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

From: Al Viro
Date: Mon Oct 20 2014 - 08:34:22 EST


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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