The patch titled autofs4: fix direct mount pending expire race has been added to the -mm tree. Its filename is autofs4-fix-direct-mount-pending-expire-race.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: autofs4: fix direct mount pending expire race From: Ian Kent <raven@xxxxxxxxxx> 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@xxxxxxxxxx> Cc: Jeff Moyer <jmoyer@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/autofs4/autofs_i.h | 3 + fs/autofs4/expire.c | 16 +++++++- fs/autofs4/root.c | 72 +++++++++++++++++++++++++++------------- 3 files changed, 65 insertions(+), 26 deletions(-) diff -puN fs/autofs4/autofs_i.h~autofs4-fix-direct-mount-pending-expire-race fs/autofs4/autofs_i.h --- a/fs/autofs4/autofs_i.h~autofs4-fix-direct-mount-pending-expire-race +++ a/fs/autofs4/autofs_i.h @@ -52,6 +52,8 @@ struct autofs_info { int flags; + struct completion expire_complete; + struct list_head active; struct list_head expiring; @@ -69,6 +71,7 @@ struct autofs_info { }; #define AUTOFS_INF_EXPIRING (1<<0) /* dentry is in the process of expiring */ +#define AUTOFS_INF_MOUNTPOINT (1<<1) /* mountpoint status for direct expire */ struct autofs_wait_queue { wait_queue_head_t queue; diff -puN fs/autofs4/expire.c~autofs4-fix-direct-mount-pending-expire-race fs/autofs4/expire.c --- a/fs/autofs4/expire.c~autofs4-fix-direct-mount-pending-expire-race +++ a/fs/autofs4/expire.c @@ -259,13 +259,15 @@ static struct dentry *autofs4_expire_dir 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_bloc 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_bl /* 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); } diff -puN fs/autofs4/root.c~autofs4-fix-direct-mount-pending-expire-race fs/autofs4/root.c --- a/fs/autofs4/root.c~autofs4-fix-direct-mount-pending-expire-race +++ a/fs/autofs4/root.c @@ -141,6 +141,7 @@ static int try_to_fill_dentry(struct den dentry, dentry->d_name.len, dentry->d_name.name); status = autofs4_wait(sbi, dentry, NFY_NONE); + wait_for_completion(&ino->expire_complete); DPRINTK("expire done status=%d", status); @@ -227,14 +228,32 @@ static void *autofs4_follow_link(struct DPRINTK("dentry=%p %.*s oz_mode=%d nd->flags=%d", dentry, dentry->d_name.len, dentry->d_name.name, oz_mode, nd->flags); - - /* If it's our master or we shouldn't trigger a mount we're done */ - lookup_type = nd->flags & (TRIGGER_FLAGS | TRIGGER_INTENTS); - if (oz_mode || - !(lookup_type || dentry->d_flags & DCACHE_AUTOFS_PENDING)) + /* + * For an expire of a covered direct or offset mount we need + * to beeak out of follow_down() at the autofs mount trigger + * (d_mounted--), so we can see the expiring flag, and manage + * the blocking and following here until the expire is completed. + */ + if (oz_mode) { + spin_lock(&sbi->fs_lock); + if (ino->flags & AUTOFS_INF_EXPIRING) { + spin_unlock(&sbi->fs_lock); + /* Follow down to our covering mount. */ + if (!follow_down(&nd->path.mnt, &nd->path.dentry)) + goto done; + /* + * We shouldn't need to do this but we have no way + * of knowing what may have been done so try a follow + * just in case. + */ + autofs4_follow_mount(&nd->path.mnt, &nd->path.dentry); + goto done; + } + spin_unlock(&sbi->fs_lock); goto done; + } - /* If an expire request is pending wait for it. */ + /* If an expire request is pending everyone must wait. */ spin_lock(&sbi->fs_lock); if (ino->flags & AUTOFS_INF_EXPIRING) { spin_unlock(&sbi->fs_lock); @@ -243,6 +262,7 @@ static void *autofs4_follow_link(struct dentry, dentry->d_name.len, dentry->d_name.name); status = autofs4_wait(sbi, dentry, NFY_NONE); + wait_for_completion(&ino->expire_complete); DPRINTK("request done status=%d", status); @@ -250,10 +270,15 @@ static void *autofs4_follow_link(struct } spin_unlock(&sbi->fs_lock); cont: + /* We trigger a mount for almost all flags */ + lookup_type = nd->flags & (TRIGGER_FLAGS | TRIGGER_INTENTS); + if (!(lookup_type || dentry->d_flags & DCACHE_AUTOFS_PENDING)) + goto done; + /* - * If the dentry contains directories then it is an - * autofs multi-mount with no root mount offset. So - * don't try to mount it again. + * If the dentry contains directories then it is an autofs + * multi-mount with no root mount offset. So don't try to + * mount it again. */ spin_lock(&dcache_lock); if (dentry->d_flags & DCACHE_AUTOFS_PENDING || @@ -264,22 +289,22 @@ cont: if (status) goto out_error; - /* - * The mount succeeded but if there is no root mount - * it must be an autofs multi-mount with no root offset - * so we don't need to follow the mount. - */ - if (d_mountpoint(dentry)) { - if (!autofs4_follow_mount(&nd->path.mnt, - &nd->path.dentry)) { - status = -ENOENT; - goto out_error; - } - } - - goto done; + goto follow; } spin_unlock(&dcache_lock); +follow: + /* + * If there is no root mount it must be an autofs + * multi-mount with no root offset so we don't need + * to follow it. + */ + if (d_mountpoint(dentry)) { + if (!autofs4_follow_mount(&nd->path.mnt, + &nd->path.dentry)) { + status = -ENOENT; + goto out_error; + } + } done: return NULL; @@ -545,6 +570,7 @@ static struct dentry *autofs4_lookup(str expiring, expiring->d_name.len, expiring->d_name.name); autofs4_wait(sbi, expiring, NFY_NONE); + wait_for_completion(&ino->expire_complete); DPRINTK("request completed"); goto cont; } _ Patches currently in -mm which might be from raven@xxxxxxxxxx are autofs4-dont-make-expiring-dentry-negative.patch autofs4-dont-make-expiring-dentry-negative-fix.patch autofs4-revert-redo-lookup-in-ttfd.patch autofs4-use-look-aside-list-for-lookups.patch autofs4-use-look-aside-list-for-lookups-autofs4-fix-symlink-name-allocation.patch autofs4-dont-release-directory-mutex-if-called-in-oz_mode.patch autofs4-use-lookup-intent-flags-to-trigger-mounts.patch autofs4-use-struct-qstr-in-waitqc.patch autofs4-fix-waitq-locking.patch autofs4-fix-pending-mount-race.patch autofs4-fix-pending-mount-race-fix.patch autofs4-check-kernel-communication-pipe-is-valid-for-write.patch autofs4-fix-waitq-memory-leak.patch autofs4-detect-invalid-direct-mount-requests.patch autofs4-indirect-dentry-must-almost-always-be-positive.patch autofs4-cleanup-redundant-readir-code.patch autofs4-fix-pending-checks.patch autofs4-fix-indirect-mount-pending-expire-race.patch autofs4-fix-direct-mount-pending-expire-race.patch autofs4-reorganize-expire-pending-wait-function-calls.patch autofs4-remove-unused-ioctls.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html