[PATCH 6/7] nonblocking aio: xfs

[Goldwyn Rodrigues <rgoldwyn@suse.de>]

From: Goldwyn Rodrigues <rgoldwyn@suse.com>

If IOCB_NONBLOCKING is set:
	+ Check if writing beyond end of file, if yes return EAGAIN
	- check if writing to a hole which does not have allocated
	  file blocks.
	- Check if i_rwsem is immediately lockable in xfs_rw_ilock()

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 fs/xfs/xfs_file.c  | 36 ++++++++++++++++++++++++++++++++----
 fs/xfs/xfs_inode.h |  2 ++
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 9a5d64b..42f055f 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -51,14 +51,20 @@ static const struct vm_operations_struct xfs_file_vm_ops;
  * Locking primitives for read and write IO paths to ensure we consistently use
  * and order the inode->i_mutex, ip->i_lock and ip->i_iolock.
  */
-static inline void
+static inline int
 xfs_rw_ilock(
 	struct xfs_inode	*ip,
 	int			type)
 {
-	if (type & XFS_IOLOCK_EXCL)
-		inode_lock(VFS_I(ip));
+	if (type & XFS_IOLOCK_EXCL) {
+		if ((type & XFS_IOLOCK_NONBLOCKING) &&
+				!inode_trylock(VFS_I(ip)))
+			return -EAGAIN;
+		else
+			inode_lock(VFS_I(ip));
+	}
 	xfs_ilock(ip, type);
+	return 0;
 }
 
 static inline void
@@ -418,6 +424,24 @@ xfs_file_aio_write_checks(
 	if (error <= 0)
 		return error;
 
+	if (iocb->ki_flags & IOCB_NONBLOCKING) {
+		struct xfs_bmbt_irec	imap;
+		xfs_fileoff_t           offset_fsb, end_fsb;
+		int			nimaps = 1, ret = 0;
+		end_fsb = XFS_B_TO_FSB(ip->i_mount, iocb->ki_pos + count);
+		if (XFS_B_TO_FSB(ip->i_mount, i_size_read(inode)) < end_fsb)
+			return -EAGAIN;
+		/* Check if it is an unallocated hole */
+		offset_fsb = XFS_B_TO_FSBT(ip->i_mount, iocb->ki_pos);
+
+		ret = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb, &imap,
+				&nimaps, 0);
+		if (ret)
+			return ret;
+		if (!nimaps || imap.br_startblock == HOLESTARTBLOCK)
+			return -EAGAIN;
+	}
+
 	error = xfs_break_layouts(inode, iolock, true);
 	if (error)
 		return error;
@@ -555,11 +579,15 @@ xfs_file_dio_aio_write(
 	    ((iocb->ki_pos + count) & mp->m_blockmask)) {
 		unaligned_io = 1;
 		iolock = XFS_IOLOCK_EXCL;
+		if (iocb->ki_flags & IOCB_NONBLOCKING)
+			iolock |= XFS_IOLOCK_NONBLOCKING;
 	} else {
 		iolock = XFS_IOLOCK_SHARED;
 	}
 
-	xfs_rw_ilock(ip, iolock);
+	ret = xfs_rw_ilock(ip, iolock);
+	if (ret)
+		return ret;
 
 	ret = xfs_file_aio_write_checks(iocb, from, &iolock);
 	if (ret)
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 71e8a81..1a2d5eb 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -283,6 +283,7 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
 #define	XFS_ILOCK_SHARED	(1<<3)
 #define	XFS_MMAPLOCK_EXCL	(1<<4)
 #define	XFS_MMAPLOCK_SHARED	(1<<5)
+#define	XFS_IOLOCK_NONBLOCKING	(1<<6)
 
 #define XFS_LOCK_MASK		(XFS_IOLOCK_EXCL | XFS_IOLOCK_SHARED \
 				| XFS_ILOCK_EXCL | XFS_ILOCK_SHARED \
@@ -291,6 +292,7 @@ static inline void xfs_ifunlock(struct xfs_inode *ip)
 #define XFS_LOCK_FLAGS \
 	{ XFS_IOLOCK_EXCL,	"IOLOCK_EXCL" }, \
 	{ XFS_IOLOCK_SHARED,	"IOLOCK_SHARED" }, \
+	{ XFS_IOLOCK_NONBLOCKING,	"IOLOCK_NONBLOCKING" }, \
 	{ XFS_ILOCK_EXCL,	"ILOCK_EXCL" }, \
 	{ XFS_ILOCK_SHARED,	"ILOCK_SHARED" }, \
 	{ XFS_MMAPLOCK_EXCL,	"MMAPLOCK_EXCL" }, \
-- 
2.10.2