6.1-stable review patch. If anyone has any objections, please let me know.
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From: Filipe Manana fdmanana@suse.com
[ Upstream commit ef07b74e1be56f9eafda6aadebb9ebba0743c9f0 ]
There's a race between checking if an inode was logged before and logging an inode that can cause us to mark an inode as not logged just after it was logged by a concurrent task:
1) We have inode X which was not logged before neither in the current transaction not in past transaction since the inode was loaded into memory, so it's ->logged_trans value is 0;
2) We are at transaction N;
3) Task A calls inode_logged() against inode X, sees that ->logged_trans is 0 and there is a log tree and so it proceeds to search in the log tree for an inode item for inode X. It doesn't see any, but before it sets ->logged_trans to N - 1...
3) Task B calls btrfs_log_inode() against inode X, logs the inode and sets ->logged_trans to N;
4) Task A now sets ->logged_trans to N - 1;
5) At this point anyone calling inode_logged() gets 0 (inode not logged) since ->logged_trans is greater than 0 and less than N, but our inode was really logged. As a consequence operations like rename, unlink and link that happen afterwards in the current transaction end up not updating the log when they should.
Fix this by ensuring inode_logged() only updates ->logged_trans in case the inode item is not found in the log tree if after tacking the inode's lock (spinlock struct btrfs_inode::lock) the ->logged_trans value is still zero, since the inode lock is what protects setting ->logged_trans at btrfs_log_inode().
Fixes: 0f8ce49821de ("btrfs: avoid inode logging during rename and link when possible") Reviewed-by: Boris Burkov boris@bur.io Signed-off-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/tree-log.c | 36 ++++++++++++++++++++++++++++++------ 1 file changed, 30 insertions(+), 6 deletions(-)
diff --git a/fs/btrfs/tree-log.c b/fs/btrfs/tree-log.c index de2b22a56c065..48274bfdeeeb8 100644 --- a/fs/btrfs/tree-log.c +++ b/fs/btrfs/tree-log.c @@ -3302,6 +3302,31 @@ int btrfs_free_log_root_tree(struct btrfs_trans_handle *trans, return 0; }
+static bool mark_inode_as_not_logged(const struct btrfs_trans_handle *trans, + struct btrfs_inode *inode) +{ + bool ret = false; + + /* + * Do this only if ->logged_trans is still 0 to prevent races with + * concurrent logging as we may see the inode not logged when + * inode_logged() is called but it gets logged after inode_logged() did + * not find it in the log tree and we end up setting ->logged_trans to a + * value less than trans->transid after the concurrent logging task has + * set it to trans->transid. As a consequence, subsequent rename, unlink + * and link operations may end up not logging new names and removing old + * names from the log. + */ + spin_lock(&inode->lock); + if (inode->logged_trans == 0) + inode->logged_trans = trans->transid - 1; + else if (inode->logged_trans == trans->transid) + ret = true; + spin_unlock(&inode->lock); + + return ret; +} + /* * Check if an inode was logged in the current transaction. This correctly deals * with the case where the inode was logged but has a logged_trans of 0, which @@ -3336,10 +3361,8 @@ static int inode_logged(struct btrfs_trans_handle *trans, * transaction's ID, to avoid the search below in a future call in case * a log tree gets created after this. */ - if (!test_bit(BTRFS_ROOT_HAS_LOG_TREE, &inode->root->state)) { - inode->logged_trans = trans->transid - 1; - return 0; - } + if (!test_bit(BTRFS_ROOT_HAS_LOG_TREE, &inode->root->state)) + return mark_inode_as_not_logged(trans, inode);
/* * We have a log tree and the inode's logged_trans is 0. We can't tell @@ -3393,8 +3416,7 @@ static int inode_logged(struct btrfs_trans_handle *trans, * Set logged_trans to a value greater than 0 and less then the * current transaction to avoid doing the search in future calls. */ - inode->logged_trans = trans->transid - 1; - return 0; + return mark_inode_as_not_logged(trans, inode); }
/* @@ -3402,7 +3424,9 @@ static int inode_logged(struct btrfs_trans_handle *trans, * the current transacion's ID, to avoid future tree searches as long as * the inode is not evicted again. */ + spin_lock(&inode->lock); inode->logged_trans = trans->transid; + spin_unlock(&inode->lock);
/* * If it's a directory, then we must set last_dir_index_offset to the