knfsd: exportfs: split out reconnecting a dentry from find_exported_dentry
There's a clear subfunctionality of reconnecting a given dentry to the main dentry tree in find_exported_dentry, that can be called both for the dentry we're looking for or it's parent directory. This patch splits the subfunctionality out into a separate helper to make the code more readable and document it's intent. As a nice side-optimization we can avoid getting a superfluous dentry reference count in the case we need to reconnect a directory on it's own. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Neil Brown <neilb@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Christoph Hellwig
Linus Torvalds
parent
dd90b50906
commit
019ab801cf
1 changed files with 141 additions and 128 deletions
|
|
@ -91,6 +91,129 @@ find_disconnected_root(struct dentry *dentry)
|
|||
return dentry;
|
||||
}
|
||||
|
||||
|
||||
/*
|
||||
* Make sure target_dir is fully connected to the dentry tree.
|
||||
*
|
||||
* It may already be, as the flag isn't always updated when connection happens.
|
||||
*/
|
||||
static int
|
||||
reconnect_path(struct super_block *sb, struct dentry *target_dir)
|
||||
{
|
||||
char nbuf[NAME_MAX+1];
|
||||
int noprogress = 0;
|
||||
int err = -ESTALE;
|
||||
|
||||
/*
|
||||
* It is possible that a confused file system might not let us complete
|
||||
* the path to the root. For example, if get_parent returns a directory
|
||||
* in which we cannot find a name for the child. While this implies a
|
||||
* very sick filesystem we don't want it to cause knfsd to spin. Hence
|
||||
* the noprogress counter. If we go through the loop 10 times (2 is
|
||||
* probably enough) without getting anywhere, we just give up
|
||||
*/
|
||||
while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
|
||||
struct dentry *pd = find_disconnected_root(target_dir);
|
||||
|
||||
if (!IS_ROOT(pd)) {
|
||||
/* must have found a connected parent - great */
|
||||
spin_lock(&pd->d_lock);
|
||||
pd->d_flags &= ~DCACHE_DISCONNECTED;
|
||||
spin_unlock(&pd->d_lock);
|
||||
noprogress = 0;
|
||||
} else if (pd == sb->s_root) {
|
||||
printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
|
||||
spin_lock(&pd->d_lock);
|
||||
pd->d_flags &= ~DCACHE_DISCONNECTED;
|
||||
spin_unlock(&pd->d_lock);
|
||||
noprogress = 0;
|
||||
} else {
|
||||
/*
|
||||
* We have hit the top of a disconnected path, try to
|
||||
* find parent and connect.
|
||||
*
|
||||
* Racing with some other process renaming a directory
|
||||
* isn't much of a problem here. If someone renames
|
||||
* the directory, it will end up properly connected,
|
||||
* which is what we want
|
||||
*
|
||||
* Getting the parent can't be supported generically,
|
||||
* the locking is too icky.
|
||||
*
|
||||
* Instead we just return EACCES. If server reboots
|
||||
* or inodes get flushed, you lose
|
||||
*/
|
||||
struct dentry *ppd = ERR_PTR(-EACCES);
|
||||
struct dentry *npd;
|
||||
|
||||
mutex_lock(&pd->d_inode->i_mutex);
|
||||
if (sb->s_export_op->get_parent)
|
||||
ppd = sb->s_export_op->get_parent(pd);
|
||||
mutex_unlock(&pd->d_inode->i_mutex);
|
||||
|
||||
if (IS_ERR(ppd)) {
|
||||
err = PTR_ERR(ppd);
|
||||
dprintk("%s: get_parent of %ld failed, err %d\n",
|
||||
__FUNCTION__, pd->d_inode->i_ino, err);
|
||||
dput(pd);
|
||||
break;
|
||||
}
|
||||
|
||||
dprintk("%s: find name of %lu in %lu\n", __FUNCTION__,
|
||||
pd->d_inode->i_ino, ppd->d_inode->i_ino);
|
||||
err = exportfs_get_name(ppd, nbuf, pd);
|
||||
if (err) {
|
||||
dput(ppd);
|
||||
dput(pd);
|
||||
if (err == -ENOENT)
|
||||
/* some race between get_parent and
|
||||
* get_name? just try again
|
||||
*/
|
||||
continue;
|
||||
break;
|
||||
}
|
||||
dprintk("%s: found name: %s\n", __FUNCTION__, nbuf);
|
||||
mutex_lock(&ppd->d_inode->i_mutex);
|
||||
npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
|
||||
mutex_unlock(&ppd->d_inode->i_mutex);
|
||||
if (IS_ERR(npd)) {
|
||||
err = PTR_ERR(npd);
|
||||
dprintk("%s: lookup failed: %d\n",
|
||||
__FUNCTION__, err);
|
||||
dput(ppd);
|
||||
dput(pd);
|
||||
break;
|
||||
}
|
||||
/* we didn't really want npd, we really wanted
|
||||
* a side-effect of the lookup.
|
||||
* hopefully, npd == pd, though it isn't really
|
||||
* a problem if it isn't
|
||||
*/
|
||||
if (npd == pd)
|
||||
noprogress = 0;
|
||||
else
|
||||
printk("%s: npd != pd\n", __FUNCTION__);
|
||||
dput(npd);
|
||||
dput(ppd);
|
||||
if (IS_ROOT(pd)) {
|
||||
/* something went wrong, we have to give up */
|
||||
dput(pd);
|
||||
break;
|
||||
}
|
||||
}
|
||||
dput(pd);
|
||||
}
|
||||
|
||||
if (target_dir->d_flags & DCACHE_DISCONNECTED) {
|
||||
/* something went wrong - oh-well */
|
||||
if (!err)
|
||||
err = -ESTALE;
|
||||
return err;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
/**
|
||||
* find_exported_dentry - helper routine to implement export_operations->decode_fh
|
||||
* @sb: The &super_block identifying the filesystem
|
||||
|
|
@ -128,13 +251,8 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
|
|||
int (*acceptable)(void *context, struct dentry *de),
|
||||
void *context)
|
||||
{
|
||||
struct dentry *result = NULL;
|
||||
struct dentry *target_dir;
|
||||
struct dentry *result, *alias;
|
||||
int err = -ESTALE;
|
||||
struct export_operations *nops = sb->s_export_op;
|
||||
struct dentry *alias;
|
||||
int noprogress;
|
||||
char nbuf[NAME_MAX+1];
|
||||
|
||||
/*
|
||||
* Attempt to find the inode.
|
||||
|
|
@ -151,8 +269,13 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
|
|||
goto err_result;
|
||||
}
|
||||
|
||||
target_dir = dget(result);
|
||||
err = reconnect_path(sb, result);
|
||||
if (err)
|
||||
goto err_result;
|
||||
} else {
|
||||
struct dentry *target_dir, *nresult;
|
||||
char nbuf[NAME_MAX+1];
|
||||
|
||||
alias = find_acceptable_alias(result, acceptable, context);
|
||||
if (alias)
|
||||
return alias;
|
||||
|
|
@ -165,129 +288,21 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
|
|||
err = PTR_ERR(target_dir);
|
||||
goto err_result;
|
||||
}
|
||||
}
|
||||
|
||||
/*
|
||||
* Now we need to make sure that target_dir is properly connected.
|
||||
* It may already be, as the flag isn't always updated when connection
|
||||
* happens.
|
||||
* So, we walk up parent links until we find a connected directory,
|
||||
* or we run out of directories. Then we find the parent, find
|
||||
* the name of the child in that parent, and do a lookup.
|
||||
* This should connect the child into the parent
|
||||
* We then repeat.
|
||||
*/
|
||||
|
||||
/* it is possible that a confused file system might not let us complete
|
||||
* the path to the root. For example, if get_parent returns a directory
|
||||
* in which we cannot find a name for the child. While this implies a
|
||||
* very sick filesystem we don't want it to cause knfsd to spin. Hence
|
||||
* the noprogress counter. If we go through the loop 10 times (2 is
|
||||
* probably enough) without getting anywhere, we just give up
|
||||
*/
|
||||
noprogress = 0;
|
||||
while (target_dir->d_flags & DCACHE_DISCONNECTED && noprogress++ < 10) {
|
||||
struct dentry *pd = find_disconnected_root(target_dir);
|
||||
|
||||
if (!IS_ROOT(pd)) {
|
||||
/* must have found a connected parent - great */
|
||||
spin_lock(&pd->d_lock);
|
||||
pd->d_flags &= ~DCACHE_DISCONNECTED;
|
||||
spin_unlock(&pd->d_lock);
|
||||
noprogress = 0;
|
||||
} else if (pd == sb->s_root) {
|
||||
printk(KERN_ERR "export: Eeek filesystem root is not connected, impossible\n");
|
||||
spin_lock(&pd->d_lock);
|
||||
pd->d_flags &= ~DCACHE_DISCONNECTED;
|
||||
spin_unlock(&pd->d_lock);
|
||||
noprogress = 0;
|
||||
} else {
|
||||
/*
|
||||
* We have hit the top of a disconnected path, try to
|
||||
* find parent and connect.
|
||||
*
|
||||
* Racing with some other process renaming a directory
|
||||
* isn't much of a problem here. If someone renames
|
||||
* the directory, it will end up properly connected,
|
||||
* which is what we want
|
||||
*
|
||||
* Getting the parent can't be supported generically,
|
||||
* the locking is too icky.
|
||||
*
|
||||
* Instead we just return EACCES. If server reboots
|
||||
* or inodes get flushed, you lose
|
||||
*/
|
||||
struct dentry *ppd = ERR_PTR(-EACCES);
|
||||
struct dentry *npd;
|
||||
|
||||
mutex_lock(&pd->d_inode->i_mutex);
|
||||
if (nops->get_parent)
|
||||
ppd = nops->get_parent(pd);
|
||||
mutex_unlock(&pd->d_inode->i_mutex);
|
||||
|
||||
if (IS_ERR(ppd)) {
|
||||
err = PTR_ERR(ppd);
|
||||
dprintk("find_exported_dentry: get_parent of %ld failed, err %d\n",
|
||||
pd->d_inode->i_ino, err);
|
||||
dput(pd);
|
||||
break;
|
||||
}
|
||||
dprintk("find_exported_dentry: find name of %lu in %lu\n", pd->d_inode->i_ino, ppd->d_inode->i_ino);
|
||||
err = exportfs_get_name(ppd, nbuf, pd);
|
||||
if (err) {
|
||||
dput(ppd);
|
||||
dput(pd);
|
||||
if (err == -ENOENT)
|
||||
/* some race between get_parent and
|
||||
* get_name? just try again
|
||||
*/
|
||||
continue;
|
||||
break;
|
||||
}
|
||||
dprintk("find_exported_dentry: found name: %s\n", nbuf);
|
||||
mutex_lock(&ppd->d_inode->i_mutex);
|
||||
npd = lookup_one_len(nbuf, ppd, strlen(nbuf));
|
||||
mutex_unlock(&ppd->d_inode->i_mutex);
|
||||
if (IS_ERR(npd)) {
|
||||
err = PTR_ERR(npd);
|
||||
dprintk("find_exported_dentry: lookup failed: %d\n", err);
|
||||
dput(ppd);
|
||||
dput(pd);
|
||||
break;
|
||||
}
|
||||
/* we didn't really want npd, we really wanted
|
||||
* a side-effect of the lookup.
|
||||
* hopefully, npd == pd, though it isn't really
|
||||
* a problem if it isn't
|
||||
*/
|
||||
if (npd == pd)
|
||||
noprogress = 0;
|
||||
else
|
||||
printk("find_exported_dentry: npd != pd\n");
|
||||
dput(npd);
|
||||
dput(ppd);
|
||||
if (IS_ROOT(pd)) {
|
||||
/* something went wrong, we have to give up */
|
||||
dput(pd);
|
||||
break;
|
||||
}
|
||||
err = reconnect_path(sb, target_dir);
|
||||
if (err) {
|
||||
dput(target_dir);
|
||||
goto err_result;
|
||||
}
|
||||
dput(pd);
|
||||
}
|
||||
|
||||
if (target_dir->d_flags & DCACHE_DISCONNECTED) {
|
||||
/* something went wrong - oh-well */
|
||||
if (!err)
|
||||
err = -ESTALE;
|
||||
goto err_target;
|
||||
}
|
||||
/* if we weren't after a directory, have one more step to go */
|
||||
if (result != target_dir) {
|
||||
struct dentry *nresult;
|
||||
/*
|
||||
* As we weren't after a directory, have one more step to go.
|
||||
*/
|
||||
err = exportfs_get_name(target_dir, nbuf, result);
|
||||
if (!err) {
|
||||
mutex_lock(&target_dir->d_inode->i_mutex);
|
||||
nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf));
|
||||
nresult = lookup_one_len(nbuf, target_dir,
|
||||
strlen(nbuf));
|
||||
mutex_unlock(&target_dir->d_inode->i_mutex);
|
||||
if (!IS_ERR(nresult)) {
|
||||
if (nresult->d_inode) {
|
||||
|
|
@ -297,8 +312,8 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
|
|||
dput(nresult);
|
||||
}
|
||||
}
|
||||
dput(target_dir);
|
||||
}
|
||||
dput(target_dir);
|
||||
|
||||
alias = find_acceptable_alias(result, acceptable, context);
|
||||
if (alias)
|
||||
|
|
@ -308,13 +323,11 @@ find_exported_dentry(struct super_block *sb, void *obj, void *parent,
|
|||
dput(result);
|
||||
/* It might be justifiable to return ESTALE here,
|
||||
* but the filehandle at-least looks reasonable good
|
||||
* and it just be a permission problem, so returning
|
||||
* and it may just be a permission problem, so returning
|
||||
* -EACCESS is safer
|
||||
*/
|
||||
return ERR_PTR(-EACCES);
|
||||
|
||||
err_target:
|
||||
dput(target_dir);
|
||||
err_result:
|
||||
dput(result);
|
||||
return ERR_PTR(err);
|
||||
|
|
|
|||
Loading…
Reference in a new issue