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authorJan Kara <jack@suse.cz>2013-06-04 12:08:56 -0400
committerTheodore Ts'o <tytso@mit.edu>2013-06-04 12:08:56 -0400
commitb34090e5e22a02fba0e4473056cce9420ad9dd0b (patch)
tree7ffb9ecd10ada2aefe9079c2df91405592132e47 /fs/jbd2
parente5a120aeb57f40ae568a5ca1dd6ace53d0213582 (diff)
downloadlinux-b34090e5e22a02fba0e4473056cce9420ad9dd0b.tar.bz2
jbd2: refine waiting for shadow buffers
Currently when we add a buffer to a transaction, we wait until the buffer is removed from BJ_Shadow list (so that we prevent any changes to the buffer that is just written to the journal). This can take unnecessarily long as a lot happens between the time the buffer is submitted to the journal and the time when we remove the buffer from BJ_Shadow list. (e.g. We wait for all data buffers in the transaction, we issue a cache flush, etc.) Also this creates a dependency of do_get_write_access() on transaction commit (namely waiting for data IO to complete) which we want to avoid when implementing transaction reservation. So we modify commit code to set new BH_Shadow flag when temporary shadowing buffer is created and we clear that flag once IO on that buffer is complete. This allows do_get_write_access() to wait only for BH_Shadow bit and thus removes the dependency on data IO completion. 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>
Diffstat (limited to 'fs/jbd2')
-rw-r--r--fs/jbd2/commit.c18
-rw-r--r--fs/jbd2/journal.c2
-rw-r--r--fs/jbd2/transaction.c44
3 files changed, 30 insertions, 34 deletions
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 7c6f7eea2316..d73a0d808ec1 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -30,15 +30,22 @@
#include <trace/events/jbd2.h>
/*
- * Default IO end handler for temporary BJ_IO buffer_heads.
+ * IO end handler for temporary buffer_heads handling writes to the journal.
*/
static void journal_end_buffer_io_sync(struct buffer_head *bh, int uptodate)
{
+ struct buffer_head *orig_bh = bh->b_private;
+
BUFFER_TRACE(bh, "");
if (uptodate)
set_buffer_uptodate(bh);
else
clear_buffer_uptodate(bh);
+ if (orig_bh) {
+ clear_bit_unlock(BH_Shadow, &orig_bh->b_state);
+ smp_mb__after_clear_bit();
+ wake_up_bit(&orig_bh->b_state, BH_Shadow);
+ }
unlock_buffer(bh);
}
@@ -832,6 +839,7 @@ start_journal_io:
bh = jh2bh(jh);
clear_buffer_jwrite(bh);
J_ASSERT_BH(bh, buffer_jbddirty(bh));
+ J_ASSERT_BH(bh, !buffer_shadow(bh));
/* The metadata is now released for reuse, but we need
to remember it against this transaction so that when
@@ -839,14 +847,6 @@ start_journal_io:
required. */
JBUFFER_TRACE(jh, "file as BJ_Forget");
jbd2_journal_file_buffer(jh, commit_transaction, BJ_Forget);
- /*
- * Wake up any transactions which were waiting for this IO to
- * complete. The barrier must be here so that changes by
- * jbd2_journal_file_buffer() take effect before wake_up_bit()
- * does the waitqueue check.
- */
- smp_mb();
- wake_up_bit(&bh->b_state, BH_Unshadow);
JBUFFER_TRACE(jh, "brelse shadowed buffer");
__brelse(bh);
}
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index b0a8d1e4703e..5ef0712e2f7a 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -451,6 +451,7 @@ repeat:
new_bh->b_size = bh_in->b_size;
new_bh->b_bdev = journal->j_dev;
new_bh->b_blocknr = blocknr;
+ new_bh->b_private = bh_in;
set_buffer_mapped(new_bh);
set_buffer_dirty(new_bh);
@@ -465,6 +466,7 @@ repeat:
spin_lock(&journal->j_list_lock);
__jbd2_journal_file_buffer(jh_in, transaction, BJ_Shadow);
spin_unlock(&journal->j_list_lock);
+ set_buffer_shadow(bh_in);
jbd_unlock_bh_state(bh_in);
return do_escape | (done_copy_out << 1);
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index f1c5392e62b6..6f4248dd8759 100644
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -619,6 +619,12 @@ static void warn_dirty_buffer(struct buffer_head *bh)
bdevname(bh->b_bdev, b), (unsigned long long)bh->b_blocknr);
}
+static int sleep_on_shadow_bh(void *word)
+{
+ io_schedule();
+ return 0;
+}
+
/*
* If the buffer is already part of the current transaction, then there
* is nothing we need to do. If it is already part of a prior
@@ -754,41 +760,29 @@ repeat:
* journaled. If the primary copy is already going to
* disk then we cannot do copy-out here. */
- if (jh->b_jlist == BJ_Shadow) {
- DEFINE_WAIT_BIT(wait, &bh->b_state, BH_Unshadow);
- wait_queue_head_t *wqh;
-
- wqh = bit_waitqueue(&bh->b_state, BH_Unshadow);
-
+ if (buffer_shadow(bh)) {
JBUFFER_TRACE(jh, "on shadow: sleep");
jbd_unlock_bh_state(bh);
- /* commit wakes up all shadow buffers after IO */
- for ( ; ; ) {
- prepare_to_wait(wqh, &wait.wait,
- TASK_UNINTERRUPTIBLE);
- if (jh->b_jlist != BJ_Shadow)
- break;
- schedule();
- }
- finish_wait(wqh, &wait.wait);
+ wait_on_bit(&bh->b_state, BH_Shadow,
+ sleep_on_shadow_bh, TASK_UNINTERRUPTIBLE);
goto repeat;
}
- /* Only do the copy if the currently-owning transaction
- * still needs it. If it is on the Forget list, the
- * committing transaction is past that stage. The
- * buffer had better remain locked during the kmalloc,
- * but that should be true --- we hold the journal lock
- * still and the buffer is already on the BUF_JOURNAL
- * list so won't be flushed.
+ /*
+ * Only do the copy if the currently-owning transaction still
+ * needs it. If buffer isn't on BJ_Metadata list, the
+ * committing transaction is past that stage (here we use the
+ * fact that BH_Shadow is set under bh_state lock together with
+ * refiling to BJ_Shadow list and at this point we know the
+ * buffer doesn't have BH_Shadow set).
*
* Subtle point, though: if this is a get_undo_access,
* then we will be relying on the frozen_data to contain
* the new value of the committed_data record after the
* transaction, so we HAVE to force the frozen_data copy
- * in that case. */
-
- if (jh->b_jlist != BJ_Forget || force_copy) {
+ * in that case.
+ */
+ if (jh->b_jlist == BJ_Metadata || force_copy) {
JBUFFER_TRACE(jh, "generate frozen data");
if (!frozen_buffer) {
JBUFFER_TRACE(jh, "allocate memory for buffer");