From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Simmons Date: Mon, 25 May 2020 18:08:06 -0400 Subject: [lustre-devel] [PATCH 29/45] lustre: llite: restore ll_dcompare() In-Reply-To: <1590444502-20533-1-git-send-email-jsimmons@infradead.org> References: <1590444502-20533-1-git-send-email-jsimmons@infradead.org> Message-ID: <1590444502-20533-30-git-send-email-jsimmons@infradead.org> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org From: Andreas Dilger Revert "LU-9868 llite: Get rid of ll_dcompare" as it is causing failures in conf-sanity test_32* due to errors with sub-mounted ext2 filesystem dentries being invalidated. This reverts commit 8f0a4c7b907a27e77ea0dd80198478747c87bfba. WC-bug-id: https://jira.whamcloud.com/browse/LU-13486 Lustre-commit: 00fa5e8ef4559 ("LU-13486 llite: restore ll_dcompare()") Signed-off-by: Andreas Dilger Reviewed-on: https://review.whamcloud.com/38498 Reviewed-by: James Simmons Reviewed-by: Alex Zhuravlev Reviewed-by: Neil Brown Reviewed-by: Oleg Drokin Signed-off-by: James Simmons --- fs/lustre/llite/dcache.c | 53 +++++++++++++++++++++++++++++++++++++++--------- 1 file changed, 43 insertions(+), 10 deletions(-) diff --git a/fs/lustre/llite/dcache.c b/fs/lustre/llite/dcache.c index 5fab108..edcc1a7 100644 --- a/fs/lustre/llite/dcache.c +++ b/fs/lustre/llite/dcache.c @@ -61,6 +61,48 @@ static void ll_release(struct dentry *de) call_rcu(&lld->lld_rcu_head, free_dentry_data); } +/* Compare if two dentries are the same. Don't match if the existing dentry + * is marked invalid. Returns 1 if different, 0 if the same. + * + * This avoids a race where ll_lookup_it() instantiates a dentry, but we get + * an AST before calling d_revalidate_it(). The dentry still exists (marked + * INVALID) so d_lookup() matches it, but we have no lock on it (so + * lock_match() fails) and we spin around real_lookup(). + * + * This race doesn't apply to lookups in d_alloc_parallel(), and for + * those we want to ensure that only one dentry with a given name is + * in ll_lookup_nd() at a time. So allow invalid dentries to match + * while d_in_lookup(). We will be called again when the lookup + * completes, and can give a different answer then. + */ +static int ll_dcompare(const struct dentry *dentry, + unsigned int len, const char *str, + const struct qstr *name) +{ + if (len != name->len) + return 1; + + if (memcmp(str, name->name, len)) + return 1; + + CDEBUG(D_DENTRY, "found name %.*s(%p) flags %#x refc %d\n", + name->len, name->name, dentry, dentry->d_flags, + d_count(dentry)); + + /* mountpoint is always valid */ + if (d_mountpoint(dentry)) + return 0; + + /* ensure exclusion against parallel lookup of the same name */ + if (d_in_lookup((struct dentry *)dentry)) + return 0; + + if (d_lustre_invalid(dentry)) + return 1; + + return 0; +} + /** * Called when last reference to a dentry is dropped and dcache wants to know * whether or not it should cache it: @@ -202,16 +244,6 @@ static int ll_revalidate_dentry(struct dentry *dentry, { struct inode *dir = d_inode(dentry->d_parent); - CDEBUG(D_VFSTRACE, "VFS Op:name=%s, flags=%u\n", - dentry->d_name.name, lookup_flags); - - /* mountpoint is always valid */ - if (d_mountpoint(dentry)) - return 1; - - if (d_lustre_invalid(dentry)) - return 0; - /* If this is intermediate component path lookup and we were able to get * to this dentry, then its lock has not been revoked and the * path component is valid. @@ -258,4 +290,5 @@ static int ll_revalidate_nd(struct dentry *dentry, unsigned int flags) .d_revalidate = ll_revalidate_nd, .d_release = ll_release, .d_delete = ll_ddelete, + .d_compare = ll_dcompare, }; -- 1.8.3.1