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

[Hugh Dickins]

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;
+}
+
+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;