diff options
Diffstat (limited to 'Documentation/filesystems')
| -rw-r--r-- | Documentation/filesystems/nfs/Exporting | 38 |
1 files changed, 23 insertions, 15 deletions
diff --git a/Documentation/filesystems/nfs/Exporting b/Documentation/filesystems/nfs/Exporting index e543b1a619cc..c8f036a9b13f 100644 --- a/Documentation/filesystems/nfs/Exporting +++ b/Documentation/filesystems/nfs/Exporting @@ -66,23 +66,31 @@ b/ A per-superblock list "s_anon" of dentries which are the roots of c/ Helper routines to allocate anonymous dentries, and to help attach loose directory dentries at lookup time. They are: - d_alloc_anon(inode) will return a dentry for the given inode. + d_obtain_alias(inode) will return a dentry for the given inode. If the inode already has a dentry, one of those is returned. If it doesn't, a new anonymous (IS_ROOT and DCACHE_DISCONNECTED) dentry is allocated and attached. In the case of a directory, care is taken that only one dentry can ever be attached. - d_splice_alias(inode, dentry) will make sure that there is a - dentry with the same name and parent as the given dentry, and - which refers to the given inode. - If the inode is a directory and already has a dentry, then that - dentry is d_moved over the given dentry. - If the passed dentry gets attached, care is taken that this is - mutually exclusive to a d_alloc_anon operation. - If the passed dentry is used, NULL is returned, else the used - dentry is returned. This corresponds to the calling pattern of - ->lookup. - + d_splice_alias(inode, dentry) or d_materialise_unique(dentry, inode) + will introduce a new dentry into the tree; either the passed-in + dentry or a preexisting alias for the given inode (such as an + anonymous one created by d_obtain_alias), if appropriate. The two + functions differ in their handling of directories with preexisting + aliases: + d_splice_alias will use any existing IS_ROOT dentry, but it will + return -EIO rather than try to move a dentry with a different + parent. This is appropriate for local filesystems, which + should never see such an alias unless the filesystem is + corrupted somehow (for example, if two on-disk directory + entries refer to the same directory.) + d_materialise_unique will attempt to move any dentry. This is + appropriate for distributed filesystems, where finding a + directory other than where we last cached it may be a normal + consequence of concurrent operations on other hosts. + Both functions return NULL when the passed-in dentry is used, + following the calling convention of ->lookup. + Filesystem Issues ----------------- @@ -120,12 +128,12 @@ struct which has the following members: fh_to_dentry (mandatory) Given a filehandle fragment, this should find the implied object and - create a dentry for it (possibly with d_alloc_anon). + create a dentry for it (possibly with d_obtain_alias). fh_to_parent (optional but strongly recommended) Given a filehandle fragment, this should find the parent of the - implied object and create a dentry for it (possibly with d_alloc_anon). - May fail if the filehandle fragment is too small. + implied object and create a dentry for it (possibly with + d_obtain_alias). May fail if the filehandle fragment is too small. get_parent (optional but strongly recommended) When given a dentry for a directory, this should return a dentry for |