diff options
Diffstat (limited to 'fs/isofs/export.c')
| -rw-r--r-- | fs/isofs/export.c | 193 |
1 files changed, 193 insertions, 0 deletions
diff --git a/fs/isofs/export.c b/fs/isofs/export.c new file mode 100644 index 0000000000..35768a63fb --- /dev/null +++ b/fs/isofs/export.c @@ -0,0 +1,193 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * fs/isofs/export.c + * + * (C) 2004 Paul Serice - The new inode scheme requires switching + * from iget() to iget5_locked() which means + * the NFS export operations have to be hand + * coded because the default routines rely on + * iget(). + * + * The following files are helpful: + * + * Documentation/filesystems/nfs/exporting.rst + * fs/exportfs/expfs.c. + */ + +#include "isofs.h" + +static struct dentry * +isofs_export_iget(struct super_block *sb, + unsigned long block, + unsigned long offset, + __u32 generation) +{ + struct inode *inode; + + if (block == 0) + return ERR_PTR(-ESTALE); + inode = isofs_iget(sb, block, offset); + if (IS_ERR(inode)) + return ERR_CAST(inode); + if (generation && inode->i_generation != generation) { + iput(inode); + return ERR_PTR(-ESTALE); + } + return d_obtain_alias(inode); +} + +/* This function is surprisingly simple. The trick is understanding + * that "child" is always a directory. So, to find its parent, you + * simply need to find its ".." entry, normalize its block and offset, + * and return the underlying inode. See the comments for + * isofs_normalize_block_and_offset(). */ +static struct dentry *isofs_export_get_parent(struct dentry *child) +{ + unsigned long parent_block = 0; + unsigned long parent_offset = 0; + struct inode *child_inode = d_inode(child); + struct iso_inode_info *e_child_inode = ISOFS_I(child_inode); + struct iso_directory_record *de = NULL; + struct buffer_head * bh = NULL; + struct dentry *rv = NULL; + + /* "child" must always be a directory. */ + if (!S_ISDIR(child_inode->i_mode)) { + printk(KERN_ERR "isofs: isofs_export_get_parent(): " + "child is not a directory!\n"); + rv = ERR_PTR(-EACCES); + goto out; + } + + /* It is an invariant that the directory offset is zero. If + * it is not zero, it means the directory failed to be + * normalized for some reason. */ + if (e_child_inode->i_iget5_offset != 0) { + printk(KERN_ERR "isofs: isofs_export_get_parent(): " + "child directory not normalized!\n"); + rv = ERR_PTR(-EACCES); + goto out; + } + + /* The child inode has been normalized such that its + * i_iget5_block value points to the "." entry. Fortunately, + * the ".." entry is located in the same block. */ + parent_block = e_child_inode->i_iget5_block; + + /* Get the block in question. */ + bh = sb_bread(child_inode->i_sb, parent_block); + if (bh == NULL) { + rv = ERR_PTR(-EACCES); + goto out; + } + + /* This is the "." entry. */ + de = (struct iso_directory_record*)bh->b_data; + + /* The ".." entry is always the second entry. */ + parent_offset = (unsigned long)isonum_711(de->length); + de = (struct iso_directory_record*)(bh->b_data + parent_offset); + + /* Verify it is in fact the ".." entry. */ + if ((isonum_711(de->name_len) != 1) || (de->name[0] != 1)) { + printk(KERN_ERR "isofs: Unable to find the \"..\" " + "directory for NFS.\n"); + rv = ERR_PTR(-EACCES); + goto out; + } + + /* Normalize */ + isofs_normalize_block_and_offset(de, &parent_block, &parent_offset); + + rv = d_obtain_alias(isofs_iget(child_inode->i_sb, parent_block, + parent_offset)); + out: + if (bh) + brelse(bh); + return rv; +} + +static int +isofs_export_encode_fh(struct inode *inode, + __u32 *fh32, + int *max_len, + struct inode *parent) +{ + struct iso_inode_info * ei = ISOFS_I(inode); + int len = *max_len; + int type = 1; + __u16 *fh16 = (__u16*)fh32; + + /* + * WARNING: max_len is 5 for NFSv2. Because of this + * limitation, we use the lower 16 bits of fh32[1] to hold the + * offset of the inode and the upper 16 bits of fh32[1] to + * hold the offset of the parent. + */ + if (parent && (len < 5)) { + *max_len = 5; + return FILEID_INVALID; + } else if (len < 3) { + *max_len = 3; + return FILEID_INVALID; + } + + len = 3; + fh32[0] = ei->i_iget5_block; + fh16[2] = (__u16)ei->i_iget5_offset; /* fh16 [sic] */ + fh16[3] = 0; /* avoid leaking uninitialized data */ + fh32[2] = inode->i_generation; + if (parent) { + struct iso_inode_info *eparent; + eparent = ISOFS_I(parent); + fh32[3] = eparent->i_iget5_block; + fh16[3] = (__u16)eparent->i_iget5_offset; /* fh16 [sic] */ + fh32[4] = parent->i_generation; + len = 5; + type = 2; + } + *max_len = len; + return type; +} + +struct isofs_fid { + u32 block; + u16 offset; + u16 parent_offset; + u32 generation; + u32 parent_block; + u32 parent_generation; +}; + +static struct dentry *isofs_fh_to_dentry(struct super_block *sb, + struct fid *fid, int fh_len, int fh_type) +{ + struct isofs_fid *ifid = (struct isofs_fid *)fid; + + if (fh_len < 3 || fh_type > 2) + return NULL; + + return isofs_export_iget(sb, ifid->block, ifid->offset, + ifid->generation); +} + +static struct dentry *isofs_fh_to_parent(struct super_block *sb, + struct fid *fid, int fh_len, int fh_type) +{ + struct isofs_fid *ifid = (struct isofs_fid *)fid; + + if (fh_len < 2 || fh_type != 2) + return NULL; + + return isofs_export_iget(sb, + fh_len > 2 ? ifid->parent_block : 0, + ifid->parent_offset, + fh_len > 4 ? ifid->parent_generation : 0); +} + +const struct export_operations isofs_export_ops = { + .encode_fh = isofs_export_encode_fh, + .fh_to_dentry = isofs_fh_to_dentry, + .fh_to_parent = isofs_fh_to_parent, + .get_parent = isofs_export_get_parent, +}; |