Re: [PATCH] f2fs: copy all valid xattr data includes the last zero

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 03/23, Chao Yu wrote:
> On 2017/3/22 22:21, Jaegeuk Kim wrote:
> > On 03/22, Chao Yu wrote:
> >> On 2017/3/22 16:42, Chao Yu wrote:
> >>> On 2017/3/22 0:18, Jaegeuk Kim wrote:
> >>>> On 03/20, Kinglong Mee wrote:
> >>>>> On 3/20/2017 11:08, Jaegeuk Kim wrote:
> >>>>>> Hi Kinglong,
> >>>>>>
> >>>>>> On 03/18, Kinglong Mee wrote:
> >>>>>>> It's better coping all valid xattr data includes the last zero. 
> >>>>>>
> >>>>>> Why do we need this?
> >>>>>>
> >>>>>> The size of txattr_addr would be larger than the space we need.
> >>>>>>
> >>>>>> Thanks,
> >>>>>>
> >>>>>>>
> >>>>>>> Signed-off-by: Kinglong Mee <kinglongmee@gmail.com>
> >>>>>>> ---
> >>>>>>>  fs/f2fs/xattr.c | 4 ++--
> >>>>>>>  fs/f2fs/xattr.h | 4 ++--
> >>>>>>>  2 files changed, 4 insertions(+), 4 deletions(-)
> >>>>>>>
> >>>>>>> diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
> >>>>>>> index aff7619..41785c9 100644
> >>>>>>> --- a/fs/f2fs/xattr.c
> >>>>>>> +++ b/fs/f2fs/xattr.c
> >>>>>>> @@ -249,7 +249,7 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage,
> >>>>>>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >>>>>>>  	void *cur_addr, *txattr_addr, *last_addr = NULL;
> >>>>>>>  	nid_t xnid = F2FS_I(inode)->i_xattr_nid;
> >>>>>>> -	unsigned int size = xnid ? VALID_XATTR_BLOCK_SIZE : 0;
> >>>>>
> >>>>> Here maybe does not copy the last zero.
> >>>>
> >>>> The below kzalloc() will make it zero. Any problem?
> >>>
> >>> There is no problem without this change, but anyway, IMO, it needs to do cleanup
> >>> as it can provider better readability making allocated size and copied size be
> >>> consistent among lookup_all_xattrs, read_all_xattrs and write_all_xattrs.
> >>>
> >>> And since during allocation we have initialize memory with zero, so I prefer to
> >>> not copy extra reserved xattr space.
> >>>
> >>> Jaegeuk, Kinglong, how about changing like below:
> >>>
> >>> ---
> >>>  fs/f2fs/xattr.c | 27 ++++++++++++---------------
> >>>  fs/f2fs/xattr.h |  3 ++-
> >>>  2 files changed, 14 insertions(+), 16 deletions(-)
> >>>
> >>> diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
> >>> index aff7619e3f96..308b06664068 100644
> >>> --- a/fs/f2fs/xattr.c
> >>> +++ b/fs/f2fs/xattr.c
> >>> @@ -250,15 +250,13 @@ static int lookup_all_xattrs(struct inode *inode, struct
> >>> page *ipage,
> >>>  	void *cur_addr, *txattr_addr, *last_addr = NULL;
> >>>  	nid_t xnid = F2FS_I(inode)->i_xattr_nid;
> >>>  	unsigned int size = xnid ? VALID_XATTR_BLOCK_SIZE : 0;
> >>> -	unsigned int inline_size = 0;
> >>> +	unsigned int inline_size = inline_xattr_size(inode);
> >>>  	int err = 0;
> >>>
> >>> -	inline_size = inline_xattr_size(inode);
> >>> -
> >>>  	if (!size && !inline_size)
> >>>  		return -ENODATA;
> >>>
> >>> -	txattr_addr = kzalloc(inline_size + size + sizeof(__u32),
> >>> +	txattr_addr = kzalloc(inline_size + size + RESERVED_XATTR_SIZE,
> >>>  							GFP_F2FS_ZERO);
> >>>  	if (!txattr_addr)
> >>>  		return -ENOMEM;
> >>> @@ -328,13 +326,14 @@ static int read_all_xattrs(struct inode *inode, struct
> >>> page *ipage,
> >>>  {
> >>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >>>  	struct f2fs_xattr_header *header;
> >>> -	size_t size = PAGE_SIZE, inline_size = 0;
> >>> +	nid_t xnid = F2FS_I(inode)->i_xattr_nid;
> >>> +	unsigned int size = xnid ? VALID_XATTR_BLOCK_SIZE : 0;
> >>
> >> Here, always should assign size with VALID_XATTR_BLOCK_SIZE for enospc case in
> >> inline xattr space while adding new xattr entry.
> > 
> > Do you mean any race condition? It seems setxattr is covered by i_mutex, but
> > listxattr does not. But, given xnid, i_xattr_nid won't be used below, so it
> > looks fine to go with xnid check.
> 
> To cover below case
> 
> - __f2fs_setxattr
>  - read_all_xattrs
>  - write_all_xattrs
>   - new_node_page
>   - memcpy

Oh, I see. This happened in your change.

Thanks,

> 
> > 
> > Thanks,
> > 
> >>
> >> unsigned int size = VALID_XATTR_BLOCK_SIZE;
> >>
> >> Thanks,
> >>
> >>> +	unsigned int inline_size = inline_xattr_size(inode);
> >>>  	void *txattr_addr;
> >>>  	int err;
> >>>
> >>> -	inline_size = inline_xattr_size(inode);
> >>> -
> >>> -	txattr_addr = kzalloc(inline_size + size, GFP_F2FS_ZERO);
> >>> +	txattr_addr = kzalloc(inline_size + size + RESERVED_XATTR_SIZE,
> >>> +							GFP_F2FS_ZERO);
> >>>  	if (!txattr_addr)
> >>>  		return -ENOMEM;
> >>>
> >>> @@ -358,19 +357,19 @@ static int read_all_xattrs(struct inode *inode, struct
> >>> page *ipage,
> >>>  	}
> >>>
> >>>  	/* read from xattr node block */
> >>> -	if (F2FS_I(inode)->i_xattr_nid) {
> >>> +	if (xnid) {
> >>>  		struct page *xpage;
> >>>  		void *xattr_addr;
> >>>
> >>>  		/* The inode already has an extended attribute block. */
> >>> -		xpage = get_node_page(sbi, F2FS_I(inode)->i_xattr_nid);
> >>> +		xpage = get_node_page(sbi, xnid);
> >>>  		if (IS_ERR(xpage)) {
> >>>  			err = PTR_ERR(xpage);
> >>>  			goto fail;
> >>>  		}
> >>>
> >>>  		xattr_addr = page_address(xpage);
> >>> -		memcpy(txattr_addr + inline_size, xattr_addr, PAGE_SIZE);
> >>> +		memcpy(txattr_addr + inline_size, xattr_addr, size);
> >>>  		f2fs_put_page(xpage, 1);
> >>>  	}
> >>>
> >>> @@ -392,14 +391,12 @@ static inline int write_all_xattrs(struct inode *inode,
> >>> __u32 hsize,
> >>>  				void *txattr_addr, struct page *ipage)
> >>>  {
> >>>  	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
> >>> -	size_t inline_size = 0;
> >>> +	size_t inline_size = inline_xattr_size(inode);
> >>>  	void *xattr_addr;
> >>>  	struct page *xpage;
> >>>  	nid_t new_nid = 0;
> >>>  	int err;
> >>>
> >>> -	inline_size = inline_xattr_size(inode);
> >>> -
> >>>  	if (hsize > inline_size && !F2FS_I(inode)->i_xattr_nid)
> >>>  		if (!alloc_nid(sbi, &new_nid))
> >>>  			return -ENOSPC;
> >>> @@ -454,7 +451,7 @@ static inline int write_all_xattrs(struct inode *inode,
> >>> __u32 hsize,
> >>>  	}
> >>>
> >>>  	xattr_addr = page_address(xpage);
> >>> -	memcpy(xattr_addr, txattr_addr + inline_size, MAX_XATTR_BLOCK_SIZE);
> 
> And this needs to be kept to avoid remain random data in newly allocated xattr
> node page.
> 
> Thanks,
> 
> >>> +	memcpy(xattr_addr, txattr_addr + inline_size, VALID_XATTR_BLOCK_SIZE);
> >>>  	set_page_dirty(xpage);
> >>>  	f2fs_put_page(xpage, 1);
> >>>
> >>> diff --git a/fs/f2fs/xattr.h b/fs/f2fs/xattr.h
> >>> index d5a94928c116..1e7db8d0806e 100644
> >>> --- a/fs/f2fs/xattr.h
> >>> +++ b/fs/f2fs/xattr.h
> >>> @@ -73,7 +73,8 @@ struct f2fs_xattr_entry {
> >>>  				!IS_XATTR_LAST_ENTRY(entry);\
> >>>  				entry = XATTR_NEXT_ENTRY(entry))
> >>>  #define MAX_XATTR_BLOCK_SIZE	(PAGE_SIZE - sizeof(struct node_footer))
> >>> -#define VALID_XATTR_BLOCK_SIZE	(MAX_XATTR_BLOCK_SIZE - sizeof(__u32))
> >>> +#define RESERVED_XATTR_SIZE	(sizeof(__u32))
> >>> +#define VALID_XATTR_BLOCK_SIZE	(MAX_XATTR_BLOCK_SIZE - RESERVED_XATTR_SIZE)
> >>>  #define MIN_OFFSET(i)		XATTR_ALIGN(inline_xattr_size(i) +	\
> >>>  						VALID_XATTR_BLOCK_SIZE)
> >>>
> > 
> > .
> > 

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