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Date: Wed, 5 Mar 2014 23:25:44 +0300
From: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Minchan Kim <minchan@...nel.org>,
Jerome Marchand <jmarchan@...hat.com>,
Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] zram: return error-valued pointer from zcomp_create()
On (03/05/14 12:13), Andrew Morton wrote:
> On Wed, 5 Mar 2014 22:56:55 +0300 Sergey Senozhatsky <sergey.senozhatsky@...il.com> wrote:
>
> > Instead of returning just NULL, return ERR_PTR from zcomp_create()
> > if compressing backend creation has failed. ERR_PTR(-EINVAL) for
> > unsupported compression algorithm request, ERR_PTR(-ENOMEM) for
> > allocation (zcomp or compression stream) error.
> >
> > Perform IS_ERR() check of returned from zcomp_create() value in
> > disksize_store() and set return code to PTR_ERR().
> >
> > Change suggested by Jerome Marchand.
> >
> > ...
> >
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -583,7 +583,7 @@ static ssize_t disksize_store(struct device *dev,
> > struct zcomp *comp;
> > struct zram_meta *meta;
> > struct zram *zram = dev_to_zram(dev);
> > - int err = -EINVAL;
> > + int err = -EBUSY;
> >
> > disksize = memparse(buf, NULL);
> > if (!disksize)
> > @@ -595,9 +595,10 @@ static ssize_t disksize_store(struct device *dev,
> > return -ENOMEM;
> >
> > comp = zcomp_create(zram->compressor, zram->max_comp_streams);
> > - if (!comp) {
> > + if (IS_ERR(comp)) {
> > pr_info("Cannot initialise %s compressing backend\n",
> > zram->compressor);
> > + err = PTR_ERR(comp);
> > goto out_cleanup;
> > }
> >
> > @@ -605,7 +606,6 @@ static ssize_t disksize_store(struct device *dev,
> > if (init_done(zram)) {
> > up_write(&zram->init_lock);
> > pr_info("Cannot change disksize for initialized device\n");
> > - err = -EBUSY;
> > goto out_cleanup;
> > }
> >
> > @@ -618,7 +618,7 @@ static ssize_t disksize_store(struct device *dev,
> > return len;
> >
> > out_cleanup:
> > - if (comp)
> > + if (!IS_ERR(comp))
> > zcomp_destroy(comp);
> > zram_meta_free(meta);
> > return err;
>
> The disksize_store() error ends up being unnecessarily inconsistent in
> its handling of `err' and in its freeing/unlocking flow. How about
> doing it this way?
>
> static ssize_t disksize_store(struct device *dev,
> struct device_attribute *attr, const char *buf, size_t len)
> {
> u64 disksize;
> struct zcomp *comp;
> struct zram_meta *meta;
> struct zram *zram = dev_to_zram(dev);
> int err;
>
> disksize = memparse(buf, NULL);
> if (!disksize)
> return -EINVAL;
>
> disksize = PAGE_ALIGN(disksize);
> meta = zram_meta_alloc(disksize);
> if (!meta)
> return -ENOMEM;
>
> comp = zcomp_create(zram->compressor, zram->max_comp_streams);
> if (IS_ERR(comp)) {
> pr_info("Cannot initialise %s compressing backend\n",
> zram->compressor);
> err = PTR_ERR(comp);
> goto out_free_meta;
> }
>
> down_write(&zram->init_lock);
> if (init_done(zram)) {
> pr_info("Cannot change disksize for initialized device\n");
> err = -EBUSY;
> goto out_destroy_comp;
> }
>
> zram->meta = meta;
> zram->comp = comp;
> zram->disksize = disksize;
> set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT);
> up_write(&zram->init_lock);
> return len;
>
> out_destroy_comp:
> up_write(&zram->init_lock);
> zcomp_destroy(comp);
> out_free_meta:
> zram_meta_free(meta);
> return err;
> }
>
> --- a/drivers/block/zram/zram_drv.c~zram-return-error-valued-pointer-from-zcomp_create-fix
> +++ a/drivers/block/zram/zram_drv.c
> @@ -583,7 +583,7 @@ static ssize_t disksize_store(struct dev
> struct zcomp *comp;
> struct zram_meta *meta;
> struct zram *zram = dev_to_zram(dev);
> - int err = -EBUSY;
> + int err;
>
> disksize = memparse(buf, NULL);
> if (!disksize)
> @@ -599,14 +599,14 @@ static ssize_t disksize_store(struct dev
> pr_info("Cannot initialise %s compressing backend\n",
> zram->compressor);
> err = PTR_ERR(comp);
> - goto out_cleanup;
> + goto out_free_meta;
> }
>
> down_write(&zram->init_lock);
> if (init_done(zram)) {
> - up_write(&zram->init_lock);
> pr_info("Cannot change disksize for initialized device\n");
> - goto out_cleanup;
> + err = -EBUSY;
> + goto out_destroy_comp;
> }
>
> zram->meta = meta;
> @@ -617,9 +617,10 @@ static ssize_t disksize_store(struct dev
>
> return len;
>
> -out_cleanup:
> - if (!IS_ERR(comp))
> - zcomp_destroy(comp);
> +out_destroy_comp:
> + up_write(&zram->init_lock);
> + zcomp_destroy(comp);
> +out_free_meta:
> zram_meta_free(meta);
> return err;
> }
yes, looks fine to me. thank you.
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
-ss
> _
>
>
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