linux-ext4 - [PATCH 4/4] ext4: Do not ask jbd2 to write data for delalloc buffers

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Date:	Wed, 30 Mar 2016 18:19:27 +0200
From:	Jan Kara <jack@...e.cz>
To:	Ted Tso <tytso@....edu>
Cc:	linux-ext4@...r.kernel.org, Weller.Huang@...bosch.com,
	Jan Kara <jack@...e.cz>
Subject: [PATCH 4/4] ext4: Do not ask jbd2 to write data for delalloc buffers

Currently we ask jbd2 to write all dirty allocated buffers before
committing a transaction when doing writeback of delay allocated blocks.
However this is unnecessary since we move all pages to writeback state
before dropping a transaction handle and then submit all the necessary
IO. We still need the transaction commit to wait for all the outstanding
writeback before flushing disk caches during transaction commit to avoid
data exposure issues though. Use the new jbd2 capability and ask it to
only wait for outstanding writeback during transaction commit when
writing back data in ext4_writepages().

Tested-by: "HUANG Weller (CM/ESW12-CN)" <Weller.Huang@...bosch.com>
Signed-off-by: Jan Kara <jack@...e.cz>
---
 fs/ext4/ext4.h        |  3 +++
 fs/ext4/ext4_jbd2.h   | 12 +++++++++++-
 fs/ext4/inode.c       | 10 +++++++---
 fs/ext4/move_extent.c |  2 +-
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 8647d1253903..118bd14c1c20 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -581,6 +581,9 @@ enum {
 #define EXT4_GET_BLOCKS_ZERO			0x0200
 #define EXT4_GET_BLOCKS_CREATE_ZERO		(EXT4_GET_BLOCKS_CREATE |\
 					EXT4_GET_BLOCKS_ZERO)
+	/* Caller will submit data before dropping transaction handle. This
+	 * allows jbd2 to avoid submitting data before commit. */
+#define EXT4_GET_BLOCKS_IO_SUBMIT		0x0400
 
 /*
  * The bit position of these flags must not overlap with any of the
diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index f1c940b38b30..09c1ef38cbe6 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -359,7 +359,8 @@ static inline int ext4_journal_force_commit(journal_t *journal)
 	return 0;
 }
 
-static inline int ext4_jbd2_file_inode(handle_t *handle, struct inode *inode)
+static inline int ext4_jbd2_inode_add_write(handle_t *handle,
+					    struct inode *inode)
 {
 	if (ext4_handle_valid(handle))
 		return jbd2_journal_inode_add_write(handle,
@@ -367,6 +368,15 @@ static inline int ext4_jbd2_file_inode(handle_t *handle, struct inode *inode)
 	return 0;
 }
 
+static inline int ext4_jbd2_inode_add_wait(handle_t *handle,
+					   struct inode *inode)
+{
+	if (ext4_handle_valid(handle))
+		return jbd2_journal_inode_add_wait(handle,
+						   EXT4_I(inode)->jinode);
+	return 0;
+}
+
 static inline void ext4_update_inode_fsync_trans(handle_t *handle,
 						 struct inode *inode,
 						 int datasync)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 8ffba0ec3b80..58e05feb999f 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -694,7 +694,10 @@ out_sem:
 		    !(map->m_flags & EXT4_MAP_UNWRITTEN) &&
 		    !(flags & EXT4_GET_BLOCKS_ZERO) &&
 		    ext4_should_order_data(inode)) {
-			ret = ext4_jbd2_file_inode(handle, inode);
+			if (flags & EXT4_GET_BLOCKS_IO_SUBMIT)
+				ret = ext4_jbd2_inode_add_wait(handle, inode);
+			else
+				ret = ext4_jbd2_inode_add_write(handle, inode);
 			if (ret)
 				return ret;
 		}
@@ -2320,7 +2323,8 @@ static int mpage_map_one_extent(handle_t *handle, struct mpage_da_data *mpd)
 	 * the data was copied into the page cache.
 	 */
 	get_blocks_flags = EXT4_GET_BLOCKS_CREATE |
-			   EXT4_GET_BLOCKS_METADATA_NOFAIL;
+			   EXT4_GET_BLOCKS_METADATA_NOFAIL |
+			   EXT4_GET_BLOCKS_IO_SUBMIT;
 	dioread_nolock = ext4_should_dioread_nolock(inode);
 	if (dioread_nolock)
 		get_blocks_flags |= EXT4_GET_BLOCKS_IO_CREATE_EXT;
@@ -3635,7 +3639,7 @@ static int __ext4_block_zero_page_range(handle_t *handle,
 		err = 0;
 		mark_buffer_dirty(bh);
 		if (ext4_should_order_data(inode))
-			err = ext4_jbd2_file_inode(handle, inode);
+			err = ext4_jbd2_inode_add_write(handle, inode);
 	}
 
 unlock:
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 4098acc701c3..93e9635bc65e 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -400,7 +400,7 @@ data_copy:
 
 	/* Even in case of data=writeback it is reasonable to pin
 	 * inode to transaction, to prevent unexpected data loss */
-	*err = ext4_jbd2_file_inode(handle, orig_inode);
+	*err = ext4_jbd2_inode_add_write(handle, orig_inode);
 
 unlock_pages:
 	unlock_page(pagep[0]);
-- 
2.6.2

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