On Wed, Jun 26, 2024 at 06:47:15AM +0900, OGAWA Hirofumi wrote:
> Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxx> writes:
>
> > Instead of only using dir_emit_dots for the root inode and explictily
> > requiring the . and .. entries to emit them, use dir_emit_dots for all
> > directories.
> >
> > That allows filesystems with directories without the . or .. entries to
> > still show them.
>
> Unacceptable to change the correct behavior to broken format. And
> unlikely break the userspace, however this still has the user visible
> change of seek pos.
>
> Thanks.
>
I agree that if this breaks userspace with a good filesystem or regresses
in a way that real applications would break, that this needs to be redone.
However, I spent a few hours doing some extra testing (I had already run
some xfstests that include directory testing) and I failed to find any
issues with this fix.
If this would break, it would have broken the root directory. In the case
of a directory including the . and .. entries, the d_off for the .. entry
will be set for the first non-dot-or-dotdot entry. For ., it will be set as
1, which, if used by telldir (or llseek), will emit the .. entry, as
expected.
For the case where both . and .. are absent, the first real entry will have
d_off as 2, and it will just work.
So everything seems to work as expected. Do you see any user visible change
that would break any applications?
Thanks.
Cascardo.
> > Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@xxxxxxxxxx>
> > ---
> > fs/fat/dir.c | 24 +++++++++---------------
> > 1 file changed, 9 insertions(+), 15 deletions(-)
> >
> > diff --git a/fs/fat/dir.c b/fs/fat/dir.c
> > index 4e4a359a1ea3..e70781569de5 100644
> > --- a/fs/fat/dir.c
> > +++ b/fs/fat/dir.c
> > @@ -583,15 +583,14 @@ static int __fat_readdir(struct inode *inode, struct file *file,
> > mutex_lock(&sbi->s_lock);
> >
> > cpos = ctx->pos;
> > - /* Fake . and .. for the root directory. */
> > - if (inode->i_ino == MSDOS_ROOT_INO) {
> > - if (!dir_emit_dots(file, ctx))
> > - goto out;
> > - if (ctx->pos == 2) {
> > - fake_offset = 1;
> > - cpos = 0;
> > - }
> > +
> > + if (!dir_emit_dots(file, ctx))
> > + goto out;
> > + if (ctx->pos == 2) {
> > + fake_offset = 1;
> > + cpos = 0;
> > }
> > +
> > if (cpos & (sizeof(struct msdos_dir_entry) - 1)) {
> > ret = -ENOENT;
> > goto out;
> > @@ -671,13 +670,8 @@ static int __fat_readdir(struct inode *inode, struct file *file,
> > if (fake_offset && ctx->pos < 2)
> > ctx->pos = 2;
> >
> > - if (!memcmp(de->name, MSDOS_DOT, MSDOS_NAME)) {
> > - if (!dir_emit_dot(file, ctx))
> > - goto fill_failed;
> > - } else if (!memcmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
> > - if (!dir_emit_dotdot(file, ctx))
> > - goto fill_failed;
> > - } else {
> > + if (memcmp(de->name, MSDOS_DOT, MSDOS_NAME) &&
> > + memcmp(de->name, MSDOS_DOTDOT, MSDOS_NAME)) {
> > unsigned long inum;
> > loff_t i_pos = fat_make_i_pos(sb, bh, de);
> > struct inode *tmp = fat_iget(sb, i_pos);
>
> --
> OGAWA Hirofumi <hirofumi@xxxxxxxxxxxxxxxxxx>
