CEPH-Devel Archive on lore.kernel.org
 help / color / Atom feed
From: Jeff Layton <jlayton@kernel.org>
To: ceph-devel@vger.kernel.org
Cc: linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org
Subject: [RFC PATCH v5 09/19] ceph: make ceph_msdc_build_path use ref-walk
Date: Fri, 26 Mar 2021 13:32:17 -0400
Message-ID: <20210326173227.96363-10-jlayton@kernel.org> (raw)
In-Reply-To: <20210326173227.96363-1-jlayton@kernel.org>

Encryption potentially requires allocation, at which point we'll need to
be in a non-atomic context. Convert ceph_msdc_build_path to take dentry
spinlocks and references instead of using rcu_read_lock to walk the
path.

This is slightly less efficient, and we may want to eventually allow
using RCU when the leaf dentry isn't encrypted.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
 fs/ceph/mds_client.c | 35 +++++++++++++++++++----------------
 1 file changed, 19 insertions(+), 16 deletions(-)

diff --git a/fs/ceph/mds_client.c b/fs/ceph/mds_client.c
index e3284de74ca4..d7a40e83f12f 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2323,7 +2323,8 @@ static inline  u64 __get_oldest_tid(struct ceph_mds_client *mdsc)
 char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
 			   int stop_on_nosnap)
 {
-	struct dentry *temp;
+	struct dentry *cur;
+	struct inode *inode;
 	char *path;
 	int pos;
 	unsigned seq;
@@ -2340,34 +2341,35 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
 	path[pos] = '\0';
 
 	seq = read_seqbegin(&rename_lock);
-	rcu_read_lock();
-	temp = dentry;
+	cur = dget(dentry);
 	for (;;) {
-		struct inode *inode;
+		struct dentry *temp;
 
-		spin_lock(&temp->d_lock);
-		inode = d_inode(temp);
+		spin_lock(&cur->d_lock);
+		inode = d_inode(cur);
 		if (inode && ceph_snap(inode) == CEPH_SNAPDIR) {
 			dout("build_path path+%d: %p SNAPDIR\n",
-			     pos, temp);
-		} else if (stop_on_nosnap && inode && dentry != temp &&
+			     pos, cur);
+		} else if (stop_on_nosnap && inode && dentry != cur &&
 			   ceph_snap(inode) == CEPH_NOSNAP) {
-			spin_unlock(&temp->d_lock);
+			spin_unlock(&cur->d_lock);
 			pos++; /* get rid of any prepended '/' */
 			break;
 		} else {
-			pos -= temp->d_name.len;
+			pos -= cur->d_name.len;
 			if (pos < 0) {
-				spin_unlock(&temp->d_lock);
+				spin_unlock(&cur->d_lock);
 				break;
 			}
-			memcpy(path + pos, temp->d_name.name, temp->d_name.len);
+			memcpy(path + pos, cur->d_name.name, cur->d_name.len);
 		}
+		temp = cur;
 		spin_unlock(&temp->d_lock);
-		temp = READ_ONCE(temp->d_parent);
+		cur = dget_parent(temp);
+		dput(temp);
 
 		/* Are we at the root? */
-		if (IS_ROOT(temp))
+		if (IS_ROOT(cur))
 			break;
 
 		/* Are we out of buffer? */
@@ -2376,8 +2378,9 @@ char *ceph_mdsc_build_path(struct dentry *dentry, int *plen, u64 *pbase,
 
 		path[pos] = '/';
 	}
-	base = ceph_ino(d_inode(temp));
-	rcu_read_unlock();
+	inode = d_inode(cur);
+	base = inode ? ceph_ino(inode) : 0;
+	dput(cur);
 
 	if (read_seqretry(&rename_lock, seq))
 		goto retry;
-- 
2.30.2


  parent reply index

Thread overview: 39+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-26 17:32 [RFC PATCH v5 00/19] ceph+fscrypt: context, filename and symlink support Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 01/19] vfs: export new_inode_pseudo Jeff Layton
2021-04-08  1:08   ` Eric Biggers
2021-04-08 16:18     ` Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 02/19] fscrypt: export fscrypt_base64_encode and fscrypt_base64_decode Jeff Layton
2021-04-08  1:06   ` Eric Biggers
2021-04-08 16:22     ` Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 03/19] fscrypt: export fscrypt_fname_encrypt and fscrypt_fname_encrypted_size Jeff Layton
2021-04-08  1:19   ` Eric Biggers
2021-03-26 17:32 ` [RFC PATCH v5 04/19] fscrypt: add fscrypt_context_for_new_inode Jeff Layton
2021-04-08  1:21   ` Eric Biggers
2021-04-08 16:27     ` Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 05/19] ceph: crypto context handling for ceph Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 06/19] ceph: implement -o test_dummy_encryption mount option Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 07/19] ceph: preallocate inode for ops that may create one Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 08/19] ceph: add routine to create fscrypt context prior to RPC Jeff Layton
2021-03-26 17:32 ` Jeff Layton [this message]
2021-03-26 17:32 ` [RFC PATCH v5 10/19] ceph: add encrypted fname handling to ceph_mdsc_build_path Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 11/19] ceph: decode alternate_name in lease info Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 12/19] ceph: send altname in MClientRequest Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 13/19] ceph: properly set DCACHE_NOKEY_NAME flag in lookup Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 14/19] ceph: make d_revalidate call fscrypt revalidator for encrypted dentries Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 15/19] ceph: add helpers for converting names for userland presentation Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 16/19] ceph: add fscrypt support to ceph_fill_trace Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 17/19] ceph: add support to readdir for encrypted filenames Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 18/19] ceph: create symlinks with encrypted and base64-encoded targets Jeff Layton
2021-03-26 17:32 ` [RFC PATCH v5 19/19] ceph: add fscrypt ioctls Jeff Layton
2021-04-06 15:38   ` Luis Henriques
2021-04-06 16:03     ` Jeff Layton
2021-04-06 16:24       ` Luis Henriques
2021-04-06 17:27         ` Jeff Layton
2021-04-06 18:04           ` Luis Henriques
2021-04-07 12:47             ` Jeff Layton
2021-03-26 18:38 ` [RFC PATCH v5 00/19] ceph+fscrypt: context, filename and symlink support Jeff Layton
2021-03-31 20:35 ` [RFC PATCH v5 20/19] ceph: make ceph_get_name decrypt filenames Jeff Layton
2021-04-01 11:14   ` Luis Henriques
2021-04-01 12:15     ` Jeff Layton
2021-04-01 13:05       ` Luis Henriques
2021-04-01 13:12         ` Jeff Layton

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210326173227.96363-10-jlayton@kernel.org \
    --to=jlayton@kernel.org \
    --cc=ceph-devel@vger.kernel.org \
    --cc=linux-fscrypt@vger.kernel.org \
    --cc=linux-fsdevel@vger.kernel.org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

CEPH-Devel Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/ceph-devel/0 ceph-devel/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 ceph-devel ceph-devel/ https://lore.kernel.org/ceph-devel \
		ceph-devel@vger.kernel.org
	public-inbox-index ceph-devel

Example config snippet for mirrors

Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.ceph-devel


AGPL code for this site: git clone https://public-inbox.org/public-inbox.git