Hi,
If a file is opened with O_SYNC|O_DIRECT, the drive cache does not get
flushed after the write completion. Instead, it's flushed *before* the
I/O is sent to the disk (in __generic_file_aio_write). This patch
attempts to fix that problem by marking an I/O as requiring a cache
flush in endio processing. I'll send a follow-on patch to the
generic write code to get rid of the bogus generic_write_sync call
when EIOCBQUEUED is returned.
Signed-off-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
---
fs/ext4/ext4.h | 4 +++
fs/ext4/inode.c | 11 ++++++-
fs/ext4/page-io.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++-----
fs/ext4/super.c | 11 ++++++++
4 files changed, 90 insertions(+), 9 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 3ce6a0c..e1478be 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -186,6 +186,7 @@ struct mpage_da_data {
#define EXT4_IO_END_QUEUED 0x0004
#define EXT4_IO_END_DIRECT 0x0008
#define EXT4_IO_END_IN_FSYNC 0x0010
+#define EXT4_IO_END_NEEDS_SYNC 0x0020
struct ext4_io_page {
struct page *p_page;
@@ -1248,6 +1249,9 @@ struct ext4_sb_info {
/* workqueue for dio unwritten */
struct workqueue_struct *dio_unwritten_wq;
+ /* workqueue for aio+dio+o_sync disk cache flushing */
+ struct workqueue_struct *aio_dio_flush_wq;
+
/* timer for periodic error stats printing */
struct timer_list s_err_report;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f6dc02b..13cdb4c 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2769,8 +2769,12 @@ static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
iocb->private = NULL;
+ /* AIO+DIO+O_SYNC I/Os need a cache flush after completion */
+ if (is_async && (IS_SYNC(inode) || (iocb->ki_filp->f_flags & O_DSYNC)))
+ io_end->flag |= EXT4_IO_END_NEEDS_SYNC;
+
/* if not aio dio with unwritten extents, just free io and return */
- if (!(io_end->flag & EXT4_IO_END_UNWRITTEN)) {
+ if (!(io_end->flag & (EXT4_IO_END_UNWRITTEN|EXT4_IO_END_NEEDS_SYNC))) {
ext4_free_io_end(io_end);
out:
if (is_async)
@@ -2785,7 +2789,10 @@ out:
io_end->iocb = iocb;
io_end->result = ret;
}
- wq = EXT4_SB(io_end->inode->i_sb)->dio_unwritten_wq;
+ if (io_end->flag & EXT4_IO_END_UNWRITTEN)
+ wq = EXT4_SB(io_end->inode->i_sb)->dio_unwritten_wq;
+ else
+ wq = EXT4_SB(io_end->inode->i_sb)->aio_dio_flush_wq;
/* Add the io_end to per-inode completed aio dio list*/
ei = EXT4_I(io_end->inode);
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index dcdeef1..baa1b84 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -82,6 +82,50 @@ void ext4_free_io_end(ext4_io_end_t *io)
}
/*
+ * This function is called in the completion path for AIO O_SYNC|O_DIRECT
+ * writes, and also in the fsync path. The purpose is to ensure that the
+ * disk caches for the journal and data devices are flushed.
+ */
+static int ext4_end_io_do_flush(ext4_io_end_t *io)
+{
+ struct inode *inode = io->inode;
+ tid_t commit_tid;
+ bool needs_barrier = false;
+ journal_t *journal = EXT4_SB(inode->i_sb)->s_journal;
+ int barriers_enabled = test_opt(inode->i_sb, BARRIER);
+ int ret = 0;
+
+ if (!barriers_enabled)
+ return 0;
+
+ /*
+ * If we are running in nojournal mode, just flush the disk
+ * cache and return.
+ */
+ if (!journal)
+ return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_NOIO, NULL);
+
+ if (ext4_should_journal_data(inode)) {
+ ret = ext4_force_commit(inode->i_sb);
+ goto out;
+ }
+
+ commit_tid = io->iocb->ki_filp->f_flags & __O_SYNC ?
+ EXT4_I(inode)->i_sync_tid : EXT4_I(inode)->i_datasync_tid;
+ if (!jbd2_trans_will_send_data_barrier(journal, commit_tid))
+ needs_barrier = true;
+
+ jbd2_log_start_commit(journal, commit_tid);
+ ret = jbd2_log_wait_commit(journal, commit_tid);
+
+ if (!ret && needs_barrier)
+ ret = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_NOIO, NULL);
+
+out:
+ return ret;
+}
+
+/*
* check a range of space and convert unwritten extents to written.
*
* Called with inode->i_mutex; we depend on this when we manipulate
@@ -98,15 +142,30 @@ int ext4_end_io_nolock(ext4_io_end_t *io)
"list->prev 0x%p\n",
io, inode->i_ino, io->list.next, io->list.prev);
- ret = ext4_convert_unwritten_extents(inode, offset, size);
- if (ret < 0) {
- ext4_msg(inode->i_sb, KERN_EMERG,
- "failed to convert unwritten extents to written "
- "extents -- potential data loss! "
- "(inode %lu, offset %llu, size %zd, error %d)",
- inode->i_ino, offset, size, ret);
+ if (io->flag & EXT4_IO_END_UNWRITTEN) {
+
+ ret = ext4_convert_unwritten_extents(inode, offset, size);
+ if (ret < 0) {
+ ext4_msg(inode->i_sb, KERN_EMERG,
+ "failed to convert unwritten extents to "
+ "written extents -- potential data loss! "
+ "(inode %lu, offset %llu, size %zd, error %d)",
+ inode->i_ino, offset, size, ret);
+ goto endio;
+ }
}
+ /*
+ * This function has two callers. The first is the end_io_work
+ * routine just below, which is an asynchronous completion context.
+ * The second is in the fsync path. For the latter path, we can't
+ * return from here until the job is done. Hence,
+ * ext4_end_io_do_flush is blocking.
+ */
+ if (io->flag & EXT4_IO_END_NEEDS_SYNC)
+ ret = ext4_end_io_do_flush(io);
+
+endio:
if (io->iocb)
aio_complete(io->iocb, io->result, 0);
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 502c61f..a24938e 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -805,6 +805,7 @@ static void ext4_put_super(struct super_block *sb)
dquot_disable(sb, -1, DQUOT_USAGE_ENABLED | DQUOT_LIMITS_ENABLED);
flush_workqueue(sbi->dio_unwritten_wq);
+ destroy_workqueue(sbi->aio_dio_flush_wq);
destroy_workqueue(sbi->dio_unwritten_wq);
lock_super(sb);
@@ -3718,6 +3719,13 @@ no_journal:
goto failed_mount_wq;
}
+ EXT4_SB(sb)->aio_dio_flush_wq =
+ alloc_workqueue("ext4-aio-dio-flush", WQ_MEM_RECLAIM | WQ_UNBOUND, 1);
+ if (!EXT4_SB(sb)->aio_dio_flush_wq) {
+ printk(KERN_ERR "EXT4-fs: failed to create flush workqueue\n");
+ goto failed_flush_wq;
+ }
+
/*
* The jbd2_journal_load will have done any necessary log recovery,
* so we can safely mount the rest of the filesystem now.
@@ -3840,6 +3848,8 @@ failed_mount4a:
sb->s_root = NULL;
failed_mount4:
ext4_msg(sb, KERN_ERR, "mount failed");
+ destroy_workqueue(EXT4_SB(sb)->aio_dio_flush_wq);
+failed_flush_wq:
destroy_workqueue(EXT4_SB(sb)->dio_unwritten_wq);
failed_mount_wq:
if (sbi->s_journal) {
@@ -4303,6 +4313,7 @@ static int ext4_sync_fs(struct super_block *sb, int wait)
trace_ext4_sync_fs(sb, wait);
flush_workqueue(sbi->dio_unwritten_wq);
+ flush_workqueue(sbi->aio_dio_flush_wq);
if (jbd2_journal_start_commit(sbi->s_journal, &target)) {
if (wait)
jbd2_log_wait_commit(sbi->s_journal, target);
--
1.7.1
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