Re: [PATCH v2 2/6] btrfs-progs: check/common: Introduce a function to find imode using INODE_REF

Nikolay Borisov
2019-09-09T13:26:02Z

On 5.09.19 г. 10:57 ч., Qu Wenruo wrote:
> Introduce a function, find_file_type(), to find filetype using
> INODE_REF.
>
> This function will:
> - Search DIR_INDEX first
> DIR_INDEX is easier since there is only one item in it.
>
> - Valid the DIR_INDEX item
> If the DIR_INDEX is valid, use the filetype and call it a day.
>
> - Search DIR_ITEM then
>
> - Valide the DIR_ITEM
> If valid, call it a day. Or return -ENOENT;
>
> This would be used as the primary method to determine the imode in later
> imode repair code.
>
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
> check/mode-common.c | 99 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 99 insertions(+)
>
> diff --git a/check/mode-common.c b/check/mode-common.c
> index 195b6efaa7aa..c0ddc50a1dd0 100644
> --- a/check/mode-common.c
> +++ b/check/mode-common.c
> @@ -16,6 +16,7 @@
>
> #include <time.h>
> #include "ctree.h"
> +#include "hash.h"
> #include "common/internal.h"
> #include "common/messages.h"
> #include "transaction.h"
> @@ -836,6 +837,104 @@ int reset_imode(struct btrfs_trans_handle *trans, struct btrfs_root *root,
> return ret;
> }
>
> +static int find_file_type(struct btrfs_root *root, u64 ino, u64 dirid,
> + u64 index, const char *name, u32 name_len,
> + u32 *imode_ret)
> +{
> + struct btrfs_path path;
> + struct btrfs_key location;
> + struct btrfs_key key;
> + struct btrfs_dir_item *di;
> + char namebuf[BTRFS_NAME_LEN] = {0};
> + unsigned long cur;
> + unsigned long end;
> + bool found = false;
> + u8 filetype;
> + u32 len;
> + int ret;
> +
> + btrfs_init_path(&path);
> +
> + /* Search DIR_INDEX first */
> + key.objectid = dirid;
> + key.offset = index;
> + key.type = BTRFS_DIR_INDEX_KEY;
> +
> + ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
> + if (ret > 0)
> + ret = -ENOENT;

Even if it returns 1 meaning there is no DIR_INDEX item perhaps it still
makes sense to go to dir_item: label to search for DIR_ITEM, what if the
corruption has affected just the DIR_INDEX item?

> + if (ret < 0)
> + goto dir_item;
nit: Use elseif to make it more explicit it is a single construct.

> + di = btrfs_item_ptr(path.nodes[0], path.slots[0],
> + struct btrfs_dir_item);
> + btrfs_dir_item_key_to_cpu(path.nodes[0], di, &location);
> +
> + /* Various basic check */
> + if (location.objectid != ino || location.type != BTRFS_INODE_ITEM_KEY ||
> + location.offset != 0)
> + goto dir_item;
> + filetype = btrfs_dir_type(path.nodes[0], di);
> + if (filetype >= BTRFS_FT_MAX || filetype == BTRFS_FT_UNKNOWN)
> + goto dir_item;
> + len = min_t(u32, btrfs_item_size_nr(path.nodes[0], path.slots[0]) -
> + sizeof(*di), BTRFS_NAME_LEN);
> + len = min_t(u32, len, btrfs_dir_name_len(path.nodes[0], di));
> + read_extent_buffer(path.nodes[0], namebuf, (unsigned long)(di + 1), len);
> + if (name_len != len || memcmp(namebuf, name, len))
> + goto dir_item;
> +
> + /* Got a correct filetype */
> + found = true;
> + *imode_ret = btrfs_type_to_imode(filetype);
> + ret = 0;
> + goto out;
> +
> +dir_item:

This function is needlessly structured in an awkward way. E.g. there is
no dependence between "searching by DIR INDEX item" and "searching by
DIR_ITEM". I think the best way is to have 3 function:

Top level find_file_type which will call find_file_type_by_dir_index if
the reeturn value is negative -> call 2nd function
find_file_type_by_dir_item. This will result in 3 fairly short and easy
to read/parse functions.

> + btrfs_release_path(&path);
> + key.objectid = dirid;
> + key.offset = btrfs_name_hash(name, name_len);
> +
> + ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
> + if (ret > 0)
> + ret = -ENOENT;
> + if (ret < 0) {
> + btrfs_release_path(&path);
> + return ret;
> + }

ditto about the else if construct

> + cur = btrfs_item_ptr_offset(path.nodes[0], path.slots[0]);
> + end = cur + btrfs_item_size_nr(path.nodes[0], path.slots[0]);
> + while (cur < end) {

Just checking : this is needed in case we have items whose names create
a crc32 collision in the DIR_ITEM offset?

> + di = (struct btrfs_dir_item *)cur;
> + btrfs_dir_item_key_to_cpu(path.nodes[0], di, &location);
> + /* Various basic check */
> + if (location.objectid != ino ||
> + location.type != BTRFS_INODE_ITEM_KEY ||
> + location.offset != 0)
> + goto next;> + filetype = btrfs_dir_type(path.nodes[0], di);
> + if (filetype >= BTRFS_FT_MAX || filetype == BTRFS_FT_UNKNOWN)
> + goto next;
> + len = min_t(u32, BTRFS_NAME_LEN,
> + btrfs_item_size_nr(path.nodes[0], path.slots[0]) -
> + sizeof(*di));
> + len = min_t(u32, len, btrfs_dir_name_len(path.nodes[0], di));
> + read_extent_buffer(path.nodes[0], namebuf,
> + (unsigned long)(di + 1), len);
> + if (name_len != len || memcmp(namebuf, name, len))
> + goto next;
> + *imode_ret = btrfs_type_to_imode(filetype);
> + found = true;
> + goto out;
> +next:
> + cur += btrfs_dir_name_len(path.nodes[0], di) + sizeof(*di);

If this line is moved right after assigning to 'di' instead of having a
'next' label you can simply use the 'continue' keyword

> + }
> +out:
> + btrfs_release_path(&path);
> + if (!found && !ret)
> + ret = -ENOENT;
> + return ret;
> +}
> +
> /*
> * Reset the inode mode of the inode specified by @path.
> *
>