Making the code data-race safe requires that reads *and* writes
happen under a mutex lock, if any of the access are writes. See
Dmitri Vyukov, "Benign data races: what could possibly go wrong?"
for more details.
The fix here was to put most of the main loop of restore_worker
under a mutex lock.
This race was detected using fsck-tests/012-leaf-corruption.
==================
WARNING: ThreadSanitizer: data race
Write of size 4 by main thread:
#0 add_cluster btrfs-progs/image/main.c:1931
#1 restore_metadump btrfs-progs/image/main.c:2566
#2 main btrfs-progs/image/main.c:2859
Previous read of size 4 by thread T6:
#0 restore_worker btrfs-progs/image/main.c:1720
Location is stack of main thread.
Thread T6 (running) created by main thread at:
#0 pthread_create <null>
#1 mdrestore_init btrfs-progs/image/main.c:1868
#2 restore_metadump btrfs-progs/image/main.c:2534
#3 main btrfs-progs/image/main.c:2859
SUMMARY: ThreadSanitizer: data race btrfs-progs/image/main.c:1931 in
add_cluster
Signed-off-by: Adam Buchbinder <abuchbinder@xxxxxxxxxx>
---
image/main.c | 16 +++++++++-------
1 file changed, 9 insertions(+), 7 deletions(-)
diff --git a/image/main.c b/image/main.c
index 1eca414..a5d01d8 100644
--- a/image/main.c
+++ b/image/main.c
@@ -1715,14 +1715,15 @@ static void *restore_worker(void *data)
}
async = list_entry(mdres->list.next, struct async_work, list);
list_del_init(&async->list);
- pthread_mutex_unlock(&mdres->mutex);
if (mdres->compress_method == COMPRESS_ZLIB) {
size = compress_size;
+ pthread_mutex_unlock(&mdres->mutex);
ret = uncompress(buffer, (unsigned long *)&size,
async->buffer, async->bufsize);
+ pthread_mutex_lock(&mdres->mutex);
if (ret != Z_OK) {
- error("decompressiion failed with %d", ret);
+ error("decompression failed with %d", ret);
err = -EIO;
}
outbuf = buffer;
@@ -1798,7 +1799,6 @@ error:
if (!mdres->multi_devices && async->start == BTRFS_SUPER_INFO_OFFSET)
write_backup_supers(outfd, outbuf);
- pthread_mutex_lock(&mdres->mutex);
if (err && !mdres->error)
mdres->error = err;
mdres->num_items--;
@@ -1899,7 +1899,7 @@ static int fill_mdres_info(struct mdrestore_struct *mdres,
ret = uncompress(buffer, (unsigned long *)&size,
async->buffer, async->bufsize);
if (ret != Z_OK) {
- error("decompressiion failed with %d", ret);
+ error("decompression failed with %d", ret);
free(buffer);
return -EIO;
}
@@ -1928,7 +1928,9 @@ static int add_cluster(struct meta_cluster *cluster,
u32 i, nritems;
int ret;
+ pthread_mutex_lock(&mdres->mutex);
mdres->compress_method = header->compress;
+ pthread_mutex_unlock(&mdres->mutex);
bytenr = le64_to_cpu(header->bytenr) + BLOCK_SIZE;
nritems = le32_to_cpu(header->nritems);
@@ -2171,7 +2173,7 @@ static int search_for_chunk_blocks(struct mdrestore_struct *mdres,
continue;
}
error(
- "unknown state after reading cluster at %llu, probably crrupted data",
+ "unknown state after reading cluster at %llu, probably corrupted data",
cluster_bytenr);
ret = -EIO;
break;
@@ -2220,7 +2222,7 @@ static int search_for_chunk_blocks(struct mdrestore_struct *mdres,
(unsigned long *)&size, tmp,
bufsize);
if (ret != Z_OK) {
- error("decompressiion failed with %d",
+ error("decompression failed with %d",
ret);
ret = -EIO;
break;
@@ -2340,7 +2342,7 @@ static int build_chunk_tree(struct mdrestore_struct *mdres,
ret = uncompress(tmp, (unsigned long *)&size,
buffer, le32_to_cpu(item->size));
if (ret != Z_OK) {
- error("decompressiion failed with %d", ret);
+ error("decompression failed with %d", ret);
free(buffer);
free(tmp);
return -EIO;
--
2.13.2.932.g7449e964c-goog
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
