> On 19.04.2015, at 17:51, Andrei Borzenkov <arvidj...@gmail.com> wrote: > > В Sun, 19 Apr 2015 17:40:16 +0300 > Toomas Soome <tso...@me.com> пишет: > >> >> the features in openzfs have different effects, some affect only writes and >> are therefore read only compatible - such feature does not need any changes >> for reads, this feature is not read only compatible and therefore, once this >> feature is enabled, reader code must be changed accordingly. >> >> so, what they did with hole_birth was they started to insert block birth >> timestamps for blocks being released to make it possible to track such >> blocks while doing zfs send (when block has birth time, you know its place >> on timeline of snapshots). as old reader code was relying on blk_birth == 0 >> to detect an hole, after hole_birth is enabled, hole blk_birth is not 0 any >> more, so the solution is to check if DVA pointers are zero instead. and >> thats exactly what its about. > > And if hole_birth is *not* enabled on a filesystem we are reading? > Should not old code be used in this case?
not really, as for holes, DVA pointers are zero anyhow. I guess the original implementation used blk_birth to save extra compare - so the new read code is compatible with old data. > >> >> reference: >> https://github.com/illumos/illumos-gate/commit/43466aae47bfcd2ad9bf501faec8e75c08095e4f >> >> >> >> >>> On 19.04.2015, at 17:11, Andrei Borzenkov <arvidj...@gmail.com> wrote: >>> >>> В Thu, 16 Apr 2015 08:22:08 +0300 >>> Toomas Soome <tso...@me.com> пишет: >>> >>> This really needs better explanation. Otherwise this looks like either >>> old code was broken to start with and it is a bug fix or new code needs >>> some conditionals on new feature. >>> >>>> >>>> --- >>>> grub-core/fs/zfs/zfs.c | 6 ++++-- >>>> include/grub/zfs/spa.h | 4 +++- >>>> 2 files changed, 7 insertions(+), 3 deletions(-) >>>> >>>> diff --git a/grub-core/fs/zfs/zfs.c b/grub-core/fs/zfs/zfs.c >>>> index 2689986..a731c3d 100644 >>>> --- a/grub-core/fs/zfs/zfs.c >>>> +++ b/grub-core/fs/zfs/zfs.c >>>> @@ -280,7 +280,9 @@ grub_crypto_cipher_handle_t (*grub_zfs_load_key) >>>> (const struct grub_zfs_key *key >>>> */ >>>> #define MAX_SUPPORTED_FEATURE_STRLEN 50 >>>> static const char *spa_feature_names[] = { >>>> - "org.illumos:lz4_compress",NULL >>>> + "org.illumos:lz4_compress", >>>> + "com.delphix:hole_birth", >>>> + NULL >>>> }; >>>> >>>> static int >>>> @@ -1751,7 +1753,7 @@ zio_read_gang (blkptr_t * bp, grub_zfs_endian_t >>>> endian, dva_t * dva, void *buf, >>>> >>>> for (i = 0; i < SPA_GBH_NBLKPTRS; i++) >>>> { >>>> - if (zio_gb->zg_blkptr[i].blk_birth == 0) >>>> + if (BP_IS_HOLE(&zio_gb->zg_blkptr[i])) >>>> continue; >>>> >>>> err = zio_read_data (&zio_gb->zg_blkptr[i], endian, buf, data); >>>> diff --git a/include/grub/zfs/spa.h b/include/grub/zfs/spa.h >>>> index 7edb8ab..df43b6b 100644 >>>> --- a/include/grub/zfs/spa.h >>>> +++ b/include/grub/zfs/spa.h >>>> @@ -279,7 +279,9 @@ typedef struct blkptr { >>>> >>>> #define BP_IDENTITY(bp) (&(bp)->blk_dva[0]) >>>> #define BP_IS_GANG(bp) DVA_GET_GANG(BP_IDENTITY(bp)) >>>> -#define BP_IS_HOLE(bp) ((bp)->blk_birth == 0) >>>> +#define DVA_IS_EMPTY(dva) ((dva)->dva_word[0] == 0ULL && \ >>>> + (dva)->dva_word[1] == 0ULL) >>>> +#define BP_IS_HOLE(bp) DVA_IS_EMPTY(BP_IDENTITY(bp)) >>>> >>>> /* BP_IS_RAIDZ(bp) assumes no block compression */ >>>> #define BP_IS_RAIDZ(bp) (DVA_GET_ASIZE(&(bp)->blk_dva[0]) > \ >>> >>> >>> _______________________________________________ >>> Grub-devel mailing list >>> Grub-devel@gnu.org >>> https://lists.gnu.org/mailman/listinfo/grub-devel >> >> >> _______________________________________________ >> Grub-devel mailing list >> Grub-devel@gnu.org >> https://lists.gnu.org/mailman/listinfo/grub-devel _______________________________________________ Grub-devel mailing list Grub-devel@gnu.org https://lists.gnu.org/mailman/listinfo/grub-devel
