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Date: Fri, 27 Jan 2012 16:15:48 -0500
From: Jeff Moyer <jmoyer@...hat.com>
To: linux-ext4@...r.kernel.org, xfs@....sgi.com,
linux-fsdevel@...r.kernel.org
Cc: Jeff Moyer <jmoyer@...hat.com>
Subject: [PATCH 2/3] ext4: honor the O_SYNC flag for aysnchronous direct I/O requests
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@...hat.com>
---
fs/ext4/ext4.h | 4 ++++
fs/ext4/inode.c | 11 +++++++++--
fs/ext4/page-io.c | 39 ++++++++++++++++++++++++++++++++-------
fs/ext4/super.c | 11 +++++++++++
4 files changed, 56 insertions(+), 9 deletions(-)
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 2d55d7c..4377ed3 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -185,6 +185,7 @@ struct mpage_da_data {
#define EXT4_IO_END_ERROR 0x0002
#define EXT4_IO_END_QUEUED 0x0004
#define EXT4_IO_END_DIRECT 0x0008
+#define EXT4_IO_END_NEEDS_SYNC 0x0010
struct ext4_io_page {
struct page *p_page;
@@ -1247,6 +1248,9 @@ 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 9e1b8eb..d07cd40 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -98,15 +98,40 @@ 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. This 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, we issue a
+ * blocking blkdev_issue_flush call.
+ */
+ if (io->flag & EXT4_IO_END_NEEDS_SYNC) {
+ /*
+ * Ideally, we'd like to know if the force_commit routine
+ * actually did send something to disk. If it didn't,
+ * then we need to issue the cache flush by hand. For now,
+ * play it safe and do both.
+ */
+ ret = ext4_force_commit(inode->i_sb);
+ if (ret)
+ goto endio;
+ ret = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_NOIO, NULL);
}
+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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