diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/filesystems/Locking | 4 | ||||
| -rw-r--r-- | Documentation/filesystems/automount-support.txt | 51 | ||||
| -rw-r--r-- | Documentation/filesystems/porting | 17 | ||||
| -rw-r--r-- | Documentation/filesystems/vfs.txt | 22 |
4 files changed, 44 insertions, 50 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index 0a926e2ba3ab..6a34a0f4d37c 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -50,8 +50,8 @@ prototypes: int (*rename2) (struct inode *, struct dentry *, struct inode *, struct dentry *, unsigned int); int (*readlink) (struct dentry *, char __user *,int); - void * (*follow_link) (struct dentry *, struct nameidata *); - void (*put_link) (struct dentry *, struct nameidata *, void *); + const char *(*follow_link) (struct dentry *, void **); + void (*put_link) (struct inode *, void *); void (*truncate) (struct inode *); int (*permission) (struct inode *, int, unsigned int); int (*get_acl)(struct inode *, int); diff --git a/Documentation/filesystems/automount-support.txt b/Documentation/filesystems/automount-support.txt index 7cac200e2a85..7eb762eb3136 100644 --- a/Documentation/filesystems/automount-support.txt +++ b/Documentation/filesystems/automount-support.txt @@ -1,41 +1,15 @@ -Support is available for filesystems that wish to do automounting support (such -as kAFS which can be found in fs/afs/). This facility includes allowing -in-kernel mounts to be performed and mountpoint degradation to be -requested. The latter can also be requested by userspace. +Support is available for filesystems that wish to do automounting +support (such as kAFS which can be found in fs/afs/ and NFS in +fs/nfs/). This facility includes allowing in-kernel mounts to be +performed and mountpoint degradation to be requested. The latter can +also be requested by userspace. ====================== IN-KERNEL AUTOMOUNTING ====================== -A filesystem can now mount another filesystem on one of its directories by the -following procedure: - - (1) Give the directory a follow_link() operation. - - When the directory is accessed, the follow_link op will be called, and - it will be provided with the location of the mountpoint in the nameidata - structure (vfsmount and dentry). - - (2) Have the follow_link() op do the following steps: - - (a) Call vfs_kern_mount() to call the appropriate filesystem to set up a - superblock and gain a vfsmount structure representing it. - - (b) Copy the nameidata provided as an argument and substitute the dentry - argument into it the copy. - - (c) Call do_add_mount() to install the new vfsmount into the namespace's - mountpoint tree, thus making it accessible to userspace. Use the - nameidata set up in (b) as the destination. - - If the mountpoint will be automatically expired, then do_add_mount() - should also be given the location of an expiration list (see further - down). - - (d) Release the path in the nameidata argument and substitute in the new - vfsmount and its root dentry. The ref counts on these will need - incrementing. +See section "Mount Traps" of Documentation/filesystems/autofs4.txt Then from userspace, you can just do something like: @@ -61,17 +35,18 @@ AUTOMATIC MOUNTPOINT EXPIRY =========================== Automatic expiration of mountpoints is easy, provided you've mounted the -mountpoint to be expired in the automounting procedure outlined above. +mountpoint to be expired in the automounting procedure outlined separately. To do expiration, you need to follow these steps: - (3) Create at least one list off which the vfsmounts to be expired can be - hung. Access to this list will be governed by the vfsmount_lock. + (1) Create at least one list off which the vfsmounts to be expired can be + hung. - (4) In step (2c) above, the call to do_add_mount() should be provided with a - pointer to this list. It will hang the vfsmount off of it if it succeeds. + (2) When a new mountpoint is created in the ->d_automount method, add + the mnt to the list using mnt_set_expiry() + mnt_set_expiry(newmnt, &afs_vfsmounts); - (5) When you want mountpoints to be expired, call mark_mounts_for_expiry() + (3) When you want mountpoints to be expired, call mark_mounts_for_expiry() with a pointer to this list. This will process the list, marking every vfsmount thereon for potential expiry on the next call. diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting index e69274de8d0c..3eae250254d5 100644 --- a/Documentation/filesystems/porting +++ b/Documentation/filesystems/porting @@ -483,3 +483,20 @@ in your dentry operations instead. -- [mandatory] ->aio_read/->aio_write are gone. Use ->read_iter/->write_iter. +--- +[recommended] + for embedded ("fast") symlinks just set inode->i_link to wherever the + symlink body is and use simple_follow_link() as ->follow_link(). +-- +[mandatory] + calling conventions for ->follow_link() have changed. Instead of returning + cookie and using nd_set_link() to store the body to traverse, we return + the body to traverse and store the cookie using explicit void ** argument. + nameidata isn't passed at all - nd_jump_link() doesn't need it and + nd_[gs]et_link() is gone. +-- +[mandatory] + calling conventions for ->put_link() have changed. It gets inode instead of + dentry, it does not get nameidata at all and it gets called only when cookie + is non-NULL. Note that link body isn't available anymore, so if you need it, + store it as cookie. diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index 5d833b32bbcd..b403b29ef710 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt @@ -350,8 +350,8 @@ struct inode_operations { int (*rename2) (struct inode *, struct dentry *, struct inode *, struct dentry *, unsigned int); int (*readlink) (struct dentry *, char __user *,int); - void * (*follow_link) (struct dentry *, struct nameidata *); - void (*put_link) (struct dentry *, struct nameidata *, void *); + const char *(*follow_link) (struct dentry *, void **); + void (*put_link) (struct inode *, void *); int (*permission) (struct inode *, int); int (*get_acl)(struct inode *, int); int (*setattr) (struct dentry *, struct iattr *); @@ -436,16 +436,18 @@ otherwise noted. follow_link: called by the VFS to follow a symbolic link to the inode it points to. Only required if you want to support - symbolic links. This method returns a void pointer cookie - that is passed to put_link(). + symbolic links. This method returns the symlink body + to traverse (and possibly resets the current position with + nd_jump_link()). If the body won't go away until the inode + is gone, nothing else is needed; if it needs to be otherwise + pinned, the data needed to release whatever we'd grabbed + is to be stored in void * variable passed by address to + follow_link() instance. put_link: called by the VFS to release resources allocated by - follow_link(). The cookie returned by follow_link() is passed - to this method as the last parameter. It is used by - filesystems such as NFS where page cache is not stable - (i.e. page that was installed when the symbolic link walk - started might not be in the page cache at the end of the - walk). + follow_link(). The cookie stored by follow_link() is passed + to this method as the last parameter; only called when + cookie isn't NULL. permission: called by the VFS to check for access rights on a POSIX-like filesystem. |