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

[Nikolay Borisov <nborisov@suse.com>]

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.
>   *
>