2007/9/12, Chris Mason <[EMAIL PROTECTED]>:
> Thanks, you've definitely found a bug in the current code, but I'm
> afraid we can't assume the start of the block group is free. There
> could be an extent allocated in the last block group that extends into
> the current one.
>
Thanks for comment.
I feel if there are extent items across block group boundary, we also
can't guarantee start of the block group is free in other tests (in
cache_block_group) . In addition, the subtraction operation in codes
like:
--------------------------------------------------------
if (found) {
hole_size = block_group->key.objectid +
block_group->key.offset - last;
}
-------------------------------------------------------
may overflow. The overflow bug can easily produce by adding a extent
item across boundary of block group 0 and block group 1.
here is the new patch . it finds the start of free block in a block
group by checking the first extent item (the one found by
btrfs_search_slot directly, it should belong to preceding block group
except for the first block group). it also add check for overflow.
Regards
YZ
diff -r 9cb5f0f5c713 extent-tree.c
--- a/extent-tree.c Thu Aug 30 12:16:51 2007 -0400
+++ b/extent-tree.c Wed Sep 12 13:08:17 2007 +0800
@@ -39,6 +39,7 @@ static int cache_block_group(struct btrf
u64 i;
u64 last = 0;
u64 hole_size;
+ u64 first_free;
int found = 0;
root = root->fs_info->extent_root;
@@ -52,6 +53,7 @@ static int cache_block_group(struct btrf
if (!path)
return -ENOMEM;
path->reada = 2;
+ first_free = block_group->key.objectid;
key.objectid = block_group->key.objectid;
key.flags = 0;
key.offset = 0;
@@ -71,13 +73,13 @@ static int cache_block_group(struct btrf
if (ret == 0) {
continue;
} else {
- if (found) {
- hole_size = block_group->key.objectid +
- block_group->key.offset - last;
- } else {
- last = block_group->key.objectid;
- hole_size = block_group->key.offset;
- }
+ if (!found)
+ last = first_free;
+ if (block_group->key.objectid +
+ block_group->key.offset < last)
+ break;
+ hole_size = block_group->key.objectid +
+ block_group->key.offset - last;
for (i = 0; i < hole_size; i++) {
set_radix_bit(extent_radix,
last + i);
@@ -86,15 +88,20 @@ static int cache_block_group(struct btrf
}
}
btrfs_disk_key_to_cpu(&key, &leaf->items[slot].key);
+ if (key.objectid < block_group->key.objectid) {
+ if (key.objectid + key.offset > first_free)
+ first_free = key.objectid + key.offset;
+ goto next;
+ }
if (key.objectid >= block_group->key.objectid +
block_group->key.offset) {
- if (found) {
- hole_size = block_group->key.objectid +
- block_group->key.offset - last;
- } else {
- last = block_group->key.objectid;
- hole_size = block_group->key.offset;
- }
+ if (!found)
+ last = first_free;
+ if (block_group->key.objectid +
+ block_group->key.offset < last)
+ break;
+ hole_size = block_group->key.objectid +
+ block_group->key.offset - last;
for (i = 0; i < hole_size; i++) {
set_radix_bit(extent_radix, last + i);
}
@@ -102,16 +109,16 @@ static int cache_block_group(struct btrf
}
if (btrfs_key_type(&key) == BTRFS_EXTENT_ITEM_KEY) {
if (!found) {
- last = key.objectid + key.offset;
+ last = first_free;
found = 1;
- } else {
- hole_size = key.objectid - last;
- for (i = 0; i < hole_size; i++) {
- set_radix_bit(extent_radix, last + i);
- }
- last = key.objectid + key.offset;
- }
- }
+ }
+ hole_size = key.objectid - last;
+ for (i = 0; i < hole_size; i++) {
+ set_radix_bit(extent_radix, last + i);
+ }
+ last = key.objectid + key.offset;
+ }
+next:
path->slots[0]++;
}
diff -r 9cb5f0f5c713 extent-tree.c
--- a/extent-tree.c Thu Aug 30 12:16:51 2007 -0400
+++ b/extent-tree.c Wed Sep 12 13:08:17 2007 +0800
@@ -39,6 +39,7 @@ static int cache_block_group(struct btrf
u64 i;
u64 last = 0;
u64 hole_size;
+ u64 first_free;
int found = 0;
root = root->fs_info->extent_root;
@@ -52,6 +53,7 @@ static int cache_block_group(struct btrf
if (!path)
return -ENOMEM;
path->reada = 2;
+ first_free = block_group->key.objectid;
key.objectid = block_group->key.objectid;
key.flags = 0;
key.offset = 0;
@@ -71,13 +73,13 @@ static int cache_block_group(struct btrf
if (ret == 0) {
continue;
} else {
- if (found) {
- hole_size = block_group->key.objectid +
- block_group->key.offset - last;
- } else {
- last = block_group->key.objectid;
- hole_size = block_group->key.offset;
- }
+ if (!found)
+ last = first_free;
+ if (block_group->key.objectid +
+ block_group->key.offset < last)
+ break;
+ hole_size = block_group->key.objectid +
+ block_group->key.offset - last;
for (i = 0; i < hole_size; i++) {
set_radix_bit(extent_radix,
last + i);
@@ -86,15 +88,20 @@ static int cache_block_group(struct btrf
}
}
btrfs_disk_key_to_cpu(&key, &leaf->items[slot].key);
+ if (key.objectid < block_group->key.objectid) {
+ if (key.objectid + key.offset > first_free)
+ first_free = key.objectid + key.offset;
+ goto next;
+ }
if (key.objectid >= block_group->key.objectid +
block_group->key.offset) {
- if (found) {
- hole_size = block_group->key.objectid +
- block_group->key.offset - last;
- } else {
- last = block_group->key.objectid;
- hole_size = block_group->key.offset;
- }
+ if (!found)
+ last = first_free;
+ if (block_group->key.objectid +
+ block_group->key.offset < last)
+ break;
+ hole_size = block_group->key.objectid +
+ block_group->key.offset - last;
for (i = 0; i < hole_size; i++) {
set_radix_bit(extent_radix, last + i);
}
@@ -102,16 +109,16 @@ static int cache_block_group(struct btrf
}
if (btrfs_key_type(&key) == BTRFS_EXTENT_ITEM_KEY) {
if (!found) {
- last = key.objectid + key.offset;
+ last = first_free;
found = 1;
- } else {
- hole_size = key.objectid - last;
- for (i = 0; i < hole_size; i++) {
- set_radix_bit(extent_radix, last + i);
- }
- last = key.objectid + key.offset;
- }
- }
+ }
+ hole_size = key.objectid - last;
+ for (i = 0; i < hole_size; i++) {
+ set_radix_bit(extent_radix, last + i);
+ }
+ last = key.objectid + key.offset;
+ }
+next:
path->slots[0]++;
}
_______________________________________________
Btrfs-devel mailing list
[email protected]
http://oss.oracle.com/mailman/listinfo/btrfs-devel
