diff options
Diffstat (limited to 'Documentation/filesystems/Locking')
| -rw-r--r-- | Documentation/filesystems/Locking | 212 |
1 files changed, 100 insertions, 112 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index b6426f15b4ae..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. @@ -176,27 +192,35 @@ 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 +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 @@ -299,47 +322,37 @@ 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); @@ -364,17 +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(). @@ -413,34 +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 @@ -450,17 +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 @@ -471,8 +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 *); @@ -507,12 +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 @@ -539,6 +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. |