[Cluster-devel] RFC: gfs2 O_SYNC fix

[Cluster-devel] RFC: gfs2 O_SYNC fix

[Christoph Hellwig]

Hi gfs2 maintainers,

can you take a look at this completely untested series?  I found some
O_SYNC handling issues during code inspection for the direct I/O
locking revamp.

[Cluster-devel] [PATCH 1/2] gfs2: move setting current->backing_dev_info

[Christoph Hellwig]

Only set current->backing_dev_info just around the buffered write calls
to prepare for the next fix.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/gfs2/file.c | 21 ++++++++++-----------
 1 file changed, 10 insertions(+), 11 deletions(-)

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 9d58295ccf7a..21d032c4b077 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -867,18 +867,15 @@ static ssize_t gfs2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	inode_lock(inode);
 	ret = generic_write_checks(iocb, from);
 	if (ret <= 0)
-		goto out;
-
-	/* We can write back this queue in page reclaim */
-	current->backing_dev_info = inode_to_bdi(inode);
+		goto out_unlock;
 
 	ret = file_remove_privs(file);
 	if (ret)
-		goto out2;
+		goto out_unlock;
 
 	ret = file_update_time(file);
 	if (ret)
-		goto out2;
+		goto out_unlock;
 
 	if (iocb->ki_flags & IOCB_DIRECT) {
 		struct address_space *mapping = file->f_mapping;
@@ -887,11 +884,13 @@ static ssize_t gfs2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 
 		written = gfs2_file_direct_write(iocb, from);
 		if (written < 0 || !iov_iter_count(from))
-			goto out2;
+			goto out_unlock;
 
+		current->backing_dev_info = inode_to_bdi(inode);
 		ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
+		current->backing_dev_info = NULL;
 		if (unlikely(ret < 0))
-			goto out2;
+			goto out_unlock;
 		buffered = ret;
 
 		/*
@@ -915,14 +914,14 @@ static ssize_t gfs2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 			 */
 		}
 	} else {
+		current->backing_dev_info = inode_to_bdi(inode);
 		ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
+		current->backing_dev_info = NULL;
 		if (likely(ret > 0))
 			iocb->ki_pos += ret;
 	}
 
-out2:
-	current->backing_dev_info = NULL;
-out:
+out_unlock:
 	inode_unlock(inode);
 	if (likely(ret > 0)) {
 		/* Handle various SYNC-type writes */
-- 
2.24.1

[Cluster-devel] [PATCH 2/2] gfs2: fix O_SYNC write handling

[Christoph Hellwig]

Don't ignore the return value from generic_write_sync for the direct to
buffered I/O callback case when written is non-zero.  Also don't bother
to call generic_write_sync for the pure direct I/O case, as iomap_dio_rw
already takes care of that.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/gfs2/file.c | 51 +++++++++++++++++++++++++-------------------------
 1 file changed, 25 insertions(+), 26 deletions(-)

diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
index 21d032c4b077..86c0e61407b6 100644
--- a/fs/gfs2/file.c
+++ b/fs/gfs2/file.c
@@ -847,7 +847,7 @@ static ssize_t gfs2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file_inode(file);
 	struct gfs2_inode *ip = GFS2_I(inode);
-	ssize_t written = 0, ret;
+	ssize_t ret = 0;
 
 	ret = gfs2_rsqa_alloc(ip);
 	if (ret)
@@ -882,52 +882,51 @@ static ssize_t gfs2_file_write_iter(struct kiocb *iocb, struct iov_iter *from)
 		loff_t pos, endbyte;
 		ssize_t buffered;
 
-		written = gfs2_file_direct_write(iocb, from);
-		if (written < 0 || !iov_iter_count(from))
+		ret = gfs2_file_direct_write(iocb, from);
+		if (ret < 0 || !iov_iter_count(from))
 			goto out_unlock;
 
 		current->backing_dev_info = inode_to_bdi(inode);
-		ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
+		buffered = iomap_file_buffered_write(iocb, from,
+						     &gfs2_iomap_ops);
 		current->backing_dev_info = NULL;
-		if (unlikely(ret < 0))
+		if (unlikely(buffered <= 0)) {
+			if (buffered < 0)
+				ret = buffered;
 			goto out_unlock;
-		buffered = ret;
+		}
 
 		/*
 		 * We need to ensure that the page cache pages are written to
 		 * disk and invalidated to preserve the expected O_DIRECT
-		 * semantics.
+		 * semantics.  If the writeback or invalidate fails only report
+		 * the direct I/O range as we don't know if the buffered pages
+		 * made it to disk.
 		 */
 		pos = iocb->ki_pos;
 		endbyte = pos + buffered - 1;
 		ret = filemap_write_and_wait_range(mapping, pos, endbyte);
-		if (!ret) {
-			iocb->ki_pos += buffered;
-			written += buffered;
-			invalidate_mapping_pages(mapping,
-						 pos >> PAGE_SHIFT,
-						 endbyte >> PAGE_SHIFT);
-		} else {
-			/*
-			 * We don't know how much we wrote, so just return
-			 * the number of bytes which were direct-written
-			 */
-		}
+		if (ret)
+			goto out_unlock;
+
+		invalidate_mapping_pages(mapping, pos >> PAGE_SHIFT,
+					 endbyte >> PAGE_SHIFT);
+		ret += buffered;
 	} else {
 		current->backing_dev_info = inode_to_bdi(inode);
 		ret = iomap_file_buffered_write(iocb, from, &gfs2_iomap_ops);
 		current->backing_dev_info = NULL;
-		if (likely(ret > 0))
-			iocb->ki_pos += ret;
+		if (unlikely(ret <= 0))
+			goto out_unlock;
 	}
 
+	iocb->ki_pos += ret;
+	inode_unlock(inode);
+	return generic_write_sync(iocb, ret);
+
 out_unlock:
 	inode_unlock(inode);
-	if (likely(ret > 0)) {
-		/* Handle various SYNC-type writes */
-		ret = generic_write_sync(iocb, ret);
-	}
-	return written ? written : ret;
+	return ret;
 }
 
 static int fallocate_chunk(struct inode *inode, loff_t offset, loff_t len,
-- 
2.24.1