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Subject[PATCH v6 5/7] xfs: add RWF_NONBLOCK support
Date
From: Christoph Hellwig <hch@lst.de>

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 <hch@lst.de>
---
fs/xfs/xfs_file.c | 32 +++++++++++++++++++++++++++-----
1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index b1f6334..0655915 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -61,6 +61,25 @@ 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,
@@ -246,10 +265,6 @@ 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)
@@ -287,7 +302,14 @@ 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);
--
1.9.1


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