Date: Thu, 23 Mar 2017 07:57:38 +0000 (UTC) From: Andriy Gapon <avg@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r315832 - stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs Message-ID: <201703230757.v2N7vci8085922@repo.freebsd.org>
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Author: avg Date: Thu Mar 23 07:57:37 2017 New Revision: 315832 URL: https://svnweb.freebsd.org/changeset/base/315832 Log: MFC r314912: MFV r314910: 7843 get_clones_stat() is suboptimal for lots of clones Modified: stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c Directory Properties: stable/11/ (props changed) Modified: stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c ============================================================================== --- stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c Thu Mar 23 07:56:13 2017 (r315831) +++ stable/11/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/dsl_dataset.c Thu Mar 23 07:57:37 2017 (r315832) @@ -1766,11 +1766,22 @@ get_clones_stat(dsl_dataset_t *ds, nvlis zap_cursor_t zc; zap_attribute_t za; nvlist_t *propval = fnvlist_alloc(); - nvlist_t *val = fnvlist_alloc(); + nvlist_t *val; ASSERT(dsl_pool_config_held(ds->ds_dir->dd_pool)); /* + * We use nvlist_alloc() instead of fnvlist_alloc() because the + * latter would allocate the list with NV_UNIQUE_NAME flag. + * As a result, every time a clone name is appended to the list + * it would be (linearly) searched for for a duplicate name. + * We already know that all clone names must be unique and we + * want avoid the quadratic complexity of double-checking that + * because we can have a large number of clones. + */ + VERIFY0(nvlist_alloc(&val, 0, KM_SLEEP)); + + /* * There may be missing entries in ds_next_clones_obj * due to a bug in a previous version of the code. * Only trust it if it has the right number of entries.
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