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author | Ian Kent <raven@themaw.net> | 2008-07-23 21:30:27 -0700 |
---|---|---|
committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-07-24 10:47:32 -0700 |
commit | 6e60a9ab5f5d314735467752f623072f5b75157a (patch) | |
tree | 1a42df40e6fad52bd6be74970af8eb56870fe6ba /fs/autofs4/expire.c | |
parent | 97e7449a7ad883bf9f516fc970778d75999c7843 (diff) | |
download | linux-6e60a9ab5f5d314735467752f623072f5b75157a.tar.gz linux-6e60a9ab5f5d314735467752f623072f5b75157a.tar.bz2 linux-6e60a9ab5f5d314735467752f623072f5b75157a.zip |
autofs4: fix direct mount pending expire race
For direct and offset type mounts that are covered by another mount we
cannot check the AUTOFS_INF_EXPIRING flag during a path walk which leads
to lookups walking into an expiring mount while it is being expired.
For example, for the direct multi-mount map entry with a couple of
offsets:
/race/mm1 / <server1>:/<path1>
/om1 <server2>:/<path2>
/om2 <server1>:/<path3>
an autofs trigger mount is mounted on /race/mm1 and when accessed it is
over mounted and trigger mounts made for /race/mm1/om1 and /race/mm1/om2.
So it isn't possible for path walks to see the expiring flag at all and
they happily walk into the file system while it is expiring.
When expiring these mounts follow_down() must stop at the autofs mount and
all processes must block in the ->follow_link() method (except the daemon)
until the expire is complete. This is done by decrementing the d_mounted
field of the autofs trigger mount root dentry until the expire is
completed. In ->follow_link() all processes wait on the expire and the
mount following is completed for the daemon until the expire is complete.
Signed-off-by: Ian Kent <raven@themaw.net>
Cc: Jeff Moyer <jmoyer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/autofs4/expire.c')
-rw-r--r-- | fs/autofs4/expire.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c index 19f5bea2704f..705b9f057fb3 100644 --- a/fs/autofs4/expire.c +++ b/fs/autofs4/expire.c @@ -259,13 +259,15 @@ static struct dentry *autofs4_expire_direct(struct super_block *sb, now = jiffies; timeout = sbi->exp_timeout; - /* Lock the tree as we must expire as a whole */ spin_lock(&sbi->fs_lock); if (!autofs4_direct_busy(mnt, root, timeout, do_now)) { struct autofs_info *ino = autofs4_dentry_ino(root); - - /* Set this flag early to catch sys_chdir and the like */ + if (d_mountpoint(root)) { + ino->flags |= AUTOFS_INF_MOUNTPOINT; + root->d_mounted--; + } ino->flags |= AUTOFS_INF_EXPIRING; + init_completion(&ino->expire_complete); spin_unlock(&sbi->fs_lock); return root; } @@ -392,6 +394,7 @@ found: expired, (int)expired->d_name.len, expired->d_name.name); ino = autofs4_dentry_ino(expired); ino->flags |= AUTOFS_INF_EXPIRING; + init_completion(&ino->expire_complete); spin_unlock(&sbi->fs_lock); spin_lock(&dcache_lock); list_move(&expired->d_parent->d_subdirs, &expired->d_u.d_child); @@ -429,6 +432,7 @@ int autofs4_expire_run(struct super_block *sb, spin_lock(&sbi->fs_lock); ino = autofs4_dentry_ino(dentry); ino->flags &= ~AUTOFS_INF_EXPIRING; + complete_all(&ino->expire_complete); spin_unlock(&sbi->fs_lock); return ret; @@ -457,8 +461,14 @@ int autofs4_expire_multi(struct super_block *sb, struct vfsmount *mnt, /* This is synchronous because it makes the daemon a little easier */ ret = autofs4_wait(sbi, dentry, NFY_EXPIRE); + spin_lock(&sbi->fs_lock); + if (ino->flags & AUTOFS_INF_MOUNTPOINT) { + sb->s_root->d_mounted++; + ino->flags &= ~AUTOFS_INF_MOUNTPOINT; + } ino->flags &= ~AUTOFS_INF_EXPIRING; + complete_all(&ino->expire_complete); spin_unlock(&sbi->fs_lock); dput(dentry); } |