> Index: linux-2.6/Documentation/filesystems/Locking
> ===================================================================
> --- linux-2.6.orig/Documentation/filesystems/Locking 2010-12-15 09:55:57.364004682 +0100
> +++ linux-2.6/Documentation/filesystems/Locking 2010-12-16 12:00:47.210004264 +0100
> @@ -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 +114,11 @@ 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);
> + int (*trim_fs) (struct super_block *, struct fstrim_range *);
>
> locking rules:
> All may block [not true, see below]
> - None have BKL
> s_umount
> alloc_inode:
> destroy_inode:
> @@ -127,6 +137,8 @@ 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)
> +trim_fs: no
>
> ->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 +151,25 @@ be the only ones operating on the quota
> 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.
>
> @@ -176,27 +194,35 @@ prototypes:
> 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 and freepage 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
> -freepage: no yes
> -direct_IO: no
> -launder_page: no yes
> + 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).
> @@ -276,9 +302,8 @@ under spinlock (it cannot block) and is
> 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
> @@ -299,47 +324,37 @@ cleaned, or an error value if not. Note
> 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);
> @@ -364,17 +379,17 @@ 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().
> @@ -413,34 +428,21 @@ 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
> @@ -450,17 +452,10 @@ mutex or just to use i_size_read() inste
> 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
> @@ -471,8 +466,6 @@ components. And there are other reasons
> ->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 *);
> @@ -507,12 +500,12 @@ 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
> @@ -539,6 +532,3 @@ 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.
> --
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