[lustre-devel] [PATCH 13/39] lustre: llite: allow DIO with unaligned IO count

[James Simmons]

From: Wang Shilong <wshilong at ddn.com>

DIO only require user buffer page aligned and
IO offset page aligned, it is ok that io count is
not page aligned, remove this unnecessary limit
so that we could use DIO with file not aligned
with PAGE SIZE.

WC-bug-id: https://jira.whamcloud.com/browse/LU-14043
Lustre-commit: 45c46c6effd827 ("LU-14043 llite: allow DIO with unaligned IO count")
Signed-off-by: Wang Shilong <wshilong at ddn.com>
Reviewed-on: https://review.whamcloud.com/40392
Reviewed-by: John L. Hammond <jhammond at whamcloud.com>
Reviewed-by: Andreas Dilger <adilger at whamcloud.com>
Reviewed-by: Alex Zhuravlev <bzzz at whamcloud.com>
Reviewed-by: Oleg Drokin <green at whamcloud.com>
Signed-off-by: James Simmons <jsimmons at infradead.org>
---
 fs/lustre/llite/rw26.c | 33 +++++++++++++++++++++++++++++++--
 1 file changed, 31 insertions(+), 2 deletions(-)

diff --git a/fs/lustre/llite/rw26.c b/fs/lustre/llite/rw26.c
index 605a326..28c0a75 100644
--- a/fs/lustre/llite/rw26.c
+++ b/fs/lustre/llite/rw26.c
@@ -181,6 +181,35 @@ static ssize_t ll_get_user_pages(int rw, struct iov_iter *iter,
 	return result;
 }
 
+/*
+ * Lustre could relax a bit for alignment, io count is not
+ * necessary page alignment.
+ */
+static unsigned long ll_iov_iter_alignment(struct iov_iter *i)
+{
+	size_t orig_size = i->count;
+	size_t count = orig_size & ~PAGE_MASK;
+	unsigned long res;
+
+	if (!count)
+		return iov_iter_alignment(i);
+
+	if (orig_size > PAGE_SIZE) {
+		iov_iter_truncate(i, orig_size - count);
+		res = iov_iter_alignment(i);
+		iov_iter_reexpand(i, orig_size);
+
+		return res;
+	}
+
+	res = iov_iter_alignment(i);
+	/* start address is page aligned */
+	if ((res & ~PAGE_MASK) == orig_size)
+		return PAGE_SIZE;
+
+	return res;
+}
+
 /* direct IO pages */
 struct ll_dio_pages {
 	struct cl_dio_aio	*ldp_aio;
@@ -325,7 +354,7 @@ static ssize_t ll_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 		return 0;
 
 	/* FIXME: io smaller than PAGE_SIZE is broken on ia64 ??? */
-	if ((file_offset & ~PAGE_MASK) || (count & ~PAGE_MASK))
+	if (file_offset & ~PAGE_MASK)
 		return -EINVAL;
 
 	CDEBUG(D_VFSTRACE,
@@ -335,7 +364,7 @@ static ssize_t ll_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 	       MAX_DIO_SIZE >> PAGE_SHIFT);
 
 	/* Check that all user buffers are aligned as well */
-	if (iov_iter_alignment(iter) & ~PAGE_MASK)
+	if (ll_iov_iter_alignment(iter) & ~PAGE_MASK)
 		return -EINVAL;
 
 	lcc = ll_cl_find(file);
-- 
1.8.3.1