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

[Jaegeuk Kim <jaegeuk@kernel.org>]

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.

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);
> > +	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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