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From: Jeff Layton <jlayton@kernel.org>
To: ceph-devel@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-fscrypt@vger.kernel.org,
	dhowells@redhat.com, xiubli@redhat.com, lhenriques@suse.de,
	khiremat@redhat.com, ebiggers@kernel.org
Subject: [RFC PATCH v8 13/24] ceph: make ceph_msdc_build_path use ref-walk
Date: Thu, 26 Aug 2021 12:20:03 -0400	[thread overview]
Message-ID: <20210826162014.73464-14-jlayton@kernel.org> (raw)
In-Reply-To: <20210826162014.73464-1-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 058480708897..518a1aee967c 100644
--- a/fs/ceph/mds_client.c
+++ b/fs/ceph/mds_client.c
@@ -2487,7 +2487,8 @@ 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;
@@ -2504,34 +2505,35 @@ 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? */
@@ -2540,8 +2542,9 @@ 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;
-- 
2.31.1


  parent reply	other threads:[~2021-08-26 16:20 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-26 16:19 [RFC PATCH v8 00/24] ceph+fscrypt: context, filename and symlink support Jeff Layton
2021-08-26 16:19 ` [RFC PATCH v8 01/24] vfs: export new_inode_pseudo Jeff Layton
2021-08-26 16:19 ` [RFC PATCH v8 02/24] fscrypt: export fscrypt_base64url_encode and fscrypt_base64url_decode Jeff Layton
2021-08-26 16:19 ` [RFC PATCH v8 03/24] fscrypt: export fscrypt_fname_encrypt and fscrypt_fname_encrypted_size Jeff Layton
2021-08-26 16:19 ` [RFC PATCH v8 04/24] fscrypt: add fscrypt_context_for_new_inode Jeff Layton
2021-08-26 16:19 ` [RFC PATCH v8 05/24] ceph: preallocate inode for ops that may create one Jeff Layton
2021-08-26 16:19 ` [RFC PATCH v8 06/24] ceph: parse new fscrypt_auth and fscrypt_file fields in inode traces Jeff Layton
2021-08-26 16:19 ` [RFC PATCH v8 07/24] ceph: add fscrypt_* handling to caps.c Jeff Layton
2021-08-26 16:19 ` [RFC PATCH v8 08/24] ceph: crypto context handling for ceph Jeff Layton
2021-08-26 16:19 ` [RFC PATCH v8 09/24] ceph: add ability to set fscrypt_auth via setattr Jeff Layton
2021-08-31  5:06   ` Xiubo Li
2021-08-31 12:43     ` Jeff Layton
2021-08-31 13:22       ` Xiubo Li
2021-08-31 13:50         ` Jeff Layton
2021-08-31 17:54           ` Eric Biggers
2021-09-01  0:53             ` Xiubo Li
2021-09-01  1:13           ` Xiubo Li
2021-09-01 12:02             ` Jeff Layton
2021-09-02  1:54               ` Xiubo Li
2021-08-26 16:20 ` [RFC PATCH v8 10/24] ceph: implement -o test_dummy_encryption mount option Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 11/24] ceph: add fscrypt ioctls Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 12/24] ceph: decode alternate_name in lease info Jeff Layton
2021-08-26 16:20 ` Jeff Layton [this message]
2021-08-26 16:20 ` [RFC PATCH v8 14/24] ceph: add encrypted fname handling to ceph_mdsc_build_path Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 15/24] ceph: send altname in MClientRequest Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 16/24] ceph: encode encrypted name in dentry release Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 17/24] ceph: properly set DCACHE_NOKEY_NAME flag in lookup Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 18/24] ceph: make d_revalidate call fscrypt revalidator for encrypted dentries Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 19/24] ceph: add helpers for converting names for userland presentation Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 20/24] ceph: add fscrypt support to ceph_fill_trace Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 21/24] ceph: add support to readdir for encrypted filenames Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 22/24] ceph: create symlinks with encrypted and base64-encoded targets Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 23/24] ceph: make ceph_get_name decrypt filenames Jeff Layton
2021-08-26 16:20 ` [RFC PATCH v8 24/24] ceph: add a new ceph.fscrypt.auth vxattr Jeff Layton

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