From 6af3e3adcac595a683bb55299a907d7d1ad61ab3 Mon Sep 17 00:00:00 2001
From: Filipe Manana <fdmanana@suse.com>
Date: Mon, 7 Sep 2015 10:41:12 +0100
Subject: Btrfs: don't initialize a space info as full to prevent ENOSPC
Commit 2e6e518335f8 ("Btrfs: fix block group ->space_info null pointer
dereference") accidently marked a space info as full when initializing
it with a value of 0 total bytes. This introduces an ENOSPC problem when
writing file data if we mount a filesystem that has no data block groups
allocated, because the data space info is initialized with 0 total bytes,
marked as full, and it never gets its total bytes incremented by a
(positive) value to unmark it as full (because there are no data block
groups loaded when the fs is mounted).
For metadata and system spaces this issue can never happen since we always
have at least one metadata block group and one system block group (even
for an empty filesystem).
So fix this by just not initializing a space info as full, reverting the
offending part of the commit mentioned above.
The following test case for fstests reproduces the issue:
seq=`basename $0`
seqres=$RESULT_DIR/$seq
echo "QA output created by $seq"
tmp=/tmp/$$
status=1 # failure is the default!
trap "_cleanup; exit \$status" 0 1 2 3 15
_cleanup()
{
rm -f $tmp.*
}
# get standard environment, filters and checks
. ./common/rc
. ./common/filter
# real QA test starts here
_need_to_be_root
_supported_fs btrfs
_supported_os Linux
_require_scratch
rm -f $seqres.full
_scratch_mkfs >>$seqres.full 2>&1
# Mount our filesystem without space caches enabled so that we do not
# get any space used from the initial data block group that mkfs creates
# (space caches used space from data block groups).
_scratch_mount "-o nospace_cache"
# Need an fs with at least 2Gb to make sure mkfs.btrfs does not create
# an fs using mixed block groups (used both for data and metadata). We
# really need to have dedicated block groups for data to reproduce the
# issue and mkfs.btrfs defaults to mixed block groups only for small
# filesystems (up to 1Gb).
_require_fs_space $SCRATCH_MNT $((2 * 1024 * 1024))
# Run balance with the purpose of deleting the unused data block group
# that mkfs created. We could also wait for the background kthread to
# automatically delete the unused block group, but we do not have a way
# to make it run and wait for it to complete, so just do a balance
# instead of some unreliable sleep
_run_btrfs_util_prog balance start -dusage=0 $SCRATCH_MNT
# Now unmount the filesystem, mount it again (either with or with space
# caches enabled, it does not matter to trigger the problem) and attempt
# to create a file with some data - this used to fail with ENOSPC
# because there were no data block groups when the filesystem was
# mounted and the data space info object was marked as full when
# initialized (because it had 0 total bytes), which prevented the file
# write path from attempting to allocate a data block group and fail
# immediately with ENOSPC.
_scratch_remount
echo "hello world" > $SCRATCH_MNT/foobar
echo "Silence is golden"
status=0
exit
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
fs/btrfs/extent-tree.c | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
(limited to 'fs/btrfs/extent-tree.c')
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 5411f0ab5683..3686315bbd66 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -3742,10 +3742,7 @@ static int update_space_info(struct btrfs_fs_info *info, u64 flags,
found->bytes_reserved = 0;
found->bytes_readonly = 0;
found->bytes_may_use = 0;
- if (total_bytes > 0)
- found->full = 0;
- else
- found->full = 1;
+ found->full = 0;
found->force_alloc = CHUNK_ALLOC_NO_FORCE;
found->chunk_alloc = 0;
found->flush = 0;
--
cgit v1.2.3-70-g09d2
From 2b9dbef272b63c561aab0a5be34fd428f7b710f5 Mon Sep 17 00:00:00 2001
From: Josef Bacik <jbacik@fb.com>
Date: Tue, 15 Sep 2015 10:07:04 -0400
Subject: Btrfs: keep dropped roots in cache until transaction commit
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
When dropping a snapshot we need to account for the qgroup changes. If we drop
the snapshot in all one go then the backref code will fail to find blocks from
the snapshot we dropped since it won't be able to find the root in the fs root
cache. This can lead to us failing to find refs from other roots that pointed
at blocks in the now deleted root. To handle this we need to not remove the fs
roots from the cache until after we process the qgroup operations. Do this by
adding dropped roots to a list on the transaction, and letting the transaction
remove the roots at the same time it drops the commit roots. This will keep all
of the backref searching code in sync properly, and fixes a problem Mark was
seeing with snapshot delete and qgroups. Thanks,
Signed-off-by: Josef Bacik <jbacik@fb.com>
Tested-by: Holger Hoffstätte <holger.hoffstaette@googlemail.com>
Signed-off-by: Chris Mason <clm@fb.com>
---
fs/btrfs/extent-tree.c | 2 +-
fs/btrfs/transaction.c | 32 ++++++++++++++++++++++++++++++++
fs/btrfs/transaction.h | 5 ++++-
3 files changed, 37 insertions(+), 2 deletions(-)
(limited to 'fs/btrfs/extent-tree.c')
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 3686315bbd66..9f9604201333 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8665,7 +8665,7 @@ int btrfs_drop_snapshot(struct btrfs_root *root,
}
if (test_bit(BTRFS_ROOT_IN_RADIX, &root->state)) {
- btrfs_drop_and_free_fs_root(tree_root->fs_info, root);
+ btrfs_add_dropped_root(trans, root);
} else {
free_extent_buffer(root->node);
free_extent_buffer(root->commit_root);
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 68ad89e23713..a2d6f7bcef6c 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -117,6 +117,18 @@ static noinline void switch_commit_roots(struct btrfs_transaction *trans,
btrfs_unpin_free_ino(root);
clear_btree_io_tree(&root->dirty_log_pages);
}
+
+ /* We can free old roots now. */
+ spin_lock(&trans->dropped_roots_lock);
+ while (!list_empty(&trans->dropped_roots)) {
+ root = list_first_entry(&trans->dropped_roots,
+ struct btrfs_root, root_list);
+ list_del_init(&root->root_list);
+ spin_unlock(&trans->dropped_roots_lock);
+ btrfs_drop_and_free_fs_root(fs_info, root);
+ spin_lock(&trans->dropped_roots_lock);
+ }
+ spin_unlock(&trans->dropped_roots_lock);
up_write(&fs_info->commit_root_sem);
}
@@ -255,11 +267,13 @@ loop:
INIT_LIST_HEAD(&cur_trans->pending_ordered);
INIT_LIST_HEAD(&cur_trans->dirty_bgs);
INIT_LIST_HEAD(&cur_trans->io_bgs);
+ INIT_LIST_HEAD(&cur_trans->dropped_roots);
mutex_init(&cur_trans->cache_write_mutex);
cur_trans->num_dirty_bgs = 0;
spin_lock_init(&cur_trans->dirty_bgs_lock);
INIT_LIST_HEAD(&cur_trans->deleted_bgs);
spin_lock_init(&cur_trans->deleted_bgs_lock);
+ spin_lock_init(&cur_trans->dropped_roots_lock);
list_add_tail(&cur_trans->list, &fs_info->trans_list);
extent_io_tree_init(&cur_trans->dirty_pages,
fs_info->btree_inode->i_mapping);
@@ -336,6 +350,24 @@ static int record_root_in_trans(struct btrfs_trans_handle *trans,
}
+void btrfs_add_dropped_root(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root)
+{
+ struct btrfs_transaction *cur_trans = trans->transaction;
+
+ /* Add ourselves to the transaction dropped list */
+ spin_lock(&cur_trans->dropped_roots_lock);
+ list_add_tail(&root->root_list, &cur_trans->dropped_roots);
+ spin_unlock(&cur_trans->dropped_roots_lock);
+
+ /* Make sure we don't try to update the root at commit time */
+ spin_lock(&root->fs_info->fs_roots_radix_lock);
+ radix_tree_tag_clear(&root->fs_info->fs_roots_radix,
+ (unsigned long)root->root_key.objectid,
+ BTRFS_ROOT_TRANS_TAG);
+ spin_unlock(&root->fs_info->fs_roots_radix_lock);
+}
+
int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
struct btrfs_root *root)
{
diff --git a/fs/btrfs/transaction.h b/fs/btrfs/transaction.h
index edc2fbc262d7..87964bf8892d 100644
--- a/fs/btrfs/transaction.h
+++ b/fs/btrfs/transaction.h
@@ -65,6 +65,7 @@ struct btrfs_transaction {
struct list_head switch_commits;
struct list_head dirty_bgs;
struct list_head io_bgs;
+ struct list_head dropped_roots;
u64 num_dirty_bgs;
/*
@@ -76,6 +77,7 @@ struct btrfs_transaction {
spinlock_t dirty_bgs_lock;
struct list_head deleted_bgs;
spinlock_t deleted_bgs_lock;
+ spinlock_t dropped_roots_lock;
struct btrfs_delayed_ref_root delayed_refs;
int aborted;
int dirty_bg_run;
@@ -216,5 +218,6 @@ int btrfs_transaction_blocked(struct btrfs_fs_info *info);
int btrfs_transaction_in_commit(struct btrfs_fs_info *info);
void btrfs_put_transaction(struct btrfs_transaction *transaction);
void btrfs_apply_pending_changes(struct btrfs_fs_info *fs_info);
-
+void btrfs_add_dropped_root(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root);
#endif
--
cgit v1.2.3-70-g09d2