diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/filesystems/Locking | 22 | ||||
| -rw-r--r-- | Documentation/filesystems/porting | 45 |
2 files changed, 57 insertions, 10 deletions
diff --git a/Documentation/filesystems/Locking b/Documentation/filesystems/Locking index 96d4293607e..bbcc15651a2 100644 --- a/Documentation/filesystems/Locking +++ b/Documentation/filesystems/Locking @@ -92,8 +92,8 @@ prototypes: void (*destroy_inode)(struct inode *); void (*dirty_inode) (struct inode *); int (*write_inode) (struct inode *, int); - void (*drop_inode) (struct inode *); - void (*delete_inode) (struct inode *); + int (*drop_inode) (struct inode *); + void (*evict_inode) (struct inode *); void (*put_super) (struct super_block *); void (*write_super) (struct super_block *); int (*sync_fs)(struct super_block *sb, int wait); @@ -101,14 +101,13 @@ prototypes: int (*unfreeze_fs) (struct super_block *); int (*statfs) (struct dentry *, struct kstatfs *); int (*remount_fs) (struct super_block *, int *, char *); - void (*clear_inode) (struct inode *); void (*umount_begin) (struct super_block *); 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); locking rules: - All may block. + All may block [not true, see below] None have BKL s_umount alloc_inode: @@ -116,22 +115,25 @@ destroy_inode: dirty_inode: (must not sleep) write_inode: drop_inode: !!!inode_lock!!! -delete_inode: +evict_inode: put_super: write write_super: read sync_fs: read freeze_fs: read unfreeze_fs: read -statfs: no -remount_fs: maybe (see below) -clear_inode: +statfs: maybe(read) (see below) +remount_fs: write umount_begin: no show_options: no (namespace_sem) quota_read: no (see below) quota_write: no (see below) -->remount_fs() will have the s_umount exclusive lock if it's already mounted. -When called from get_sb_single, it does NOT have the s_umount lock. +->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 +the superblock down when we only have dev_t given us by userland to +identify the superblock. Everything else (statfs(), fstatfs(), etc.) +doesn't hold it when calling ->statfs() - superblock is pinned down +by resolving the pathname passed to syscall. ->quota_read() and ->quota_write() functions are both guaranteed to 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 diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting index a7e9746ee7e..b12c8953868 100644 --- a/Documentation/filesystems/porting +++ b/Documentation/filesystems/porting @@ -273,3 +273,48 @@ it's safe to remove it. If you don't need it, remove it. deliberate; as soon as struct block_device * is propagated in a reasonable way by that code fixing will become trivial; until then nothing can be done. + +[mandatory] + + block truncatation on error exit from ->write_begin, and ->direct_IO +moved from generic methods (block_write_begin, cont_write_begin, +nobh_write_begin, blockdev_direct_IO*) to callers. Take a look at +ext2_write_failed and callers for an example. + +[mandatory] + + ->truncate is going away. The whole truncate sequence needs to be +implemented in ->setattr, which is now mandatory for filesystems +implementing on-disk size changes. Start with a copy of the old inode_setattr +and vmtruncate, and the reorder the vmtruncate + foofs_vmtruncate sequence to +be in order of zeroing blocks using block_truncate_page or similar helpers, +size update and on finally on-disk truncation which should not fail. +inode_change_ok now includes the size checks for ATTR_SIZE and must be called +in the beginning of ->setattr unconditionally. + +[mandatory] + + ->clear_inode() and ->delete_inode() are gone; ->evict_inode() should +be used instead. It gets called whenever the inode is evicted, whether it has +remaining links or not. Caller does *not* evict the pagecache or inode-associated +metadata buffers; getting rid of those is responsibility of method, as it had +been for ->delete_inode(). + ->drop_inode() returns int now; it's called on final iput() with inode_lock +held and it returns true if filesystems wants the inode to be dropped. As before, +generic_drop_inode() is still the default and it's been updated appropriately. +generic_delete_inode() is also alive and it consists simply of return 1. Note that +all actual eviction work is done by caller after ->drop_inode() returns. + clear_inode() is gone; use end_writeback() instead. As before, it must +be called exactly once on each call of ->evict_inode() (as it used to be for +each call of ->delete_inode()). Unlike before, if you are using inode-associated +metadata buffers (i.e. mark_buffer_dirty_inode()), it's your responsibility to +call invalidate_inode_buffers() before end_writeback(). + No async writeback (and thus no calls of ->write_inode()) will happen +after end_writeback() returns, so actions that should not overlap with ->write_inode() +(e.g. freeing on-disk inode if i_nlink is 0) ought to be done after that call. + + NOTE: checking i_nlink in the beginning of ->write_inode() and bailing out +if it's zero is not *and* *never* *had* *been* enough. Final unlink() and iput() +may happen while the inode is in the middle of ->write_inode(); e.g. if you blindly +free the on-disk inode, you may end up doing that while ->write_inode() is writing +to it. |