linux/fs/exportfs/expfs.c

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#include <linux/exportfs.h>
#include <linux/fs.h>
#include <linux/file.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/namei.h>
#define dprintk(fmt, args...) do{}while(0)
static int get_name(struct dentry *dentry, char *name,
struct dentry *child);
static struct dentry *exportfs_get_dentry(struct super_block *sb, void *obj)
{
struct dentry *result = ERR_PTR(-ESTALE);
if (sb->s_export_op->get_dentry) {
result = sb->s_export_op->get_dentry(sb, obj);
if (!result)
result = ERR_PTR(-ESTALE);
}
return result;
}
static int exportfs_get_name(struct dentry *dir, char *name,
struct dentry *child)
{
struct export_operations *nop = dir->d_sb->s_export_op;
if (nop->get_name)
return nop->get_name(dir, name, child);
else
return get_name(dir, name, child);
}
/*
* Check if the dentry or any of it's aliases is acceptable.
*/
static struct dentry *
find_acceptable_alias(struct dentry *result,
int (*acceptable)(void *context, struct dentry *dentry),
void *context)
{
struct dentry *dentry, *toput = NULL;
if (acceptable(context, result))
return result;
spin_lock(&dcache_lock);
list_for_each_entry(dentry, &result->d_inode->i_dentry, d_alias) {
dget_locked(dentry);
spin_unlock(&dcache_lock);
if (toput)
dput(toput);
if (dentry != result && acceptable(context, dentry)) {
dput(result);
return dentry;
}
spin_lock(&dcache_lock);
toput = dentry;
}
spin_unlock(&dcache_lock);
if (toput)
dput(toput);
return NULL;
}
/*
* Find root of a disconnected subtree and return a reference to it.
*/
static struct dentry *
find_disconnected_root(struct dentry *dentry)
{
dget(dentry);
spin_lock(&dentry->d_lock);
while (!IS_ROOT(dentry) &&
(dentry->d_parent->d_flags & DCACHE_DISCONNECTED)) {
struct dentry *parent = dentry->d_parent;
dget(parent);
spin_unlock(&dentry->d_lock);
dput(dentry);
dentry = parent;
spin_lock(&dentry->d_lock);
}
spin_unlock(&dentry->d_lock);
return dentry;
}
/**
* find_exported_dentry - helper routine to implement export_operations->decode_fh
* @sb: The &super_block identifying the filesystem
* @obj: An opaque identifier of the object to be found - passed to
* get_inode
* @parent: An optional opqaue identifier of the parent of the object.
* @acceptable: A function used to test possible &dentries to see if they are
* acceptable
* @context: A parameter to @acceptable so that it knows on what basis to
* judge.
*
* find_exported_dentry is the central helper routine to enable file systems
* to provide the decode_fh() export_operation. It's main task is to take
* an &inode, find or create an appropriate &dentry structure, and possibly
* splice this into the dcache in the correct place.
*
* The decode_fh() operation provided by the filesystem should call
* find_exported_dentry() with the same parameters that it received except
* that instead of the file handle fragment, pointers to opaque identifiers
* for the object and optionally its parent are passed. The default decode_fh
* routine passes one pointer to the start of the filehandle fragment, and
* one 8 bytes into the fragment. It is expected that most filesystems will
* take this approach, though the offset to the parent identifier may well be
* different.
*
* find_exported_dentry() will call get_dentry to get an dentry pointer from
* the file system. If any &dentry in the d_alias list is acceptable, it will
* be returned. Otherwise find_exported_dentry() will attempt to splice a new
* &dentry into the dcache using get_name() and get_parent() to find the
* appropriate place.
*/
struct dentry *
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;
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.
*/
result = exportfs_get_dentry(sb, obj);
if (IS_ERR(result))
return result;
if (S_ISDIR(result->d_inode->i_mode)) {
if (!(result->d_flags & DCACHE_DISCONNECTED)) {
if (acceptable(context, result))
return result;
err = -EACCES;
goto err_result;
}
target_dir = dget(result);
} else {
alias = find_acceptable_alias(result, acceptable, context);
if (alias)
return alias;
if (parent == NULL)
goto err_result;
target_dir = exportfs_get_dentry(sb,parent);
if (IS_ERR(target_dir)) {
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;
}
}
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;
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));
mutex_unlock(&target_dir->d_inode->i_mutex);
if (!IS_ERR(nresult)) {
if (nresult->d_inode) {
dput(result);
result = nresult;
} else
dput(nresult);
}
}
}
dput(target_dir);
alias = find_acceptable_alias(result, acceptable, context);
if (alias)
return alias;
/* drat - I just cannot find anything acceptable */
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
* -EACCESS is safer
*/
return ERR_PTR(-EACCES);
err_target:
dput(target_dir);
err_result:
dput(result);
return ERR_PTR(err);
}
struct getdents_callback {
char *name; /* name that was found. It already points to a
buffer NAME_MAX+1 is size */
unsigned long ino; /* the inum we are looking for */
int found; /* inode matched? */
int sequence; /* sequence counter */
};
/*
* A rather strange filldir function to capture
* the name matching the specified inode number.
*/
static int filldir_one(void * __buf, const char * name, int len,
[PATCH] VFS: Make filldir_t and struct kstat deal in 64-bit inode numbers These patches make the kernel pass 64-bit inode numbers internally when communicating to userspace, even on a 32-bit system. They are required because some filesystems have intrinsic 64-bit inode numbers: NFS3+ and XFS for example. The 64-bit inode numbers are then propagated to userspace automatically where the arch supports it. Problems have been seen with userspace (eg: ld.so) using the 64-bit inode number returned by stat64() or getdents64() to differentiate files, and failing because the 64-bit inode number space was compressed to 32-bits, and so overlaps occur. This patch: Make filldir_t take a 64-bit inode number and struct kstat carry a 64-bit inode number so that 64-bit inode numbers can be passed back to userspace. The stat functions then returns the full 64-bit inode number where available and where possible. If it is not possible to represent the inode number supplied by the filesystem in the field provided by userspace, then error EOVERFLOW will be issued. Similarly, the getdents/readdir functions now pass the full 64-bit inode number to userspace where possible, returning EOVERFLOW instead when a directory entry is encountered that can't be properly represented. Note that this means that some inodes will not be stat'able on a 32-bit system with old libraries where they were before - but it does mean that there will be no ambiguity over what a 32-bit inode number refers to. Note similarly that directory scans may be cut short with an error on a 32-bit system with old libraries where the scan would work before for the same reasons. It is judged unlikely that this situation will occur because modern glibc uses 64-bit capable versions of stat and getdents class functions exclusively, and that older systems are unlikely to encounter unrepresentable inode numbers anyway. [akpm: alpha build fix] Signed-off-by: David Howells <dhowells@redhat.com> Cc: Trond Myklebust <trond.myklebust@fys.uio.no> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:13:46 +00:00
loff_t pos, u64 ino, unsigned int d_type)
{
struct getdents_callback *buf = __buf;
int result = 0;
buf->sequence++;
if (buf->ino == ino) {
memcpy(buf->name, name, len);
buf->name[len] = '\0';
buf->found = 1;
result = -1;
}
return result;
}
/**
* get_name - default export_operations->get_name function
* @dentry: the directory in which to find a name
* @name: a pointer to a %NAME_MAX+1 char buffer to store the name
* @child: the dentry for the child directory.
*
* calls readdir on the parent until it finds an entry with
* the same inode number as the child, and returns that.
*/
static int get_name(struct dentry *dentry, char *name,
struct dentry *child)
{
struct inode *dir = dentry->d_inode;
int error;
struct file *file;
struct getdents_callback buffer;
error = -ENOTDIR;
if (!dir || !S_ISDIR(dir->i_mode))
goto out;
error = -EINVAL;
if (!dir->i_fop)
goto out;
/*
* Open the directory ...
*/
file = dentry_open(dget(dentry), NULL, O_RDONLY);
error = PTR_ERR(file);
if (IS_ERR(file))
goto out;
error = -EINVAL;
if (!file->f_op->readdir)
goto out_close;
buffer.name = name;
buffer.ino = child->d_inode->i_ino;
buffer.found = 0;
buffer.sequence = 0;
while (1) {
int old_seq = buffer.sequence;
error = vfs_readdir(file, filldir_one, &buffer);
if (error < 0)
break;
error = 0;
if (buffer.found)
break;
error = -ENOENT;
if (old_seq == buffer.sequence)
break;
}
out_close:
fput(file);
out:
return error;
}
/**
* export_encode_fh - default export_operations->encode_fh function
* @dentry: the dentry to encode
* @fh: where to store the file handle fragment
* @max_len: maximum length to store there
* @connectable: whether to store parent information
*
* This default encode_fh function assumes that the 32 inode number
* is suitable for locating an inode, and that the generation number
* can be used to check that it is still valid. It places them in the
* filehandle fragment where export_decode_fh expects to find them.
*/
static int export_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
int connectable)
{
struct inode * inode = dentry->d_inode;
int len = *max_len;
int type = 1;
if (len < 2 || (connectable && len < 4))
return 255;
len = 2;
fh[0] = inode->i_ino;
fh[1] = inode->i_generation;
if (connectable && !S_ISDIR(inode->i_mode)) {
struct inode *parent;
spin_lock(&dentry->d_lock);
parent = dentry->d_parent->d_inode;
fh[2] = parent->i_ino;
fh[3] = parent->i_generation;
spin_unlock(&dentry->d_lock);
len = 4;
type = 2;
}
*max_len = len;
return type;
}
/**
* export_decode_fh - default export_operations->decode_fh function
* @sb: The superblock
* @fh: pointer to the file handle fragment
* @fh_len: length of file handle fragment
* @acceptable: function for testing acceptability of dentrys
* @context: context for @acceptable
*
* This is the default decode_fh() function.
* a fileid_type of 1 indicates that the filehandlefragment
* just contains an object identifier understood by get_dentry.
* a fileid_type of 2 says that there is also a directory
* identifier 8 bytes in to the filehandlefragement.
*/
static struct dentry *export_decode_fh(struct super_block *sb, __u32 *fh, int fh_len,
int fileid_type,
int (*acceptable)(void *context, struct dentry *de),
void *context)
{
__u32 parent[2];
parent[0] = parent[1] = 0;
if (fh_len < 2 || fileid_type > 2)
return NULL;
if (fileid_type == 2) {
if (fh_len > 2) parent[0] = fh[2];
if (fh_len > 3) parent[1] = fh[3];
}
return find_exported_dentry(sb, fh, parent,
acceptable, context);
}
int exportfs_encode_fh(struct dentry *dentry, __u32 *fh, int *max_len,
int connectable)
{
struct export_operations *nop = dentry->d_sb->s_export_op;
int error;
if (nop->encode_fh)
error = nop->encode_fh(dentry, fh, max_len, connectable);
else
error = export_encode_fh(dentry, fh, max_len, connectable);
return error;
}
EXPORT_SYMBOL_GPL(exportfs_encode_fh);
struct dentry *exportfs_decode_fh(struct vfsmount *mnt, __u32 *fh, int fh_len,
int fileid_type, int (*acceptable)(void *, struct dentry *),
void *context)
{
struct export_operations *nop = mnt->mnt_sb->s_export_op;
struct dentry *result;
if (nop->decode_fh) {
result = nop->decode_fh(mnt->mnt_sb, fh, fh_len, fileid_type,
acceptable, context);
} else {
result = export_decode_fh(mnt->mnt_sb, fh, fh_len, fileid_type,
acceptable, context);
}
return result;
}
EXPORT_SYMBOL_GPL(exportfs_decode_fh);
EXPORT_SYMBOL(find_exported_dentry);
MODULE_LICENSE("GPL");