[Devel] Re: [PATCH][SHMEM] Factor out sbi->free_inodes manipulations

[Andrew Morton]

On Fri, 23 Nov 2007 13:41:55 +0000 (GMT) Hugh Dickins <hugh at veritas.com> wrote:

> Looks good, but we can save slightly more there (depending on config),
> and I found your inc/dec names a little confusing, since the count is
> going the other way: how do you feel about this version?  (I'd like it
> better if those helpers could take a struct inode *, but they cannot.)
> Hugh
> 
> 
> From: Pavel Emelyanov <xemul at openvz.org>
> 
> The shmem_sb_info structure has a number of free_inodes. This
> value is altered in appropriate places under spinlock and with
> the sbi->max_inodes != 0 check.
> 
> Consolidate these manipulations into two helpers.
> 
> This is minus 42 bytes of shmem.o and minus 4 :) lines of code.
> 
> Signed-off-by: Pavel Emelyanov <xemul at openvz.org>
> Signed-off-by: Hugh Dickins <hugh at veritas.com>
> ---
> 
>  mm/shmem.c |   72 ++++++++++++++++++++++++---------------------------
>  1 file changed, 34 insertions(+), 38 deletions(-)
> 
> --- 2.6.24-rc3/mm/shmem.c	2007-11-07 04:21:45.000000000 +0000
> +++ linux/mm/shmem.c	2007-11-23 12:43:28.000000000 +0000
> @@ -207,6 +207,31 @@ static void shmem_free_blocks(struct ino
>  	}
>  }
>  
> +static int shmem_reserve_inode(struct super_block *sb)
> +{
> +	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
> +	if (sbinfo->max_inodes) {
> +		spin_lock(&sbinfo->stat_lock);
> +		if (!sbinfo->free_inodes) {
> +			spin_unlock(&sbinfo->stat_lock);
> +			return -ENOMEM;
> +		}
> +		sbinfo->free_inodes--;
> +		spin_unlock(&sbinfo->stat_lock);
> +	}
> +	return 0;
> +}

It is peculair to (wrongly) return -ENOMEM

> +	if (shmem_reserve_inode(inode->i_sb))
> +		return -ENOSPC;

and to then correct it in the caller..


Something boringly conventional such as the below, perhaps?

--- a/mm/shmem.c~shmem-factor-out-sbi-free_inodes-manipulations-fix
+++ a/mm/shmem.c
@@ -212,7 +212,7 @@ static int shmem_reserve_inode(struct su
 		spin_lock(&sbinfo->stat_lock);
 		if (!sbinfo->free_inodes) {
 			spin_unlock(&sbinfo->stat_lock);
-			return -ENOMEM;
+			return -ENOSPC;
 		}
 		sbinfo->free_inodes--;
 		spin_unlock(&sbinfo->stat_lock);
@@ -1679,14 +1679,16 @@ static int shmem_create(struct inode *di
 static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentry *dentry)
 {
 	struct inode *inode = old_dentry->d_inode;
+	int ret;
 
 	/*
 	 * No ordinary (disk based) filesystem counts links as inodes;
 	 * but each new link needs a new dentry, pinning lowmem, and
 	 * tmpfs dentries cannot be pruned until they are unlinked.
 	 */
-	if (shmem_reserve_inode(inode->i_sb))
-		return -ENOSPC;
+	ret = shmem_reserve_inode(inode->i_sb);
+	if (ret)
+		goto out;
 
 	dir->i_size += BOGO_DIRENT_SIZE;
 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
@@ -1694,7 +1696,8 @@ static int shmem_link(struct dentry *old
 	atomic_inc(&inode->i_count);	/* New dentry reference */
 	dget(dentry);		/* Extra pinning count for the created dentry */
 	d_instantiate(dentry, inode);
-	return 0;
+out:
+	return ret;
 }
 
 static int shmem_unlink(struct inode *dir, struct dentry *dentry)
_