From 3188b2955de3d01949ec54eb2c9ff1ecaa0a752d Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Mon, 23 Mar 2015 13:37:39 +1100 Subject: ovl: rearrange ovl_follow_link to it doesn't need to call ->put_link ovl_follow_link current calls ->put_link on an error path. However ->put_link is about to change in a way that it will be impossible to call it from ovl_follow_link. So rearrange the code to avoid the need for that error path. Specifically: move the kmalloc() call before the ->follow_link() call to the subordinate filesystem. Signed-off-by: NeilBrown Signed-off-by: Al Viro --- fs/overlayfs/inode.c | 25 ++++++++++++------------- 1 file changed, 12 insertions(+), 13 deletions(-) (limited to 'fs/overlayfs') diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 04f124884687..1b4b9c5e51b7 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -145,6 +145,7 @@ static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd) void *ret; struct dentry *realdentry; struct inode *realinode; + struct ovl_link_data *data = NULL; realdentry = ovl_dentry_real(dentry); realinode = realdentry->d_inode; @@ -152,25 +153,23 @@ static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd) if (WARN_ON(!realinode->i_op->follow_link)) return ERR_PTR(-EPERM); - ret = realinode->i_op->follow_link(realdentry, nd); - if (IS_ERR(ret)) - return ret; - if (realinode->i_op->put_link) { - struct ovl_link_data *data; - data = kmalloc(sizeof(struct ovl_link_data), GFP_KERNEL); - if (!data) { - realinode->i_op->put_link(realdentry, nd, ret); + if (!data) return ERR_PTR(-ENOMEM); - } data->realdentry = realdentry; - data->cookie = ret; + } - return data; - } else { - return NULL; + ret = realinode->i_op->follow_link(realdentry, nd); + if (IS_ERR(ret)) { + kfree(data); + return ret; } + + if (data) + data->cookie = ret; + + return data; } static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c) -- cgit v1.2.3 From 680baacbca69d18a6d7315374ad83d05ac9c0977 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 2 May 2015 13:32:22 -0400 Subject: new ->follow_link() and ->put_link() calling conventions a) instead of storing the symlink body (via nd_set_link()) and returning an opaque pointer later passed to ->put_link(), ->follow_link() _stores_ that opaque pointer (into void * passed by address by caller) and returns the symlink body. Returning ERR_PTR() on error, NULL on jump (procfs magic symlinks) and pointer to symlink body for normal symlinks. Stored pointer is ignored in all cases except the last one. Storing NULL for opaque pointer (or not storing it at all) means no call of ->put_link(). b) the body used to be passed to ->put_link() implicitly (via nameidata). Now only the opaque pointer is. In the cases when we used the symlink body to free stuff, ->follow_link() now should store it as opaque pointer in addition to returning it. Signed-off-by: Al Viro --- fs/overlayfs/inode.c | 18 ++++++++++-------- 1 file changed, 10 insertions(+), 8 deletions(-) (limited to 'fs/overlayfs') diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 1b4b9c5e51b7..235ad42afb57 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -140,12 +140,12 @@ struct ovl_link_data { void *cookie; }; -static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd) +static const char *ovl_follow_link(struct dentry *dentry, void **cookie, struct nameidata *nd) { - void *ret; struct dentry *realdentry; struct inode *realinode; struct ovl_link_data *data = NULL; + const char *ret; realdentry = ovl_dentry_real(dentry); realinode = realdentry->d_inode; @@ -160,19 +160,21 @@ static void *ovl_follow_link(struct dentry *dentry, struct nameidata *nd) data->realdentry = realdentry; } - ret = realinode->i_op->follow_link(realdentry, nd); - if (IS_ERR(ret)) { + ret = realinode->i_op->follow_link(realdentry, cookie, nd); + if (IS_ERR_OR_NULL(ret)) { kfree(data); return ret; } if (data) - data->cookie = ret; + data->cookie = *cookie; - return data; + *cookie = data; + + return ret; } -static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c) +static void ovl_put_link(struct dentry *dentry, void *c) { struct inode *realinode; struct ovl_link_data *data = c; @@ -181,7 +183,7 @@ static void ovl_put_link(struct dentry *dentry, struct nameidata *nd, void *c) return; realinode = data->realdentry->d_inode; - realinode->i_op->put_link(data->realdentry, nd, data->cookie); + realinode->i_op->put_link(data->realdentry, data->cookie); kfree(data); } -- cgit v1.2.3 From 6e77137b363b8d866ac29c5a0c95e953614fb2d8 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Sat, 2 May 2015 13:37:52 -0400 Subject: don't pass nameidata to ->follow_link() its only use is getting passed to nd_jump_link(), which can obtain it from current->nameidata Signed-off-by: Al Viro --- fs/overlayfs/inode.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/overlayfs') diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 235ad42afb57..9986833c9fcc 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -140,7 +140,7 @@ struct ovl_link_data { void *cookie; }; -static const char *ovl_follow_link(struct dentry *dentry, void **cookie, struct nameidata *nd) +static const char *ovl_follow_link(struct dentry *dentry, void **cookie) { struct dentry *realdentry; struct inode *realinode; @@ -160,7 +160,7 @@ static const char *ovl_follow_link(struct dentry *dentry, void **cookie, struct data->realdentry = realdentry; } - ret = realinode->i_op->follow_link(realdentry, cookie, nd); + ret = realinode->i_op->follow_link(realdentry, cookie); if (IS_ERR_OR_NULL(ret)) { kfree(data); return ret; -- cgit v1.2.3 From 5f2c4179e129bdc47870a81a65d0aff85aa18293 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 7 May 2015 11:14:26 -0400 Subject: switch ->put_link() from dentry to inode only one instance looks at that argument at all; that sole exception wants inode rather than dentry. Signed-off-by: Al Viro --- fs/overlayfs/inode.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'fs/overlayfs') diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c index 9986833c9fcc..308379b2d0b2 100644 --- a/fs/overlayfs/inode.c +++ b/fs/overlayfs/inode.c @@ -174,7 +174,7 @@ static const char *ovl_follow_link(struct dentry *dentry, void **cookie) return ret; } -static void ovl_put_link(struct dentry *dentry, void *c) +static void ovl_put_link(struct inode *unused, void *c) { struct inode *realinode; struct ovl_link_data *data = c; @@ -183,7 +183,7 @@ static void ovl_put_link(struct dentry *dentry, void *c) return; realinode = data->realdentry->d_inode; - realinode->i_op->put_link(data->realdentry, data->cookie); + realinode->i_op->put_link(realinode, data->cookie); kfree(data); } -- cgit v1.2.3