6.10-stable review patch. If anyone has any objections, please let me know.
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From: Jan Kara jack@suse.cz
commit 27ba5b67312a944576addc4df44ac3b709aabede upstream.
Commit 9f356e5a4f12 ("jbd2: Account descriptor blocks into t_outstanding_credits") started to account descriptor blocks into transactions outstanding credits. However it didn't appropriately decrease the maximum amount of credits available to userspace. Thus if the filesystem requests a transaction smaller than j_max_transaction_buffers but large enough that when descriptor blocks are added the size exceeds j_max_transaction_buffers, we confuse add_transaction_credits() into thinking previous handles have grown the transaction too much and enter infinite journal commit loop in start_this_handle() -> add_transaction_credits() trying to create transaction with enough credits available.
Fix the problem by properly accounting for transaction space reserved for descriptor blocks when verifying requested transaction handle size.
CC: stable@vger.kernel.org Fixes: 9f356e5a4f12 ("jbd2: Account descriptor blocks into t_outstanding_credits") Reported-by: Alexander Coffin alex.coffin@maticrobots.com Link: https://lore.kernel.org/all/CA+hUFcuGs04JHZ_WzA1zGN57+ehL2qmHOt5a7RMpo+rv6Vy... Signed-off-by: Jan Kara jack@suse.cz Reviewed-by: Zhang Yi yi.zhang@huawei.com Link: https://patch.msgid.link/20240624170127.3253-3-jack@suse.cz Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/jbd2/transaction.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-)
--- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -191,6 +191,13 @@ static void sub_reserved_credits(journal wake_up(&journal->j_wait_reserved); }
+/* Maximum number of blocks for user transaction payload */ +static int jbd2_max_user_trans_buffers(journal_t *journal) +{ + return journal->j_max_transaction_buffers - + journal->j_transaction_overhead_buffers; +} + /* * Wait until we can add credits for handle to the running transaction. Called * with j_state_lock held for reading. Returns 0 if handle joined the running @@ -240,12 +247,12 @@ __must_hold(&journal->j_state_lock) * big to fit this handle? Wait until reserved credits are freed. */ if (atomic_read(&journal->j_reserved_credits) + total > - journal->j_max_transaction_buffers) { + jbd2_max_user_trans_buffers(journal)) { read_unlock(&journal->j_state_lock); jbd2_might_wait_for_commit(journal); wait_event(journal->j_wait_reserved, atomic_read(&journal->j_reserved_credits) + total <= - journal->j_max_transaction_buffers); + jbd2_max_user_trans_buffers(journal)); __acquire(&journal->j_state_lock); /* fake out sparse */ return 1; } @@ -285,14 +292,14 @@ __must_hold(&journal->j_state_lock)
needed = atomic_add_return(rsv_blocks, &journal->j_reserved_credits); /* We allow at most half of a transaction to be reserved */ - if (needed > journal->j_max_transaction_buffers / 2) { + if (needed > jbd2_max_user_trans_buffers(journal) / 2) { sub_reserved_credits(journal, rsv_blocks); atomic_sub(total, &t->t_outstanding_credits); read_unlock(&journal->j_state_lock); jbd2_might_wait_for_commit(journal); wait_event(journal->j_wait_reserved, atomic_read(&journal->j_reserved_credits) + rsv_blocks - <= journal->j_max_transaction_buffers / 2); + <= jbd2_max_user_trans_buffers(journal) / 2); __acquire(&journal->j_state_lock); /* fake out sparse */ return 1; } @@ -322,12 +329,12 @@ static int start_this_handle(journal_t * * size and limit the number of total credits to not exceed maximum * transaction size per operation. */ - if ((rsv_blocks > journal->j_max_transaction_buffers / 2) || - (rsv_blocks + blocks > journal->j_max_transaction_buffers)) { + if (rsv_blocks > jbd2_max_user_trans_buffers(journal) / 2 || + rsv_blocks + blocks > jbd2_max_user_trans_buffers(journal)) { printk(KERN_ERR "JBD2: %s wants too many credits " "credits:%d rsv_credits:%d max:%d\n", current->comm, blocks, rsv_blocks, - journal->j_max_transaction_buffers); + jbd2_max_user_trans_buffers(journal)); WARN_ON(1); return -ENOSPC; }