[PATCH] erofs: avoid useless memory allocation

[浅井登]

2023年3月3日(金) 18:39 Yue Hu <zbestahu at gmail.com>:

> On Fri,  3 Mar 2023 16:52:18 +0900
> Noboru Asai <asai at sijam.com> wrote:
>
> > The variable 'vi->xattr_shared_count' could be ZERO.
> >
> > Signed-off-by: Noboru Asai <asai at sijam.com>
> > ---
> >  fs/erofs/xattr.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
> > index 60729b1220b6..5164813a693b 100644
> > --- a/fs/erofs/xattr.c
> > +++ b/fs/erofs/xattr.c
> > @@ -80,6 +80,8 @@ static int init_inode_xattrs(struct inode *inode)
> >
> >       ih = (struct erofs_xattr_ibody_header *)(it.kaddr + it.ofs);
> >       vi->xattr_shared_count = ih->h_shared_count;
> > +     if (!vi->xattr_shared_count)
> > +             goto out_unlock;
>
> Questions: ret = 0? no need to erofs_put_metabuf?
>

You are right. this patch needs to call erofs_put_metabuf() before goto
out_unlock.


> I think we can keep current since kmalloc_array() will check whether the
> size(->xattr_shared_count) is zero size or not. rt?
>

In case of xattr_shared_count == 0, kmalloc_array() return ZERO_SIZE_PTR.
And kfree() do noting in this case (safe).

#define ZERO_SIZE_PTR ((void *)16)



> >       vi->xattr_shared_xattrs = kmalloc_array(vi->xattr_shared_count,
> >                                               sizeof(uint), GFP_KERNEL);
> >       if (!vi->xattr_shared_xattrs) {
>
>
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