From 1dfc3220d963385a317264b11154c462a83596ed Mon Sep 17 00:00:00 2001 From: Josef Bacik Date: Thu, 17 Apr 2008 10:38:59 -0400 Subject: [PATCH] jbd2: fix possible journal overflow issues There are several cases where the running transaction can get buffers added to its BJ_Metadata list which it never dirtied, which makes its t_nr_buffers counter end up larger than its t_outstanding_credits counter. This will cause issues when starting new transactions as while we are logging buffers we decrement t_outstanding_buffers, so when t_outstanding_buffers goes negative, we will report that we need less space in the journal than we actually need, so transactions will be started even though there may not be enough room for them. In the worst case scenario (which admittedly is almost impossible to reproduce) this will result in the journal running out of space. The fix is to only refile buffers from the committing transaction to the running transactions BJ_Modified list when b_modified is set on that journal, which is the only way to be sure if the running transaction has modified that buffer. This patch also fixes an accounting error in journal_forget, it is possible that we can call journal_forget on a buffer without having modified it, only gotten write access to it, so instead of freeing a credit, we only do so if the buffer was modified. The assert will help catch if this problem occurs. Without these two patches I could hit this assert within minutes of running postmark, with them this issue no longer arises. Cc: Cc: Jan Kara Signed-off-by: Josef Bacik Signed-off-by: Andrew Morton Signed-off-by: "Theodore Ts'o" --- fs/jbd2/commit.c | 3 +++ fs/jbd2/transaction.c | 21 ++++++++++++++++++--- 2 files changed, 21 insertions(+), 3 deletions(-) diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c index 988fbec1143..e0139786f71 100644 --- a/fs/jbd2/commit.c +++ b/fs/jbd2/commit.c @@ -568,6 +568,9 @@ void jbd2_journal_commit_transaction(journal_t *journal) stats.u.run.rs_blocks = commit_transaction->t_outstanding_credits; stats.u.run.rs_blocks_logged = 0; + J_ASSERT(commit_transaction->t_nr_buffers <= + commit_transaction->t_outstanding_credits); + descriptor = NULL; bufs = 0; while (commit_transaction->t_buffers) { diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index 9dc71a6b62e..70245d6638b 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -1243,6 +1243,7 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh) struct journal_head *jh; int drop_reserve = 0; int err = 0; + int was_modified = 0; BUFFER_TRACE(bh, "entry"); @@ -1261,6 +1262,9 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh) goto not_jbd; } + /* keep track of wether or not this transaction modified us */ + was_modified = jh->b_modified; + /* * The buffer's going from the transaction, we must drop * all references -bzzz @@ -1278,7 +1282,12 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh) JBUFFER_TRACE(jh, "belongs to current transaction: unfile"); - drop_reserve = 1; + /* + * we only want to drop a reference if this transaction + * modified the buffer + */ + if (was_modified) + drop_reserve = 1; /* * We are no longer going to journal this buffer. @@ -1318,7 +1327,13 @@ int jbd2_journal_forget (handle_t *handle, struct buffer_head *bh) if (jh->b_next_transaction) { J_ASSERT(jh->b_next_transaction == transaction); jh->b_next_transaction = NULL; - drop_reserve = 1; + + /* + * only drop a reference if this transaction modified + * the buffer + */ + if (was_modified) + drop_reserve = 1; } } @@ -2090,7 +2105,7 @@ void __jbd2_journal_refile_buffer(struct journal_head *jh) jh->b_transaction = jh->b_next_transaction; jh->b_next_transaction = NULL; __jbd2_journal_file_buffer(jh, jh->b_transaction, - was_dirty ? BJ_Metadata : BJ_Reserved); + jh->b_modified ? BJ_Metadata : BJ_Reserved); J_ASSERT_JH(jh, jh->b_transaction->t_state == T_RUNNING); if (was_dirty) -- 2.20.1