Re: [PATCH 1/2] fat: Fix d_splice_alias() return code checking

[Al Viro]

On Sun, Oct 19, 2014 at 12:39:43PM +0200, Richard Weinberger wrote:
> d_splice_alias() can return a valid dentry, NULL or an ERR_PTR.
> Currently the code checks not for ERR_PTR.
> Fix this by using IS_ERR_OR_NULL().

Why do we need to set ->d_time for non-NULL inode anyway?  AFAICS,
it's never checked for positive dentries, and the moment when positive
dentry become negative is when we want to set it anyway.

What am I missing here?  Why not simply do this:

diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index 6df8d3d..e2dc6bf 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -725,15 +725,14 @@ static struct dentry *vfat_lookup(struct inode *dir, 
struct dentry *dentry,
                        inode = NULL;
                        goto out;
                }
-               goto error;
+               inode = ERR_PTR(inode);
+               goto out;
        }
 
        inode = fat_build_inode(sb, sinfo.de, sinfo.i_pos);
        brelse(sinfo.bh);
-       if (IS_ERR(inode)) {
-               err = PTR_ERR(inode);
-               goto error;
-       }
+       if (IS_ERR(inode))
+               goto out;
 
        alias = d_find_alias(inode);
        if (alias && !vfat_d_anon_disconn(alias)) {
@@ -754,16 +753,10 @@ static struct dentry *vfat_lookup(struct inode *dir, 
struct dentry *dentry,
                dput(alias);
 
 out:
+       if (!inode)
+               dentry->d_time = dir->i_version;
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
-       dentry->d_time = dentry->d_parent->d_inode->i_version;
-       dentry = d_splice_alias(inode, dentry);
-       if (dentry)
-               dentry->d_time = dentry->d_parent->d_inode->i_version;
-       return dentry;
-
-error:
-       mutex_unlock(&MSDOS_SB(sb)->s_lock);
-       return ERR_PTR(err);
+       return d_splice_alias(inode, dentry);
 }
 
 static int vfat_create(struct inode *dir, struct dentry *dentry, umode_t mode,
@@ -793,7 +786,6 @@ static int vfat_create(struct inode *dir, struct dentry 
*dentry, umode_t mode,
        inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
        /* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
-       dentry->d_time = dentry->d_parent->d_inode->i_version;
        d_instantiate(dentry, inode);
 out:
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
@@ -824,6 +816,7 @@ static int vfat_rmdir(struct inode *dir, struct dentry 
*dentry)
        clear_nlink(inode);
        inode->i_mtime = inode->i_atime = CURRENT_TIME_SEC;
        fat_detach(inode);
+       dentry->d_time = dir->i_version;
 out:
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
 
@@ -849,6 +842,7 @@ static int vfat_unlink(struct inode *dir, struct dentry 
*dentry)
        clear_nlink(inode);
        inode->i_mtime = inode->i_atime = CURRENT_TIME_SEC;
        fat_detach(inode);
+       dentry->d_time = dir->i_version;
 out:
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
 
@@ -889,7 +883,6 @@ static int vfat_mkdir(struct inode *dir, struct dentry 
*dentry, umode_t mode)
        inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
        /* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
-       dentry->d_time = dentry->d_parent->d_inode->i_version;
        d_instantiate(dentry, inode);
 
        mutex_unlock(&MSDOS_SB(sb)->s_lock);
--
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