В Sun, 19 Apr 2015 17:57:04 +0300 Toomas Soome <tso...@me.com> пишет:
> > > 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. Committed with explanatory text for non-insiders. > > > > > >> > >> 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
