> Regards,
> Ryusuke Konishi
>
> > 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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