diff options
Diffstat (limited to 'fs/exportfs/expfs.c')
| -rw-r--r-- | fs/exportfs/expfs.c | 819 |
1 files changed, 411 insertions, 408 deletions
diff --git a/fs/exportfs/expfs.c b/fs/exportfs/expfs.c index c49d6254379..b01fbfb51f4 100644 --- a/fs/exportfs/expfs.c +++ b/fs/exportfs/expfs.c @@ -1,318 +1,238 @@ - +/* + * Copyright (C) Neil Brown 2002 + * Copyright (C) Christoph Hellwig 2007 + * + * This file contains the code mapping from inodes to NFS file handles, + * and for mapping back from file handles to dentries. + * + * For details on why we do all the strange and hairy things in here + * take a look at Documentation/filesystems/nfs/Exporting. + */ +#include <linux/exportfs.h> #include <linux/fs.h> #include <linux/file.h> #include <linux/module.h> -#include <linux/smp_lock.h> +#include <linux/mount.h> #include <linux/namei.h> +#include <linux/sched.h> -struct export_operations export_op_default; +#define dprintk(fmt, args...) do{}while(0) -#define CALL(ops,fun) ((ops->fun)?(ops->fun):export_op_default.fun) -#define dprintk(fmt, args...) do{}while(0) +static int get_name(const struct path *path, char *name, struct dentry *child); -/** - * 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) +static int exportfs_get_name(struct vfsmount *mnt, struct dentry *dir, + char *name, struct dentry *child) { - struct dentry *result = NULL; - struct dentry *target_dir; - int err; - struct export_operations *nops = sb->s_export_op; - struct list_head *le, *head; - struct dentry *toput = NULL; - int noprogress; - char nbuf[NAME_MAX+1]; + const struct export_operations *nop = dir->d_sb->s_export_op; + struct path path = {.mnt = mnt, .dentry = dir}; - /* - * Attempt to find the inode. - */ - result = CALL(sb->s_export_op,get_dentry)(sb,obj); - err = -ESTALE; - if (result == NULL) - goto err_out; - if (IS_ERR(result)) { - err = PTR_ERR(result); - goto err_out; - } - if (S_ISDIR(result->d_inode->i_mode) && - (result->d_flags & DCACHE_DISCONNECTED)) { - /* it is an unconnected directory, we must connect it */ - ; - } else { - if (acceptable(context, result)) - return result; - if (S_ISDIR(result->d_inode->i_mode)) { - /* there is no other dentry, so fail */ - goto err_result; - } - /* try any other aliases */ - spin_lock(&dcache_lock); - head = &result->d_inode->i_dentry; - list_for_each(le, head) { - struct dentry *dentry = list_entry(le, struct dentry, d_alias); - dget_locked(dentry); - spin_unlock(&dcache_lock); - if (toput) - dput(toput); - toput = NULL; - if (dentry != result && - acceptable(context, dentry)) { - dput(result); - return dentry; - } - spin_lock(&dcache_lock); - toput = dentry; - } - spin_unlock(&dcache_lock); - if (toput) - dput(toput); - } - - /* It's a directory, or we are required to confirm the file's - * location in the tree based on the parent information - */ - dprintk("find_exported_dentry: need to look harder for %s/%d\n",sb->s_id,*(int*)obj); - if (S_ISDIR(result->d_inode->i_mode)) - target_dir = dget(result); - else { - if (parent == NULL) - goto err_result; - - target_dir = CALL(sb->s_export_op,get_dentry)(sb,parent); - if (IS_ERR(target_dir)) - err = PTR_ERR(target_dir); - if (target_dir == NULL || IS_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. - */ + if (nop->get_name) + return nop->get_name(dir, name, child); + else + return get_name(&path, name, child); +} - /* 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 = target_dir; - - dget(pd); - spin_lock(&pd->d_lock); - while (!IS_ROOT(pd) && - (pd->d_parent->d_flags&DCACHE_DISCONNECTED)) { - struct dentry *parent = pd->d_parent; - - dget(parent); - spin_unlock(&pd->d_lock); - dput(pd); - pd = parent; - spin_lock(&pd->d_lock); - } - spin_unlock(&pd->d_lock); - - 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 - * note: 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 - */ - struct dentry *ppd; - struct dentry *npd; - - down(&pd->d_inode->i_sem); - ppd = CALL(nops,get_parent)(pd); - up(&pd->d_inode->i_sem); - - 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 = CALL(nops,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); - down(&ppd->d_inode->i_sem); - npd = lookup_one_len(nbuf, ppd, strlen(nbuf)); - up(&ppd->d_inode->i_sem); - 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); - } +/* + * 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; + struct inode *inode; - 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 = CALL(nops,get_name)(target_dir, nbuf, result); - if (!err) { - down(&target_dir->d_inode->i_sem); - nresult = lookup_one_len(nbuf, target_dir, strlen(nbuf)); - up(&target_dir->d_inode->i_sem); - if (!IS_ERR(nresult)) { - if (nresult->d_inode) { - dput(result); - result = nresult; - } else - dput(nresult); - } - } - } - dput(target_dir); - /* now result is properly connected, it is our best bet */ if (acceptable(context, result)) return result; - /* one last try of the aliases.. */ - spin_lock(&dcache_lock); - toput = NULL; - head = &result->d_inode->i_dentry; - list_for_each(le, head) { - struct dentry *dentry = list_entry(le, struct dentry, d_alias); - dget_locked(dentry); - spin_unlock(&dcache_lock); - if (toput) dput(toput); - if (dentry != result && - acceptable(context, dentry)) { + + inode = result->d_inode; + spin_lock(&inode->i_lock); + hlist_for_each_entry(dentry, &inode->i_dentry, d_alias) { + dget(dentry); + spin_unlock(&inode->i_lock); + if (toput) + dput(toput); + if (dentry != result && acceptable(context, dentry)) { dput(result); return dentry; } - spin_lock(&dcache_lock); + spin_lock(&inode->i_lock); toput = dentry; } - spin_unlock(&dcache_lock); + spin_unlock(&inode->i_lock); + if (toput) dput(toput); + return NULL; +} - /* 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); - err_out: - return ERR_PTR(err); +static bool dentry_connected(struct dentry *dentry) +{ + dget(dentry); + while (dentry->d_flags & DCACHE_DISCONNECTED) { + struct dentry *parent = dget_parent(dentry); + + dput(dentry); + if (IS_ROOT(dentry)) { + dput(parent); + return false; + } + dentry = parent; + } + dput(dentry); + return true; } +static void clear_disconnected(struct dentry *dentry) +{ + dget(dentry); + while (dentry->d_flags & DCACHE_DISCONNECTED) { + struct dentry *parent = dget_parent(dentry); + + WARN_ON_ONCE(IS_ROOT(dentry)); + spin_lock(&dentry->d_lock); + dentry->d_flags &= ~DCACHE_DISCONNECTED; + spin_unlock(&dentry->d_lock); -static struct dentry *get_parent(struct dentry *child) + dput(dentry); + dentry = parent; + } + dput(dentry); +} + +/* + * Reconnect a directory dentry with its parent. + * + * This can return a dentry, or NULL, or an error. + * + * In the first case the returned dentry is the parent of the given + * dentry, and may itself need to be reconnected to its parent. + * + * In the NULL case, a concurrent VFS operation has either renamed or + * removed this directory. The concurrent operation has reconnected our + * dentry, so we no longer need to. + */ +static struct dentry *reconnect_one(struct vfsmount *mnt, + struct dentry *dentry, char *nbuf) { - /* get_parent cannot be supported generically, the locking - * is too icky. - * instead, we just return EACCES. If server reboots or inodes - * get flushed, you lose + struct dentry *parent; + struct dentry *tmp; + int err; + + parent = ERR_PTR(-EACCES); + mutex_lock(&dentry->d_inode->i_mutex); + if (mnt->mnt_sb->s_export_op->get_parent) + parent = mnt->mnt_sb->s_export_op->get_parent(dentry); + mutex_unlock(&dentry->d_inode->i_mutex); + + if (IS_ERR(parent)) { + dprintk("%s: get_parent of %ld failed, err %d\n", + __func__, dentry->d_inode->i_ino, PTR_ERR(parent)); + return parent; + } + + dprintk("%s: find name of %lu in %lu\n", __func__, + dentry->d_inode->i_ino, parent->d_inode->i_ino); + err = exportfs_get_name(mnt, parent, nbuf, dentry); + if (err == -ENOENT) + goto out_reconnected; + if (err) + goto out_err; + dprintk("%s: found name: %s\n", __func__, nbuf); + mutex_lock(&parent->d_inode->i_mutex); + tmp = lookup_one_len(nbuf, parent, strlen(nbuf)); + mutex_unlock(&parent->d_inode->i_mutex); + if (IS_ERR(tmp)) { + dprintk("%s: lookup failed: %d\n", __func__, PTR_ERR(tmp)); + goto out_err; + } + if (tmp != dentry) { + dput(tmp); + goto out_reconnected; + } + dput(tmp); + if (IS_ROOT(dentry)) { + err = -ESTALE; + goto out_err; + } + return parent; + +out_err: + dput(parent); + return ERR_PTR(err); +out_reconnected: + dput(parent); + /* + * Someone must have renamed our entry into another parent, in + * which case it has been reconnected by the rename. + * + * Or someone removed it entirely, in which case filehandle + * lookup will succeed but the directory is now IS_DEAD and + * subsequent operations on it will fail. + * + * Alternatively, maybe there was no race at all, and the + * filesystem is just corrupt and gave us a parent that doesn't + * actually contain any entry pointing to this inode. So, + * double check that this worked and return -ESTALE if not: */ - return ERR_PTR(-EACCES); + if (!dentry_connected(dentry)) + return ERR_PTR(-ESTALE); + return NULL; } +/* + * Make sure target_dir is fully connected to the dentry tree. + * + * On successful return, DCACHE_DISCONNECTED will be cleared on + * target_dir, and target_dir->d_parent->...->d_parent will reach the + * root of the filesystem. + * + * Whenever DCACHE_DISCONNECTED is unset, target_dir is fully connected. + * But the converse is not true: target_dir may have DCACHE_DISCONNECTED + * set but already be connected. In that case we'll verify the + * connection to root and then clear the flag. + * + * Note that target_dir could be removed by a concurrent operation. In + * that case reconnect_path may still succeed with target_dir fully + * connected, but further operations using the filehandle will fail when + * necessary (due to S_DEAD being set on the directory). + */ +static int +reconnect_path(struct vfsmount *mnt, struct dentry *target_dir, char *nbuf) +{ + struct dentry *dentry, *parent; + + dentry = dget(target_dir); + + while (dentry->d_flags & DCACHE_DISCONNECTED) { + BUG_ON(dentry == mnt->mnt_sb->s_root); + + if (IS_ROOT(dentry)) + parent = reconnect_one(mnt, dentry, nbuf); + else + parent = dget_parent(dentry); + + if (!parent) + break; + dput(dentry); + if (IS_ERR(parent)) + return PTR_ERR(parent); + dentry = parent; + } + dput(dentry); + clear_disconnected(target_dir); + return 0; +} struct getdents_callback { + struct dir_context ctx; 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 */ + u64 ino; /* the inum we are looking for */ int found; /* inode matched? */ int sequence; /* sequence counter */ }; @@ -322,13 +242,13 @@ struct getdents_callback { * the name matching the specified inode number. */ static int filldir_one(void * __buf, const char * name, int len, - loff_t pos, ino_t ino, unsigned int d_type) + loff_t pos, u64 ino, unsigned int d_type) { struct getdents_callback *buf = __buf; int result = 0; buf->sequence++; - if (buf->ino == ino) { + if (buf->ino == ino && len <= NAME_MAX) { memcpy(buf->name, name, len); buf->name[len] = '\0'; buf->found = 1; @@ -339,20 +259,28 @@ static int filldir_one(void * __buf, const char * name, int len, /** * get_name - default export_operations->get_name function - * @dentry: the directory in which to find a name + * @path: 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) +static int get_name(const struct path *path, char *name, struct dentry *child) { - struct inode *dir = dentry->d_inode; + const struct cred *cred = current_cred(); + struct inode *dir = path->dentry->d_inode; int error; struct file *file; - struct getdents_callback buffer; + struct kstat stat; + struct path child_path = { + .mnt = path->mnt, + .dentry = child, + }; + struct getdents_callback buffer = { + .ctx.actor = filldir_one, + .name = name, + }; error = -ENOTDIR; if (!dir || !S_ISDIR(dir->i_mode)) @@ -361,32 +289,40 @@ static int get_name(struct dentry *dentry, char *name, if (!dir->i_fop) goto out; /* + * inode->i_ino is unsigned long, kstat->ino is u64, so the + * former would be insufficient on 32-bit hosts when the + * filesystem supports 64-bit inode numbers. So we need to + * actually call ->getattr, not just read i_ino: + */ + error = vfs_getattr_nosec(&child_path, &stat); + if (error) + return error; + buffer.ino = stat.ino; + /* * Open the directory ... */ - file = dentry_open(dget(dentry), NULL, O_RDONLY); + file = dentry_open(path, O_RDONLY, cred); error = PTR_ERR(file); if (IS_ERR(file)) goto out; error = -EINVAL; - if (!file->f_op->readdir) + if (!file->f_op->iterate) 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); + error = iterate_dir(file, &buffer.ctx); + if (buffer.found) { + error = 0; + break; + } if (error < 0) break; - error = 0; - if (buffer.found) - break; error = -ENOENT; if (old_seq == buffer.sequence) break; @@ -398,143 +334,210 @@ out: return error; } - -static struct dentry *export_iget(struct super_block *sb, unsigned long ino, __u32 generation) -{ - - /* iget isn't really right if the inode is currently unallocated!! - * This should really all be done inside each filesystem - * - * ext2fs' read_inode has been strengthed to return a bad_inode if - * the inode had been deleted. - * - * Currently we don't know the generation for parent directory, so - * a generation of 0 means "accept any" - */ - struct inode *inode; - struct dentry *result; - if (ino == 0) - return ERR_PTR(-ESTALE); - inode = iget(sb, ino); - if (inode == NULL) - return ERR_PTR(-ENOMEM); - if (is_bad_inode(inode) - || (generation && inode->i_generation != generation) - ) { - /* we didn't find the right inode.. */ - dprintk("fh_verify: Inode %lu, Bad count: %d %d or version %u %u\n", - inode->i_ino, - inode->i_nlink, atomic_read(&inode->i_count), - inode->i_generation, - generation); - - iput(inode); - return ERR_PTR(-ESTALE); - } - /* now to find a dentry. - * If possible, get a well-connected one - */ - result = d_alloc_anon(inode); - if (!result) { - iput(inode); - return ERR_PTR(-ENOMEM); - } - return result; -} - - -static struct dentry *get_object(struct super_block *sb, void *vobjp) -{ - __u32 *objp = vobjp; - unsigned long ino = objp[0]; - __u32 generation = objp[1]; - - return export_iget(sb, ino, generation); -} - - /** * export_encode_fh - default export_operations->encode_fh function - * @dentry: the dentry to encode - * @fh: where to store the file handle fragment + * @inode: the object to encode + * @fid: where to store the file handle fragment * @max_len: maximum length to store there - * @connectable: whether to store parent information + * @parent: parent directory inode, if wanted * * 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) +static int export_encode_fh(struct inode *inode, struct fid *fid, + int *max_len, struct inode *parent) { - struct inode * inode = dentry->d_inode; int len = *max_len; - int type = 1; - - if (len < 2 || (connectable && len < 4)) - return 255; + int type = FILEID_INO32_GEN; + + if (parent && (len < 4)) { + *max_len = 4; + return FILEID_INVALID; + } else if (len < 2) { + *max_len = 2; + return FILEID_INVALID; + } 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); + fid->i32.ino = inode->i_ino; + fid->i32.gen = inode->i_generation; + if (parent) { + fid->i32.parent_ino = parent->i_ino; + fid->i32.parent_gen = parent->i_generation; len = 4; - type = 2; + type = FILEID_INO32_GEN_PARENT; } *max_len = len; return type; } +int exportfs_encode_inode_fh(struct inode *inode, struct fid *fid, + int *max_len, struct inode *parent) +{ + const struct export_operations *nop = inode->i_sb->s_export_op; -/** - * 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) + if (nop && nop->encode_fh) + return nop->encode_fh(inode, fid->raw, max_len, parent); + + return export_encode_fh(inode, fid, max_len, parent); +} +EXPORT_SYMBOL_GPL(exportfs_encode_inode_fh); + +int exportfs_encode_fh(struct dentry *dentry, struct fid *fid, int *max_len, + int connectable) { - __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]; + int error; + struct dentry *p = NULL; + struct inode *inode = dentry->d_inode, *parent = NULL; + + if (connectable && !S_ISDIR(inode->i_mode)) { + p = dget_parent(dentry); + /* + * note that while p might've ceased to be our parent already, + * it's still pinned by and still positive. + */ + parent = p->d_inode; } - return find_exported_dentry(sb, fh, parent, - acceptable, context); + + error = exportfs_encode_inode_fh(inode, fid, max_len, parent); + dput(p); + + return error; } +EXPORT_SYMBOL_GPL(exportfs_encode_fh); -struct export_operations export_op_default = { - .decode_fh = export_decode_fh, - .encode_fh = export_encode_fh, +struct dentry *exportfs_decode_fh(struct vfsmount *mnt, struct fid *fid, + int fh_len, int fileid_type, + int (*acceptable)(void *, struct dentry *), void *context) +{ + const struct export_operations *nop = mnt->mnt_sb->s_export_op; + struct dentry *result, *alias; + char nbuf[NAME_MAX+1]; + int err; - .get_name = get_name, - .get_parent = get_parent, - .get_dentry = get_object, -}; + /* + * Try to get any dentry for the given file handle from the filesystem. + */ + if (!nop || !nop->fh_to_dentry) + return ERR_PTR(-ESTALE); + result = nop->fh_to_dentry(mnt->mnt_sb, fid, fh_len, fileid_type); + if (!result) + result = ERR_PTR(-ESTALE); + if (IS_ERR(result)) + return result; + + if (S_ISDIR(result->d_inode->i_mode)) { + /* + * This request is for a directory. + * + * On the positive side there is only one dentry for each + * directory inode. On the negative side this implies that we + * to ensure our dentry is connected all the way up to the + * filesystem root. + */ + if (result->d_flags & DCACHE_DISCONNECTED) { + err = reconnect_path(mnt, result, nbuf); + if (err) + goto err_result; + } + + if (!acceptable(context, result)) { + err = -EACCES; + goto err_result; + } + + return result; + } else { + /* + * It's not a directory. Life is a little more complicated. + */ + struct dentry *target_dir, *nresult; + + /* + * See if either the dentry we just got from the filesystem + * or any alias for it is acceptable. This is always true + * if this filesystem is exported without the subtreecheck + * option. If the filesystem is exported with the subtree + * check option there's a fair chance we need to look at + * the parent directory in the file handle and make sure + * it's connected to the filesystem root. + */ + alias = find_acceptable_alias(result, acceptable, context); + if (alias) + return alias; + + /* + * Try to extract a dentry for the parent directory from the + * file handle. If this fails we'll have to give up. + */ + err = -ESTALE; + if (!nop->fh_to_parent) + goto err_result; + + target_dir = nop->fh_to_parent(mnt->mnt_sb, fid, + fh_len, fileid_type); + if (!target_dir) + goto err_result; + err = PTR_ERR(target_dir); + if (IS_ERR(target_dir)) + goto err_result; + + /* + * And as usual we need to make sure the parent directory is + * connected to the filesystem root. The VFS really doesn't + * like disconnected directories.. + */ + err = reconnect_path(mnt, target_dir, nbuf); + if (err) { + dput(target_dir); + goto err_result; + } + + /* + * Now that we've got both a well-connected parent and a + * dentry for the inode we're after, make sure that our + * inode is actually connected to the parent. + */ + err = exportfs_get_name(mnt, 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); + } + } + + /* + * At this point we are done with the parent, but it's pinned + * by the child dentry anyway. + */ + dput(target_dir); + + /* + * And finally make sure the dentry is actually acceptable + * to NFSD. + */ + alias = find_acceptable_alias(result, acceptable, context); + if (!alias) { + err = -EACCES; + goto err_result; + } -EXPORT_SYMBOL(export_op_default); -EXPORT_SYMBOL(find_exported_dentry); + return alias; + } + + err_result: + dput(result); + return ERR_PTR(err); +} +EXPORT_SYMBOL_GPL(exportfs_decode_fh); MODULE_LICENSE("GPL"); |