Re: [PATCH v1 03/22] libext2fs: add functions to operate on extended attribute

["Darrick J. Wong" <darrick.wong@oracle.com>]

On Fri, Aug 02, 2013 at 05:49:30PM +0800, Zheng Liu wrote:
> From: Zheng Liu <wenqing.lz@taobao.com>
> 
> We need to define some functions to operate extended attribute in order
> to support inline data.
> 
> Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
> Signed-off-by: Theodore Ts'o <tytso@mit.edu>
> ---
>  lib/ext2fs/ext2_err.et.in  |    3 +
>  lib/ext2fs/ext2_ext_attr.h |   31 ++++++++
>  lib/ext2fs/ext2fs.h        |    9 +++
>  lib/ext2fs/ext_attr.c      |  186 ++++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 229 insertions(+)
> 
> diff --git a/lib/ext2fs/ext2_err.et.in b/lib/ext2fs/ext2_err.et.in
> index d20c6b7..7e6d6e5 100644
> --- a/lib/ext2fs/ext2_err.et.in
> +++ b/lib/ext2fs/ext2_err.et.in
> @@ -476,4 +476,7 @@ ec	EXT2_ET_MMP_CSUM_INVALID,
>  ec	EXT2_ET_FILE_EXISTS,
>  	"Ext2 file already exists"
>  
> +ec	EXT2_ET_EXT_ATTR_CURRUPTED,
> +	"Extended attribute currupted"

"corrupted".

(Or maybe shorten that to "corrupt"?)

--D
> +
>  	end
> diff --git a/lib/ext2fs/ext2_ext_attr.h b/lib/ext2fs/ext2_ext_attr.h
> index bbb0aaa..99ad849 100644
> --- a/lib/ext2fs/ext2_ext_attr.h
> +++ b/lib/ext2fs/ext2_ext_attr.h
> @@ -15,6 +15,10 @@
>  /* Maximum number of references to one attribute block */
>  #define EXT2_EXT_ATTR_REFCOUNT_MAX	1024
>  
> +/* Name indexes */
> +#define EXT4_EXT_ATTR_INDEX_SYSTEM	7
> +#define EXT4_EXT_ATTR_SYSTEM_DATA	"data"
> +
>  struct ext2_ext_attr_header {
>  	__u32	h_magic;	/* magic number for identification */
>  	__u32	h_refcount;	/* reference count */
> @@ -25,6 +29,10 @@ struct ext2_ext_attr_header {
>  	__u32	h_reserved[3];	/* zero right now */
>  };
>  
> +struct ext2_ext_attr_ibody_header {
> +	__u32	h_magic;
> +};
> +
>  struct ext2_ext_attr_entry {
>  	__u8	e_name_len;	/* length of name */
>  	__u8	e_name_index;	/* attribute name index */
> @@ -57,6 +65,29 @@ struct ext2_ext_attr_entry {
>  #define EXT2_XATTR_SIZE(size) \
>  	(((size) + EXT2_EXT_ATTR_ROUND) & ~EXT2_EXT_ATTR_ROUND)
>  
> +#define IHDR(inode) \
> +	((struct ext2_ext_attr_ibody_header *) \
> +		((char *)inode + \
> +		EXT2_GOOD_OLD_INODE_SIZE + \
> +		inode->i_extra_isize))
> +#define IFIRST(hdr) ((struct ext2_ext_attr_entry *)((hdr)+1))
> +#define EXT2_ZERO_EXT_ATTR_VALUE ((void *)-1)
> +
> +struct ext2_ext_attr_info {
> +	int name_index;
> +	const char *name;
> +	const void *value;
> +	size_t value_len;
> +};
> +
> +struct ext2_ext_attr_search {
> +	struct ext2_ext_attr_entry *first;
> +	void *base;
> +	void *end;
> +	struct ext2_ext_attr_entry *here;
> +	int not_found;
> +};
> +
>  #ifdef __KERNEL__
>  # ifdef CONFIG_EXT2_FS_EXT_ATTR
>  extern int ext2_get_ext_attr(struct inode *, const char *, char *, size_t, int);
> diff --git a/lib/ext2fs/ext2fs.h b/lib/ext2fs/ext2fs.h
> index 3346c00..8c30197 100644
> --- a/lib/ext2fs/ext2fs.h
> +++ b/lib/ext2fs/ext2fs.h
> @@ -1136,6 +1136,15 @@ extern errcode_t ext2fs_adjust_ea_refcount3(ext2_filsys fs, blk64_t blk,
>  					   char *block_buf,
>  					   int adjust, __u32 *newcount,
>  					   ext2_ino_t inum);
> +extern errcode_t ext2fs_ext_attr_ibody_find(ext2_filsys fs,
> +					    struct ext2_inode_large *inode,
> +					    struct ext2_ext_attr_info *i,
> +					    struct ext2_ext_attr_search *s);
> +extern errcode_t ext2fs_ext_attr_find_entry(struct ext2_ext_attr_entry **pentry,
> +					    int name_index, const char *name,
> +					    size_t size, int sorted);
> +extern errcode_t ext2fs_ext_attr_set_entry(struct ext2_ext_attr_info *i,
> +					   struct ext2_ext_attr_search *s);
>  
>  /* extent.c */
>  extern errcode_t ext2fs_extent_header_verify(void *ptr, int size);
> diff --git a/lib/ext2fs/ext_attr.c b/lib/ext2fs/ext_attr.c
> index 9649a14..6d55340 100644
> --- a/lib/ext2fs/ext_attr.c
> +++ b/lib/ext2fs/ext_attr.c
> @@ -186,3 +186,189 @@ errcode_t ext2fs_adjust_ea_refcount(ext2_filsys fs, blk_t blk,
>  	return ext2fs_adjust_ea_refcount2(fs, blk, block_buf, adjust,
>  					  newcount);
>  }
> +
> +static errcode_t
> +ext2fs_ext_attr_check_names(struct ext2_ext_attr_entry *entry, void *end)
> +{
> +	while (!EXT2_EXT_IS_LAST_ENTRY(entry)) {
> +		struct ext2_ext_attr_entry *next = EXT2_EXT_ATTR_NEXT(entry);
> +		if ((void *)next >= end)
> +			return EXT2_ET_EXT_ATTR_CURRUPTED;
> +		entry = next;
> +	}
> +	return 0;
> +}
> +
> +static inline errcode_t
> +ext2fs_ext_attr_check_entry(struct ext2_ext_attr_entry *entry, size_t size)
> +{
> +	size_t value_size = entry->e_value_size;
> +
> +	if (entry->e_value_block != 0 || value_size > size ||
> +	    entry->e_value_offs + value_size > size)
> +		return EXT2_ET_EXT_ATTR_CURRUPTED;
> +	return 0;
> +}
> +
> +errcode_t ext2fs_ext_attr_find_entry(struct ext2_ext_attr_entry **pentry,
> +				     int name_index, const char *name,
> +				     size_t size, int sorted)
> +{
> +	struct ext2_ext_attr_entry *entry;
> +	size_t name_len;
> +	int cmp = 1;
> +
> +	if (name == NULL)
> +		return EXT2_ET_INVALID_ARGUMENT;
> +	name_len = strlen(name);
> +	for (entry = *pentry; !EXT2_EXT_IS_LAST_ENTRY(entry);
> +	     entry = EXT2_EXT_ATTR_NEXT(entry)) {
> +		cmp = name_index - entry->e_name_index;
> +		if (!cmp)
> +			cmp = name_len - entry->e_name_len;
> +		if (!cmp)
> +			cmp = memcmp(name, EXT2_EXT_ATTR_NAME(entry),
> +				     name_len);
> +		if (cmp <= 0 && (sorted || cmp == 0))
> +			break;
> +	}
> +	*pentry = entry;
> +	if (!cmp && ext2fs_ext_attr_check_entry(entry, size))
> +		return EXT2_ET_EXT_ATTR_CURRUPTED;
> +	return cmp ? ENODATA : 0;
> +}
> +
> +errcode_t ext2fs_ext_attr_ibody_find(ext2_filsys fs,
> +				     struct ext2_inode_large *inode,
> +				     struct ext2_ext_attr_info *i,
> +				     struct ext2_ext_attr_search *s)
> +{
> +	struct ext2_ext_attr_ibody_header *header;
> +	errcode_t error;
> +
> +	if (inode->i_extra_isize == 0)
> +		return 0;
> +	header = IHDR(inode);
> +	s->base = s->first = IFIRST(header);
> +	s->here = s->first;
> +	s->end = (char *)inode + EXT2_INODE_SIZE(fs->super);
> +
> +	error = ext2fs_ext_attr_check_names(IFIRST(header), s->end);
> +	if (error)
> +		return error;
> +	/* Find the named attribute. */
> +	error = ext2fs_ext_attr_find_entry(&s->here, i->name_index,
> +					   i->name, (char *)s->end -
> +					   (char *)s->base, 0);
> +	if (error && error != ENODATA)
> +		return error;
> +	s->not_found = error;
> +	return 0;
> +}
> +
> +errcode_t ext2fs_ext_attr_set_entry(struct ext2_ext_attr_info *i,
> +				    struct ext2_ext_attr_search *s)
> +{
> +	struct ext2_ext_attr_entry *last;
> +	size_t freesize, min_offs = (char *)s->end - (char *)s->base;
> +	size_t name_len = strlen(i->name);
> +
> +	/* Compute min_offs and last. */
> +	last = s->first;
> +	for (; !EXT2_EXT_IS_LAST_ENTRY(last); last = EXT2_EXT_ATTR_NEXT(last)) {
> +		if (!last->e_value_block && last->e_value_size) {
> +			size_t offs = last->e_value_offs;
> +			if (offs < min_offs)
> +				min_offs = offs;
> +		}
> +	}
> +	freesize = min_offs - ((char *)last - (char *)s->base) - sizeof(__u32);
> +	if (!s->not_found) {
> +		if (!s->here->e_value_block && s->here->e_value_size) {
> +			size_t size = s->here->e_value_size;
> +			freesize += EXT2_EXT_ATTR_SIZE(size);
> +		}
> +		freesize += EXT2_EXT_ATTR_LEN(name_len);
> +	}
> +	if (i->value) {
> +		if (freesize < EXT2_EXT_ATTR_SIZE(i->value_len) ||
> +		    freesize < EXT2_EXT_ATTR_LEN(name_len) +
> +			   EXT2_EXT_ATTR_SIZE(i->value_len))
> +			return ENOSPC;
> +	}
> +
> +	if (i->value && s->not_found) {
> +		/* Insert the new name. */
> +		size_t size = EXT2_EXT_ATTR_LEN(name_len);
> +		size_t rest = (char *)last - (char *)s->here + sizeof(__u32);
> +		memmove((char *)s->here + size, s->here, rest);
> +		memset(s->here, 0, size);
> +		s->here->e_name_index = i->name_index;
> +		s->here->e_name_len = name_len;
> +		memcpy(EXT2_EXT_ATTR_NAME(s->here), i->name, name_len);
> +	} else {
> +		if (!s->here->e_value_block && s->here->e_value_size) {
> +			char *first_val = (char *) s->base + min_offs;
> +			size_t offs = s->here->e_value_offs;
> +			char *val = (char *)s->base + offs;
> +			size_t size = EXT2_EXT_ATTR_SIZE(s->here->e_value_size);
> +
> +			if (i->value && size == EXT2_EXT_ATTR_SIZE(i->value_len)) {
> +				/* The old and the new value have the same
> +				 * size. Just replace. */
> +				s->here->e_value_size = i->value_len;
> +				if (i->value == EXT2_ZERO_EXT_ATTR_VALUE) {
> +					memset(val, 0, size);
> +				} else {
> +					memset(val + size - EXT2_EXT_ATTR_PAD, 0,
> +						EXT2_EXT_ATTR_PAD);
> +					memcpy(val, i->value, i->value_len);
> +				}
> +				return 0;
> +			}
> +
> +			/* Remove the old value. */
> +			memmove(first_val + size, first_val, val - first_val);
> +			memset(first_val, 0, size);
> +			s->here->e_value_size = 0;
> +			s->here->e_value_offs = 0;
> +			min_offs += size;
> +
> +			/* Adjust all value offsets. */
> +			last = s->first;
> +			while (!EXT2_EXT_IS_LAST_ENTRY(last)) {
> +				size_t o = last->e_value_offs;
> +				if (!last->e_value_block &&
> +				    last->e_value_size && o < offs)
> +					last->e_value_offs = o + size;
> +				last = EXT2_EXT_ATTR_NEXT(last);
> +			}
> +		}
> +		if (!i->value) {
> +			/* Remove the old name. */
> +			size_t size = EXT2_EXT_ATTR_LEN(name_len);
> +			last = (struct ext2_ext_attr_entry *)last - size;
> +			memmove(s->here, (char *)s->here + size,
> +				(char *)last - (char *)s->here + sizeof(__u32));
> +			memset(last, 0, size);
> +		}
> +	}
> +
> +	if (i->value) {
> +		/* Insert the new value. */
> +		s->here->e_value_size = i->value_len;
> +		if (i->value_len) {
> +			size_t size = EXT2_EXT_ATTR_SIZE(i->value_len);
> +			char *val = (char *)s->base + min_offs - size;
> +			s->here->e_value_offs = min_offs - size;
> +			if (i->value == EXT2_ZERO_EXT_ATTR_VALUE) {
> +				memset(val, 0, size);
> +			} else {
> +				memset(val + size - EXT2_EXT_ATTR_PAD, 0,
> +					EXT2_EXT_ATTR_PAD);
> +				memcpy(val, i->value, i->value_len);
> +			}
> +		}
> +	}
> +	return 0;
> +}
> -- 
> 1.7.9.7
> 
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