[PATCH 1/5] btrfs-progs: lowmem check: Add check for overlapping dev extents

[Qu Wenruo]

Add such check at check_dev_item(), since at that timing we're also
iterating dev extents for dev item accounting.

Signed-off-by: Qu Wenruo <w...@suse.com>
---
 check/mode-lowmem.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c
index 1bce44f5658a..d387423639e6 100644
--- a/check/mode-lowmem.c
+++ b/check/mode-lowmem.c
@@ -4065,6 +4065,8 @@ static int check_dev_item(struct btrfs_fs_info *fs_info,
        u64 dev_id;
        u64 used;
        u64 total = 0;
+       u64 prev_devid = 0;
+       u64 prev_dev_ext_end = 0;
        int ret;
 
        dev_item = btrfs_item_ptr(eb, slot, struct btrfs_dev_item);
@@ -4086,8 +4088,16 @@ static int check_dev_item(struct btrfs_fs_info *fs_info,
                return REFERENCER_MISSING;
        }
 
-       /* Iterate dev_extents to calculate the used space of a device */
+       /*
+        * Iterate dev_extents to calculate the used space of a device
+        *
+        * Also make sure no dev extents overlap and end beyond device boundary
+        */
        while (1) {
+               u64 devid;
+               u64 physical_offset;
+               u64 physical_len;
+
                if (path.slots[0] >= btrfs_header_nritems(path.nodes[0]))
                        goto next;
 
@@ -4099,7 +4109,25 @@ static int check_dev_item(struct btrfs_fs_info *fs_info,
 
                ptr = btrfs_item_ptr(path.nodes[0], path.slots[0],
                                     struct btrfs_dev_extent);
-               total += btrfs_dev_extent_length(path.nodes[0], ptr);
+               devid = key.objectid;
+               physical_offset = key.offset;
+               physical_len = btrfs_dev_extent_length(path.nodes[0], ptr);
+
+               if (prev_devid == devid && physical_offset < prev_dev_ext_end) {
+                       error(
+"dev extent devid %llu offset %llu len %llu overlap with previous dev extent 
end %llu",
+                             devid, physical_offset, physical_len,
+                             prev_dev_ext_end);
+                       return ACCOUNTING_MISMATCH;
+               }
+               if (physical_offset + physical_len > total_bytes) {
+                       error(
+"dev extent devid %llu offset %llu len %llu is beyond device boundary %llu",
+                             devid, physical_offset, physical_len,
+                             total_bytes);
+                       return ACCOUNTING_MISMATCH;
+               }
+               total += physical_len;
 next:
                ret = btrfs_next_item(dev_root, &path);
                if (ret)
-- 
2.19.0