From: Venkatesh Srinivas <me@endeavour.zapto.org>
Date: Wed, 23 Feb 2011 15:12:20 +0000 (-0800)
Subject: kernel -- Add O_FRNONBLOCKING, to allow reads which do not block on disk accesses.
X-Git-Tag: v2.11.0~267^2~23
X-Git-Url: https://gitweb.dragonflybsd.org/dragonfly.git/commitdiff_plain/638e2d2dbe6f53c8cedaba64a0c882abf747f667

kernel -- Add O_FRNONBLOCKING, to allow reads which do not block on disk accesses.

Using extpread() or extpreadv() with O_FRNONBLOCKING on HAMMER file systems now allows
reads to return EWOULDBLOCK when the requested data is not in the buffer cache.
---

diff --git a/sys/kern/vfs_vnops.c b/sys/kern/vfs_vnops.c
index 5acce8e6bb..60f3237f3d 100644
--- a/sys/kern/vfs_vnops.c
+++ b/sys/kern/vfs_vnops.c
@@ -643,7 +643,9 @@ vn_read(struct file *fp, struct uio *uio, struct ucred *cred, int flags)
 	vp = (struct vnode *)fp->f_data;
 
 	ioflag = 0;
-	if (flags & O_FBLOCKING) {
+	if (flags & O_FRNONBLOCKING) {
+		ioflag |= (IO_NDELAY | IO_NRDELAY);
+	} else if (flags & O_FBLOCKING) {
 		/* ioflag &= ~IO_NDELAY; */
 	} else if (flags & O_FNONBLOCKING) {
 		ioflag |= IO_NDELAY;
diff --git a/sys/sys/fcntl.h b/sys/sys/fcntl.h
index 8faca3e0f8..353ab9b643 100644
--- a/sys/sys/fcntl.h
+++ b/sys/sys/fcntl.h
@@ -110,6 +110,7 @@
 #define O_FUNBUFFERED	0x01000000	/* force unbuffered (direct) I/O */
 #define O_FBUFFERED	0x02000000	/* force buffered I/O */
 #define O_MAPONREAD	0x04000000	/* memory map read buffer */
+#define O_FRNONBLOCKING	0x08000000	/* nonblocking I/O no disk wait */
 
 #if defined(_KERNEL) || defined(_KERNEL_STRUCTURES)
 #define FREVOKED	0x10000000	/* revoked by fdrevoke() */
@@ -120,7 +121,7 @@
 
 #define O_FMASK		(O_FBLOCKING|O_FNONBLOCKING|O_FAPPEND|O_FOFFSET|\
 			 O_FSYNCWRITE|O_FASYNCWRITE|O_FUNBUFFERED|O_FBUFFERED|\
-			 O_MAPONREAD)
+			 O_MAPONREAD|O_FRNONBLOCKING)
 
 #ifdef _KERNEL
 /* convert from open() flags to/from fflags; convert O_RD/WR to FREAD/FWRITE */
diff --git a/sys/sys/vnode.h b/sys/sys/vnode.h
index e9c6cedbdd..5adb977bc8 100644
--- a/sys/sys/vnode.h
+++ b/sys/sys/vnode.h
@@ -329,6 +329,7 @@ struct vnode {
 #define	IO_DIRECT	0x0100		/* attempt to bypass buffer cache */
 #define	IO_RECURSE	0x0200		/* possibly device-recursive (vn) */
 #define	IO_CORE		0x0400		/* I/O is part of core dump */
+#define	IO_NRDELAY	0x8000		/* do not block on disk reads */
 
 #define	IO_SEQMAX	0x7F		/* seq heuristic max value */
 #define	IO_SEQSHIFT	16		/* seq heuristic in upper 16 bits */
diff --git a/sys/vfs/hammer/hammer_vnops.c b/sys/vfs/hammer/hammer_vnops.c
index fa1d68bdf9..ba7f37ae3b 100644
--- a/sys/vfs/hammer/hammer_vnops.c
+++ b/sys/vfs/hammer/hammer_vnops.c
@@ -374,6 +374,9 @@ hammer_vop_read(struct vop_read_args *ap)
 		if (bp) {
 			error = 0;
 			goto skip;
+		} else {
+			if (ap->a_ioflag & (IO_NDELAY | IO_NRDELAY))
+				return (EWOULDBLOCK);
 		}
 
 		/*