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Thu, 15 Feb 2024 12:53:34 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id CRevKU4JzmXdEgAAn2gu4w (envelope-from ); Thu, 15 Feb 2024 12:53:34 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 5CB18A0809; Thu, 15 Feb 2024 13:53:34 +0100 (CET) Date: Thu, 15 Feb 2024 13:53:34 +0100 From: Jan Kara To: Chuck Lever Cc: viro@zeniv.linux.org.uk, brauner@kernel.org, jack@suse.cz, hughd@google.com, akpm@linux-foundation.org, Liam.Howlett@oracle.com, oliver.sang@intel.com, feng.tang@intel.com, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, maple-tree@lists.infradead.org, linux-mm@kvack.org, lkp@intel.com Subject: Re: [PATCH RFC 3/7] libfs: Add simple_offset_empty() Message-ID: <20240215125334.2buxkbd4d3ax2kpi@quack3> References: <170785993027.11135.8830043889278631735.stgit@91.116.238.104.host.secureserver.net> <170786025969.11135.16880338029664682984.stgit@91.116.238.104.host.secureserver.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <170786025969.11135.16880338029664682984.stgit@91.116.238.104.host.secureserver.net> X-Rspamd-Queue-Id: 8DF7610000E X-Rspam-User: X-Stat-Signature: 1mcadawk9go4ds6thhozif3ya3zdue1g X-Rspamd-Server: rspam01 X-HE-Tag: 1708001617-44521 X-HE-Meta: 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 ytYsr1jE peARG4fdaYOhvIDCOYn6TVb47bvA5aD827YV30ft2QA0eta4j6jNFHc9TAWNV7jEipAsnNK9EKewLuqmntw8po0y69gfX/hPgXUjNTO9pokWf3RaJXhqRNzLRFQdPlR2QqrYwnaI085aG72M+mX70XtHpC+tBtm8zB1qHIDTib1Ux8JCykl+F/rKvVT0WG3ka3iyYQDye2oqkDuyXjVp0h+QZmml8mlGwS00lhzlFdnm2bj9LRbynmYcC2EpwfTxUVqh5S4npWZRvCAPUtdpoNscDPfVP+zuNJIqdhMHxIyeJnMDdMtoDrTkqA6p8xGre9uO0BL1MevZ1tHUmi27eZDv1GHJeURIEEkvq X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue 13-02-24 16:37:39, Chuck Lever wrote: > From: Chuck Lever > > For simple filesystems that use directory offset mapping, rely > strictly on the directory offset map to tell when a directory has > no children. > > After this patch is applied, the emptiness test holds only the RCU > read lock when the directory being tested has no children. > > In addition, this adds another layer of confirmation that > simple_offset_add/remove() are working as expected. > > Signed-off-by: Chuck Lever Makes sense. Feel free to add: Reviewed-by: Jan Kara Honza > --- > fs/libfs.c | 32 ++++++++++++++++++++++++++++++++ > include/linux/fs.h | 1 + > mm/shmem.c | 4 ++-- > 3 files changed, 35 insertions(+), 2 deletions(-) > > diff --git a/fs/libfs.c b/fs/libfs.c > index a38af72f4719..3cf773950f93 100644 > --- a/fs/libfs.c > +++ b/fs/libfs.c > @@ -313,6 +313,38 @@ void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry) > offset_set(dentry, 0); > } > > +/** > + * simple_offset_empty - Check if a dentry can be unlinked > + * @dentry: dentry to be tested > + * > + * Returns 0 if @dentry is a non-empty directory; otherwise returns 1. > + */ > +int simple_offset_empty(struct dentry *dentry) > +{ > + struct inode *inode = d_inode(dentry); > + struct offset_ctx *octx; > + struct dentry *child; > + unsigned long index; > + int ret = 1; > + > + if (!inode || !S_ISDIR(inode->i_mode)) > + return ret; > + > + index = 2; > + octx = inode->i_op->get_offset_ctx(inode); > + xa_for_each(&octx->xa, index, child) { > + spin_lock(&child->d_lock); > + if (simple_positive(child)) { > + spin_unlock(&child->d_lock); > + ret = 0; > + break; > + } > + spin_unlock(&child->d_lock); > + } > + > + return ret; > +} > + > /** > * simple_offset_rename_exchange - exchange rename with directory offsets > * @old_dir: parent of dentry being moved > diff --git a/include/linux/fs.h b/include/linux/fs.h > index ed5966a70495..03d141809a2c 100644 > --- a/include/linux/fs.h > +++ b/include/linux/fs.h > @@ -3267,6 +3267,7 @@ struct offset_ctx { > void simple_offset_init(struct offset_ctx *octx); > int simple_offset_add(struct offset_ctx *octx, struct dentry *dentry); > void simple_offset_remove(struct offset_ctx *octx, struct dentry *dentry); > +int simple_offset_empty(struct dentry *dentry); > int simple_offset_rename_exchange(struct inode *old_dir, > struct dentry *old_dentry, > struct inode *new_dir, > diff --git a/mm/shmem.c b/mm/shmem.c > index d7c84ff62186..6fed524343cb 100644 > --- a/mm/shmem.c > +++ b/mm/shmem.c > @@ -3374,7 +3374,7 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry) > > static int shmem_rmdir(struct inode *dir, struct dentry *dentry) > { > - if (!simple_empty(dentry)) > + if (!simple_offset_empty(dentry)) > return -ENOTEMPTY; > > drop_nlink(d_inode(dentry)); > @@ -3431,7 +3431,7 @@ static int shmem_rename2(struct mnt_idmap *idmap, > return simple_offset_rename_exchange(old_dir, old_dentry, > new_dir, new_dentry); > > - if (!simple_empty(new_dentry)) > + if (!simple_offset_empty(new_dentry)) > return -ENOTEMPTY; > > if (flags & RENAME_WHITEOUT) { > > -- Jan Kara SUSE Labs, CR