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jbd2: avoid infinite transaction commit loop

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Commit 9f356e5a4f ("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: 9f356e5a4f ("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+rv6Vyxtw@mail.gmail.com
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>
This commit is contained in:
Jan Kara 2024-06-24 19:01:19 +02:00 committed by Theodore Ts'o
parent e3a00a2378
commit 27ba5b6731
1 changed files with 14 additions and 7 deletions
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21
fs/jbd2/transaction.c
View File

@ -191,6 +191,13 @@ static void sub_reserved_credits(journal_t *journal, int blocks)
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 *journal, handle_t *handle,
* 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;
}