[v7,5/5] xfs: add RWF_NONBLOCK support

Commit Message

Milosz Tanski March 16, 2015, 6:27 p.m. UTC

From: Christoph Hellwig <[e-mail]>

Add support for non-blocking reads.  The guts are handled by the generic
code, the only addition is a non-blocking variant of xfs_rw_ilock.

Signed-off-by: Christoph Hellwig <[e-mail]>
---
 fs/xfs/xfs_file.c | 32 +++++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

Comments

Dave Chinner March 16, 2015, 10:04 p.m. UTC | #1

On Mon, Mar 16, 2015 at 02:27:15PM -0400, Milosz Tanski wrote:
> From: Christoph Hellwig <[e-mail]>
> 
> Add support for non-blocking reads.  The guts are handled by the generic
> code, the only addition is a non-blocking variant of xfs_rw_ilock.
> 
> Signed-off-by: Christoph Hellwig <[e-mail]>

Change looks good, but I haven't tested it, so:

Acked-by: Dave Chinner <[e-mail]>

Patch

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index a38ddc1..69333a7 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -59,6 +59,25 @@  xfs_rw_ilock(
 	xfs_ilock(ip, type);
 }
 
+static inline bool
+xfs_rw_ilock_nowait(
+	struct xfs_inode	*ip,
+	int			type)
+{
+	if (type & XFS_IOLOCK_EXCL) {
+		if (!mutex_trylock(&VFS_I(ip)->i_mutex))
+			return false;
+		if (!xfs_ilock_nowait(ip, type)) {
+			mutex_unlock(&VFS_I(ip)->i_mutex);
+			return false;
+		}
+	} else {
+		if (!xfs_ilock_nowait(ip, type))
+			return false;
+	}
+	return true;
+}
+
 static inline void
 xfs_rw_iunlock(
 	struct xfs_inode	*ip,
@@ -280,10 +299,6 @@  xfs_file_read_iter(
 
 	XFS_STATS_INC(xs_read_calls);
 
-	/* XXX: need a non-blocking iolock helper, shouldn't be too hard */
-	if (iocb->ki_rwflags & RWF_NONBLOCK)
-		return -EAGAIN;
-
 	if (unlikely(file->f_flags & O_DIRECT))
 		ioflags |= XFS_IO_ISDIRECT;
 	if (file->f_mode & FMODE_NOCMTIME)
@@ -321,7 +336,14 @@  xfs_file_read_iter(
 	 * This allows the normal direct IO case of no page cache pages to
 	 * proceeed concurrently without serialisation.
 	 */
-	xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
+	if (iocb->ki_rwflags & RWF_NONBLOCK) {
+		if (ioflags & XFS_IO_ISDIRECT)
+			return -EAGAIN;
+		if (!xfs_rw_ilock_nowait(ip, XFS_IOLOCK_SHARED))
+			return -EAGAIN;
+	} else {
+		xfs_rw_ilock(ip, XFS_IOLOCK_SHARED);
+	}
 	if ((ioflags & XFS_IO_ISDIRECT) && inode->i_mapping->nrpages) {
 		xfs_rw_iunlock(ip, XFS_IOLOCK_SHARED);
 		xfs_rw_ilock(ip, XFS_IOLOCK_EXCL);