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authorAdam Buchbinder <abuchbinder@google.com>2017-07-12 13:05:10 -0700
committerDavid Sterba <dsterba@suse.com>2017-07-20 17:43:43 +0200
commit76daaec5ccbda11f6cd343f85f6f47a56626fe00 (patch)
treed3d71fde3ac2ca0eb90f307161d8fdec0235f373 /image
parent1639cc2a511cb6f2a40b706b3c41e5cb4e01b809 (diff)
btrfs-progs: image: Fix data races when reporting progress
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@google.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'image')
-rw-r--r--image/main.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/image/main.c b/image/main.c
index fac9b760..2100f204 100644
--- a/image/main.c
+++ b/image/main.c
@@ -1720,12 +1720,13 @@ 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);
err = -EIO;
@@ -1803,7 +1804,6 @@ 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--;
@@ -1933,7 +1933,9 @@ 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);