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From: Miklos Szeredi <mszeredi@redhat.com>
To: linux-unionfs@vger.kernel.org
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 06/28] ovl: Add helper ovl_already_copied_up()
Date: Tue, 29 May 2018 16:45:50 +0200	[thread overview]
Message-ID: <20180529144612.16675-7-mszeredi@redhat.com> (raw)
In-Reply-To: <20180529144612.16675-1-mszeredi@redhat.com>

From: Vivek Goyal <vgoyal@redhat.com>

There are couple of places where we need to know if file is already copied
up (in lockless manner).  Right now its open coded and there are only two
conditions to check.  Soon this patch series will introduce another
condition to check and Amir wants to introduce one more.  So introduce a
helper instead to check this so that code is easier to read.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
 fs/overlayfs/copy_up.c   | 20 ++------------------
 fs/overlayfs/overlayfs.h |  1 +
 fs/overlayfs/util.c      | 26 +++++++++++++++++++++++++-
 3 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 38cfd1acc196..6247617fea0b 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -761,21 +761,7 @@ int ovl_copy_up_flags(struct dentry *dentry, int flags)
 		struct dentry *next;
 		struct dentry *parent = NULL;
 
-		/*
-		 * Check if copy-up has happened as well as for upper alias (in
-		 * case of hard links) is there.
-		 *
-		 * Both checks are lockless:
-		 *  - false negatives: will recheck under oi->lock
-		 *  - false positives:
-		 *    + ovl_dentry_upper() uses memory barriers to ensure the
-		 *      upper dentry is up-to-date
-		 *    + ovl_dentry_has_upper_alias() relies on locking of
-		 *      upper parent i_rwsem to prevent reordering copy-up
-		 *      with rename.
-		 */
-		if (ovl_dentry_upper(dentry) &&
-		    (ovl_dentry_has_upper_alias(dentry) || disconnected))
+		if (ovl_already_copied_up(dentry))
 			break;
 
 		next = dget(dentry);
@@ -803,9 +789,7 @@ int ovl_copy_up_flags(struct dentry *dentry, int flags)
 static bool ovl_open_need_copy_up(struct dentry *dentry, int flags)
 {
 	/* Copy up of disconnected dentry does not set upper alias */
-	if (ovl_dentry_upper(dentry) &&
-	    (ovl_dentry_has_upper_alias(dentry) ||
-	     (dentry->d_flags & DCACHE_DISCONNECTED)))
+	if (ovl_already_copied_up(dentry))
 		return false;
 
 	if (special_file(d_inode(dentry)->i_mode))
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 9172d3d5d870..2a9c5a80ae48 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -238,6 +238,7 @@ bool ovl_is_whiteout(struct dentry *dentry);
 struct file *ovl_path_open(struct path *path, int flags);
 int ovl_copy_up_start(struct dentry *dentry);
 void ovl_copy_up_end(struct dentry *dentry);
+bool ovl_already_copied_up(struct dentry *dentry);
 bool ovl_check_origin_xattr(struct dentry *dentry);
 bool ovl_check_dir_xattr(struct dentry *dentry, const char *name);
 int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index 25d202b47326..43235294e77b 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -377,13 +377,37 @@ struct file *ovl_path_open(struct path *path, int flags)
 	return dentry_open(path, flags | O_NOATIME, current_cred());
 }
 
+bool ovl_already_copied_up(struct dentry *dentry)
+{
+	bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
+
+	/*
+	 * Check if copy-up has happened as well as for upper alias (in
+	 * case of hard links) is there.
+	 *
+	 * Both checks are lockless:
+	 *  - false negatives: will recheck under oi->lock
+	 *  - false positives:
+	 *    + ovl_dentry_upper() uses memory barriers to ensure the
+	 *      upper dentry is up-to-date
+	 *    + ovl_dentry_has_upper_alias() relies on locking of
+	 *      upper parent i_rwsem to prevent reordering copy-up
+	 *      with rename.
+	 */
+	if (ovl_dentry_upper(dentry) &&
+	    (ovl_dentry_has_upper_alias(dentry) || disconnected))
+		return true;
+
+	return false;
+}
+
 int ovl_copy_up_start(struct dentry *dentry)
 {
 	struct ovl_inode *oi = OVL_I(d_inode(dentry));
 	int err;
 
 	err = mutex_lock_interruptible(&oi->lock);
-	if (!err && ovl_dentry_has_upper_alias(dentry)) {
+	if (!err && ovl_already_copied_up(dentry)) {
 		err = 1; /* Already copied up */
 		mutex_unlock(&oi->lock);
 	}
-- 
2.14.3

  parent reply	other threads:[~2018-05-29 14:46 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-29 14:45 [PATCH 00/28] overlayfs: Delayed copy up of data Miklos Szeredi
2018-05-29 14:45 ` [PATCH 01/28] ovl: Initialize ovl_inode->redirect in ovl_get_inode() Miklos Szeredi
2018-05-29 14:45 ` [PATCH 02/28] ovl: Move the copy up helpers to copy_up.c Miklos Szeredi
2018-05-29 14:45 ` [PATCH 03/28] ovl: Provide a mount option metacopy=on/off for metadata copyup Miklos Szeredi
2018-05-29 20:44   ` Randy Dunlap
2018-05-30  8:27     ` Miklos Szeredi
2018-05-29 14:45 ` [PATCH 04/28] ovl: During copy up, first copy up metadata and then data Miklos Szeredi
2018-05-29 14:45 ` [PATCH 05/28] ovl: Copy up only metadata during copy up where it makes sense Miklos Szeredi
2018-05-29 14:45 ` Miklos Szeredi [this message]
2018-05-29 14:45 ` [PATCH 07/28] ovl: A new xattr OVL_XATTR_METACOPY for file on upper Miklos Szeredi
2018-05-29 14:45 ` [PATCH 08/28] ovl: Use out_err instead of out_nomem Miklos Szeredi
2018-05-29 14:45 ` [PATCH 09/28] ovl: Modify ovl_lookup() and friends to lookup metacopy dentry Miklos Szeredi
2018-05-29 14:45 ` [PATCH 10/28] ovl: Copy up meta inode data from lowest data inode Miklos Szeredi
2018-05-29 14:45 ` [PATCH 11/28] ovl: Add helper ovl_dentry_lowerdata() to get lower data dentry Miklos Szeredi
2018-05-29 14:45 ` [PATCH 12/28] ovl: Fix ovl_getattr() to get number of blocks from lower Miklos Szeredi
2018-05-29 14:45 ` [PATCH 13/28] ovl: Store lower data inode in ovl_inode Miklos Szeredi
2018-05-29 14:45 ` [PATCH 14/28] ovl: Add helper ovl_inode_realdata() Miklos Szeredi
2018-05-29 14:45 ` [PATCH 15/28] ovl: Open file with data except for the case of fsync Miklos Szeredi
2018-05-30 14:30   ` Vivek Goyal
2018-05-30 15:12     ` Miklos Szeredi
2018-05-30 15:48       ` Vivek Goyal
2018-05-29 14:46 ` [PATCH 16/28] ovl: Do not expose metacopy only dentry from d_real() Miklos Szeredi
2018-05-30 21:05   ` Vivek Goyal
2018-05-31  4:30     ` Amir Goldstein
2018-05-29 14:46 ` [PATCH 17/28] ovl: Move some dir related ovl_lookup_single() code in else block Miklos Szeredi
2018-05-29 14:46 ` [PATCH 18/28] ovl: Check redirects for metacopy files Miklos Szeredi
2018-05-29 14:46 ` [PATCH 19/28] ovl: Treat metacopy dentries as type OVL_PATH_MERGE Miklos Szeredi
2018-05-29 14:46 ` [PATCH 20/28] ovl: Add an inode flag OVL_CONST_INO Miklos Szeredi
2018-05-29 14:46 ` [PATCH 21/28] ovl: Do not set dentry type ORIGIN for broken hardlinks Miklos Szeredi
2018-05-29 14:46 ` [PATCH 22/28] ovl: Set redirect on metacopy files upon rename Miklos Szeredi
2018-05-29 14:46 ` [PATCH 23/28] ovl: Set redirect on upper inode when it is linked Miklos Szeredi
2018-05-29 14:46 ` [PATCH 24/28] ovl: Check redirect on index as well Miklos Szeredi
2018-05-29 14:46 ` [PATCH 25/28] ovl: Disbale metacopy for MAP_SHARED mmap() Miklos Szeredi
2018-05-29 14:46 ` [PATCH 26/28] ovl: Do not do metadata only copy-up for truncate operation Miklos Szeredi
2018-05-29 14:46 ` [PATCH 27/28] ovl: Do not do metacopy only for ioctl modifying file attr Miklos Szeredi
2018-05-29 14:46 ` [PATCH 28/28] ovl: Enable metadata only feature Miklos Szeredi

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