[XFS] DMAPI deadlock prevention when interacting with the IO path.

SGI Modid: xfs-linux:xfs-kern:167547a

fs/xfs/linux/xfs_lrw.c

@@ -730,7 +730,7 @@ xfs_write(
 	if ((DM_EVENT_ENABLED(vp->v_vfsp, xip, DM_EVENT_WRITE) &&
 	    !(ioflags & IO_INVIS) && !eventsent)) {
 		loff_t		savedsize = *offset;
-		int dmflags = FILP_DELAY_FLAG(file) | DM_SEM_FLAG(ioflags);
+		int dmflags = FILP_DELAY_FLAG(file) | DM_SEM_FLAG_RD(ioflags);
 
 		xfs_iunlock(xip, XFS_ILOCK_EXCL);
 		error = XFS_SEND_DATA(xip->i_mount, DM_EVENT_WRITE, vp,

fs/xfs/xfs_dmapi.h

@@ -169,19 +169,22 @@ typedef enum {
 #if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,0)
 #if LINUX_VERSION_CODE > KERNEL_VERSION(2,4,21)
 /* i_alloc_sem was added in 2.4.22-pre1 */
-#define DM_FLAGS_IALLOCSEM	0x010	/* thread holds i_alloc_sem */
+#define DM_FLAGS_IALLOCSEM_RD	0x010	/* thread holds i_alloc_sem rd */
+#define DM_FLAGS_IALLOCSEM_WR	0x020	/* thread holds i_alloc_sem wr */
 #endif
 #endif
 
 /*
  *	Based on IO_ISDIRECT, decide which i_ flag is set.
  */
-#ifdef DM_FLAGS_IALLOCSEM
-#define DM_SEM_FLAG(ioflags) (((ioflags) & IO_ISDIRECT) ? \
-			      DM_FLAGS_IALLOCSEM : DM_FLAGS_ISEM)
+#ifdef DM_FLAGS_IALLOCSEM_RD
+#define DM_SEM_FLAG_RD(ioflags) (((ioflags) & IO_ISDIRECT) ? \
+			      DM_FLAGS_IALLOCSEM_RD : DM_FLAGS_ISEM)
+#define DM_SEM_FLAG_WR	(DM_FLAGS_IALLOCSEM_WR | DM_FLAGS_ISEM)
 #else
-#define DM_SEM_FLAG(ioflags) (((ioflags) & IO_ISDIRECT) ? \
+#define DM_SEM_FLAG_RD(ioflags) (((ioflags) & IO_ISDIRECT) ? \
 			      0 : DM_FLAGS_ISEM)
+#define DM_SEM_FLAG_WR	(DM_FLAGS_ISEM)
 #endif
 
 /*

fs/xfs/xfs_vnodeops.c

@@ -413,8 +413,9 @@ xfs_setattr(
 	} else {
 		if (DM_EVENT_ENABLED (vp->v_vfsp, ip, DM_EVENT_TRUNCATE) &&
 		    !(flags & ATTR_DMI)) {
+			int dmflags = AT_DELAY_FLAG(flags) | DM_SEM_FLAG_WR;
 			code = XFS_SEND_DATA(mp, DM_EVENT_TRUNCATE, vp,
-				vap->va_size, 0, AT_DELAY_FLAG(flags), NULL);
+				vap->va_size, 0, dmflags, NULL);
 			if (code) {
 				lock_flags = 0;
 				goto error_return;