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Only sleep interruptible while waiting for suspension end when

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filesystem specified VFCF_SBDRY flag, i.e. for NFS.

There are two issues with the sleeps.  First, applications may get
unexpected EINTR from the disk i/o syscalls.  Second, interruptible
sleep allows the stop of the process, and since mount point is
referenced while thread sleeps, unmount cannot free mount point
structure' memory, blocking unmount indefinitely.

Even for NFS, it is probably only reasonable to enable PCATCH for intr
mounts, but this information is currently not available at VFS level.

Reported and tested by:	pho (previous version)
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
This commit is contained in:
Konstantin Belousov 2014-12-13 16:07:01 +00:00
parent ea117d1735
commit 0061ddb3ed
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=275744
1 changed files with 8 additions and 5 deletions
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13
sys/kern/vfs_vnops.c
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@ -1600,7 +1600,7 @@ vn_suspendable(struct vnode *vp, struct mount **mpp)
static int
vn_start_write_locked(struct mount *mp, int flags)
{
int error;
int error, mflags;
mtx_assert(MNT_MTX(mp), MA_OWNED);
error = 0;
@ -1610,13 +1610,15 @@ vn_start_write_locked(struct mount *mp, int flags)
*/
if ((curthread->td_pflags & TDP_IGNSUSP) == 0 ||
mp->mnt_susp_owner != curthread) {
mflags = ((mp->mnt_vfc->vfc_flags & VFCF_SBDRY) != 0 ?
(flags & PCATCH) : 0) | (PUSER - 1);
while ((mp->mnt_kern_flag & MNTK_SUSPEND) != 0) {
if (flags & V_NOWAIT) {
error = EWOULDBLOCK;
goto unlock;
}
error = msleep(&mp->mnt_flag, MNT_MTX(mp),
(PUSER - 1) | (flags & PCATCH), "suspfs", 0);
error = msleep(&mp->mnt_flag, MNT_MTX(mp), mflags,
"suspfs", 0);
if (error)
goto unlock;
}
@ -1732,8 +1734,9 @@ vn_start_secondary_write(vp, mpp, flags)
/*
* Wait for the suspension to finish.
*/
error = msleep(&mp->mnt_flag, MNT_MTX(mp),
(PUSER - 1) | (flags & PCATCH) | PDROP, "suspfs", 0);
error = msleep(&mp->mnt_flag, MNT_MTX(mp), (PUSER - 1) | PDROP |
((mp->mnt_vfc->vfc_flags & VFCF_SBDRY) != 0 ? (flags & PCATCH) : 0),
"suspfs", 0);
vfs_rel(mp);
if (error == 0)
goto retry;