Re: [PATCH v5 04/14] xfs: Add xfs_has_attr and subroutines

[Allison Collins <allison.henderson@xxxxxxxxxx>]

On 12/13/19 6:08 AM, Brian Foster wrote:
> On Wed, Dec 11, 2019 at 09:15:03PM -0700, Allison Collins wrote:
> > From: Allison Henderson <allison.henderson@xxxxxxxxxx>
> >
> > This patch adds a new functions to check for the existence of
> > an attribute.  Subroutines are also added to handle the cases
> > of leaf blocks, nodes or shortform.  Common code that appears
> > in existing attr add and remove functions have been factored
> > out to help reduce the appearance of duplicated code.  We will
> > need these routines later for delayed attributes since delayed
> > operations cannot return error codes.
> >
> > Signed-off-by: Allison Collins <allison.henderson@xxxxxxxxxx>
> > ---
> >   fs/xfs/libxfs/xfs_attr.c      | 166 +++++++++++++++++++++++++++---------------
> >   fs/xfs/libxfs/xfs_attr.h      |   1 +
> >   fs/xfs/libxfs/xfs_attr_leaf.c | 110 +++++++++++++++++-----------
> >   fs/xfs/libxfs/xfs_attr_leaf.h |   3 +
> >   4 files changed, 182 insertions(+), 98 deletions(-)
> >
> > diff --git a/fs/xfs/libxfs/xfs_attr.c b/fs/xfs/libxfs/xfs_attr.c
> > index 9628ed8..88de43c 100644
> > --- a/fs/xfs/libxfs/xfs_attr.c
> > +++ b/fs/xfs/libxfs/xfs_attr.c
> ...
> > @@ -310,6 +313,36 @@ xfs_attr_set_args(
> >   }
> >   
> >   /*
> > + * Return EEXIST if attr is found, or ENOATTR if not
> > + */
> > +int
> > +xfs_has_attr(
> > +	struct xfs_da_args      *args)
> > +{
> > +	struct xfs_inode	*dp = args->dp;
> > +
> > +	if (!xfs_inode_hasattr(dp))
> > +		return -ENOATTR;
> > +
> > +	if (dp->i_d.di_aformat == XFS_DINODE_FMT_LOCAL) {
> > +		ASSERT(dp->i_afp->if_flags & XFS_IFINLINE);
> > +		return xfs_attr_sf_findname(args, NULL, NULL);
> > +	}
> > +
> > +	if (xfs_bmap_one_block(dp, XFS_ATTR_FORK)) {
> > +		struct xfs_buf	*bp = NULL;
> > +		int		error = xfs_attr_leaf_hasname(args, &bp);
> > +
>
> I'd prefer to not obfuscate function calls in variable declarations like
> this. I'd say just declare bp and error at the top and let this be:
Sure, this style was a suggestion from Christoph in the last review so I 
tried to combine everyones requests as best as possible.  I'm not very 
particular about the aesthetics, so I don't mind moving things around, 
but if people feel strongly one way or another, please chime in.

> 		error = xfs_attr_leaf_hasname(...)
>
> > +		if (bp)
> > +			xfs_trans_brelse(args->trans, bp);
> > +
> > +		return error;
> > +	}
> > +
> > +	return xfs_attr_node_hasname(args, NULL);
> > +}
> > +
> > +/*
> >    * Remove the attribute specified in @args.
> >    */
> >   int
> > @@ -583,26 +616,20 @@ STATIC int
> >   xfs_attr_leaf_addname(
> >   	struct xfs_da_args	*args)
> >   {
> > -	struct xfs_inode	*dp;
> >   	struct xfs_buf		*bp;
> >   	int			retval, error, forkoff;
> > +	struct xfs_inode	*dp = args->dp;
> >   
> >   	trace_xfs_attr_leaf_addname(args);
> >   
> >   	/*
> > -	 * Read the (only) block in the attribute list in.
> > -	 */
> > -	dp = args->dp;
> > -	args->blkno = 0;
> > -	error = xfs_attr3_leaf_read(args->trans, args->dp, args->blkno, &bp);
> > -	if (error)
> > -		return error;
> > -
> > -	/*
> >   	 * Look up the given attribute in the leaf block.  Figure out if
> >   	 * the given flags produce an error or call for an atomic rename.
> >   	 */
> > -	retval = xfs_attr3_leaf_lookup_int(bp, args);
> > +	retval = xfs_attr_leaf_hasname(args, &bp);
> > +	if (retval != -ENOATTR && retval != -EEXIST)
> > +		return retval;
> > +
>
> Do we need to call xfs_trans_brelse() in certain cases before we return?
> For example, consider if the read succeeds but the lookup returns
> something other than -ENOATTR or -EEXIST. Perhaps the _hasname() func
> should just call brelse() itself if it's returning an unexpected error
> after reading in the buf so the caller doesn't need to care about it..
Generally it should be released at some point if the call is successful 
(so on -EEXIST).  Later when we get into the state machine, we don't 
release right away, because we need to hold it across the transaction rolls.

I think though I might be able to factor up releasing the buffer on 
error though.  I'll see if I can work that into the next version.

> >   	if ((args->name.type & ATTR_REPLACE) && (retval == -ENOATTR)) {
> >   		xfs_trans_brelse(args->trans, bp);
> >   		return retval;
> ...
> > @@ -864,20 +940,17 @@ xfs_attr_node_addname(
> >   	dp = args->dp;
> >   	mp = dp->i_mount;
> >   restart:
> > -	state = xfs_da_state_alloc();
> > -	state->args = args;
> > -	state->mp = mp;
> > -
> >   	/*
> >   	 * Search to see if name already exists, and get back a pointer
> >   	 * to where it should go.
> >   	 */
> > -	error = xfs_da3_node_lookup_int(state, &retval);
> > -	if (error)
> > +	retval = xfs_attr_node_hasname(args, &state);
> > +	if (retval != -ENOATTR)
> >   		goto out;
>
> The else case below checks for -EEXIST, but it looks like we'd return
> here..
>
> Brian

Ok, will clean out.  Thx!
Allison

> > +
> >   	blk = &state->path.blk[ state->path.active-1 ];
> >   	ASSERT(blk->magic == XFS_ATTR_LEAF_MAGIC);
> > -	if ((args->name.type & ATTR_REPLACE) && (retval == -ENOATTR)) {
> > +	if (args->name.type & ATTR_REPLACE) {
> >   		goto out;
> >   	} else if (retval == -EEXIST) {
> >   		if (args->name.type & ATTR_CREATE)
> > @@ -1079,29 +1152,15 @@ xfs_attr_node_removename(
> >   {
> >   	struct xfs_da_state	*state;
> >   	struct xfs_da_state_blk	*blk;
> > -	struct xfs_inode	*dp;
> >   	struct xfs_buf		*bp;
> >   	int			retval, error, forkoff;
> > +	struct xfs_inode	*dp = args->dp;
> >   
> >   	trace_xfs_attr_node_removename(args);
> >   
> > -	/*
> > -	 * Tie a string around our finger to remind us where we are.
> > -	 */
> > -	dp = args->dp;
> > -	state = xfs_da_state_alloc();
> > -	state->args = args;
> > -	state->mp = dp->i_mount;
> > -
> > -	/*
> > -	 * Search to see if name exists, and get back a pointer to it.
> > -	 */
> > -	error = xfs_da3_node_lookup_int(state, &retval);
> > -	if (error || (retval != -EEXIST)) {
> > -		if (error == 0)
> > -			error = retval;
> > +	error = xfs_attr_node_hasname(args, &state);
> > +	if (error != -EEXIST)
> >   		goto out;
> > -	}
> >   
> >   	/*
> >   	 * If there is an out-of-line value, de-allocate the blocks.
> > @@ -1196,7 +1255,8 @@ xfs_attr_node_removename(
> >   	error = 0;
> >   
> >   out:
> > -	xfs_da_state_free(state);
> > +	if (state)
> > +		xfs_da_state_free(state);
> >   	return error;
> >   }
> >   
> > @@ -1316,31 +1376,23 @@ xfs_attr_node_get(xfs_da_args_t *args)
> >   {
> >   	xfs_da_state_t *state;
> >   	xfs_da_state_blk_t *blk;
> > -	int error, retval;
> > +	int error;
> >   	int i;
> >   
> >   	trace_xfs_attr_node_get(args);
> >   
> > -	state = xfs_da_state_alloc();
> > -	state->args = args;
> > -	state->mp = args->dp->i_mount;
> > -
> >   	/*
> >   	 * Search to see if name exists, and get back a pointer to it.
> >   	 */
> > -	error = xfs_da3_node_lookup_int(state, &retval);
> > -	if (error) {
> > -		retval = error;
> > -		goto out_release;
> > -	}
> > -	if (retval != -EEXIST)
> > +	error = xfs_attr_node_hasname(args, &state);
> > +	if (error != -EEXIST)
> >   		goto out_release;
> >   
> >   	/*
> >   	 * Get the value, local or "remote"
> >   	 */
> >   	blk = &state->path.blk[state->path.active - 1];
> > -	retval = xfs_attr3_leaf_getvalue(blk->bp, args);
> > +	error = xfs_attr3_leaf_getvalue(blk->bp, args);
> >   
> >   	/*
> >   	 * If not in a transaction, we have to release all the buffers.
> > @@ -1352,7 +1404,7 @@ xfs_attr_node_get(xfs_da_args_t *args)
> >   	}
> >   
> >   	xfs_da_state_free(state);
> > -	return retval;
> > +	return error;
> >   }
> >   
> >   /* Returns true if the attribute entry name is valid. */
> > diff --git a/fs/xfs/libxfs/xfs_attr.h b/fs/xfs/libxfs/xfs_attr.h
> > index 44dd07a..3b5dad4 100644
> > --- a/fs/xfs/libxfs/xfs_attr.h
> > +++ b/fs/xfs/libxfs/xfs_attr.h
> > @@ -150,6 +150,7 @@ int xfs_attr_set(struct xfs_inode *dp, struct xfs_name *name,
> >   		 unsigned char *value, int valuelen, int flags);
> >   int xfs_attr_set_args(struct xfs_da_args *args);
> >   int xfs_attr_remove(struct xfs_inode *dp, struct xfs_name *name, int flags);
> > +int xfs_has_attr(struct xfs_da_args *args);
> >   int xfs_attr_remove_args(struct xfs_da_args *args);
> >   int xfs_attr_list(struct xfs_inode *dp, char *buffer, int bufsize,
> >   		  int flags, struct attrlist_cursor_kern *cursor);
> > diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c
> > index 5465446..ef96971 100644
> > --- a/fs/xfs/libxfs/xfs_attr_leaf.c
> > +++ b/fs/xfs/libxfs/xfs_attr_leaf.c
> > @@ -654,18 +654,66 @@ xfs_attr_shortform_create(xfs_da_args_t *args)
> >   }
> >   
> >   /*
> > + * Return -EEXIST if attr is found, or -ENOATTR if not
> > + * args:  args containing attribute name and namelen
> > + * sfep:  If not null, pointer will be set to the last attr entry found on
> > +	  -EEXIST.  On -ENOATTR pointer is left at the last entry in the list
> > + * basep: If not null, pointer is set to the byte offset of the entry in the
> > + *	  list on -EEXIST.  On -ENOATTR, pointer is left at the byte offset of
> > + *	  the last entry in the list
> > + */
> > +int
> > +xfs_attr_sf_findname(
> > +	struct xfs_da_args	 *args,
> > +	struct xfs_attr_sf_entry **sfep,
> > +	unsigned int		 *basep)
> > +{
> > +	struct xfs_attr_shortform *sf;
> > +	struct xfs_attr_sf_entry *sfe;
> > +	unsigned int		base = sizeof(struct xfs_attr_sf_hdr);
> > +	int			size = 0;
> > +	int			end;
> > +	int			i;
> > +
> > +	sf = (struct xfs_attr_shortform *)args->dp->i_afp->if_u1.if_data;
> > +	sfe = &sf->list[0];
> > +	end = sf->hdr.count;
> > +	for (i = 0; i < end; sfe = XFS_ATTR_SF_NEXTENTRY(sfe),
> > +			base += size, i++) {
> > +		size = XFS_ATTR_SF_ENTSIZE(sfe);
> > +		if (sfe->namelen != args->name.len)
> > +			continue;
> > +		if (memcmp(sfe->nameval, args->name.name, args->name.len) != 0)
> > +			continue;
> > +		if (!xfs_attr_namesp_match(args->name.type, sfe->flags))
> > +			continue;
> > +		break;
> > +	}
> > +
> > +	if (sfep != NULL)
> > +		*sfep = sfe;
> > +
> > +	if (basep != NULL)
> > +		*basep = base;
> > +
> > +	if (i == end)
> > +		return -ENOATTR;
> > +	return -EEXIST;
> > +}
> > +
> > +/*
> >    * Add a name/value pair to the shortform attribute list.
> >    * Overflow from the inode has already been checked for.
> >    */
> >   void
> > -xfs_attr_shortform_add(xfs_da_args_t *args, int forkoff)
> > +xfs_attr_shortform_add(struct xfs_da_args *args, int forkoff)
> >   {
> > -	xfs_attr_shortform_t *sf;
> > -	xfs_attr_sf_entry_t *sfe;
> > -	int i, offset, size;
> > -	xfs_mount_t *mp;
> > -	xfs_inode_t *dp;
> > -	struct xfs_ifork *ifp;
> > +	struct xfs_attr_shortform	*sf;
> > +	struct xfs_attr_sf_entry	*sfe;
> > +	int				offset, size, error;
> > +	struct xfs_mount		*mp;
> > +	struct xfs_inode		*dp;
> > +	struct xfs_ifork		*ifp;
> >   
> >   	trace_xfs_attr_sf_add(args);
> >   
> > @@ -676,18 +724,8 @@ xfs_attr_shortform_add(xfs_da_args_t *args, int forkoff)
> >   	ifp = dp->i_afp;
> >   	ASSERT(ifp->if_flags & XFS_IFINLINE);
> >   	sf = (xfs_attr_shortform_t *)ifp->if_u1.if_data;
> > -	sfe = &sf->list[0];
> > -	for (i = 0; i < sf->hdr.count; sfe = XFS_ATTR_SF_NEXTENTRY(sfe), i++) {
> > -#ifdef DEBUG
> > -		if (sfe->namelen != args->name.len)
> > -			continue;
> > -		if (memcmp(args->name.name, sfe->nameval, args->name.len) != 0)
> > -			continue;
> > -		if (!xfs_attr_namesp_match(args->name.type, sfe->flags))
> > -			continue;
> > -		ASSERT(0);
> > -#endif
> > -	}
> > +	error = xfs_attr_sf_findname(args, &sfe, NULL);
> > +	ASSERT(error != -EEXIST);
> >   
> >   	offset = (char *)sfe - (char *)sf;
> >   	size = XFS_ATTR_SF_ENTSIZE_BYNAME(args->name.len, args->valuelen);
> > @@ -730,35 +768,25 @@ xfs_attr_fork_remove(
> >    * Remove an attribute from the shortform attribute list structure.
> >    */
> >   int
> > -xfs_attr_shortform_remove(xfs_da_args_t *args)
> > +xfs_attr_shortform_remove(struct xfs_da_args *args)
> >   {
> > -	xfs_attr_shortform_t *sf;
> > -	xfs_attr_sf_entry_t *sfe;
> > -	int base, size=0, end, totsize, i;
> > -	xfs_mount_t *mp;
> > -	xfs_inode_t *dp;
> > +	struct xfs_attr_shortform	*sf;
> > +	struct xfs_attr_sf_entry	*sfe;
> > +	int				base, size = 0, end, totsize;
> > +	struct xfs_mount		*mp;
> > +	struct xfs_inode		*dp;
> > +	int				error;
> >   
> >   	trace_xfs_attr_sf_remove(args);
> >   
> >   	dp = args->dp;
> >   	mp = dp->i_mount;
> > -	base = sizeof(xfs_attr_sf_hdr_t);
> >   	sf = (xfs_attr_shortform_t *)dp->i_afp->if_u1.if_data;
> > -	sfe = &sf->list[0];
> > -	end = sf->hdr.count;
> > -	for (i = 0; i < end; sfe = XFS_ATTR_SF_NEXTENTRY(sfe),
> > -					base += size, i++) {
> > -		size = XFS_ATTR_SF_ENTSIZE(sfe);
> > -		if (sfe->namelen != args->name.len)
> > -			continue;
> > -		if (memcmp(sfe->nameval, args->name.name, args->name.len) != 0)
> > -			continue;
> > -		if (!xfs_attr_namesp_match(args->name.type, sfe->flags))
> > -			continue;
> > -		break;
> > -	}
> > -	if (i == end)
> > -		return -ENOATTR;
> > +
> > +	error = xfs_attr_sf_findname(args, &sfe, &base);
> > +	if (error != -EEXIST)
> > +		return error;
> > +	size = XFS_ATTR_SF_ENTSIZE(sfe);
> >   
> >   	/*
> >   	 * Fix up the attribute fork data, covering the hole
> > diff --git a/fs/xfs/libxfs/xfs_attr_leaf.h b/fs/xfs/libxfs/xfs_attr_leaf.h
> > index f4a188e..f6165ff 100644
> > --- a/fs/xfs/libxfs/xfs_attr_leaf.h
> > +++ b/fs/xfs/libxfs/xfs_attr_leaf.h
> > @@ -62,6 +62,9 @@ int	xfs_attr_shortform_getvalue(struct xfs_da_args *args);
> >   int	xfs_attr_shortform_to_leaf(struct xfs_da_args *args,
> >   			struct xfs_buf **leaf_bp);
> >   int	xfs_attr_shortform_remove(struct xfs_da_args *args);
> > +int	xfs_attr_sf_findname(struct xfs_da_args *args,
> > +			     struct xfs_attr_sf_entry **sfep,
> > +			     unsigned int *basep);
> >   int	xfs_attr_shortform_allfit(struct xfs_buf *bp, struct xfs_inode *dp);
> >   int	xfs_attr_shortform_bytesfit(struct xfs_inode *dp, int bytes);
> >   xfs_failaddr_t xfs_attr_shortform_verify(struct xfs_inode *ip);
> > --
> > 2.7.4