[PATCH 4/4] fs/ext4,jbd2: add support for passing write-hint with journal.

Kanchan Joshi
2019-01-09T15:31:01Z

For NAND based SSDs, mixing of data with different life-time reduces
efficiency of internal garbage-collection. During FS operations, series
of journal updates will follow/precede series of data/meta updates, causing
intermixing inside SSD. By passing a write-hint with journal, its write
can be isolated from other data/meta writes, leading to endurance/performance
benefit on SSD.

This patch introduces "j_writehint" member in JBD2 journal, using which
Ext4 specifies write-hint (as SHORT) for journal.

Signed-off-by: Kanchan Joshi <joshi.k at samsung.com>
---
fs/ext4/super.c | 2 ++
fs/jbd2/commit.c | 11 +++++++----
fs/jbd2/journal.c | 3 ++-
fs/jbd2/revoke.c | 3 ++-
include/linux/jbd2.h | 8 ++++++++
5 files changed, 21 insertions(+), 6 deletions(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index d6c142d..3af4049 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4289,6 +4289,8 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)

set_task_ioprio(sbi->s_journal->j_task, journal_ioprio);

+ sbi->s_journal->j_writehint = KERN_WRITE_LIFE_SHORT;
+
sbi->s_journal->j_commit_callback = ext4_journal_commit_callback;

no_journal:
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
index 2eb55c3..6da4c28 100644
--- a/fs/jbd2/commit.c
+++ b/fs/jbd2/commit.c
@@ -153,10 +153,12 @@ static int journal_submit_commit_record(journal_t *journal,

if (journal->j_flags & JBD2_BARRIER &&
!jbd2_has_feature_async_commit(journal))
- ret = submit_bh(REQ_OP_WRITE,
- REQ_SYNC | REQ_PREFLUSH | REQ_FUA, bh);
+ ret = submit_bh_write_hint(REQ_OP_WRITE,
+ REQ_SYNC | REQ_PREFLUSH | REQ_FUA, bh,
+ journal->j_writehint);
else
- ret = submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
+ ret = submit_bh_write_hint(REQ_OP_WRITE, REQ_SYNC, bh,
+ journal->j_writehint);

*cbh = bh;
return ret;
@@ -711,7 +713,8 @@ void jbd2_journal_commit_transaction(journal_t *journal)
clear_buffer_dirty(bh);
set_buffer_uptodate(bh);
bh->b_end_io = journal_end_buffer_io_sync;
- submit_bh(REQ_OP_WRITE, REQ_SYNC, bh);
+ submit_bh_write_hint(REQ_OP_WRITE, REQ_SYNC,
+ bh, journal->j_writehint);
}
cond_resched();
stats.run.rs_blocks_logged += bufs;
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 8ef6b6d..804dc2c 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1384,7 +1384,8 @@ static int jbd2_write_superblock(journal_t *journal, int write_flags)
jbd2_superblock_csum_set(journal, sb);
get_bh(bh);
bh->b_end_io = end_buffer_write_sync;
- ret = submit_bh(REQ_OP_WRITE, write_flags, bh);
+ ret = submit_bh_write_hint(REQ_OP_WRITE, write_flags, bh,
+ journal->j_writehint);
wait_on_buffer(bh);
if (buffer_write_io_error(bh)) {
clear_buffer_write_io_error(bh);
diff --git a/fs/jbd2/revoke.c b/fs/jbd2/revoke.c
index a1143e5..376b1d8 100644
--- a/fs/jbd2/revoke.c
+++ b/fs/jbd2/revoke.c
@@ -642,7 +642,8 @@ static void flush_descriptor(journal_t *journal,
set_buffer_jwrite(descriptor);
BUFFER_TRACE(descriptor, "write");
set_buffer_dirty(descriptor);
- write_dirty_buffer(descriptor, REQ_SYNC);
+ write_dirty_buffer_with_hint(descriptor, REQ_SYNC,
+ journal->j_writehint);
}
#endif

diff --git a/include/linux/jbd2.h b/include/linux/jbd2.h
index 0f919d5..918f21e 100644
--- a/include/linux/jbd2.h
+++ b/include/linux/jbd2.h
@@ -1139,6 +1139,14 @@ struct journal_s
*/
__u32 j_csum_seed;

+ /**
+ * @j_writehint:
+ *
+ * write-hint for journal (set by FS).
+ */
+ enum rw_hint j_writehint;
+
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
/**
* @j_trans_commit_map:
--
2.7.4