Messages in this thread | | | From | Miklos Szeredi <> | Date | Thu, 28 Oct 2021 10:43:43 +0200 | Subject | Re: [PATCH bpf-next v2 1/3] libfs: support RENAME_EXCHANGE in simple_rename() |
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On Thu, Oct 28, 2021 at 1:46 AM Daniel Borkmann <daniel@iogearbox.net> wrote: > > [ Adding Miklos & Greg to Cc for review given e0e0be8a8355 ("libfs: support RENAME_NOREPLACE in > simple_rename()"). If you have a chance, would be great if you could take a look, thanks! ] > > On 10/21/21 5:15 PM, Lorenz Bauer wrote: > > Allow atomic exchange via RENAME_EXCHANGE when using simple_rename. > > This affects binderfs, ramfs, hubetlbfs and bpffs. There isn't much > > to do except update the various *time fields. > > > > Signed-off-by: Lorenz Bauer <lmb@cloudflare.com> > > --- > > fs/libfs.c | 6 +++++- > > 1 file changed, 5 insertions(+), 1 deletion(-) > > > > diff --git a/fs/libfs.c b/fs/libfs.c > > index 51b4de3b3447..93c03d593749 100644 > > --- a/fs/libfs.c > > +++ b/fs/libfs.c > > @@ -455,9 +455,12 @@ int simple_rename(struct user_namespace *mnt_userns, struct inode *old_dir, > > struct inode *inode = d_inode(old_dentry); > > int they_are_dirs = d_is_dir(old_dentry); > > > > - if (flags & ~RENAME_NOREPLACE) > > + if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE)) > > return -EINVAL; > > > > + if (flags & RENAME_EXCHANGE) > > + goto done; > > +
This is not sufficient. RENAME_EXCHANGE can swap a dir and a non-dir, in which case the parent nlink counters need to be fixed up.
See shmem_exchange(). My suggestion is to move that function to libfs.c:simple_rename_exchange().
Thanks, Miklos
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