1 files changed, 106 insertions, 113 deletions

diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking
index a91f30890011..33fa3e5d38fd 100644
--- a/Documentation/filesystems/Locking
+++ b/Documentation/filesystems/Locking
@@ -18,7 +18,6 @@ prototypes:
         char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
 
 locking rules:
-        none have BKL
                 dcache_lock     rename_lock     ->d_lock        may block
 d_revalidate:   no              no              no              yes
 d_hash          no              no              no              yes
@@ -42,18 +41,23 @@ ata *);
         int (*rename) (struct inode *, struct dentry *,
                         struct inode *, struct dentry *);
         int (*readlink) (struct dentry *, char __user *,int);
-        int (*follow_link) (struct dentry *, struct nameidata *);
+        void * (*follow_link) (struct dentry *, struct nameidata *);
+        void (*put_link) (struct dentry *, struct nameidata *, void *);
         void (*truncate) (struct inode *);
         int (*permission) (struct inode *, int, struct nameidata *);
+        int (*check_acl)(struct inode *, int);
         int (*setattr) (struct dentry *, struct iattr *);
         int (*getattr) (struct vfsmount *, struct dentry *, struct kstat *);
         int (*setxattr) (struct dentry *, const char *,const void *,size_t,int);
         ssize_t (*getxattr) (struct dentry *, const char *, void *, size_t);
         ssize_t (*listxattr) (struct dentry *, char *, size_t);
         int (*removexattr) (struct dentry *, const char *);
+        void (*truncate_range)(struct inode *, loff_t, loff_t);
+        long (*fallocate)(struct inode *inode, int mode, loff_t offset, loff_t len);
+        int (*fiemap)(struct inode *, struct fiemap_extent_info *, u64 start, u64 len);
 
 locking rules:
-        all may block, none have BKL
+        all may block
                 i_mutex(inode)
 lookup:         yes
 create:         yes
@@ -66,19 +70,24 @@ rmdir:		yes (both)	(see below)
 rename:         yes (all)       (see below)
 readlink:       no
 follow_link:    no
+put_link:       no
 truncate:       yes             (see below)
 setattr:        yes
 permission:     no
+check_acl:      no
 getattr:        no
 setxattr:       yes
 getxattr:       no
 listxattr:      no
 removexattr:    yes
+truncate_range: yes
+fallocate:      no
+fiemap:         no
         Additionally, ->rmdir(), ->unlink() and ->rename() have ->i_mutex on
 victim.
         cross-directory ->rename() has (per-superblock) ->s_vfs_rename_sem.
         ->truncate() is never called directly - it's a callback, not a
-method. It's called by vmtruncate() - library function normally used by
+method. It's called by vmtruncate() - deprecated library function used by
 ->setattr(). Locking information above applies to that call (i.e. is
 inherited from ->setattr() - vmtruncate() is used when ATTR_SIZE had been
 passed).
@@ -91,7 +100,7 @@ prototypes:
         struct inode *(*alloc_inode)(struct super_block *sb);
         void (*destroy_inode)(struct inode *);
         void (*dirty_inode) (struct inode *);
-        int (*write_inode) (struct inode *, int);
+        int (*write_inode) (struct inode *, struct writeback_control *wbc);
         int (*drop_inode) (struct inode *);
         void (*evict_inode) (struct inode *);
         void (*put_super) (struct super_block *);
@@ -105,10 +114,10 @@ prototypes:
         int (*show_options)(struct seq_file *, struct vfsmount *);
         ssize_t (*quota_read)(struct super_block *, int, char *, size_t, loff_t);
         ssize_t (*quota_write)(struct super_block *, int, const char *, size_t, loff_t);
+        int (*bdev_try_to_free_page)(struct super_block*, struct page*, gfp_t);
 
 locking rules:
         All may block [not true, see below]
-        None have BKL
                         s_umount
 alloc_inode:
 destroy_inode:
@@ -127,6 +136,7 @@ umount_begin:		no
 show_options:           no              (namespace_sem)
 quota_read:             no              (see below)
 quota_write:            no              (see below)
+bdev_try_to_free_page:  no              (see below)
 
 ->statfs() has s_umount (shared) when called by ustat(2) (native or
 compat), but that's an accident of bad API; s_umount is used to pin
@@ -139,19 +149,25 @@ be the only ones operating on the quota file by the quota code (via
 dqio_sem) (unless an admin really wants to screw up something and
 writes to quota files with quotas on). For other details about locking
 see also dquot_operations section.
+->bdev_try_to_free_page is called from the ->releasepage handler of
+the block device inode.  See there for more details.
 
 --------------------------- file_system_type ---------------------------
 prototypes:
         int (*get_sb) (struct file_system_type *, int,
                        const char *, void *, struct vfsmount *);
+        struct dentry *(*mount) (struct file_system_type *, int,
+                       const char *, void *);
         void (*kill_sb) (struct super_block *);
 locking rules:
-                may block       BKL
-get_sb          yes             no
-kill_sb         yes             no
+                may block
+get_sb          yes
+mount           yes
+kill_sb         yes
 
 ->get_sb() returns error or 0 with locked superblock attached to the vfsmount
 (exclusive on ->s_umount).
+->mount() returns ERR_PTR or the root dentry.
 ->kill_sb() takes a write-locked superblock, does all shutdown work on it,
 unlocks and drops the reference.
 
@@ -173,28 +189,38 @@ prototypes:
         sector_t (*bmap)(struct address_space *, sector_t);
         int (*invalidatepage) (struct page *, unsigned long);
         int (*releasepage) (struct page *, int);
+        void (*freepage)(struct page *);
         int (*direct_IO)(int, struct kiocb *, const struct iovec *iov,
                         loff_t offset, unsigned long nr_segs);
-        int (*launder_page) (struct page *);
+        int (*get_xip_mem)(struct address_space *, pgoff_t, int, void **,
+                                unsigned long *);
+        int (*migratepage)(struct address_space *, struct page *, struct page *);
+        int (*launder_page)(struct page *);
+        int (*is_partially_uptodate)(struct page *, read_descriptor_t *, unsigned long);
+        int (*error_remove_page)(struct address_space *, struct page *);
 
 locking rules:
-        All except set_page_dirty may block
-
-                        BKL     PageLocked(page)        i_mutex
-writepage:              no      yes, unlocks (see below)
-readpage:               no      yes, unlocks
-sync_page:              no      maybe
-writepages:             no
-set_page_dirty          no      no
-readpages:              no
-write_begin:            no      locks the page          yes
-write_end:              no      yes, unlocks            yes
-perform_write:          no      n/a                     yes
-bmap:                   no
-invalidatepage:         no      yes
-releasepage:            no      yes
-direct_IO:              no
-launder_page:           no      yes
+        All except set_page_dirty and freepage may block
+
+                        PageLocked(page)        i_mutex
+writepage:              yes, unlocks (see below)
+readpage:               yes, unlocks
+sync_page:              maybe
+writepages:
+set_page_dirty          no
+readpages:
+write_begin:            locks the page          yes
+write_end:              yes, unlocks            yes
+bmap:
+invalidatepage:         yes
+releasepage:            yes
+freepage:               yes
+direct_IO:
+get_xip_mem:                                    maybe
+migratepage:            yes (both)
+launder_page:           yes
+is_partially_uptodate:  yes
+error_remove_page:      yes
 
         ->write_begin(), ->write_end(), ->sync_page() and ->readpage()
 may be called from the request handler (/dev/loop).
@@ -274,9 +300,8 @@ under spinlock (it cannot block) and is sometimes called with the page
 not locked.
 
         ->bmap() is currently used by legacy ioctl() (FIBMAP) provided by some
-filesystems and by the swapper. The latter will eventually go away. All
-instances do not actually need the BKL. Please, keep it that way and don't
-breed new callers.
+filesystems and by the swapper. The latter will eventually go away.  Please,
+keep it that way and don't breed new callers.
 
         ->invalidatepage() is called when the filesystem must attempt to drop
 some or all of the buffers from the page when it is being truncated.  It
@@ -288,53 +313,46 @@ buffers from the page in preparation for freeing it.  It returns zero to
 indicate that the buffers are (or may be) freeable.  If ->releasepage is zero,
 the kernel assumes that the fs has no private interest in the buffers.
 
+        ->freepage() is called when the kernel is done dropping the page
+from the page cache.
+
         ->launder_page() may be called prior to releasing a page if
 it is still found to be dirty. It returns zero if the page was successfully
 cleaned, or an error value if not. Note that in order to prevent the page
 getting mapped back in and redirtied, it needs to be kept locked
 across the entire operation.
 
-        Note: currently almost all instances of address_space methods are
-using BKL for internal serialization and that's one of the worst sources
-of contention. Normally they are calling library functions (in fs/buffer.c)
-and pass foo_get_block() as a callback (on local block-based filesystems,
-indeed). BKL is not needed for library stuff and is usually taken by
-foo_get_block(). It's an overkill, since block bitmaps can be protected by
-internal fs locking and real critical areas are much smaller than the areas
-filesystems protect now.
-
 ----------------------- file_lock_operations ------------------------------
 prototypes:
-        void (*fl_insert)(struct file_lock *);  /* lock insertion callback */
-        void (*fl_remove)(struct file_lock *);  /* lock removal callback */
         void (*fl_copy_lock)(struct file_lock *, struct file_lock *);
         void (*fl_release_private)(struct file_lock *);
 
 
 locking rules:
-                        BKL     may block
-fl_insert:              yes     no
-fl_remove:              yes     no
-fl_copy_lock:           yes     no
-fl_release_private:     yes     yes
+                        file_lock_lock  may block
+fl_copy_lock:           yes             no
+fl_release_private:     maybe           no
 
 ----------------------- lock_manager_operations ---------------------------
 prototypes:
         int (*fl_compare_owner)(struct file_lock *, struct file_lock *);
         void (*fl_notify)(struct file_lock *);  /* unblock callback */
+        int (*fl_grant)(struct file_lock *, struct file_lock *, int);
         void (*fl_release_private)(struct file_lock *);
         void (*fl_break)(struct file_lock *); /* break_lease callback */
+        int (*fl_mylease)(struct file_lock *, struct file_lock *);
+        int (*fl_change)(struct file_lock **, int);
 
 locking rules:
-                        BKL     may block
-fl_compare_owner:       yes     no
-fl_notify:              yes     no
-fl_release_private:     yes     yes
-fl_break:               yes     no
-
-        Currently only NFSD and NLM provide instances of this class. None of the
-them block. If you have out-of-tree instances - please, show up. Locking
-in that area will change.
+                        file_lock_lock  may block
+fl_compare_owner:       yes             no
+fl_notify:              yes             no
+fl_grant:               no              no
+fl_release_private:     maybe           no
+fl_break:               yes             no
+fl_mylease:             yes             no
+fl_change               yes             no
+
 --------------------------- buffer_head -----------------------------------
 prototypes:
         void (*b_end_io)(struct buffer_head *bh, int uptodate);
@@ -359,17 +377,17 @@ prototypes:
         void (*swap_slot_free_notify) (struct block_device *, unsigned long);
 
 locking rules:
-                        BKL     bd_mutex
-open:                   no      yes
-release:                no      yes
-ioctl:                  no      no
-compat_ioctl:           no      no
-direct_access:          no      no
-media_changed:          no      no
-unlock_native_capacity: no      no
-revalidate_disk:        no      no
-getgeo:                 no      no
-swap_slot_free_notify:  no      no      (see below)
+                        bd_mutex
+open:                   yes
+release:                yes
+ioctl:                  no
+compat_ioctl:           no
+direct_access:          no
+media_changed:          no
+unlock_native_capacity: no
+revalidate_disk:        no
+getgeo:                 no
+swap_slot_free_notify:  no      (see below)
 
 media_changed, unlock_native_capacity and revalidate_disk are called only from
 check_disk_change().
@@ -408,34 +426,21 @@ prototypes:
         unsigned long (*get_unmapped_area)(struct file *, unsigned long,
                         unsigned long, unsigned long, unsigned long);
         int (*check_flags)(int);
+        int (*flock) (struct file *, int, struct file_lock *);
+        ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, loff_t *,
+                        size_t, unsigned int);
+        ssize_t (*splice_read)(struct file *, loff_t *, struct pipe_inode_info *,
+                        size_t, unsigned int);
+        int (*setlease)(struct file *, long, struct file_lock **);
 };
 
 locking rules:
-        All may block.
-                        BKL
-llseek:                 no      (see below)
-read:                   no
-aio_read:               no
-write:                  no
-aio_write:              no
-readdir:                no
-poll:                   no
-unlocked_ioctl:         no
-compat_ioctl:           no
-mmap:                   no
-open:                   no
-flush:                  no
-release:                no
-fsync:                  no      (see below)
-aio_fsync:              no
-fasync:                 no
-lock:                   yes
-readv:                  no
-writev:                 no
-sendfile:               no
-sendpage:               no
-get_unmapped_area:      no
-check_flags:            no
+        All may block except for ->setlease.
+        No VFS locks held on entry except for ->fsync and ->setlease.
+
+->fsync() has i_mutex on inode.
+
+->setlease has the file_list_lock held and must not sleep.
 
 ->llseek() locking has moved from llseek to the individual llseek
 implementations.  If your fs is not using generic_file_llseek, you
@@ -445,17 +450,10 @@ mutex or just to use i_size_read() instead.
 Note: this does not protect the file->f_pos against concurrent modifications
 since this is something the userspace has to take care about.
 
-Note: ext2_release() was *the* source of contention on fs-intensive
-loads and dropping BKL on ->release() helps to get rid of that (we still
-grab BKL for cases when we close a file that had been opened r/w, but that
-can and should be done using the internal locking with smaller critical areas).
-Current worst offender is ext2_get_block()...
-
-->fasync() is called without BKL protection, and is responsible for
-maintaining the FASYNC bit in filp->f_flags.  Most instances call
-fasync_helper(), which does that maintenance, so it's not normally
-something one needs to worry about.  Return values > 0 will be mapped to
-zero in the VFS layer.
+->fasync() is responsible for maintaining the FASYNC bit in filp->f_flags.
+Most instances call fasync_helper(), which does that maintenance, so it's
+not normally something one needs to worry about.  Return values > 0 will be
+mapped to zero in the VFS layer.
 
 ->readdir() and ->ioctl() on directories must be changed. Ideally we would
 move ->readdir() to inode_operations and use a separate method for directory
@@ -466,8 +464,6 @@ components. And there are other reasons why the current interface is a mess...
 ->read on directories probably must go away - we should just enforce -EISDIR
 in sys_read() and friends.
 
-->fsync() has i_mutex on inode.
-
 --------------------------- dquot_operations -------------------------------
 prototypes:
         int (*write_dquot) (struct dquot *);
@@ -502,12 +498,12 @@ prototypes:
         int (*access)(struct vm_area_struct *, unsigned long, void*, int, int);
 
 locking rules:
-                BKL     mmap_sem        PageLocked(page)
-open:           no      yes
-close:          no      yes
-fault:          no      yes             can return with page locked
-page_mkwrite:   no      yes             can return with page locked
-access:         no      yes
+                mmap_sem        PageLocked(page)
+open:           yes
+close:          yes
+fault:          yes             can return with page locked
+page_mkwrite:   yes             can return with page locked
+access:         yes
 
         ->fault() is called when a previously not present pte is about
 to be faulted in. The filesystem must find and return the page associated
@@ -534,6 +530,3 @@ VM_IO | VM_PFNMAP VMAs.
 
 (if you break something or notice that it is broken and do not fix it yourself
 - at least put it here)
-
-ipc/shm.c::shm_delete() - may need BKL.
-->read() and ->write() in many drivers are (probably) missing BKL.