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replace ->follow_link() with new method that could stay in RCU mode

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new method: ->get_link(); replacement of ->follow_link().  The differences
are:
	* inode and dentry are passed separately
	* might be called both in RCU and non-RCU mode;
the former is indicated by passing it a NULL dentry.
	* when called that way it isn't allowed to block
and should return ERR_PTR(-ECHILD) if it needs to be called
in non-RCU mode.

It's a flagday change - the old method is gone, all in-tree instances
converted.  Conversion isn't hard; said that, so far very few instances
do not immediately bail out when called in RCU mode.  That'll change
in the next commits.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro
2015-11-17 10:20:54 -05:00
parent 21fc61c73c
commit 6b2553918d
45 changed files with 234 additions and 132 deletions
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22
fs/proc/base.c
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@@ -1564,12 +1564,15 @@ static int proc_exe_link(struct dentry *dentry, struct path *exe_path)
return -ENOENT;
}
static const char *proc_pid_follow_link(struct dentry *dentry, void **cookie)
static const char *proc_pid_get_link(struct dentry *dentry,
struct inode *inode, void **cookie)
{
struct inode *inode = d_inode(dentry);
struct path path;
int error = -EACCES;
if (!dentry)
return ERR_PTR(-ECHILD);
/* Are we allowed to snoop on the tasks file descriptors? */
if (!proc_fd_access_allowed(inode))
goto out;
@@ -1630,7 +1633,7 @@ out:
const struct inode_operations proc_pid_link_inode_operations = {
.readlink = proc_pid_readlink,
.follow_link = proc_pid_follow_link,
.get_link = proc_pid_get_link,
.setattr = proc_setattr,
};
@@ -1895,7 +1898,7 @@ static const struct dentry_operations tid_map_files_dentry_operations = {
.d_delete = pid_delete_dentry,
};
static int proc_map_files_get_link(struct dentry *dentry, struct path *path)
static int map_files_get_link(struct dentry *dentry, struct path *path)
{
unsigned long vm_start, vm_end;
struct vm_area_struct *vma;
@@ -1945,20 +1948,21 @@ struct map_files_info {
* path to the file in question.
*/
static const char *
proc_map_files_follow_link(struct dentry *dentry, void **cookie)
proc_map_files_get_link(struct dentry *dentry,
struct inode *inode, void **cookie)
{
if (!capable(CAP_SYS_ADMIN))
return ERR_PTR(-EPERM);
return proc_pid_follow_link(dentry, NULL);
return proc_pid_get_link(dentry, inode, NULL);
}
/*
* Identical to proc_pid_link_inode_operations except for follow_link()
* Identical to proc_pid_link_inode_operations except for get_link()
*/
static const struct inode_operations proc_map_files_link_inode_operations = {
.readlink = proc_pid_readlink,
.follow_link = proc_map_files_follow_link,
.get_link = proc_map_files_get_link,
.setattr = proc_setattr,
};
@@ -1975,7 +1979,7 @@ proc_map_files_instantiate(struct inode *dir, struct dentry *dentry,
return -ENOENT;
ei = PROC_I(inode);
ei->op.proc_get_link = proc_map_files_get_link;
ei->op.proc_get_link = map_files_get_link;
inode->i_op = &proc_map_files_link_inode_operations;
inode->i_size = 64;