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authorLinus Torvalds <torvalds@linux-foundation.org>2016-07-28 22:59:05 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-07-28 22:59:05 +0300
commit6784725ab0b9473ce44bfad91a256bd72b5cddc1 (patch)
treef31e2bfc4795c2ee490b0eb9fb752be58060568f /Documentation/filesystems
parent554828ee0db41618d101d9549db8808af9fd9d65 (diff)
parent47be61845c775643f1aa4d2a54343549f943c94c (diff)
downloadlinux-6784725ab0b9473ce44bfad91a256bd72b5cddc1.tar.xz
Merge branch 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
Pull vfs updates from Al Viro: "Assorted cleanups and fixes. Probably the most interesting part long-term is ->d_init() - that will have a bunch of followups in (at least) ceph and lustre, but we'll need to sort the barrier-related rules before it can get used for really non-trivial stuff. Another fun thing is the merge of ->d_iput() callers (dentry_iput() and dentry_unlink_inode()) and a bunch of ->d_compare() ones (all except the one in __d_lookup_lru())" * 'work.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs: (26 commits) fs/dcache.c: avoid soft-lockup in dput() vfs: new d_init method vfs: Update lookup_dcache() comment bdev: get rid of ->bd_inodes Remove last traces of ->sync_page new helper: d_same_name() dentry_cmp(): use lockless_dereference() instead of smp_read_barrier_depends() vfs: clean up documentation vfs: document ->d_real() vfs: merge .d_select_inode() into .d_real() unify dentry_iput() and dentry_unlink_inode() binfmt_misc: ->s_root is not going anywhere drop redundant ->owner initializations ufs: get rid of redundant checks orangefs: constify inode_operations missed comment updates from ->direct_IO() prototype change file_inode(f)->i_mapping is f->f_mapping trim fsnotify hooks a bit 9p: new helper - v9fs_parent_fid() debugfs: ->d_parent is never NULL or negative ...
Diffstat (limited to 'Documentation/filesystems')
-rw-r--r--Documentation/filesystems/Locking18
-rw-r--r--Documentation/filesystems/vfs.txt51
2 files changed, 39 insertions, 30 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index 5a7386e38e2d..ef46d3ac5774 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -15,11 +15,14 @@ prototypes:
int (*d_compare)(const struct dentry *, const struct dentry *,
unsigned int, const char *, const struct qstr *);
int (*d_delete)(struct dentry *);
+ int (*d_init)(struct dentry *);
void (*d_release)(struct dentry *);
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
struct vfsmount *(*d_automount)(struct path *path);
int (*d_manage)(struct dentry *, bool);
+ struct dentry *(*d_real)(struct dentry *, const struct inode *,
+ unsigned int);
locking rules:
rename_lock ->d_lock may block rcu-walk
@@ -28,12 +31,14 @@ d_weak_revalidate:no no yes no
d_hash no no no maybe
d_compare: yes no no maybe
d_delete: no yes no no
+d_init: no no yes no
d_release: no no yes no
d_prune: no yes no no
d_iput: no no yes no
d_dname: no no no no
d_automount: no no yes no
d_manage: no no yes (ref-walk) maybe
+d_real no no yes no
--------------------------- inode_operations ---------------------------
prototypes:
@@ -66,7 +71,6 @@ prototypes:
struct file *, unsigned open_flag,
umode_t create_mode, int *opened);
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
- int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
locking rules:
all may block
@@ -95,7 +99,6 @@ fiemap: no
update_time: no
atomic_open: yes
tmpfile: no
-dentry_open: no
Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
victim.
@@ -179,7 +182,6 @@ unlocks and drops the reference.
prototypes:
int (*writepage)(struct page *page, struct writeback_control *wbc);
int (*readpage)(struct file *, struct page *);
- int (*sync_page)(struct page *);
int (*writepages)(struct address_space *, struct writeback_control *);
int (*set_page_dirty)(struct page *page);
int (*readpages)(struct file *filp, struct address_space *mapping,
@@ -210,7 +212,6 @@ locking rules:
PageLocked(page) i_mutex
writepage: yes, unlocks (see below)
readpage: yes, unlocks
-sync_page: maybe
writepages:
set_page_dirty no
readpages:
@@ -230,8 +231,8 @@ error_remove_page: yes
swap_activate: no
swap_deactivate: no
- ->write_begin(), ->write_end(), ->sync_page() and ->readpage()
-may be called from the request handler (/dev/loop).
+ ->write_begin(), ->write_end() and ->readpage() may be called from
+the request handler (/dev/loop).
->readpage() unlocks the page, either synchronously or via I/O
completion.
@@ -287,11 +288,6 @@ will leave the page itself marked clean but it will be tagged as dirty in the
radix tree. This incoherency can lead to all sorts of hard-to-debug problems
in the filesystem like having dirty inodes at umount and losing written data.
- ->sync_page() locking rules are not well-defined - usually it is called
-with lock on page, but that is not guaranteed. Considering the currently
-existing instances of this method ->sync_page() itself doesn't look
-well-defined...
-
->writepages() is used for periodic writeback and for syscall-initiated
sync operations. The address_space should start I/O against at least
*nr_to_write pages. *nr_to_write must be decremented for each page which is
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
index 900360cbcdae..8a196851f01d 100644
--- a/Documentation/filesystems/vfs.txt
+++ b/Documentation/filesystems/vfs.txt
@@ -364,7 +364,6 @@ struct inode_operations {
int (*atomic_open)(struct inode *, struct dentry *, struct file *,
unsigned open_flag, umode_t create_mode, int *opened);
int (*tmpfile) (struct inode *, struct dentry *, umode_t);
- int (*dentry_open)(struct dentry *, struct file *, const struct cred *);
};
Again, all methods are called without any locks being held, unless
@@ -534,9 +533,7 @@ __sync_single_inode) to check if ->writepages has been successful in
writing out the whole address_space.
The Writeback tag is used by filemap*wait* and sync_page* functions,
-via filemap_fdatawait_range, to wait for all writeback to
-complete. While waiting ->sync_page (if defined) will be called on
-each page that is found to require writeback.
+via filemap_fdatawait_range, to wait for all writeback to complete.
An address_space handler may attach extra information to a page,
typically using the 'private' field in the 'struct page'. If such
@@ -554,8 +551,8 @@ address_space has finer control of write sizes.
The read process essentially only requires 'readpage'. The write
process is more complicated and uses write_begin/write_end or
-set_page_dirty to write data into the address_space, and writepage,
-sync_page, and writepages to writeback data to storage.
+set_page_dirty to write data into the address_space, and writepage
+and writepages to writeback data to storage.
Adding and removing pages to/from an address_space is protected by the
inode's i_mutex.
@@ -701,13 +698,6 @@ struct address_space_operations {
but instead uses bmap to find out where the blocks in the file
are and uses those addresses directly.
- dentry_open: *WARNING: probably going away soon, do not use!* This is an
- alternative to f_op->open(), the difference is that this method may open
- a file not necessarily originating from the same filesystem as the one
- i_op->open() was called on. It may be useful for stacking filesystems
- which want to allow native I/O directly on underlying files.
-
-
invalidatepage: If a page has PagePrivate set, then invalidatepage
will be called when part or all of the page is to be removed
from the address space. This generally corresponds to either a
@@ -944,11 +934,14 @@ struct dentry_operations {
int (*d_compare)(const struct dentry *, const struct dentry *,
unsigned int, const char *, const struct qstr *);
int (*d_delete)(const struct dentry *);
+ int (*d_init)(struct dentry *);
void (*d_release)(struct dentry *);
void (*d_iput)(struct dentry *, struct inode *);
char *(*d_dname)(struct dentry *, char *, int);
struct vfsmount *(*d_automount)(struct path *);
int (*d_manage)(struct dentry *, bool);
+ struct dentry *(*d_real)(struct dentry *, const struct inode *,
+ unsigned int);
};
d_revalidate: called when the VFS needs to revalidate a dentry. This
@@ -1014,6 +1007,8 @@ struct dentry_operations {
always cache a reachable dentry. d_delete must be constant and
idempotent.
+ d_init: called when a dentry is allocated
+
d_release: called when a dentry is really deallocated
d_iput: called when a dentry loses its inode (just prior to its
@@ -1033,6 +1028,14 @@ struct dentry_operations {
at the end of the buffer, and returns a pointer to the first char.
dynamic_dname() helper function is provided to take care of this.
+ Example :
+
+ static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
+ {
+ return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
+ dentry->d_inode->i_ino);
+ }
+
d_automount: called when an automount dentry is to be traversed (optional).
This should create a new VFS mount record and return the record to the
caller. The caller is supplied with a path parameter giving the
@@ -1071,13 +1074,23 @@ struct dentry_operations {
This function is only used if DCACHE_MANAGE_TRANSIT is set on the
dentry being transited from.
-Example :
+ d_real: overlay/union type filesystems implement this method to return one of
+ the underlying dentries hidden by the overlay. It is used in three
+ different modes:
-static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
-{
- return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
- dentry->d_inode->i_ino);
-}
+ Called from open it may need to copy-up the file depending on the
+ supplied open flags. This mode is selected with a non-zero flags
+ argument. In this mode the d_real method can return an error.
+
+ Called from file_dentry() it returns the real dentry matching the inode
+ argument. The real dentry may be from a lower layer already copied up,
+ but still referenced from the file. This mode is selected with a
+ non-NULL inode argument. This will always succeed.
+
+ With NULL inode and zero flags the topmost real underlying dentry is
+ returned. This will always succeed.
+
+ This method is never called with both non-NULL inode and non-zero flags.
Each dentry has a pointer to its parent dentry, as well as a hash list
of child dentries. Child dentries are basically like files in a