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Re: [Cluster-devel] [GFS2 PATCH] GFS2: Extend the life of the reservations structure



Hi,

On Thu, 2012-04-12 at 11:43 -0400, Bob Peterson wrote:
> Hi,
> 
> This patch lengthens the life of the reservations structure.
> See notes below.
> 
> Regards,
> 
> Bob Peterson
> Red Hat GFS
> 
> Signed-off-by: Bob Peterson <rpeterso redhat com> 
> --
> Author: Bob Peterson <rpeterso redhat com>
> Date:   Thu Apr 12 11:37:24 2012 -0500
> 
>     GFS2: Extend the life of the reservations structure
>     
>     This patch lengthens the lifespan of the reservations structure for
>     inodes. Before, they were allocated and deallocated for every write
>     operation. With this patch, they are allocated when the first write
>     occurs, and deallocated when the last process closes the file.
>     It's more efficient to do it this way because it saves GFS2 a lot of
>     unnecessary allocates and frees. It also gives us more flexibility
>     for the future: (1) we can now fold the qadata structure back into
>     the structure and save those alloc/frees, (2) we can use this for
>     multi-block reservations.
> 
> diff --git a/fs/gfs2/aops.c b/fs/gfs2/aops.c
> index 56dc1f0..a793957 100644
> --- a/fs/gfs2/aops.c
> +++ b/fs/gfs2/aops.c
> @@ -879,7 +879,7 @@ static int gfs2_write_end(struct file *file, struct address_space *mapping,
>  	brelse(dibh);
>  failed:
>  	gfs2_trans_end(sdp);
> -	if (ip->i_res)
> +	if (gfs2_mb_reserved(ip))
>  		gfs2_inplace_release(ip);
>  	if (qa) {
>  		gfs2_quota_unlock(ip);
> diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c
> index 31b199f..3a1a60a 100644
> --- a/fs/gfs2/file.c
> +++ b/fs/gfs2/file.c
> @@ -384,6 +384,10 @@ static int gfs2_page_mkwrite(struct vm_area_struct *vma, struct vm_fault *vmf)
>  	set_bit(GLF_DIRTY, &ip->i_gl->gl_flags);
>  	set_bit(GIF_SW_PAGED, &ip->i_flags);
>  
> +	ret = gfs2_rs_alloc(ip);
> +	if (ret)
> +		goto out_unlock;
> +
I don't think the locking is quite right here... at least I can't see
any locking at all in this case.

>  	if (!gfs2_write_alloc_required(ip, pos, PAGE_CACHE_SIZE)) {
>  		lock_page(page);
>  		if (!PageUptodate(page) || page->mapping != inode->i_mapping) {
> @@ -569,10 +573,17 @@ static int gfs2_release(struct inode *inode, struct file *file)
>  {
>  	struct gfs2_sbd *sdp = inode->i_sb->s_fs_info;
>  	struct gfs2_file *fp;
> +	struct gfs2_inode *ip = GFS2_I(inode);
>  
>  	fp = file->private_data;
>  	file->private_data = NULL;
>  
> +	if (file->f_mode & FMODE_WRITE) {
> +		mutex_lock(&inode->i_mutex);
> +		if (ip->i_res && (atomic_read(&inode->i_writecount) == 1))
> +			gfs2_rs_delete(ip);
> +		mutex_unlock(&inode->i_mutex);
> +	}
>  	if (gfs2_assert_warn(sdp, fp))
>  		return -EIO;
>  
> @@ -653,12 +664,16 @@ static ssize_t gfs2_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
>  				   unsigned long nr_segs, loff_t pos)
>  {
>  	struct file *file = iocb->ki_filp;
> +	struct dentry *dentry = file->f_dentry;
> +	struct gfs2_inode *ip = GFS2_I(dentry->d_inode);
> +	int ret;
> +
> +	ret = gfs2_rs_alloc(ip);
> +	if (ret)
> +		return ret;
Again, there is no locking here.

>  
>  	if (file->f_flags & O_APPEND) {
> -		struct dentry *dentry = file->f_dentry;
> -		struct gfs2_inode *ip = GFS2_I(dentry->d_inode);
>  		struct gfs2_holder gh;
> -		int ret;
>  
>  		ret = gfs2_glock_nq_init(ip->i_gl, LM_ST_SHARED, 0, &gh);
>  		if (ret)
> diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
> index a9ba244..127b1a4 100644
> --- a/fs/gfs2/inode.c
> +++ b/fs/gfs2/inode.c
> @@ -681,6 +681,10 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
>  	if (error)
>  		goto fail_gunlock;
>  
> +	error = gfs2_rs_alloc(dip);
> +	if (error)
> +		goto fail_gunlock;
> +
>  	error = alloc_dinode(dip, &inum.no_addr, &generation);
>  	if (error)
>  		goto fail_gunlock;
> @@ -704,6 +708,11 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
>  	if (error)
>  		goto fail_gunlock2;
>  
> +	/* the new inode needs a reservation so it can allocate xattrs. */
> +	error = gfs2_rs_alloc(GFS2_I(inode));
> +	if (error)
> +		goto fail_gunlock2;
> +
>  	error = gfs2_acl_create(dip, inode);
>  	if (error)
>  		goto fail_gunlock2;
> @@ -722,7 +731,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
>  	gfs2_trans_end(sdp);
>  	/* Check if we reserved space in the rgrp. Function link_dinode may
>  	   not, depending on whether alloc is required. */
> -	if (dip->i_res)
> +	if (gfs2_mb_reserved(dip))
>  		gfs2_inplace_release(dip);
>  	gfs2_quota_unlock(dip);
>  	gfs2_qadata_put(dip);
> @@ -734,6 +743,7 @@ static int gfs2_create_inode(struct inode *dir, struct dentry *dentry,
>  fail_gunlock2:
>  	gfs2_glock_dq_uninit(ghs + 1);
>  fail_gunlock:
> +	gfs2_rs_delete(dip);
>  	gfs2_glock_dq_uninit(ghs);
>  	if (inode && !IS_ERR(inode)) {
>  		set_bit(GIF_ALLOC_FAILED, &GFS2_I(inode)->i_flags);
> diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
> index 146c3d2..af590de 100644
> --- a/fs/gfs2/rgrp.c
> +++ b/fs/gfs2/rgrp.c
> @@ -418,6 +418,34 @@ void gfs2_free_clones(struct gfs2_rgrpd *rgd)
>  	}
>  }
>  
> +/**
> + * gfs2_rs_alloc - make sure we have a reservation assigned to the inode
> + * @ip: the inode for this reservation
> + */
> +int gfs2_rs_alloc(struct gfs2_inode *ip)
> +{
> +	if (ip->i_res)
> +		return 0;
> +	ip->i_res = kmem_cache_zalloc(gfs2_rsrv_cachep, GFP_NOFS);
> +	if (!ip->i_res)
> +		return -ENOMEM;
> +	return 0;
> +}
> +
I wonder whether it would be better to do this at open/create time,
assuming that the file is being opened or created for writing. That
means fewer cases to catch. The only issue I can see with that is
catching files that are created and then never opened for writing - not
sure if that is possible, but worth checking I think.

So I think the locking needs sorting out here, but otherwise it looks
good,

Steve.

> +/**
> + * gfs2_rs_delete - delete a reservation
> + * @ip: The inode for this reservation
> + *
> + */
> +void gfs2_rs_delete(struct gfs2_inode *ip)
> +{
> +	if (ip->i_res == NULL)
> +		return;
> +
> +	kmem_cache_free(gfs2_rsrv_cachep, ip->i_res);
> +	ip->i_res = NULL;
> +}
> +
>  void gfs2_clear_rgrpd(struct gfs2_sbd *sdp)
>  {
>  	struct rb_node *n;
> @@ -1001,22 +1029,6 @@ struct gfs2_qadata *gfs2_qadata_get(struct gfs2_inode *ip)
>  }
>  
>  /**
> - * gfs2_blkrsv_get - get the struct gfs2_blkreserv structure for an inode
> - * @ip: the incore GFS2 inode structure
> - *
> - * Returns: the struct gfs2_qadata
> - */
> -
> -static int gfs2_blkrsv_get(struct gfs2_inode *ip)
> -{
> -	BUG_ON(ip->i_res != NULL);
> -	ip->i_res = kmem_cache_zalloc(gfs2_rsrv_cachep, GFP_NOFS);
> -	if (!ip->i_res)
> -		return -ENOMEM;
> -	return 0;
> -}
> -
> -/**
>   * try_rgrp_fit - See if a given reservation will fit in a given RG
>   * @rgd: the RG data
>   * @ip: the inode
> @@ -1170,13 +1182,6 @@ static int get_local_rgrp(struct gfs2_inode *ip, u64 *last_unlinked)
>  	return -ENOSPC;
>  }
>  
> -static void gfs2_blkrsv_put(struct gfs2_inode *ip)
> -{
> -	BUG_ON(ip->i_res == NULL);
> -	kmem_cache_free(gfs2_rsrv_cachep, ip->i_res);
> -	ip->i_res = NULL;
> -}
> -
>  /**
>   * gfs2_inplace_reserve - Reserve space in the filesystem
>   * @ip: the inode to reserve space for
> @@ -1189,14 +1194,10 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, u32 requested)
>  {
>  	struct gfs2_sbd *sdp = GFS2_SB(&ip->i_inode);
>  	struct gfs2_blkreserv *rs;
> -	int error;
> +	int error = 0;
>  	u64 last_unlinked = NO_BLOCK;
>  	int tries = 0;
>  
> -	error = gfs2_blkrsv_get(ip);
> -	if (error)
> -		return error;
> -
>  	rs = ip->i_res;
>  	rs->rs_requested = requested;
>  	if (gfs2_assert_warn(sdp, requested)) {
> @@ -1221,7 +1222,7 @@ int gfs2_inplace_reserve(struct gfs2_inode *ip, u32 requested)
>  
>  out:
>  	if (error)
> -		gfs2_blkrsv_put(ip);
> +		rs->rs_requested = 0;
>  	return error;
>  }
>  
> @@ -1238,7 +1239,7 @@ void gfs2_inplace_release(struct gfs2_inode *ip)
>  
>  	if (rs->rs_rgd_gh.gh_gl)
>  		gfs2_glock_dq_uninit(&rs->rs_rgd_gh);
> -	gfs2_blkrsv_put(ip);
> +	rs->rs_requested = 0;
>  }
>  
>  /**
> @@ -1506,7 +1507,7 @@ int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *nblocks,
>  	/* Only happens if there is a bug in gfs2, return something distinctive
>  	 * to ensure that it is noticed.
>  	 */
> -	if (ip->i_res == NULL)
> +	if (ip->i_res->rs_requested == 0)
>  		return -ECANCELED;
>  
>  	rgd = ip->i_rgd;
> diff --git a/fs/gfs2/rgrp.h b/fs/gfs2/rgrp.h
> index b4b10f4..d9eda5f 100644
> --- a/fs/gfs2/rgrp.h
> +++ b/fs/gfs2/rgrp.h
> @@ -43,6 +43,8 @@ extern void gfs2_inplace_release(struct gfs2_inode *ip);
>  extern int gfs2_alloc_blocks(struct gfs2_inode *ip, u64 *bn, unsigned int *n,
>  			     bool dinode, u64 *generation);
>  
> +extern int gfs2_rs_alloc(struct gfs2_inode *ip);
> +extern void gfs2_rs_delete(struct gfs2_inode *ip);
>  extern void __gfs2_free_blocks(struct gfs2_inode *ip, u64 bstart, u32 blen, int meta);
>  extern void gfs2_free_meta(struct gfs2_inode *ip, u64 bstart, u32 blen);
>  extern void gfs2_free_di(struct gfs2_rgrpd *rgd, struct gfs2_inode *ip);
> @@ -68,4 +70,12 @@ extern int gfs2_rgrp_send_discards(struct gfs2_sbd *sdp, u64 offset,
>  				   const struct gfs2_bitmap *bi, unsigned minlen, u64 *ptrimmed);
>  extern int gfs2_fitrim(struct file *filp, void __user *argp);
>  
> +/* This is how to tell if a reservation is "inplace" reserved: */
> +static inline int gfs2_mb_reserved(struct gfs2_inode *ip)
> +{
> +	if (ip->i_res && ip->i_res->rs_requested)
> +		return 1;
> +	return 0;
> +}
> +
>  #endif /* __RGRP_DOT_H__ */
> diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
> index 6172fa7..a42df66 100644
> --- a/fs/gfs2/super.c
> +++ b/fs/gfs2/super.c
> @@ -1554,6 +1554,7 @@ out_unlock:
>  out:
>  	/* Case 3 starts here */
>  	truncate_inode_pages(&inode->i_data, 0);
> +	gfs2_rs_delete(ip);
>  	end_writeback(inode);
>  	gfs2_dir_hash_inval(ip);
>  	ip->i_gl->gl_object = NULL;
> @@ -1576,6 +1577,7 @@ static struct inode *gfs2_alloc_inode(struct super_block *sb)
>  		ip->i_flags = 0;
>  		ip->i_gl = NULL;
>  		ip->i_rgd = NULL;
> +		ip->i_res = NULL;
>  	}
>  	return &ip->i_inode;
>  }
> diff --git a/fs/gfs2/trans.h b/fs/gfs2/trans.h
> index 125d457..41f42cd 100644
> --- a/fs/gfs2/trans.h
> +++ b/fs/gfs2/trans.h
> @@ -31,7 +31,7 @@ struct gfs2_glock;
>  static inline unsigned int gfs2_rg_blocks(const struct gfs2_inode *ip)
>  {
>  	const struct gfs2_blkreserv *rs = ip->i_res;
> -	if (rs->rs_requested < ip->i_rgd->rd_length)
> +	if (rs && rs->rs_requested < ip->i_rgd->rd_length)
>  		return rs->rs_requested + 1;
>  	return ip->i_rgd->rd_length;
>  }
> 



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