parallel lookups: actual switch to rwsem
ta-da! The main issue is the lack of down_write_killable(), so the places like readdir.c switched to plain inode_lock(); once killable variants of rwsem primitives appear, that'll be dealt with. lockdep side also might need more work Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
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@ -539,3 +539,21 @@ in your dentry operations instead.
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it's a symlink. Checking ->i_mode is really needed now. In-tree we had
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to fix shmem_destroy_callback() that used to take that kind of shortcut;
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watch out, since that shortcut is no longer valid.
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--
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[mandatory]
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->i_mutex is replaced with ->i_rwsem now. inode_lock() et.al. work as
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they used to - they just take it exclusive. However, ->lookup() may be
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called with parent locked shared. Its instances must not
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* use d_instantiate) and d_rehash() separately - use d_add() or
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d_splice_alias() instead.
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* use d_rehash() alone - call d_add(new_dentry, NULL) instead.
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* in the unlikely case when (read-only) access to filesystem
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data structures needs exclusion for some reason, arrange it
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yourself. None of the in-tree filesystems needed that.
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* rely on ->d_parent and ->d_name not changing after dentry has
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been fed to d_add() or d_splice_alias(). Again, none of the
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in-tree instances relied upon that.
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We are guaranteed that lookups of the same name in the same directory
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will not happen in parallel ("same" in the sense of your ->d_compare()).
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Lookups on different names in the same directory can and do happen in
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parallel now.
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@ -837,9 +837,11 @@ static noinline int btrfs_mksubvol(struct path *parent,
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struct dentry *dentry;
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int error;
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error = mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
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if (error == -EINTR)
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return error;
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inode_lock_nested(dir, I_MUTEX_PARENT);
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// XXX: should've been
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// mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
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// if (error == -EINTR)
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// return error;
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dentry = lookup_one_len(name, parent->dentry, namelen);
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error = PTR_ERR(dentry);
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@ -2366,9 +2368,11 @@ static noinline int btrfs_ioctl_snap_destroy(struct file *file,
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goto out;
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err = mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
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if (err == -EINTR)
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goto out_drop_write;
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inode_lock_nested(dir, I_MUTEX_PARENT);
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// XXX: should've been
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// err = mutex_lock_killable_nested(&dir->i_mutex, I_MUTEX_PARENT);
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// if (err == -EINTR)
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// goto out_drop_write;
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dentry = lookup_one_len(vol_args->name, parent, namelen);
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if (IS_ERR(dentry)) {
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err = PTR_ERR(dentry);
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@ -2558,7 +2562,7 @@ out_dput:
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dput(dentry);
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out_unlock_dir:
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inode_unlock(dir);
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out_drop_write:
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//out_drop_write:
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mnt_drop_write_file(file);
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out:
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kfree(vol_args);
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@ -156,7 +156,7 @@ static void configfs_set_inode_lock_class(struct configfs_dirent *sd,
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if (depth > 0) {
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if (depth <= ARRAY_SIZE(default_group_class)) {
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lockdep_set_class(&inode->i_mutex,
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lockdep_set_class(&inode->i_rwsem,
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&default_group_class[depth - 1]);
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} else {
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/*
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@ -2932,7 +2932,8 @@ struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
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static int __d_unalias(struct inode *inode,
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struct dentry *dentry, struct dentry *alias)
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{
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struct mutex *m1 = NULL, *m2 = NULL;
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struct mutex *m1 = NULL;
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struct rw_semaphore *m2 = NULL;
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int ret = -ESTALE;
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/* If alias and dentry share a parent, then no extra locks required */
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@ -2943,15 +2944,15 @@ static int __d_unalias(struct inode *inode,
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if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
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goto out_err;
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m1 = &dentry->d_sb->s_vfs_rename_mutex;
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if (!inode_trylock(alias->d_parent->d_inode))
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if (!inode_trylock_shared(alias->d_parent->d_inode))
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goto out_err;
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m2 = &alias->d_parent->d_inode->i_mutex;
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m2 = &alias->d_parent->d_inode->i_rwsem;
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out_unalias:
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__d_move(alias, dentry, false);
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ret = 0;
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out_err:
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if (m2)
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mutex_unlock(m2);
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up_read(m2);
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if (m1)
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mutex_unlock(m1);
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return ret;
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@ -824,7 +824,7 @@ static int init_inodes(struct gfs2_sbd *sdp, int undo)
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* i_mutex on quota files is special. Since this inode is hidden system
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* file, we are safe to define locking ourselves.
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*/
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lockdep_set_class(&sdp->sd_quota_inode->i_mutex,
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lockdep_set_class(&sdp->sd_quota_inode->i_rwsem,
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&gfs2_quota_imutex_key);
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error = gfs2_rindex_update(sdp);
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12
fs/inode.c
12
fs/inode.c
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@ -166,8 +166,8 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
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spin_lock_init(&inode->i_lock);
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lockdep_set_class(&inode->i_lock, &sb->s_type->i_lock_key);
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mutex_init(&inode->i_mutex);
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lockdep_set_class(&inode->i_mutex, &sb->s_type->i_mutex_key);
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init_rwsem(&inode->i_rwsem);
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lockdep_set_class(&inode->i_rwsem, &sb->s_type->i_mutex_key);
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atomic_set(&inode->i_dio_count, 0);
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@ -925,13 +925,13 @@ void lockdep_annotate_inode_mutex_key(struct inode *inode)
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struct file_system_type *type = inode->i_sb->s_type;
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/* Set new key only if filesystem hasn't already changed it */
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if (lockdep_match_class(&inode->i_mutex, &type->i_mutex_key)) {
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if (lockdep_match_class(&inode->i_rwsem, &type->i_mutex_key)) {
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/*
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* ensure nobody is actually holding i_mutex
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*/
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mutex_destroy(&inode->i_mutex);
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mutex_init(&inode->i_mutex);
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lockdep_set_class(&inode->i_mutex,
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// mutex_destroy(&inode->i_mutex);
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init_rwsem(&inode->i_rwsem);
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lockdep_set_class(&inode->i_rwsem,
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&type->i_mutex_dir_key);
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}
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}
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@ -1607,7 +1607,7 @@ static struct dentry *lookup_slow(const struct qstr *name,
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struct inode *inode = dir->d_inode;
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DECLARE_WAIT_QUEUE_HEAD_ONSTACK(wq);
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inode_lock(inode);
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inode_lock_shared(inode);
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/* Don't go there if it's already dead */
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if (unlikely(IS_DEADDIR(inode)))
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goto out;
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@ -1638,7 +1638,7 @@ again:
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}
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}
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out:
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inode_unlock(inode);
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inode_unlock_shared(inode);
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return dentry;
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}
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@ -262,7 +262,7 @@ static int ocfs2_init_locked_inode(struct inode *inode, void *opaque)
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inode->i_ino = args->fi_ino;
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OCFS2_I(inode)->ip_blkno = args->fi_blkno;
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if (args->fi_sysfile_type != 0)
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lockdep_set_class(&inode->i_mutex,
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lockdep_set_class(&inode->i_rwsem,
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&ocfs2_sysfile_lock_key[args->fi_sysfile_type]);
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if (args->fi_sysfile_type == USER_QUOTA_SYSTEM_INODE ||
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args->fi_sysfile_type == GROUP_QUOTA_SYSTEM_INODE ||
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@ -218,7 +218,9 @@ static int ovl_check_whiteouts(struct dentry *dir, struct ovl_readdir_data *rdd)
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cap_raise(override_cred->cap_effective, CAP_DAC_OVERRIDE);
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old_cred = override_creds(override_cred);
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err = mutex_lock_killable(&dir->d_inode->i_mutex);
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inode_lock(dir->d_inode);
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err = 0;
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// XXX: err = mutex_lock_killable(&dir->d_inode->i_mutex);
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if (!err) {
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while (rdd->first_maybe_whiteout) {
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p = rdd->first_maybe_whiteout;
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@ -32,9 +32,10 @@ int iterate_dir(struct file *file, struct dir_context *ctx)
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if (res)
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goto out;
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res = mutex_lock_killable(&inode->i_mutex);
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if (res)
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goto out;
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inode_lock(inode);
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// res = mutex_lock_killable(&inode->i_mutex);
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// if (res)
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// goto out;
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res = -ENOENT;
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if (!IS_DEADDIR(inode)) {
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@ -647,7 +647,7 @@ struct inode {
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/* Misc */
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unsigned long i_state;
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struct mutex i_mutex;
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struct rw_semaphore i_rwsem;
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unsigned long dirtied_when; /* jiffies of first dirtying */
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unsigned long dirtied_time_when;
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static inline void inode_lock(struct inode *inode)
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{
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mutex_lock(&inode->i_mutex);
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down_write(&inode->i_rwsem);
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}
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static inline void inode_unlock(struct inode *inode)
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{
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mutex_unlock(&inode->i_mutex);
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up_write(&inode->i_rwsem);
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}
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static inline void inode_lock_shared(struct inode *inode)
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{
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down_read(&inode->i_rwsem);
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}
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static inline void inode_unlock_shared(struct inode *inode)
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{
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up_read(&inode->i_rwsem);
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}
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static inline int inode_trylock(struct inode *inode)
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{
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return mutex_trylock(&inode->i_mutex);
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return down_write_trylock(&inode->i_rwsem);
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}
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static inline int inode_trylock_shared(struct inode *inode)
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{
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return down_read_trylock(&inode->i_rwsem);
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}
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static inline int inode_is_locked(struct inode *inode)
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{
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return mutex_is_locked(&inode->i_mutex);
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return rwsem_is_locked(&inode->i_rwsem);
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}
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static inline void inode_lock_nested(struct inode *inode, unsigned subclass)
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{
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mutex_lock_nested(&inode->i_mutex, subclass);
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down_write_nested(&inode->i_rwsem, subclass);
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}
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void lock_two_nondirectories(struct inode *, struct inode*);
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