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https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-11-24 01:40:53 +07:00
new helper: traverse_mounts()
common guts of follow_down() and follow_managed() taken to a new helper - traverse_mounts(). The remnants of follow_managed() are folded into its sole remaining caller (handle_mounts()). Calling conventions of handle_mounts() slightly sanitized - instead of the weird "1 for success, -E... for failure" that used to be imposed by the calling conventions of walk_component() et.al. we can use the normal "0 for success, -E... for failure". Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
parent
ea936aeb3e
commit
9deed3ebca
177
fs/namei.c
177
fs/namei.c
@ -1168,91 +1168,79 @@ static int follow_automount(struct path *path, int *count, unsigned lookup_flags
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}
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/*
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* Handle a dentry that is managed in some way.
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* - Flagged for transit management (autofs)
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* - Flagged as mountpoint
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* - Flagged as automount point
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*
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* This may only be called in refwalk mode.
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* On success path->dentry is known positive.
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*
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* Serialization is taken care of in namespace.c
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* mount traversal - out-of-line part. One note on ->d_flags accesses -
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* dentries are pinned but not locked here, so negative dentry can go
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* positive right under us. Use of smp_load_acquire() provides a barrier
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* sufficient for ->d_inode and ->d_flags consistency.
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*/
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static int follow_managed(struct path *path, struct nameidata *nd)
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static int __traverse_mounts(struct path *path, unsigned flags, bool *jumped,
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int *count, unsigned lookup_flags)
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{
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struct vfsmount *mnt = path->mnt; /* held by caller, must be left alone */
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unsigned flags;
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struct vfsmount *mnt = path->mnt;
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bool need_mntput = false;
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int ret = 0;
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/* Given that we're not holding a lock here, we retain the value in a
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* local variable for each dentry as we look at it so that we don't see
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* the components of that value change under us */
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while (flags = smp_load_acquire(&path->dentry->d_flags),
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unlikely(flags & DCACHE_MANAGED_DENTRY)) {
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while (flags & DCACHE_MANAGED_DENTRY) {
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/* Allow the filesystem to manage the transit without i_mutex
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* being held. */
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if (flags & DCACHE_MANAGE_TRANSIT) {
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BUG_ON(!path->dentry->d_op);
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BUG_ON(!path->dentry->d_op->d_manage);
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ret = path->dentry->d_op->d_manage(path, false);
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flags = smp_load_acquire(&path->dentry->d_flags);
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if (ret < 0)
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break;
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}
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/* Transit to a mounted filesystem. */
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if (flags & DCACHE_MOUNTED) {
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if (flags & DCACHE_MOUNTED) { // something's mounted on it..
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struct vfsmount *mounted = lookup_mnt(path);
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if (mounted) {
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if (mounted) { // ... in our namespace
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dput(path->dentry);
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if (need_mntput)
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mntput(path->mnt);
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path->mnt = mounted;
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path->dentry = dget(mounted->mnt_root);
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// here we know it's positive
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flags = path->dentry->d_flags;
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need_mntput = true;
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continue;
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}
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/* Something is mounted on this dentry in another
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* namespace and/or whatever was mounted there in this
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* namespace got unmounted before lookup_mnt() could
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* get it */
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}
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/* Handle an automount point */
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if (flags & DCACHE_NEED_AUTOMOUNT) {
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ret = follow_automount(path, &nd->total_link_count,
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nd->flags);
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if (ret < 0)
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break;
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continue;
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}
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if (!(flags & DCACHE_NEED_AUTOMOUNT))
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break;
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/* We didn't change the current path point */
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break;
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// uncovered automount point
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ret = follow_automount(path, count, lookup_flags);
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flags = smp_load_acquire(&path->dentry->d_flags);
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if (ret < 0)
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break;
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}
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if (need_mntput) {
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if (path->mnt == mnt)
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mntput(path->mnt);
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if (unlikely(nd->flags & LOOKUP_NO_XDEV))
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ret = -EXDEV;
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else
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nd->flags |= LOOKUP_JUMPED;
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}
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if (ret == -EISDIR || !ret)
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ret = 1;
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if (ret > 0 && unlikely(d_flags_negative(flags)))
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if (ret == -EISDIR)
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ret = 0;
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// possible if you race with several mount --move
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if (need_mntput && path->mnt == mnt)
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mntput(path->mnt);
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if (!ret && unlikely(d_flags_negative(flags)))
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ret = -ENOENT;
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if (unlikely(ret < 0)) {
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dput(path->dentry);
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if (path->mnt != nd->path.mnt)
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mntput(path->mnt);
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}
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*jumped = need_mntput;
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return ret;
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}
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static inline int traverse_mounts(struct path *path, bool *jumped,
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int *count, unsigned lookup_flags)
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{
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unsigned flags = smp_load_acquire(&path->dentry->d_flags);
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/* fastpath */
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if (likely(!(flags & DCACHE_MANAGED_DENTRY))) {
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*jumped = false;
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if (unlikely(d_flags_negative(flags)))
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return -ENOENT;
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return 0;
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}
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return __traverse_mounts(path, flags, jumped, count, lookup_flags);
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}
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int follow_down_one(struct path *path)
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{
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struct vfsmount *mounted;
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@ -1269,6 +1257,23 @@ int follow_down_one(struct path *path)
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}
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EXPORT_SYMBOL(follow_down_one);
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/*
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* Follow down to the covering mount currently visible to userspace. At each
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* point, the filesystem owning that dentry may be queried as to whether the
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* caller is permitted to proceed or not.
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*/
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int follow_down(struct path *path)
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{
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struct vfsmount *mnt = path->mnt;
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bool jumped;
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int ret = traverse_mounts(path, &jumped, NULL, 0);
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if (path->mnt != mnt)
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mntput(mnt);
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return ret;
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}
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EXPORT_SYMBOL(follow_down);
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/*
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* Try to skip to top of mountpoint pile in rcuwalk mode. Fail if
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* we meet a managed dentry that would need blocking.
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@ -1325,6 +1330,7 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
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struct path *path, struct inode **inode,
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unsigned int *seqp)
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{
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bool jumped;
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int ret;
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path->mnt = nd->path.mnt;
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@ -1334,15 +1340,25 @@ static inline int handle_mounts(struct nameidata *nd, struct dentry *dentry,
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if (unlikely(!*inode))
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return -ENOENT;
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if (likely(__follow_mount_rcu(nd, path, inode, seqp)))
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return 1;
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return 0;
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if (unlazy_child(nd, dentry, seq))
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return -ECHILD;
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// *path might've been clobbered by __follow_mount_rcu()
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path->mnt = nd->path.mnt;
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path->dentry = dentry;
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}
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ret = follow_managed(path, nd);
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if (likely(ret >= 0)) {
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ret = traverse_mounts(path, &jumped, &nd->total_link_count, nd->flags);
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if (jumped) {
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if (unlikely(nd->flags & LOOKUP_NO_XDEV))
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ret = -EXDEV;
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else
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nd->flags |= LOOKUP_JUMPED;
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}
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if (unlikely(ret)) {
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dput(path->dentry);
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if (path->mnt != nd->path.mnt)
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mntput(path->mnt);
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} else {
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*inode = d_backing_inode(path->dentry);
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*seqp = 0; /* out of RCU mode, so the value doesn't matter */
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}
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@ -1410,55 +1426,6 @@ static int follow_dotdot_rcu(struct nameidata *nd)
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return 0;
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}
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/*
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* Follow down to the covering mount currently visible to userspace. At each
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* point, the filesystem owning that dentry may be queried as to whether the
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* caller is permitted to proceed or not.
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*/
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int follow_down(struct path *path)
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{
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unsigned managed;
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int ret;
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while (managed = READ_ONCE(path->dentry->d_flags),
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unlikely(managed & DCACHE_MANAGED_DENTRY)) {
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/* Allow the filesystem to manage the transit without i_mutex
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* being held.
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*
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* We indicate to the filesystem if someone is trying to mount
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* something here. This gives autofs the chance to deny anyone
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* other than its daemon the right to mount on its
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* superstructure.
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*
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* The filesystem may sleep at this point.
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*/
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if (managed & DCACHE_MANAGE_TRANSIT) {
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BUG_ON(!path->dentry->d_op);
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BUG_ON(!path->dentry->d_op->d_manage);
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ret = path->dentry->d_op->d_manage(path, false);
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if (ret < 0)
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return ret == -EISDIR ? 0 : ret;
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}
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/* Transit to a mounted filesystem. */
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if (managed & DCACHE_MOUNTED) {
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struct vfsmount *mounted = lookup_mnt(path);
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if (!mounted)
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break;
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dput(path->dentry);
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mntput(path->mnt);
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path->mnt = mounted;
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path->dentry = dget(mounted->mnt_root);
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continue;
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}
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/* Don't handle automount points here */
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break;
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}
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return 0;
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}
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EXPORT_SYMBOL(follow_down);
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/*
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* Skip to top of mountpoint pile in refwalk mode for follow_dotdot()
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*/
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