<div dir="ltr">To support arbitrary page size for superblock,include 4K/8K/64K currently, the off_set of SB_SECTOR should be a LCM(least common multiple) and that is 64. I redefine macro SB_SECTOR and BDEV_DATA_START_DEFAULT just as bellow patch showed: diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c index ef567cd..1622f44 100644 --- a/drivers/md/bcache/super.c +++ b/drivers/md/bcache/super.c @@ -74,7 +74,7 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev, { const char *err; struct cache_sb *s; - struct buffer_head *bh = __bread(bdev, 1, SB_SIZE); + struct buffer_head *bh = __bread(bdev, 16, SB_SIZE); unsigned i; if (!bh) diff --git a/include/uapi/linux/bcache.h b/include/uapi/linux/bcache.h index 22b6ad3..eb948c8 100644 --- a/include/uapi/linux/bcache.h +++ b/include/uapi/linux/bcache.h @@ -144,14 +144,14 @@ static inline struct bkey *bkey_idx(const struct bkey *k, unsigned nr_keys) #define BCACHE_SB_VERSION_BDEV_WITH_OFFSET 4 #define BCACHE_SB_MAX_VERSION 4 -#define SB_SECTOR 8 +#define SB_SECTOR 128 #define SB_SIZE 4096 #define SB_LABEL_SIZE 32 #define SB_JOURNAL_BUCKETS 256U /* SB_JOURNAL_BUCKETS must be divisible by BITS_PER_LONG */ #define MAX_CACHES_PER_SET 8 -#define BDEV_DATA_START_DEFAULT 16 /* sectors */ +#define BDEV_DATA_START_DEFAULT 256 /* sectors */ struct cache_sb { __u64 csum; <div class="gmail_extra"> </div><div class="gmail_extra">The second arg of __bread(bdev, 16, SB_SIZE) has unit of block size and it need be relocated too.</div><div class="gmail_extra">To suitable this change, bcache-tools need be fixed up too. </div><div class="gmail_extra">As for btree_node_size issues about page size, expecting somebody to commit a patch.</div><div class="gmail_extra"> </div><div class="gmail_extra">Kent, maybe you could use qemu to simulate ARM64 arch and there is always ubuntu image for ARM64 on the internet. </div><div class="gmail_extra"> <div class="gmail_quote">2016-06-02 7:16 GMT+08:00 Kent Overstreet <<a href="mailto:kent.overstreet@gmail.com" target="_blank">kent.overstreet@gmail.com</a>>: <blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left-width:1px;border-left-color:rgb(204,204,204);border-left-style:solid;padding-left:1ex"><div class=""><div class="h5">On Wed, Jun 01, 2016 at 11:05:20AM -0700, Eric Wheeler wrote: > On Wed, 1 Jun 2016, Zhengyuan Liu wrote: > > > Hi, I have created a mapped block device (bcach0) using make-bcache on > > ARM64 server which has kernel enable 64K page size. However, the > > bcach0 disappeared after the server reboot and there is no or dirty > > metadata on super block of both cache device and back device . The > > output of command bcache-super-show was as bellow showed: > > [root@master Linux-4.4-LTS-storage]# bcache-super-show /dev/sdb > > sb.magic bad magic > > Invalid superblock (bad magic) > > /dev/sdb was the backing device and cache device got bad magic too. > > > > I tried to traced the written process of super block in bcache source > > code and found that is the issue of PAGE_SIZE. It seems that the > > bcache was designed only considering for 4K PAGE_SIZE and it works > > right only on 4K PAGE_SIZE exactly. To make bcache work correctly on > > 64K PAGE_SIZE, I committed a patch as bellow showd: > > diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c > > index 330cd6e..ef567cd 100644 > > --- a/drivers/md/bcache/super.c > > +++ b/drivers/md/bcache/super.c > > @@ -224,6 +224,12 @@ static void __write_super(struct cache_sb > > *sb, struct bio *bio > > bio->bi_iter.bi_size = SB_SIZE; > > bch_bio_map(bio, NULL); > > > > +#ifdef CONFIG_ARM64_64K_PAGES > > + out = (struct cache_sb *)((char *)out + (SB_SECTOR<<9)); > > + pr_debug("sb_page_adress %x, sb_address %x,page_size > > %d\n",page_address(bio > > + bio->bi_io_vec[0].bv_offset = (SB_SECTOR<<9); > > +#endif > > > > out->offset = cpu_to_le64(sb->offset); > > out->version = cpu_to_le64(sb->version); > > > > Does it not recommend to use bcache on 64K PAGE_SIZE? or it only > > considers for 4K PAGE_SIZE for bcache currently? > > Maybe it is more suitable for me to redefine some macro such as > > SB_SECTOR, BDEV_DATA_START_DEFAULT to make bcache work correctly on > > both 64K PAGE_SIZE and 4K PAGE_SIZE. > > I think a patch to support arbitrary page size would be great. Can > you write the macros in terms of PAGE_SIZE or PAGE_SHIFT? </div></div>It shouldn't be referencing PAGE_SIZE at all - creating a new macro (BCH_SB_SIZE, perhaps) is the correct approach. The code that allocates the buffer for the superblock will have to be fixed too - right now it's probably using __get_free_page(), it should probably just be switched to kmalloc(). > (Out of curiosity, what ARM64 hardware are you using?) > > Kent, this may affect bcachefs too. Can you think of any other places > that might have PAGE_SIZE!=4k issues? Oh, there's probably a couple. There's probably some stuff that'll break if btree_node_size is smaller than PAGE_SIZE, too... If it turns out to be too much for Zhengyuan, I can probably fix upstream too (but I don't have any hardware to test with). </blockquote></div> </div></div>