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 30 bytes of shmem.o and minus 4 :) lines of code.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

---

diff --git a/mm/shmem.c b/mm/shmem.c
index e0d4b2e..abba17c 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -205,6 +205,29 @@ static void shmem_free_blocks(struct inode *inode, long pages)
 	}
 }
 
+static int shmem_inc_inodes(struct shmem_sb_info *sbinfo)
+{
+	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;
+}
+
+static void shmem_dec_inodes(struct shmem_sb_info *sbinfo)
+{
+	if (sbinfo->max_inodes) {
+		spin_lock(&sbinfo->stat_lock);
+		sbinfo->free_inodes++;
+		spin_unlock(&sbinfo->stat_lock);
+	}
+}
+
 /*
  * shmem_recalc_inode - recalculate the size of an inode
  *
@@ -777,11 +800,7 @@ static void shmem_delete_inode(struct inode *inode)
 		}
 	}
 	BUG_ON(inode->i_blocks);
-	if (sbinfo->max_inodes) {
-		spin_lock(&sbinfo->stat_lock);
-		sbinfo->free_inodes++;
-		spin_unlock(&sbinfo->stat_lock);
-	}
+	shmem_dec_inodes(sbinfo);
 	clear_inode(inode);
 }
 
@@ -1370,15 +1389,8 @@ shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
 	struct shmem_inode_info *info;
 	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 NULL;
-		}
-		sbinfo->free_inodes--;
-		spin_unlock(&sbinfo->stat_lock);
-	}
+	if (shmem_inc_inodes(sbinfo))
+		return NULL;
 
 	inode = new_inode(sb);
 	if (inode) {
@@ -1422,11 +1434,8 @@ shmem_get_inode(struct super_block *sb, int mode, dev_t dev)
 						NULL);
 			break;
 		}
-	} else if (sbinfo->max_inodes) {
-		spin_lock(&sbinfo->stat_lock);
-		sbinfo->free_inodes++;
-		spin_unlock(&sbinfo->stat_lock);
-	}
+	} else
+		shmem_dec_inodes(sbinfo);
 	return inode;
 }
 
@@ -1676,15 +1685,8 @@ static int shmem_link(struct dentry *old_dentry, struct inode *dir, struct dentr
 	 * but each new link needs a new dentry, pinning lowmem, and
 	 * tmpfs dentries cannot be pruned until they are unlinked.
 	 */
-	if (sbinfo->max_inodes) {
-		spin_lock(&sbinfo->stat_lock);
-		if (!sbinfo->free_inodes) {
-			spin_unlock(&sbinfo->stat_lock);
-			return -ENOSPC;
-		}
-		sbinfo->free_inodes--;
-		spin_unlock(&sbinfo->stat_lock);
-	}
+	if (shmem_inc_inodes(sbinfo))
+		return -ENOSPC;
 
 	dir->i_size += BOGO_DIRENT_SIZE;
 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
@@ -1699,14 +1701,8 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry)
 {
 	struct inode *inode = dentry->d_inode;
 
-	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
-		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
-		if (sbinfo->max_inodes) {
-			spin_lock(&sbinfo->stat_lock);
-			sbinfo->free_inodes++;
-			spin_unlock(&sbinfo->stat_lock);
-		}
-	}
+	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
+		shmem_dec_inodes(SHMEM_SB(inode->i_sb));
 
 	dir->i_size -= BOGO_DIRENT_SIZE;
 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;

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@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@openvz.org>
Signed-off-by: Hugh Dickins <hugh@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;
+}
+
+static void shmem_free_inode(struct super_block *sb)
+{
+	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
+	if (sbinfo->max_inodes) {
+		spin_lock(&sbinfo->stat_lock);
+		sbinfo->free_inodes++;
+		spin_unlock(&sbinfo->stat_lock);
+	}
+}
+
 /*
  * shmem_recalc_inode - recalculate the size of an inode
  *
@@ -762,7 +787,6 @@ static int shmem_notify_change(struct de
 
 static void shmem_delete_inode(struct inode *inode)
 {
-	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 	struct shmem_inode_info *info = SHMEM_I(inode);
 
 	if (inode->i_op->truncate == shmem_truncate) {
@@ -777,11 +801,7 @@ static void shmem_delete_inode(struct in
 		}
 	}
 	BUG_ON(inode->i_blocks);
-	if (sbinfo->max_inodes) {
-		spin_lock(&sbinfo->stat_lock);
-		sbinfo->free_inodes++;
-		spin_unlock(&sbinfo->stat_lock);
-	}
+	shmem_free_inode(inode->i_sb);
 	clear_inode(inode);
 }
 
@@ -1398,15 +1418,8 @@ shmem_get_inode(struct super_block *sb, 
 	struct shmem_inode_info *info;
 	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 NULL;
-		}
-		sbinfo->free_inodes--;
-		spin_unlock(&sbinfo->stat_lock);
-	}
+	if (shmem_reserve_inode(sb))
+		return NULL;
 
 	inode = new_inode(sb);
 	if (inode) {
@@ -1450,11 +1463,8 @@ shmem_get_inode(struct super_block *sb, 
 						NULL);
 			break;
 		}
-	} else if (sbinfo->max_inodes) {
-		spin_lock(&sbinfo->stat_lock);
-		sbinfo->free_inodes++;
-		spin_unlock(&sbinfo->stat_lock);
-	}
+	} else
+		shmem_free_inode(sb);
 	return inode;
 }
 
@@ -1797,22 +1807,14 @@ 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;
-	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
 
 	/*
 	 * 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 (sbinfo->max_inodes) {
-		spin_lock(&sbinfo->stat_lock);
-		if (!sbinfo->free_inodes) {
-			spin_unlock(&sbinfo->stat_lock);
-			return -ENOSPC;
-		}
-		sbinfo->free_inodes--;
-		spin_unlock(&sbinfo->stat_lock);
-	}
+	if (shmem_reserve_inode(inode->i_sb))
+		return -ENOSPC;
 
 	dir->i_size += BOGO_DIRENT_SIZE;
 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
@@ -1827,14 +1829,8 @@ static int shmem_unlink(struct inode *di
 {
 	struct inode *inode = dentry->d_inode;
 
-	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
-		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
-		if (sbinfo->max_inodes) {
-			spin_lock(&sbinfo->stat_lock);
-			sbinfo->free_inodes++;
-			spin_unlock(&sbinfo->stat_lock);
-		}
-	}
+	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
+		shmem_free_inode(inode->i_sb);
 
 	dir->i_size -= BOGO_DIRENT_SIZE;
 	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;

Hugh Dickins 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

This is perfect =) Thanks for the masterclass!

> better if those helpers could take a struct inode *, but they cannot.)
> Hugh
> 
> 
> From: Pavel Emelyanov <xemul@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@openvz.org>
> Signed-off-by: Hugh Dickins <hugh@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;
> +}
> +
> +static void shmem_free_inode(struct super_block *sb)
> +{
> +	struct shmem_sb_info *sbinfo = SHMEM_SB(sb);
> +	if (sbinfo->max_inodes) {
> +		spin_lock(&sbinfo->stat_lock);
> +		sbinfo->free_inodes++;
> +		spin_unlock(&sbinfo->stat_lock);
> +	}
> +}
> +
>  /*
>   * shmem_recalc_inode - recalculate the size of an inode
>   *
> @@ -762,7 +787,6 @@ static int shmem_notify_change(struct de
>  
>  static void shmem_delete_inode(struct inode *inode)
>  {
> -	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
>  	struct shmem_inode_info *info = SHMEM_I(inode);
>  
>  	if (inode->i_op->truncate == shmem_truncate) {
> @@ -777,11 +801,7 @@ static void shmem_delete_inode(struct in
>  		}
>  	}
>  	BUG_ON(inode->i_blocks);
> -	if (sbinfo->max_inodes) {
> -		spin_lock(&sbinfo->stat_lock);
> -		sbinfo->free_inodes++;
> -		spin_unlock(&sbinfo->stat_lock);
> -	}
> +	shmem_free_inode(inode->i_sb);
>  	clear_inode(inode);
>  }
>  
> @@ -1398,15 +1418,8 @@ shmem_get_inode(struct super_block *sb, 
>  	struct shmem_inode_info *info;
>  	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 NULL;
> -		}
> -		sbinfo->free_inodes--;
> -		spin_unlock(&sbinfo->stat_lock);
> -	}
> +	if (shmem_reserve_inode(sb))
> +		return NULL;
>  
>  	inode = new_inode(sb);
>  	if (inode) {
> @@ -1450,11 +1463,8 @@ shmem_get_inode(struct super_block *sb, 
>  						NULL);
>  			break;
>  		}
> -	} else if (sbinfo->max_inodes) {
> -		spin_lock(&sbinfo->stat_lock);
> -		sbinfo->free_inodes++;
> -		spin_unlock(&sbinfo->stat_lock);
> -	}
> +	} else
> +		shmem_free_inode(sb);
>  	return inode;
>  }
>  
> @@ -1797,22 +1807,14 @@ 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;
> -	struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
>  
>  	/*
>  	 * 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 (sbinfo->max_inodes) {
> -		spin_lock(&sbinfo->stat_lock);
> -		if (!sbinfo->free_inodes) {
> -			spin_unlock(&sbinfo->stat_lock);
> -			return -ENOSPC;
> -		}
> -		sbinfo->free_inodes--;
> -		spin_unlock(&sbinfo->stat_lock);
> -	}
> +	if (shmem_reserve_inode(inode->i_sb))
> +		return -ENOSPC;
>  
>  	dir->i_size += BOGO_DIRENT_SIZE;
>  	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
> @@ -1827,14 +1829,8 @@ static int shmem_unlink(struct inode *di
>  {
>  	struct inode *inode = dentry->d_inode;
>  
> -	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)) {
> -		struct shmem_sb_info *sbinfo = SHMEM_SB(inode->i_sb);
> -		if (sbinfo->max_inodes) {
> -			spin_lock(&sbinfo->stat_lock);
> -			sbinfo->free_inodes++;
> -			spin_unlock(&sbinfo->stat_lock);
> -		}
> -	}
> +	if (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode))
> +		shmem_free_inode(inode->i_sb);
>  
>  	dir->i_size -= BOGO_DIRENT_SIZE;
>  	inode->i_ctime = dir->i_ctime = dir->i_mtime = CURRENT_TIME;
>

On Fri, 23 Nov 2007 13:41:55 +0000 (GMT) Hugh Dickins <hugh@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@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@openvz.org>
> Signed-off-by: Hugh Dickins <hugh@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)
_

On Mon, 26 Nov 2007, Andrew Morton wrote:
> 
> It is peculair to (wrongly) return -ENOMEM
> 
> > +	if (shmem_reserve_inode(inode->i_sb))
> > +		return -ENOSPC;
> 
> and to then correct it in the caller..

Oops, I missed that completely.

> Something boringly conventional such as the below, perhaps?

Much better, thanks.

Hugh