| Message ID | 20230920173445.3943581-4-bschubert@ddn.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | fuse: full atomic open and atomic-open-revalidate | expand |
On Wed, Sep 20, 2023 at 8:51 PM Bernd Schubert <bschubert@ddn.com> wrote: > > From: Miklos Szeredi <miklos@szeredi.hu> > > atomic_open() will do an open-by-name or create-and-open > depending on the flags. > > If file was created, then the old positive dentry is obviously > stale, so it will be invalidated and a new one will be allocated. > > If not created, then check whether it's the same inode (same as in > ->d_revalidate()) and if not, invalidate & allocate new dentry. > > Co-developed-by: Bernd Schubert <bschubert@ddn.com> > Signed-off-by: Miklos Szeredi <miklos@szeredi.hu> > Signed-off-by: Bernd Schubert <bschubert@ddn.com> > Cc: Christian Brauner <brauner@kernel.org> > Cc: Al Viro <viro@zeniv.linux.org.uk> > Cc: Dharmendra Singh <dsingh@ddn.com> > Cc: linux-fsdevel@vger.kernel.org > --- > fs/namei.c | 25 ++++++++++++++++++++----- > include/linux/namei.h | 7 +++++++ > 2 files changed, 27 insertions(+), 5 deletions(-) > > diff --git a/fs/namei.c b/fs/namei.c > index e56ff39a79bc..f01b278ac0ef 100644 > --- a/fs/namei.c > +++ b/fs/namei.c > @@ -858,7 +858,7 @@ static inline int d_revalidate(struct dentry *dentry, unsigned int flags) > if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) > return dentry->d_op->d_revalidate(dentry, flags); > else > - return 1; > + return D_REVALIDATE_VALID; > } > > /** > @@ -1611,10 +1611,11 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name, > } > EXPORT_SYMBOL(lookup_one_qstr_excl); > > -static struct dentry *lookup_fast(struct nameidata *nd) > +static struct dentry *lookup_fast(struct nameidata *nd, bool *atomic_revalidate) > { > struct dentry *dentry, *parent = nd->path.dentry; > int status = 1; > + *atomic_revalidate = false; > > /* > * Rename seqlock is not required here because in the off chance > @@ -1656,6 +1657,10 @@ static struct dentry *lookup_fast(struct nameidata *nd) > dput(dentry); > return ERR_PTR(status); > } > + > + if (status == D_REVALIDATE_ATOMIC) > + *atomic_revalidate = true; > + > return dentry; > } > > @@ -1981,6 +1986,7 @@ static const char *handle_dots(struct nameidata *nd, int type) > static const char *walk_component(struct nameidata *nd, int flags) > { > struct dentry *dentry; > + bool atomic_revalidate; > /* > * "." and ".." are special - ".." especially so because it has > * to be able to know about the current root directory and > @@ -1991,7 +1997,7 @@ static const char *walk_component(struct nameidata *nd, int flags) > put_link(nd); > return handle_dots(nd, nd->last_type); > } > - dentry = lookup_fast(nd); > + dentry = lookup_fast(nd, &atomic_revalidate); > if (IS_ERR(dentry)) > return ERR_CAST(dentry); > if (unlikely(!dentry)) { > @@ -1999,6 +2005,9 @@ static const char *walk_component(struct nameidata *nd, int flags) > if (IS_ERR(dentry)) > return ERR_CAST(dentry); > } > + > + WARN_ON(atomic_revalidate); > + WARN_ON_ONCE should be enough in most cases to signal bad code without spamming the log. Is there an error path that can be taken in this case? Thanks, Amir. > if (!(flags & WALK_MORE) && nd->depth) > put_link(nd); > return step_into(nd, flags, dentry); > @@ -3430,7 +3439,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file, > dput(dentry); > dentry = NULL; > } > - if (dentry->d_inode) { > + if (dentry->d_inode && error != D_REVALIDATE_ATOMIC) { > /* Cached positive dentry: will open in f_op->open */ > return dentry; > } > @@ -3523,12 +3532,18 @@ static const char *open_last_lookups(struct nameidata *nd, > } > > if (!(open_flag & O_CREAT)) { > + bool atomic_revalidate; > + > if (nd->last.name[nd->last.len]) > nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; > /* we _can_ be in RCU mode here */ > - dentry = lookup_fast(nd); > + dentry = lookup_fast(nd, &atomic_revalidate); > if (IS_ERR(dentry)) > return ERR_CAST(dentry); > + if (dentry && unlikely(atomic_revalidate)) { > + dput(dentry); > + dentry = NULL; > + } > if (likely(dentry)) > goto finish_lookup; > > diff --git a/include/linux/namei.h b/include/linux/namei.h > index 1463cbda4888..a70e87d2b2a9 100644 > --- a/include/linux/namei.h > +++ b/include/linux/namei.h > @@ -47,6 +47,13 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT}; > /* LOOKUP_* flags which do scope-related checks based on the dirfd. */ > #define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT) > > +/* ->d_revalidate return codes */ > +enum { > + D_REVALIDATE_INVALID = 0, /* invalid dentry */ > + D_REVALIDATE_VALID = 1, /* valid dentry */ > + D_REVALIDATE_ATOMIC = 2, /* atomic_open will revalidate */ > +}; > + > extern int path_pts(struct path *path); > > extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty); > -- > 2.39.2 >
diff --git a/fs/namei.c b/fs/namei.c index e56ff39a79bc..f01b278ac0ef 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -858,7 +858,7 @@ static inline int d_revalidate(struct dentry *dentry, unsigned int flags) if (unlikely(dentry->d_flags & DCACHE_OP_REVALIDATE)) return dentry->d_op->d_revalidate(dentry, flags); else - return 1; + return D_REVALIDATE_VALID; } /** @@ -1611,10 +1611,11 @@ struct dentry *lookup_one_qstr_excl(const struct qstr *name, } EXPORT_SYMBOL(lookup_one_qstr_excl); -static struct dentry *lookup_fast(struct nameidata *nd) +static struct dentry *lookup_fast(struct nameidata *nd, bool *atomic_revalidate) { struct dentry *dentry, *parent = nd->path.dentry; int status = 1; + *atomic_revalidate = false; /* * Rename seqlock is not required here because in the off chance @@ -1656,6 +1657,10 @@ static struct dentry *lookup_fast(struct nameidata *nd) dput(dentry); return ERR_PTR(status); } + + if (status == D_REVALIDATE_ATOMIC) + *atomic_revalidate = true; + return dentry; } @@ -1981,6 +1986,7 @@ static const char *handle_dots(struct nameidata *nd, int type) static const char *walk_component(struct nameidata *nd, int flags) { struct dentry *dentry; + bool atomic_revalidate; /* * "." and ".." are special - ".." especially so because it has * to be able to know about the current root directory and @@ -1991,7 +1997,7 @@ static const char *walk_component(struct nameidata *nd, int flags) put_link(nd); return handle_dots(nd, nd->last_type); } - dentry = lookup_fast(nd); + dentry = lookup_fast(nd, &atomic_revalidate); if (IS_ERR(dentry)) return ERR_CAST(dentry); if (unlikely(!dentry)) { @@ -1999,6 +2005,9 @@ static const char *walk_component(struct nameidata *nd, int flags) if (IS_ERR(dentry)) return ERR_CAST(dentry); } + + WARN_ON(atomic_revalidate); + if (!(flags & WALK_MORE) && nd->depth) put_link(nd); return step_into(nd, flags, dentry); @@ -3430,7 +3439,7 @@ static struct dentry *lookup_open(struct nameidata *nd, struct file *file, dput(dentry); dentry = NULL; } - if (dentry->d_inode) { + if (dentry->d_inode && error != D_REVALIDATE_ATOMIC) { /* Cached positive dentry: will open in f_op->open */ return dentry; } @@ -3523,12 +3532,18 @@ static const char *open_last_lookups(struct nameidata *nd, } if (!(open_flag & O_CREAT)) { + bool atomic_revalidate; + if (nd->last.name[nd->last.len]) nd->flags |= LOOKUP_FOLLOW | LOOKUP_DIRECTORY; /* we _can_ be in RCU mode here */ - dentry = lookup_fast(nd); + dentry = lookup_fast(nd, &atomic_revalidate); if (IS_ERR(dentry)) return ERR_CAST(dentry); + if (dentry && unlikely(atomic_revalidate)) { + dput(dentry); + dentry = NULL; + } if (likely(dentry)) goto finish_lookup; diff --git a/include/linux/namei.h b/include/linux/namei.h index 1463cbda4888..a70e87d2b2a9 100644 --- a/include/linux/namei.h +++ b/include/linux/namei.h @@ -47,6 +47,13 @@ enum {LAST_NORM, LAST_ROOT, LAST_DOT, LAST_DOTDOT}; /* LOOKUP_* flags which do scope-related checks based on the dirfd. */ #define LOOKUP_IS_SCOPED (LOOKUP_BENEATH | LOOKUP_IN_ROOT) +/* ->d_revalidate return codes */ +enum { + D_REVALIDATE_INVALID = 0, /* invalid dentry */ + D_REVALIDATE_VALID = 1, /* valid dentry */ + D_REVALIDATE_ATOMIC = 2, /* atomic_open will revalidate */ +}; + extern int path_pts(struct path *path); extern int user_path_at_empty(int, const char __user *, unsigned, struct path *, int *empty);