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authorLinus Torvalds <torvalds@linux-foundation.org>2014-08-11 22:44:11 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-08-11 22:44:11 +0400
commitf6f993328b2abcab86a3c99d7bd9f2066ab03d36 (patch)
treeea6f3902a0fa546493731b3b52a31d98cc747a90 /Documentation
parentc7a19c795b4b0a3232c157ed29eea85077e95da6 (diff)
parent12a5b5294cb1896e9a3c9fca8ff5a7e3def4e8c6 (diff)
downloadlinux-f6f993328b2abcab86a3c99d7bd9f2066ab03d36.tar.xz
Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs updates from Al Viro: "Stuff in here: - acct.c fixes and general rework of mnt_pin mechanism. That allows to go for delayed-mntput stuff, which will permit mntput() on deep stack without worrying about stack overflows - fs shutdown will happen on shallow stack. IOW, we can do Eric's umount-on-rmdir series without introducing tons of stack overflows on new mntput() call chains it introduces. - Bruce's d_splice_alias() patches - more Miklos' rename() stuff. - a couple of regression fixes (stable fodder, in the end of branch) and a fix for API idiocy in iov_iter.c. There definitely will be another pile, maybe even two. I'd like to get Eric's series in this time, but even if we miss it, it'll go right in the beginning of for-next in the next cycle - the tricky part of prereqs is in this pile" * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (40 commits) fix copy_tree() regression __generic_file_write_iter(): fix handling of sync error after DIO switch iov_iter_get_pages() to passing maximal number of pages fs: mark __d_obtain_alias static dcache: d_splice_alias should detect loops exportfs: update Exporting documentation dcache: d_find_alias needn't recheck IS_ROOT && DCACHE_DISCONNECTED dcache: remove unused d_find_alias parameter dcache: d_obtain_alias callers don't all want DISCONNECTED dcache: d_splice_alias should ignore DCACHE_DISCONNECTED dcache: d_splice_alias mustn't create directory aliases dcache: close d_move race in d_splice_alias dcache: move d_splice_alias namei: trivial fix to vfs_rename_dir comment VFS: allow ->d_manage() to declare -EISDIR in rcu_walk mode. cifs: support RENAME_NOREPLACE hostfs: support rename flags shmem: support RENAME_EXCHANGE shmem: support RENAME_NOREPLACE btrfs: add RENAME_NOREPLACE ...
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/filesystems/nfs/Exporting38
-rw-r--r--Documentation/filesystems/vfs.txt3
2 files changed, 25 insertions, 16 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
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index a1d0d7a30165..61d65cc65c54 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -1053,7 +1053,8 @@ struct dentry_operations {
If the 'rcu_walk' parameter is true, then the caller is doing a
pathwalk in RCU-walk mode. Sleeping is not permitted in this mode,
and the caller can be asked to leave it and call again by returning
- -ECHILD.
+ -ECHILD. -EISDIR may also be returned to tell pathwalk to
+ ignore d_automount or any mounts.
This function is only used if DCACHE_MANAGE_TRANSIT is set on the
dentry being transited from.