xiaomi-sm8450/android_kernel_xiaomi_sm8450
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btrfs: kill the subvol_srcu

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Now that we have proper root ref counting everywhere we can kill the
subvol_srcu.

* removal of fs_info::subvol_srcu reduces size of fs_info by 1176 bytes

* the refcount_t used for the references checks for accidental 0->1
  in cases where the root lifetime would not be properly protected

* there's a leak detector for roots to catch unfreed roots at umount
  time

* SRCU served us well over the years but is was not a proper
  synchronization mechanism for some cases

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ update changelog ]
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik
2020-02-14 16:11:47 -05:00
committed by David Sterba
parent efc3453494
commit c75e839414
8 changed files with 14 additions and 88 deletions
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21
fs/btrfs/export.c
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@@ -65,8 +65,6 @@ struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
struct btrfs_root *root;
struct inode *inode;
struct btrfs_key key;
int index;
int err = 0;
if (objectid < BTRFS_FIRST_FREE_OBJECTID)
return ERR_PTR(-ESTALE);
@@ -75,13 +73,9 @@ struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
key.type = BTRFS_ROOT_ITEM_KEY;
key.offset = (u64)-1;
index = srcu_read_lock(&fs_info->subvol_srcu);
root = btrfs_get_fs_root(fs_info, &key, true);
if (IS_ERR(root)) {
err = PTR_ERR(root);
goto fail;
}
if (IS_ERR(root))
return ERR_CAST(root);
key.objectid = objectid;
key.type = BTRFS_INODE_ITEM_KEY;
@@ -89,12 +83,8 @@ struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
inode = btrfs_iget(sb, &key, root);
btrfs_put_root(root);
if (IS_ERR(inode)) {
err = PTR_ERR(inode);
goto fail;
}
srcu_read_unlock(&fs_info->subvol_srcu, index);
if (IS_ERR(inode))
return ERR_CAST(inode);
if (check_generation && generation != inode->i_generation) {
iput(inode);
@@ -102,9 +92,6 @@ struct dentry *btrfs_get_dentry(struct super_block *sb, u64 objectid,
}
return d_obtain_alias(inode);
fail:
srcu_read_unlock(&fs_info->subvol_srcu, index);
return ERR_PTR(err);
}
static struct dentry *btrfs_fh_to_parent(struct super_block *sb, struct fid *fh,