[src/trunk]: src/sys/fs/puffs Make sure ioflush does not sleep in PUFFS code ...

[manu <manu%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/29bd985b9c14
branches:  trunk
changeset: 769748:29bd985b9c14
user:      manu <manu%NetBSD.org@localhost>
date:      Wed Sep 21 15:36:33 2011 +0000

description:
Make sure ioflush does not sleep in PUFFS code path, waiting for a mutex,
a memory allocation, or a response from the filesystem.

This avoids deadlocks in the following situations:
1) when memory is low: ioflush waits the fileystem, the fielsystem waits
   for memory
2) when the filesystem does not respond (e.g.: network outage ona
   distributed filesystem)

diffstat:

 sys/fs/puffs/puffs_vfsops.c |   9 +++++----
 sys/fs/puffs/puffs_vnops.c  |  28 +++++++++++++++++++++++-----
 2 files changed, 28 insertions(+), 9 deletions(-)

diffs (115 lines):

diff -r 2deb66cc29f3 -r 29bd985b9c14 sys/fs/puffs/puffs_vfsops.c
--- a/sys/fs/puffs/puffs_vfsops.c       Wed Sep 21 15:26:47 2011 +0000
+++ b/sys/fs/puffs/puffs_vfsops.c       Wed Sep 21 15:36:33 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: puffs_vfsops.c,v 1.96 2011/06/12 03:35:54 rmind Exp $  */
+/*     $NetBSD: puffs_vfsops.c,v 1.97 2011/09/21 15:36:33 manu Exp $   */
 
 /*
  * Copyright (c) 2005, 2006  Antti Kantee.  All Rights Reserved.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: puffs_vfsops.c,v 1.96 2011/06/12 03:35:54 rmind Exp $");
+__KERNEL_RCSID(0, "$NetBSD: puffs_vfsops.c,v 1.97 2011/09/21 15:36:33 manu Exp $");
 
 #include <sys/param.h>
 #include <sys/mount.h>
@@ -513,9 +513,10 @@
 {
        struct puffs_node *pn;
        struct vnode *vp, *mvp;
-       int error, rv;
+       int error, rv, fsyncwait;
 
        error = 0;
+       fsyncwait = (waitfor == MNT_WAIT) ? FSYNC_WAIT : 0;
 
        /* Allocate a marker vnode. */
        if ((mvp = vnalloc(mp)) == NULL)
@@ -574,7 +575,7 @@
                        pn->pn_stat |= PNODE_FAF;
                        mutex_exit(vp->v_interlock);
                }
-               rv = VOP_FSYNC(vp, cred, waitfor, 0, 0);
+               rv = VOP_FSYNC(vp, cred, fsyncwait, 0, 0);
                if (waitfor == MNT_LAZY) {
                        mutex_enter(vp->v_interlock);
                        pn->pn_stat &= ~PNODE_FAF;
diff -r 2deb66cc29f3 -r 29bd985b9c14 sys/fs/puffs/puffs_vnops.c
--- a/sys/fs/puffs/puffs_vnops.c        Wed Sep 21 15:26:47 2011 +0000
+++ b/sys/fs/puffs/puffs_vnops.c        Wed Sep 21 15:36:33 2011 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: puffs_vnops.c,v 1.155 2011/08/29 04:12:45 manu Exp $   */
+/*     $NetBSD: puffs_vnops.c,v 1.156 2011/09/21 15:36:33 manu Exp $   */
 
 /*
  * Copyright (c) 2005, 2006, 2007  Antti Kantee.  All Rights Reserved.
@@ -30,7 +30,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: puffs_vnops.c,v 1.155 2011/08/29 04:12:45 manu Exp $");
+__KERNEL_RCSID(0, "$NetBSD: puffs_vnops.c,v 1.156 2011/09/21 15:36:33 manu Exp $");
 
 #include <sys/param.h>
 #include <sys/buf.h>
@@ -50,6 +50,8 @@
 #include <miscfs/genfs/genfs.h>
 #include <miscfs/specfs/specdev.h>
 
+extern struct lwp *updateproc;
+
 int    puffs_vnop_lookup(void *);
 int    puffs_vnop_create(void *);
 int    puffs_vnop_access(void *);
@@ -1357,7 +1359,21 @@
        struct puffs_mount *pmp = MPTOPUFFSMP(vp->v_mount);
        int error, dofaf;
 
-       mutex_enter(&pn->pn_sizemtx);
+       /*
+        * Make sure ioflush does not get stuck in low
+        * memory conditions: it should not wait for the
+        * mutex.
+        */
+       if (curlwp == updateproc)
+               KASSERT((ap->a_flags & FSYNC_WAIT) == 0);
+
+       if (ap->a_flags & FSYNC_WAIT) {
+               mutex_enter(&pn->pn_sizemtx);
+       } else {
+               if (mutex_tryenter(&pn->pn_sizemtx) == 0)
+                       return EDEADLK;
+       }
+
        error = flushvncache(vp, ap->a_offlo, ap->a_offhi,
            (ap->a_flags & FSYNC_WAIT) == FSYNC_WAIT);
        if (error)
@@ -2211,12 +2227,13 @@
        struct buf *bp;
        size_t argsize;
        size_t tomove, moved;
-       int error, dofaf, dobiodone;
+       int error, dofaf, cansleep, dobiodone;
 
        pmp = MPTOPUFFSMP(vp->v_mount);
        bp = ap->a_bp;
        error = 0;
        dofaf = 0;
+       cansleep = 0;
        pn = VPTOPP(vp);
        park_rw = NULL; /* explicit */
        dobiodone = 1;
@@ -2264,8 +2281,9 @@
        /* allocate transport structure */
        tomove = PUFFS_TOMOVE(bp->b_bcount, pmp);
        argsize = sizeof(struct puffs_vnmsg_rw);
+       cansleep = (dofaf || (curlwp == updateproc)) ? 0 : 1; 
        error = puffs_msgmem_alloc(argsize + tomove, &park_rw,
-           (void *)&rw_msg, dofaf ? 0 : 1);
+           (void *)&rw_msg, cansleep);
        if (error)
                goto out;
        RWARGS(rw_msg, 0, tomove, bp->b_blkno << DEV_BSHIFT, FSCRED);