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Fix getfsstat(2) with MNT_WAIT to not skip filesystems that are in the

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process of being unmounted.  Previously it would skip them, even if the
unmount eventually failed eg due to the filesystem being busy.

This behaviour broke autounmountd(8) - if you tried to manually unmount
a mounted filesystem, using 'automount -u', and the autounmountd attempted
to refresh the filesystem list in that very moment, it would conclude that
the filesystem got unmounted and not try to unmount it afterwards.

Reviewed by:	kib@
Tested by:	pho@
MFC after:	1 month
Differential Revision:	https://reviews.freebsd.org/D8030
This commit is contained in:
trasz 2016-11-02 09:43:19 +00:00
parent 8381908c9b
commit 2c0de38912
1 changed files with 27 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

36
sys/kern/vfs_syscalls.c
View File

@ -446,16 +446,19 @@ kern_getfsstat(struct thread *td, struct statfs **buf, size_t bufsize,
size_t *countp, enum uio_seg bufseg, int flags) size_t *countp, enum uio_seg bufseg, int flags)
{ {
struct mount *mp, *nmp; struct mount *mp, *nmp;
struct statfs *sfsp, *sp, sb; struct statfs *sfsp, *sp, sb, *tofree;
size_t count, maxcount; size_t count, maxcount;
int error; int error;
restart:
maxcount = bufsize / sizeof(struct statfs); maxcount = bufsize / sizeof(struct statfs);
if (bufsize == 0) if (bufsize == 0) {
sfsp = NULL; sfsp = NULL;
else if (bufseg == UIO_USERSPACE) tofree = NULL;
} else if (bufseg == UIO_USERSPACE) {
sfsp = *buf; sfsp = *buf;
else /* if (bufseg == UIO_SYSSPACE) */ { tofree = NULL;
} else /* if (bufseg == UIO_SYSSPACE) */ {
count = 0; count = 0;
mtx_lock(&mountlist_mtx); mtx_lock(&mountlist_mtx);
TAILQ_FOREACH(mp, &mountlist, mnt_list) { TAILQ_FOREACH(mp, &mountlist, mnt_list) {
@ -464,8 +467,8 @@ kern_getfsstat(struct thread *td, struct statfs **buf, size_t bufsize,
mtx_unlock(&mountlist_mtx); mtx_unlock(&mountlist_mtx);
if (maxcount > count) if (maxcount > count)
maxcount = count; maxcount = count;
sfsp = *buf = malloc(maxcount * sizeof(struct statfs), M_TEMP, tofree = sfsp = *buf = malloc(maxcount * sizeof(struct statfs),
M_WAITOK); M_TEMP, M_WAITOK);
} }
count = 0; count = 0;
mtx_lock(&mountlist_mtx); mtx_lock(&mountlist_mtx);
@ -480,9 +483,24 @@ kern_getfsstat(struct thread *td, struct statfs **buf, size_t bufsize,
continue; continue;
} }
#endif #endif
if (vfs_busy(mp, MBF_NOWAIT | MBF_MNTLSTLOCK)) { if (flags == MNT_WAIT) {
nmp = TAILQ_NEXT(mp, mnt_list); if (vfs_busy(mp, MBF_MNTLSTLOCK) != 0) {
continue; /*
* If vfs_busy() failed, and MBF_NOWAIT
* wasn't passed, then the mp is gone.
* Furthermore, because of MBF_MNTLSTLOCK,
* the mountlist_mtx was dropped. We have
* no other choice than to start over.
*/
mtx_unlock(&mountlist_mtx);
free(tofree, M_TEMP);
goto restart;
}
} else {
if (vfs_busy(mp, MBF_NOWAIT | MBF_MNTLSTLOCK) != 0) {
nmp = TAILQ_NEXT(mp, mnt_list);
continue;
}
} }
if (sfsp && count < maxcount) { if (sfsp && count < maxcount) {
sp = &mp->mnt_stat; sp = &mp->mnt_stat;