jbd2: cleanup needed free block estimates when starting a transaction

__jbd2_log_space_left() and jbd_space_needed() were kind of odd.
jbd_space_needed() accounted also credits needed for currently
committing transaction while it didn't account for credits needed for
control blocks.  __jbd2_log_space_left() then accounted for control
blocks as a fraction of free space.  Since results of these two
functions are always only compared against each other, this works
correct but is somewhat strange.  Move the estimates so that
jbd_space_needed() returns number of blocks needed for a transaction
including control blocks and __jbd2_log_space_left() returns free
space in the journal (with the committing transaction already
subtracted).  Rename functions to jbd2_log_space_left() and
jbd2_space_needed() while we are changing them.

Reviewed-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 5 insertions, 4 deletions

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index 60361c634b5d..f9cd43190b43 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -283,12 +283,12 @@ repeat:
          * reduce the free space arbitrarily.  Be careful to account for
          * those buffers when checkpointing.
          */
-        if (__jbd2_log_space_left(journal) < jbd_space_needed(journal)) {
+        if (jbd2_log_space_left(journal) < jbd2_space_needed(journal)) {
                 jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
                 atomic_sub(nblocks, &transaction->t_outstanding_credits);
                 read_unlock(&journal->j_state_lock);
                 write_lock(&journal->j_state_lock);
-                if (__jbd2_log_space_left(journal) < jbd_space_needed(journal))
+                if (jbd2_log_space_left(journal) < jbd2_space_needed(journal))
                         __jbd2_log_wait_for_space(journal);
                 write_unlock(&journal->j_state_lock);
                 goto repeat;
@@ -306,7 +306,7 @@ repeat:
         jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
                   handle, nblocks,
                   atomic_read(&transaction->t_outstanding_credits),
-                  __jbd2_log_space_left(journal));
+                  jbd2_log_space_left(journal));
         read_unlock(&journal->j_state_lock);
 
         lock_map_acquire(&handle->h_lockdep_map);
@@ -441,7 +441,8 @@ int jbd2_journal_extend(handle_t *handle, int nblocks)
                 goto unlock;
         }
 
-        if (wanted > __jbd2_log_space_left(journal)) {
+        if (wanted + (wanted >> JBD2_CONTROL_BLOCKS_SHIFT) >
+            jbd2_log_space_left(journal)) {
                 jbd_debug(3, "denied handle %p %d blocks: "
                           "insufficient log space\n", handle, nblocks);
                 goto unlock;