diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/dcache.h | 18 | ||||
| -rw-r--r-- | include/linux/fs.h | 105 |
2 files changed, 117 insertions, 6 deletions
diff --git a/include/linux/dcache.h b/include/linux/dcache.h index a98c3fe940c0..6cf86c3e301c 100644 --- a/include/linux/dcache.h +++ b/include/linux/dcache.h @@ -117,12 +117,18 @@ d_iput: no no yes * renamed" and has to be * deleted on the last dput() */ -#define DCACHE_DISCONNECTED 0x0004 /* This dentry is not currently connected to the - * dcache tree. Its parent will either be itself, - * or will have this flag as well. - * If this dentry points to a directory, then - * s_nfsd_free_path semaphore will be down - */ +#define DCACHE_DISCONNECTED 0x0004 + /* This dentry is possibly not currently connected to the dcache tree, + * in which case its parent will either be itself, or will have this + * flag as well. nfsd will not use a dentry with this bit set, but will + * first endeavour to clear the bit either by discovering that it is + * connected, or by performing lookup operations. Any filesystem which + * supports nfsd_operations MUST have a lookup function which, if it finds + * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move + * that dentry into place and return that dentry rather than the passed one, + * typically using d_splice_alias. + */ + #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */ extern spinlock_t dcache_lock; diff --git a/include/linux/fs.h b/include/linux/fs.h index 17b3b586df2c..1e990e477adf 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -701,6 +701,7 @@ struct super_block { struct file_system_type *s_type; struct super_operations *s_op; struct dquot_operations *dq_op; + struct export_operations *s_export_op; unsigned long s_flags; unsigned long s_magic; struct dentry *s_root; @@ -936,6 +937,110 @@ struct dquot_operations { int (*transfer) (struct inode *, struct iattr *); }; + +/** + * &export_operations - for nfsd to communicate with file systems + * decode_fh: decode a file handle fragment and return a &struct dentry + * encode_fh: encode a file handle fragment from a dentry + * get_name: find the name for a given inode in a given directory + * get_parent: find the parent of a given directory + * get_dentry: find a dentry for the inode given a file handle sub-fragment + * + * Description: + * The export_operations structure provides a means for nfsd to communicate + * with a particular exported file system - particularly enabling nfsd and + * the filesystem to co-operate when dealing with file handles. + * + * export_operations contains two basic operation for dealing with file handles, + * decode_fh() and encode_fh(), and allows for some other operations to be defined + * which standard helper routines use to get specific information from the + * filesystem. + * + * nfsd encodes information use to determine which filesystem a filehandle + * applies to in the initial part of the file handle. The remainder, termed a + * file handle fragment, is controlled completely by the filesystem. + * The standard helper routines assume that this fragment will contain one or two + * sub-fragments, one which identifies the file, and one which may be used to + * identify the (a) directory containing the file. + * + * In some situations, nfsd needs to get a dentry which is connected into a + * specific part of the file tree. To allow for this, it passes the function + * acceptable() together with a @context which can be used to see if the dentry + * is acceptable. As there can be multiple dentrys for a given file, the filesystem + * should check each one for acceptability before looking for the next. As soon + * as an acceptable one is found, it should be returned. + * + * decode_fh: + * @decode_fh is given a &struct super_block (@sb), a file handle fragment (@fh, @fh_len) + * and an acceptability testing function (@acceptable, @context). It should return + * a &struct dentry which refers to the same file that the file handle fragment refers + * to, and which passes the acceptability test. If it cannot, it should return + * a %NULL pointer if the file was found but no acceptable &dentries were available, or + * a %ERR_PTR error code indicating why it couldn't be found (e.g. %ENOENT or %ENOMEM). + * + * encode_fh: + * @encode_fh should store in the file handle fragment @fh (using at most @max_len bytes) + * information that can be used by @decode_fh to recover the file refered to by the + * &struct dentry @de. If the @connectable flag is set, the encode_fh() should store + * sufficient information so that a good attempt can be made to find not only + * the file but also it's place in the filesystem. This typically means storing + * a reference to de->d_parent in the filehandle fragment. + * encode_fh() should return the number of bytes stored or a negative error code + * such as %-ENOSPC + * + * get_name: + * @get_name should find a name for the given @child in the given @parent directory. + * The name should be stored in the @name (with the understanding that it is already + * pointing to a a %NAME_MAX+1 sized buffer. get_name() should return %0 on success, + * a negative error code or error. + * @get_name will be called without @parent->i_sem held. + * + * get_parent: + * @get_parent should find the parent directory for the given @child which is also + * a directory. In the event that it cannot be found, or storage space cannot be + * allocated, a %ERR_PTR should be returned. + * + * get_dentry: + * Given a &super_block (@sb) and a pointer to a file-system specific inode identifier, + * possibly an inode number, (@inump) get_dentry() should find the identified inode and + * return a dentry for that inode. + * Any suitable dentry can be returned including, if necessary, a new dentry created + * with d_alloc_root. The caller can then find any other extant dentrys by following the + * d_alias links. If a new dentry was created using d_alloc_root, DCACHE_NFSD_DISCONNECTED + * should be set, and the dentry should be d_rehash()ed. + * + * If the inode cannot be found, either a %NULL pointer or an %ERR_PTR code can be returned. + * The @inump will be whatever was passed to nfsd_find_fh_dentry() in either the + * @obj or @parent parameters. + * + * Locking rules: + * get_parent is called with child->d_inode->i_sem down + * get_name is not (which is possibly inconsistent) + */ + +struct export_operations { + struct dentry *(*decode_fh)(struct super_block *sb, __u32 *fh, int fh_len, int fh_type, + int (*acceptable)(void *context, struct dentry *de), + void *context); + int (*encode_fh)(struct dentry *de, __u32 *fh, int *max_len, + int connectable); + + /* the following are only called from the filesystem itself */ + int (*get_name)(struct dentry *parent, char *name, + struct dentry *child); + struct dentry * (*get_parent)(struct dentry *child); + struct dentry * (*get_dentry)(struct super_block *sb, void *inump); + + /* This is set by the exporting module to a standard helper */ + struct dentry * (*find_exported_dentry)( + struct super_block *sb, void *obj, void *parent, + int (*acceptable)(void *context, struct dentry *de), + void *context); + + +}; + + struct file_system_type { const char *name; int fs_flags; |