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>

3 files changed, 53 insertions, 26 deletions

diff --git a/include/linux/jbd.h b/include/linux/jbd.h
index 9c505f1aa1fd..2439054a6c9a 100644
--- a/include/linux/jbd.h
+++ b/include/linux/jbd.h
@@ -244,6 +244,31 @@ typedef struct journal_superblock_s
 
 #include <linux/fs.h>
 #include <linux/sched.h>
+
+enum jbd_state_bits {
+	BH_JBD			/* Has an attached ext3 journal_head */
+	  = BH_PrivateStart,
+	BH_JWrite,		/* Being written to log (@@@ DEBUGGING) */
+	BH_Freed,		/* Has been freed (truncated) */
+	BH_Revoked,		/* Has been revoked from the log */
+	BH_RevokeValid,		/* Revoked flag is valid */
+	BH_JBDDirty,		/* Is dirty but journaled */
+	BH_State,		/* Pins most journal_head state */
+	BH_JournalHead,		/* Pins bh->b_private and jh->b_bh */
+	BH_Unshadow,		/* Dummy bit, for BJ_Shadow wakeup filtering */
+	BH_JBDPrivateStart,	/* First bit available for private use by FS */
+};
+
+BUFFER_FNS(JBD, jbd)
+BUFFER_FNS(JWrite, jwrite)
+BUFFER_FNS(JBDDirty, jbddirty)
+TAS_BUFFER_FNS(JBDDirty, jbddirty)
+BUFFER_FNS(Revoked, revoked)
+TAS_BUFFER_FNS(Revoked, revoked)
+BUFFER_FNS(RevokeValid, revokevalid)
+TAS_BUFFER_FNS(RevokeValid, revokevalid)
+BUFFER_FNS(Freed, freed)
+
 #include <linux/jbd_common.h>
 
 #define J_ASSERT(assert)	BUG_ON(!(assert))
diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index b7dc40da99e0..e33e84b3d5c8 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -302,6 +302,34 @@ typedef struct journal_superblock_s
 
 #include <linux/fs.h>
 #include <linux/sched.h>
+
+enum jbd_state_bits {
+	BH_JBD			/* Has an attached ext3 journal_head */
+	  = BH_PrivateStart,
+	BH_JWrite,		/* Being written to log (@@@ DEBUGGING) */
+	BH_Freed,		/* Has been freed (truncated) */
+	BH_Revoked,		/* Has been revoked from the log */
+	BH_RevokeValid,		/* Revoked flag is valid */
+	BH_JBDDirty,		/* Is dirty but journaled */
+	BH_State,		/* Pins most journal_head state */
+	BH_JournalHead,		/* Pins bh->b_private and jh->b_bh */
+	BH_Shadow,		/* IO on shadow buffer is running */
+	BH_Verified,		/* Metadata block has been verified ok */
+	BH_JBDPrivateStart,	/* First bit available for private use by FS */
+};
+
+BUFFER_FNS(JBD, jbd)
+BUFFER_FNS(JWrite, jwrite)
+BUFFER_FNS(JBDDirty, jbddirty)
+TAS_BUFFER_FNS(JBDDirty, jbddirty)
+BUFFER_FNS(Revoked, revoked)
+TAS_BUFFER_FNS(Revoked, revoked)
+BUFFER_FNS(RevokeValid, revokevalid)
+TAS_BUFFER_FNS(RevokeValid, revokevalid)
+BUFFER_FNS(Freed, freed)
+BUFFER_FNS(Shadow, shadow)
+BUFFER_FNS(Verified, verified)
+
 #include <linux/jbd_common.h>
 
 #define J_ASSERT(assert)	BUG_ON(!(assert))
diff --git a/include/linux/jbd_common.h b/include/linux/jbd_common.h
index 6133679bc4c0..b1f708976ffd 100644
--- a/include/linux/jbd_common.h
+++ b/include/linux/jbd_common.h
@@ -1,32 +1,6 @@
 #ifndef _LINUX_JBD_STATE_H
 #define _LINUX_JBD_STATE_H
 
-enum jbd_state_bits {
-	BH_JBD			/* Has an attached ext3 journal_head */
-	  = BH_PrivateStart,
-	BH_JWrite,		/* Being written to log (@@@ DEBUGGING) */
-	BH_Freed,		/* Has been freed (truncated) */
-	BH_Revoked,		/* Has been revoked from the log */
-	BH_RevokeValid,		/* Revoked flag is valid */
-	BH_JBDDirty,		/* Is dirty but journaled */
-	BH_State,		/* Pins most journal_head state */
-	BH_JournalHead,		/* Pins bh->b_private and jh->b_bh */
-	BH_Unshadow,		/* Dummy bit, for BJ_Shadow wakeup filtering */
-	BH_Verified,		/* Metadata block has been verified ok */
-	BH_JBDPrivateStart,	/* First bit available for private use by FS */
-};
-
-BUFFER_FNS(JBD, jbd)
-BUFFER_FNS(JWrite, jwrite)
-BUFFER_FNS(JBDDirty, jbddirty)
-TAS_BUFFER_FNS(JBDDirty, jbddirty)
-BUFFER_FNS(Revoked, revoked)
-TAS_BUFFER_FNS(Revoked, revoked)
-BUFFER_FNS(RevokeValid, revokevalid)
-TAS_BUFFER_FNS(RevokeValid, revokevalid)
-BUFFER_FNS(Freed, freed)
-BUFFER_FNS(Verified, verified)
-
 static inline struct buffer_head *jh2bh(struct journal_head *jh)
 {
 	return jh->b_bh;