Discussion:
[PATCH 2/2] ocfs2: Fix d_splice_alias() return code checking
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Richard Weinberger
2014-10-19 10:39:44 UTC
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d_splice_alias() can return a valid dentry, NULL or an ERR_PTR.
Currently the code checks not for ERR_PTR and my oops in
ocfs2_dentry_attach_lock().
Fix this by using IS_ERR_OR_NULL().

Cc: Mark Fasheh <***@suse.com>
Cc: Joel Becker <***@evilplan.org>
Cc: ocfs2-***@oss.oracle.com
Signed-off-by: Richard Weinberger <***@nod.at>
---
fs/ocfs2/namei.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ocfs2/namei.c b/fs/ocfs2/namei.c
index 8add6f1..b931e04 100644
--- a/fs/ocfs2/namei.c
+++ b/fs/ocfs2/namei.c
@@ -158,7 +158,7 @@ bail_add:
* NOTE: This dentry already has ->d_op set from
* ocfs2_get_parent() and ocfs2_get_dentry()
*/
- if (ret)
+ if (!IS_ERR_OR_NULL(ret))
dentry = ret;

status = ocfs2_dentry_attach_lock(dentry, inode,
--
2.1.0
Al Viro
2014-10-20 12:34:15 UTC
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Post by Richard Weinberger
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);
OGAWA Hirofumi
2014-10-23 15:21:04 UTC
Permalink
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Post by Al Viro
Post by Richard Weinberger
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.
Hm, at least, this changes behavior though (old one drops if parent
changed after target dentry created, then when become negative. New one
drops if changed parent after target became negative.).

However, looks like new behavior is workable. And I think it is worth to try.

Can you add Signed-off-by:?
Post by Al Viro
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);
+ 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;
-
- 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);
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;
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;
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);
--
OGAWA Hirofumi <***@mail.parknet.co.jp>
Andrew Morton
2014-10-20 23:12:19 UTC
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Raw Message
Post by Richard Weinberger
d_splice_alias() can return a valid dentry, NULL or an ERR_PTR.
Currently the code checks not for ERR_PTR and my oops in
ocfs2_dentry_attach_lock().
It's unclear what the second sentence is trying to tell us. The patch
fixes an oops? If so, a copy of the trace would be useful, as would an
explanation of why it occurred. If not, I'm all confused.

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Richard Weinberger
2014-10-22 20:33:59 UTC
Permalink
Raw Message
Post by Andrew Morton
Post by Richard Weinberger
d_splice_alias() can return a valid dentry, NULL or an ERR_PTR.
Currently the code checks not for ERR_PTR and my oops in
ocfs2_dentry_attach_lock().
It's unclear what the second sentence is trying to tell us. The patch
fixes an oops? If so, a copy of the trace would be useful, as would an
explanation of why it occurred. If not, I'm all confused.
ocfs2_dentry_attach_lock() derefs the dentry pointer.
If d_splice_alias() returns ERR_PTR(-EIO) it will oops.

Thanks,
//richard
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