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authorLinus Torvalds <torvalds@linux-foundation.org>2018-01-31 20:25:20 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-01-31 20:25:20 +0300
commit19e7b5f99474107e8d0b4b3e4652fa19ddb87efc (patch)
tree49f15b76c07b4c90d6fbd17b49d69017c81a4b58 /Documentation
parent26064ea409b4d4acb05903a36f3fe2fdccb3d8aa (diff)
parentce4c253573ad184603e0fa77876ba155b0cde46d (diff)
downloadlinux-19e7b5f99474107e8d0b4b3e4652fa19ddb87efc.tar.xz
Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull misc vfs updates from Al Viro: "All kinds of misc stuff, without any unifying topic, from various people. Neil's d_anon patch, several bugfixes, introduction of kvmalloc analogue of kmemdup_user(), extending bitfield.h to deal with fixed-endians, assorted cleanups all over the place..." * 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (28 commits) alpha: osf_sys.c: use timespec64 where appropriate alpha: osf_sys.c: fix put_tv32 regression jffs2: Fix use-after-free bug in jffs2_iget()'s error handling path dcache: delete unused d_hash_mask dcache: subtract d_hash_shift from 32 in advance fs/buffer.c: fold init_buffer() into init_page_buffers() fs: fold __inode_permission() into inode_permission() fs: add RWF_APPEND sctp: use vmemdup_user() rather than badly open-coding memdup_user() snd_ctl_elem_init_enum_names(): switch to vmemdup_user() replace_user_tlv(): switch to vmemdup_user() new primitive: vmemdup_user() memdup_user(): switch to GFP_USER eventfd: fold eventfd_ctx_get() into eventfd_ctx_fileget() eventfd: fold eventfd_ctx_read() into eventfd_read() eventfd: convert to use anon_inode_getfd() nfs4file: get rid of pointless include of btrfs.h uvc_v4l2: clean copyin/copyout up vme_user: don't use __copy_..._user() usx2y: don't bother with memdup_user() for 16-byte structure ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/nfs/Exporting27
1 files changed, 19 insertions, 8 deletions
diff --git a/Documentation/filesystems/nfs/Exporting b/Documentation/filesystems/nfs/Exporting
index 520a4becb75c..63889149f532 100644
--- a/Documentation/filesystems/nfs/Exporting
+++ b/Documentation/filesystems/nfs/Exporting
@@ -56,13 +56,25 @@ a/ A dentry flag DCACHE_DISCONNECTED which is set on
any dentry that might not be part of the proper prefix.
This is set when anonymous dentries are created, and cleared when a
dentry is noticed to be a child of a dentry which is in the proper
- prefix.
-
-b/ A per-superblock list "s_anon" of dentries which are the roots of
- subtrees that are not in the proper prefix. These dentries, as
- well as the proper prefix, need to be released at unmount time. As
- these dentries will not be hashed, they are linked together on the
- d_hash list_head.
+ prefix. If the refcount on a dentry with this flag set
+ becomes zero, the dentry is immediately discarded, rather than being
+ kept in the dcache. If a dentry that is not already in the dcache
+ is repeatedly accessed by filehandle (as NFSD might do), an new dentry
+ will be a allocated for each access, and discarded at the end of
+ the access.
+
+ Note that such a dentry can acquire children, name, ancestors, etc.
+ without losing DCACHE_DISCONNECTED - that flag is only cleared when
+ subtree is successfully reconnected to root. Until then dentries
+ in such subtree are retained only as long as there are references;
+ refcount reaching zero means immediate eviction, same as for unhashed
+ dentries. That guarantees that we won't need to hunt them down upon
+ umount.
+
+b/ A primitive for creation of secondary roots - d_obtain_root(inode).
+ Those do _not_ bear DCACHE_DISCONNECTED. They are placed on the
+ per-superblock list (->s_roots), so they can be located at umount
+ time for eviction purposes.
c/ Helper routines to allocate anonymous dentries, and to help attach
loose directory dentries at lookup time. They are:
@@ -77,7 +89,6 @@ c/ Helper routines to allocate anonymous dentries, and to help attach
(such as an anonymous one created by d_obtain_alias), if appropriate.
It returns NULL when the passed-in dentry is used, following the calling
convention of ->lookup.
-
Filesystem Issues
-----------------