Hello, On (03/03/14 07:30), Minchan Kim wrote: > Hello Andrew, > > I'm not in office now and I would be off in this week, maybe > so I don't have source code on top of Sergey's recent change > but it seems below code has same problem. > > Pz, Sergey or Jerome Could you confirm it instead of me? > > On Fri, Feb 28, 2014 at 04:32:06PM -0800, Andrew Morton wrote: > > On Fri, 28 Feb 2014 08:56:29 +0900 Minchan Kim <minc...@kernel.org> wrote: > > > > > Sasha reported following below lockdep spew of zram. > > > > > > It was introduced by [1] in recent linux-next but it's false positive > > > because zram_meta_alloc with down_write(init_lock) couldn't be called > > > during zram is working as swap device so we could annotate the lock. > > > > > > But I don't think it's worthy because it would make greate lockdep > > > less effective. Instead, move zram_meta_alloc out of the lock as good > > > old day so we could do unnecessary allocation/free of zram_meta for > > > initialied device as Sergey claimed in [1] but it wouldn't be common > > > and be harmful if someone might do it. Rather than, I'd like to respect > > > lockdep which is great tool to prevent upcoming subtle bugs. > > > > > > [1] zram: delete zram_init_device > > > > > > ... > > > > > > --- a/drivers/block/zram/zram_drv.c > > > +++ b/drivers/block/zram/zram_drv.c > > > @@ -537,26 +537,27 @@ static ssize_t disksize_store(struct device *dev, > > > struct device_attribute *attr, const char *buf, size_t len) > > > { > > > u64 disksize; > > > + struct zram_meta *meta; > > > struct zram *zram = dev_to_zram(dev); > > > > > > disksize = memparse(buf, NULL); > > > if (!disksize) > > > return -EINVAL; > > > > > > + disksize = PAGE_ALIGN(disksize); > > > + meta = zram_meta_alloc(disksize); > > > + if (!meta) > > > + return -ENOMEM; > > > + > > > down_write(&zram->init_lock); > > > if (init_done(zram)) { > > > + zram_meta_free(meta); > > > up_write(&zram->init_lock); > > > pr_info("Cannot change disksize for initialized device\n"); > > > return -EBUSY; > > > } > > > > > > - disksize = PAGE_ALIGN(disksize); > > > - zram->meta = zram_meta_alloc(disksize); > > > - if (!zram->meta) { > > > - up_write(&zram->init_lock); > > > - return -ENOMEM; > > > - } > > > - > > > + zram->meta = meta; > > > zram->disksize = disksize; > > > set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT); > > > up_write(&zram->init_lock); > > > > When applying zram-use-zcomp-compressing-backends.patch on top of this > > we get a bit of a mess, and simple conflict resolution results in a > > leak. > > > > disksize_store() was one of those nasty functions which does multiple > > "return" statements after performing locking and resource allocation. > > As usual, this led to a resource leak. Remember folks, "return" is a > > goto in disguise. > > > > > > Here's what I ended up with. Please review. > > > > static ssize_t disksize_store(struct device *dev, > > struct device_attribute *attr, const char *buf, size_t len) > > { > > u64 disksize; > > 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; > > > > down_write(&zram->init_lock); > > if (init_done(zram)) { > > pr_info("Cannot change disksize for initialized device\n"); > > err = -EBUSY; > > goto out_free_meta; > > } > > > > zram->comp = zcomp_create(default_compressor); > > AFAIR, zcomp_create try to allocate memory with GFP_KERNEL so it could > make a same problem. If so, let's allocate it out of the lock. > > Please check it. >
good catch. you're right, zcomp allocation use GPF_KERNEL. since Minchan is out of the office this week should I send out a patch (combined Minchan's original patch + Andrew's rework) or, Andrew, you will handle it? -ss > > if (!zram->comp) { > > pr_info("Cannot initialise %s compressing backend\n", > > default_compressor); > > err = -EINVAL; > > goto out_free_meta; > > } > > > > zram->meta = meta; > > zram->disksize = disksize; > > set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT); > > up_write(&zram->init_lock); > > > > return len; > > > > out_free_meta: > > up_write(&zram->init_lock); > > zram_meta_free(meta); > > return err; > > } > > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/