| Message ID | 20221205095122.17011-3-robbieko@synology.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | btrfs: fix unexpected -ENOMEM with percpu_counter_init when create snapshot | expand |
On Mon, Dec 5, 2022 at 10:30 AM robbieko <robbieko@synology.com> wrote: > > From: Robbie Ko <robbieko@synology.com> > > Change snapshot_lock to dynamic pointer to allocate memory > at the beginning of creating a subvolume/snapshot. > > Signed-off-by: Robbie Ko <robbieko@synology.com> > --- > fs/btrfs/ctree.h | 2 +- > fs/btrfs/disk-io.c | 10 ++++++++-- > fs/btrfs/file.c | 8 ++++---- > fs/btrfs/inode.c | 12 ++++++------ > fs/btrfs/ioctl.c | 4 ++-- > 5 files changed, 21 insertions(+), 15 deletions(-) > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h > index 9e6d48ff4597..99003b0dd407 100644 > --- a/fs/btrfs/ctree.h > +++ b/fs/btrfs/ctree.h > @@ -1429,7 +1429,7 @@ struct btrfs_root { > */ > int dedupe_in_progress; > /* For exclusion of snapshot creation and nocow writes */ > - struct btrfs_drew_lock snapshot_lock; > + struct btrfs_drew_lock *snapshot_lock; > > atomic_t snapshot_force_cow; > > diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c > index afe16e1f0b18..5760c2b1a100 100644 > --- a/fs/btrfs/disk-io.c > +++ b/fs/btrfs/disk-io.c > @@ -1464,12 +1464,17 @@ static int btrfs_init_fs_root(struct btrfs_root *root, > int ret; > unsigned int nofs_flag; > > + root->snapshot_lock = kzalloc(sizeof(*root->snapshot_lock), GFP_NOFS); > + if (!root->snapshot_lock) { > + ret = -ENOMEM; > + goto fail; > + } > /* > * We might be called under a transaction (e.g. indirect backref > * resolution) which could deadlock if it triggers memory reclaim > */ > nofs_flag = memalloc_nofs_save(); > - ret = btrfs_drew_lock_init(&root->snapshot_lock); > + ret = btrfs_drew_lock_init(root->snapshot_lock); > memalloc_nofs_restore(nofs_flag); > if (ret) > goto fail; > @@ -2180,7 +2185,8 @@ void btrfs_put_root(struct btrfs_root *root) > WARN_ON(test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state)); > if (root->anon_dev) > free_anon_bdev(root->anon_dev); > - btrfs_drew_lock_destroy(&root->snapshot_lock); > + if (root->snapshot_lock) > + btrfs_drew_lock_destroy(root->snapshot_lock); This is leaking the memory allocated for the lock, it needs a kfree(root->snapshot_lock) too. Thanks. > free_root_extent_buffers(root); > #ifdef CONFIG_BTRFS_DEBUG > spin_lock(&root->fs_info->fs_roots_radix_lock); > diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c > index d01631d47806..a338fbd34472 100644 > --- a/fs/btrfs/file.c > +++ b/fs/btrfs/file.c > @@ -1379,7 +1379,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, > if (!(inode->flags & (BTRFS_INODE_NODATACOW | BTRFS_INODE_PREALLOC))) > return 0; > > - if (!btrfs_drew_try_write_lock(&root->snapshot_lock)) > + if (!btrfs_drew_try_write_lock(root->snapshot_lock)) > return -EAGAIN; > > lockstart = round_down(pos, fs_info->sectorsize); > @@ -1389,7 +1389,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, > > if (nowait) { > if (!btrfs_try_lock_ordered_range(inode, lockstart, lockend)) { > - btrfs_drew_write_unlock(&root->snapshot_lock); > + btrfs_drew_write_unlock(root->snapshot_lock); > return -EAGAIN; > } > } else { > @@ -1398,7 +1398,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, > ret = can_nocow_extent(&inode->vfs_inode, lockstart, &num_bytes, > NULL, NULL, NULL, nowait, false); > if (ret <= 0) > - btrfs_drew_write_unlock(&root->snapshot_lock); > + btrfs_drew_write_unlock(root->snapshot_lock); > else > *write_bytes = min_t(size_t, *write_bytes , > num_bytes - pos + lockstart); > @@ -1409,7 +1409,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, > > void btrfs_check_nocow_unlock(struct btrfs_inode *inode) > { > - btrfs_drew_write_unlock(&inode->root->snapshot_lock); > + btrfs_drew_write_unlock(inode->root->snapshot_lock); > } > > static void update_time_for_write(struct inode *inode) > diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c > index 0e516aefbf51..8fe4b00d31f4 100644 > --- a/fs/btrfs/inode.c > +++ b/fs/btrfs/inode.c > @@ -5167,16 +5167,16 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr) > * truncation, it must capture all writes that happened before > * this truncation. > */ > - btrfs_drew_write_lock(&root->snapshot_lock); > + btrfs_drew_write_lock(root->snapshot_lock); > ret = btrfs_cont_expand(BTRFS_I(inode), oldsize, newsize); > if (ret) { > - btrfs_drew_write_unlock(&root->snapshot_lock); > + btrfs_drew_write_unlock(root->snapshot_lock); > return ret; > } > > trans = btrfs_start_transaction(root, 1); > if (IS_ERR(trans)) { > - btrfs_drew_write_unlock(&root->snapshot_lock); > + btrfs_drew_write_unlock(root->snapshot_lock); > return PTR_ERR(trans); > } > > @@ -5184,7 +5184,7 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr) > btrfs_inode_safe_disk_i_size_write(BTRFS_I(inode), 0); > pagecache_isize_extended(inode, oldsize, newsize); > ret = btrfs_update_inode(trans, root, BTRFS_I(inode)); > - btrfs_drew_write_unlock(&root->snapshot_lock); > + btrfs_drew_write_unlock(root->snapshot_lock); > btrfs_end_transaction(trans); > } else { > struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); > @@ -11026,7 +11026,7 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file, > * completes before the first write into the swap file after it is > * activated, than that write would fallback to COW. > */ > - if (!btrfs_drew_try_write_lock(&root->snapshot_lock)) { > + if (!btrfs_drew_try_write_lock(root->snapshot_lock)) { > btrfs_exclop_finish(fs_info); > btrfs_warn(fs_info, > "cannot activate swapfile because snapshot creation is in progress"); > @@ -11199,7 +11199,7 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file, > if (ret) > btrfs_swap_deactivate(file); > > - btrfs_drew_write_unlock(&root->snapshot_lock); > + btrfs_drew_write_unlock(root->snapshot_lock); > > btrfs_exclop_finish(fs_info); > > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c > index 5785336ab7cf..9f1b81ff37a3 100644 > --- a/fs/btrfs/ioctl.c > +++ b/fs/btrfs/ioctl.c > @@ -1008,7 +1008,7 @@ static noinline int btrfs_mksnapshot(const struct path *parent, > * possible. This is to avoid later writeback (running dealloc) to > * fallback to COW mode and unexpectedly fail with ENOSPC. > */ > - btrfs_drew_read_lock(&root->snapshot_lock); > + btrfs_drew_read_lock(root->snapshot_lock); > > ret = btrfs_start_delalloc_snapshot(root, false); > if (ret) > @@ -1029,7 +1029,7 @@ static noinline int btrfs_mksnapshot(const struct path *parent, > out: > if (snapshot_force_cow) > atomic_dec(&root->snapshot_force_cow); > - btrfs_drew_read_unlock(&root->snapshot_lock); > + btrfs_drew_read_unlock(root->snapshot_lock); > return ret; > } > > -- > 2.17.1 >
Filipe Manana 於 2022/12/13 上午1:05 寫道: > On Mon, Dec 5, 2022 at 10:30 AM robbieko <robbieko@synology.com> wrote: >> From: Robbie Ko <robbieko@synology.com> >> >> Change snapshot_lock to dynamic pointer to allocate memory >> at the beginning of creating a subvolume/snapshot. >> >> Signed-off-by: Robbie Ko <robbieko@synology.com> >> --- >> fs/btrfs/ctree.h | 2 +- >> fs/btrfs/disk-io.c | 10 ++++++++-- >> fs/btrfs/file.c | 8 ++++---- >> fs/btrfs/inode.c | 12 ++++++------ >> fs/btrfs/ioctl.c | 4 ++-- >> 5 files changed, 21 insertions(+), 15 deletions(-) >> >> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h >> index 9e6d48ff4597..99003b0dd407 100644 >> --- a/fs/btrfs/ctree.h >> +++ b/fs/btrfs/ctree.h >> @@ -1429,7 +1429,7 @@ struct btrfs_root { >> */ >> int dedupe_in_progress; >> /* For exclusion of snapshot creation and nocow writes */ >> - struct btrfs_drew_lock snapshot_lock; >> + struct btrfs_drew_lock *snapshot_lock; >> >> atomic_t snapshot_force_cow; >> >> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c >> index afe16e1f0b18..5760c2b1a100 100644 >> --- a/fs/btrfs/disk-io.c >> +++ b/fs/btrfs/disk-io.c >> @@ -1464,12 +1464,17 @@ static int btrfs_init_fs_root(struct btrfs_root *root, >> int ret; >> unsigned int nofs_flag; >> >> + root->snapshot_lock = kzalloc(sizeof(*root->snapshot_lock), GFP_NOFS); >> + if (!root->snapshot_lock) { >> + ret = -ENOMEM; >> + goto fail; >> + } >> /* >> * We might be called under a transaction (e.g. indirect backref >> * resolution) which could deadlock if it triggers memory reclaim >> */ >> nofs_flag = memalloc_nofs_save(); >> - ret = btrfs_drew_lock_init(&root->snapshot_lock); >> + ret = btrfs_drew_lock_init(root->snapshot_lock); >> memalloc_nofs_restore(nofs_flag); >> if (ret) >> goto fail; >> @@ -2180,7 +2185,8 @@ void btrfs_put_root(struct btrfs_root *root) >> WARN_ON(test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state)); >> if (root->anon_dev) >> free_anon_bdev(root->anon_dev); >> - btrfs_drew_lock_destroy(&root->snapshot_lock); >> + if (root->snapshot_lock) >> + btrfs_drew_lock_destroy(root->snapshot_lock); > This is leaking the memory allocated for the lock, it needs a > kfree(root->snapshot_lock) too. I missed the release, I will fix it. Thanks > Thanks. > >> free_root_extent_buffers(root); >> #ifdef CONFIG_BTRFS_DEBUG >> spin_lock(&root->fs_info->fs_roots_radix_lock); >> diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c >> index d01631d47806..a338fbd34472 100644 >> --- a/fs/btrfs/file.c >> +++ b/fs/btrfs/file.c >> @@ -1379,7 +1379,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, >> if (!(inode->flags & (BTRFS_INODE_NODATACOW | BTRFS_INODE_PREALLOC))) >> return 0; >> >> - if (!btrfs_drew_try_write_lock(&root->snapshot_lock)) >> + if (!btrfs_drew_try_write_lock(root->snapshot_lock)) >> return -EAGAIN; >> >> lockstart = round_down(pos, fs_info->sectorsize); >> @@ -1389,7 +1389,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, >> >> if (nowait) { >> if (!btrfs_try_lock_ordered_range(inode, lockstart, lockend)) { >> - btrfs_drew_write_unlock(&root->snapshot_lock); >> + btrfs_drew_write_unlock(root->snapshot_lock); >> return -EAGAIN; >> } >> } else { >> @@ -1398,7 +1398,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, >> ret = can_nocow_extent(&inode->vfs_inode, lockstart, &num_bytes, >> NULL, NULL, NULL, nowait, false); >> if (ret <= 0) >> - btrfs_drew_write_unlock(&root->snapshot_lock); >> + btrfs_drew_write_unlock(root->snapshot_lock); >> else >> *write_bytes = min_t(size_t, *write_bytes , >> num_bytes - pos + lockstart); >> @@ -1409,7 +1409,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, >> >> void btrfs_check_nocow_unlock(struct btrfs_inode *inode) >> { >> - btrfs_drew_write_unlock(&inode->root->snapshot_lock); >> + btrfs_drew_write_unlock(inode->root->snapshot_lock); >> } >> >> static void update_time_for_write(struct inode *inode) >> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c >> index 0e516aefbf51..8fe4b00d31f4 100644 >> --- a/fs/btrfs/inode.c >> +++ b/fs/btrfs/inode.c >> @@ -5167,16 +5167,16 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr) >> * truncation, it must capture all writes that happened before >> * this truncation. >> */ >> - btrfs_drew_write_lock(&root->snapshot_lock); >> + btrfs_drew_write_lock(root->snapshot_lock); >> ret = btrfs_cont_expand(BTRFS_I(inode), oldsize, newsize); >> if (ret) { >> - btrfs_drew_write_unlock(&root->snapshot_lock); >> + btrfs_drew_write_unlock(root->snapshot_lock); >> return ret; >> } >> >> trans = btrfs_start_transaction(root, 1); >> if (IS_ERR(trans)) { >> - btrfs_drew_write_unlock(&root->snapshot_lock); >> + btrfs_drew_write_unlock(root->snapshot_lock); >> return PTR_ERR(trans); >> } >> >> @@ -5184,7 +5184,7 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr) >> btrfs_inode_safe_disk_i_size_write(BTRFS_I(inode), 0); >> pagecache_isize_extended(inode, oldsize, newsize); >> ret = btrfs_update_inode(trans, root, BTRFS_I(inode)); >> - btrfs_drew_write_unlock(&root->snapshot_lock); >> + btrfs_drew_write_unlock(root->snapshot_lock); >> btrfs_end_transaction(trans); >> } else { >> struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); >> @@ -11026,7 +11026,7 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file, >> * completes before the first write into the swap file after it is >> * activated, than that write would fallback to COW. >> */ >> - if (!btrfs_drew_try_write_lock(&root->snapshot_lock)) { >> + if (!btrfs_drew_try_write_lock(root->snapshot_lock)) { >> btrfs_exclop_finish(fs_info); >> btrfs_warn(fs_info, >> "cannot activate swapfile because snapshot creation is in progress"); >> @@ -11199,7 +11199,7 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file, >> if (ret) >> btrfs_swap_deactivate(file); >> >> - btrfs_drew_write_unlock(&root->snapshot_lock); >> + btrfs_drew_write_unlock(root->snapshot_lock); >> >> btrfs_exclop_finish(fs_info); >> >> diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c >> index 5785336ab7cf..9f1b81ff37a3 100644 >> --- a/fs/btrfs/ioctl.c >> +++ b/fs/btrfs/ioctl.c >> @@ -1008,7 +1008,7 @@ static noinline int btrfs_mksnapshot(const struct path *parent, >> * possible. This is to avoid later writeback (running dealloc) to >> * fallback to COW mode and unexpectedly fail with ENOSPC. >> */ >> - btrfs_drew_read_lock(&root->snapshot_lock); >> + btrfs_drew_read_lock(root->snapshot_lock); >> >> ret = btrfs_start_delalloc_snapshot(root, false); >> if (ret) >> @@ -1029,7 +1029,7 @@ static noinline int btrfs_mksnapshot(const struct path *parent, >> out: >> if (snapshot_force_cow) >> atomic_dec(&root->snapshot_force_cow); >> - btrfs_drew_read_unlock(&root->snapshot_lock); >> + btrfs_drew_read_unlock(root->snapshot_lock); >> return ret; >> } >> >> -- >> 2.17.1 >>
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 9e6d48ff4597..99003b0dd407 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1429,7 +1429,7 @@ struct btrfs_root { */ int dedupe_in_progress; /* For exclusion of snapshot creation and nocow writes */ - struct btrfs_drew_lock snapshot_lock; + struct btrfs_drew_lock *snapshot_lock; atomic_t snapshot_force_cow; diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index afe16e1f0b18..5760c2b1a100 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1464,12 +1464,17 @@ static int btrfs_init_fs_root(struct btrfs_root *root, int ret; unsigned int nofs_flag; + root->snapshot_lock = kzalloc(sizeof(*root->snapshot_lock), GFP_NOFS); + if (!root->snapshot_lock) { + ret = -ENOMEM; + goto fail; + } /* * We might be called under a transaction (e.g. indirect backref * resolution) which could deadlock if it triggers memory reclaim */ nofs_flag = memalloc_nofs_save(); - ret = btrfs_drew_lock_init(&root->snapshot_lock); + ret = btrfs_drew_lock_init(root->snapshot_lock); memalloc_nofs_restore(nofs_flag); if (ret) goto fail; @@ -2180,7 +2185,8 @@ void btrfs_put_root(struct btrfs_root *root) WARN_ON(test_bit(BTRFS_ROOT_DEAD_RELOC_TREE, &root->state)); if (root->anon_dev) free_anon_bdev(root->anon_dev); - btrfs_drew_lock_destroy(&root->snapshot_lock); + if (root->snapshot_lock) + btrfs_drew_lock_destroy(root->snapshot_lock); free_root_extent_buffers(root); #ifdef CONFIG_BTRFS_DEBUG spin_lock(&root->fs_info->fs_roots_radix_lock); diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index d01631d47806..a338fbd34472 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1379,7 +1379,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, if (!(inode->flags & (BTRFS_INODE_NODATACOW | BTRFS_INODE_PREALLOC))) return 0; - if (!btrfs_drew_try_write_lock(&root->snapshot_lock)) + if (!btrfs_drew_try_write_lock(root->snapshot_lock)) return -EAGAIN; lockstart = round_down(pos, fs_info->sectorsize); @@ -1389,7 +1389,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, if (nowait) { if (!btrfs_try_lock_ordered_range(inode, lockstart, lockend)) { - btrfs_drew_write_unlock(&root->snapshot_lock); + btrfs_drew_write_unlock(root->snapshot_lock); return -EAGAIN; } } else { @@ -1398,7 +1398,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, ret = can_nocow_extent(&inode->vfs_inode, lockstart, &num_bytes, NULL, NULL, NULL, nowait, false); if (ret <= 0) - btrfs_drew_write_unlock(&root->snapshot_lock); + btrfs_drew_write_unlock(root->snapshot_lock); else *write_bytes = min_t(size_t, *write_bytes , num_bytes - pos + lockstart); @@ -1409,7 +1409,7 @@ int btrfs_check_nocow_lock(struct btrfs_inode *inode, loff_t pos, void btrfs_check_nocow_unlock(struct btrfs_inode *inode) { - btrfs_drew_write_unlock(&inode->root->snapshot_lock); + btrfs_drew_write_unlock(inode->root->snapshot_lock); } static void update_time_for_write(struct inode *inode) diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c index 0e516aefbf51..8fe4b00d31f4 100644 --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -5167,16 +5167,16 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr) * truncation, it must capture all writes that happened before * this truncation. */ - btrfs_drew_write_lock(&root->snapshot_lock); + btrfs_drew_write_lock(root->snapshot_lock); ret = btrfs_cont_expand(BTRFS_I(inode), oldsize, newsize); if (ret) { - btrfs_drew_write_unlock(&root->snapshot_lock); + btrfs_drew_write_unlock(root->snapshot_lock); return ret; } trans = btrfs_start_transaction(root, 1); if (IS_ERR(trans)) { - btrfs_drew_write_unlock(&root->snapshot_lock); + btrfs_drew_write_unlock(root->snapshot_lock); return PTR_ERR(trans); } @@ -5184,7 +5184,7 @@ static int btrfs_setsize(struct inode *inode, struct iattr *attr) btrfs_inode_safe_disk_i_size_write(BTRFS_I(inode), 0); pagecache_isize_extended(inode, oldsize, newsize); ret = btrfs_update_inode(trans, root, BTRFS_I(inode)); - btrfs_drew_write_unlock(&root->snapshot_lock); + btrfs_drew_write_unlock(root->snapshot_lock); btrfs_end_transaction(trans); } else { struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb); @@ -11026,7 +11026,7 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file, * completes before the first write into the swap file after it is * activated, than that write would fallback to COW. */ - if (!btrfs_drew_try_write_lock(&root->snapshot_lock)) { + if (!btrfs_drew_try_write_lock(root->snapshot_lock)) { btrfs_exclop_finish(fs_info); btrfs_warn(fs_info, "cannot activate swapfile because snapshot creation is in progress"); @@ -11199,7 +11199,7 @@ static int btrfs_swap_activate(struct swap_info_struct *sis, struct file *file, if (ret) btrfs_swap_deactivate(file); - btrfs_drew_write_unlock(&root->snapshot_lock); + btrfs_drew_write_unlock(root->snapshot_lock); btrfs_exclop_finish(fs_info); diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c index 5785336ab7cf..9f1b81ff37a3 100644 --- a/fs/btrfs/ioctl.c +++ b/fs/btrfs/ioctl.c @@ -1008,7 +1008,7 @@ static noinline int btrfs_mksnapshot(const struct path *parent, * possible. This is to avoid later writeback (running dealloc) to * fallback to COW mode and unexpectedly fail with ENOSPC. */ - btrfs_drew_read_lock(&root->snapshot_lock); + btrfs_drew_read_lock(root->snapshot_lock); ret = btrfs_start_delalloc_snapshot(root, false); if (ret) @@ -1029,7 +1029,7 @@ static noinline int btrfs_mksnapshot(const struct path *parent, out: if (snapshot_force_cow) atomic_dec(&root->snapshot_force_cow); - btrfs_drew_read_unlock(&root->snapshot_lock); + btrfs_drew_read_unlock(root->snapshot_lock); return ret; }