
-			err |= NBYTES_ERROR;
-			error("root %llu INODE[%llu] size (%llu) should have a file extent hole",
-			      root->objectid, inode_id, isize);
+			if (repair)
+				ret = punch_extent_hole(root, inode_id,
+						extent_end, isize - extent_end);
+			if (!repair || ret) {
+				err |= NBYTES_ERROR;
+				error(
+	"root %llu INODE[%llu] size %llu should have a file extent hole",
+				      root->objectid, inode_id, isize);
+			}
 		}
 
 		if (nbytes != extent_size) {