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Message-ID: <e843605d-4ef4-520d-6cc2-a6ceb50b6ee5@paragon-software.com>
Date: Tue, 28 Sep 2021 21:01:38 +0300
From: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
To: Kari Argillander <kari.argillander@...il.com>
CC: <ntfs3@...ts.linux.dev>, <linux-kernel@...r.kernel.org>,
<linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH 2/3] fs/ntfs3: Remove locked argument in ntfs_set_ea
On 27.09.2021 22:10, Kari Argillander wrote:
> On Mon, Sep 27, 2021 at 06:10:00PM +0300, Konstantin Komarov wrote:
>>
>>
>> On 25.09.2021 11:49, Kari Argillander wrote:
>>> On Fri, Sep 24, 2021 at 07:15:50PM +0300, Konstantin Komarov wrote:
>>>> We always need to lock now, because locks became smaller
>>>> (see "Move ni_lock_dir and ni_unlock into ntfs_create_inode").
>>>
>>> So basically this actually fixes that commit?
>>>
>>> Fixes: d562e901f25d ("fs/ntfs3: Move ni_lock_dir and ni_unlock into ntfs_create_inode")
>>>
>>> Or if you do not use fixes atleast use
>>>
>>> d562e901f25d ("fs/ntfs3: Move ni_lock_dir and ni_unlock into ntfs_create_inode")
>>>
>>> You can add these to your gitconfig
>>>
>>> [core]
>>> abbrev = 12
>>> [pretty]
>>> fixes = Fixes: %h (\"%s\")
>>> fixed = Fixes: %h (\"%s\")
>>>
>>> And get this annotation with
>>> git show --pretty=fixes <sha>
>>>
>>> Have some comments below also.
>>>
>>>>
>>>> Signed-off-by: Konstantin Komarov <almaz.alexandrovich@...agon-software.com>
>>>> ---
>>>> fs/ntfs3/xattr.c | 28 +++++++++++++---------------
>>>> 1 file changed, 13 insertions(+), 15 deletions(-)
>>>>
>>>> diff --git a/fs/ntfs3/xattr.c b/fs/ntfs3/xattr.c
>>>> index 253a07d9aa7b..1ab109723b10 100644
>>>> --- a/fs/ntfs3/xattr.c
>>>> +++ b/fs/ntfs3/xattr.c
>>>> @@ -257,7 +257,7 @@ static int ntfs_get_ea(struct inode *inode, const char *name, size_t name_len,
>>>>
>>>> static noinline int ntfs_set_ea(struct inode *inode, const char *name,
>>>> size_t name_len, const void *value,
>>>> - size_t val_size, int flags, int locked)
>
> Maybe we should leave int locked and ...
>
>>>> + size_t val_size, int flags)
>>>> {
>>>> struct ntfs_inode *ni = ntfs_i(inode);
>>>> struct ntfs_sb_info *sbi = ni->mi.sbi;
>>>> @@ -276,8 +276,7 @@ static noinline int ntfs_set_ea(struct inode *inode, const char *name,
>>>> u64 new_sz;
>>>> void *p;
>>>>
>>>> - if (!locked)
>>>> - ni_lock(ni);
>>>> + ni_lock(ni);
>>>>
>>>> run_init(&ea_run);
>>>>
>>>> @@ -465,8 +464,7 @@ static noinline int ntfs_set_ea(struct inode *inode, const char *name,
>>>> mark_inode_dirty(&ni->vfs_inode);
>>>>
>>>> out:
>>>> - if (!locked)
>>>> - ni_unlock(ni);
>>>> + ni_unlock(ni);
>>>>
>>>> run_close(&ea_run);
>>>> kfree(ea_all);
>>>> @@ -537,7 +535,7 @@ struct posix_acl *ntfs_get_acl(struct inode *inode, int type)
>>>>
>>>> static noinline int ntfs_set_acl_ex(struct user_namespace *mnt_userns,
>>>> struct inode *inode, struct posix_acl *acl,
>>>> - int type, int locked)
>>>> + int type)
>>>> {
>>>> const char *name;
>>>> size_t size, name_len;
>>>> @@ -594,7 +592,7 @@ static noinline int ntfs_set_acl_ex(struct user_namespace *mnt_userns,
>>>> flags = 0;
>>>> }
>>>>
>>>> - err = ntfs_set_ea(inode, name, name_len, value, size, flags, locked);
>>>> + err = ntfs_set_ea(inode, name, name_len, value, size, flags);
>>>> if (err == -ENODATA && !size)
>>>> err = 0; /* Removing non existed xattr. */
>>>> if (!err)
>>>> @@ -612,7 +610,7 @@ static noinline int ntfs_set_acl_ex(struct user_namespace *mnt_userns,
>>>> int ntfs_set_acl(struct user_namespace *mnt_userns, struct inode *inode,
>>>> struct posix_acl *acl, int type)
>>>> {
>>>> - return ntfs_set_acl_ex(mnt_userns, inode, acl, type, 0);
>>>> + return ntfs_set_acl_ex(mnt_userns, inode, acl, type);
>>>> }
>>>>
>>>> static int ntfs_xattr_get_acl(struct user_namespace *mnt_userns,
>>>> @@ -693,7 +691,7 @@ int ntfs_init_acl(struct user_namespace *mnt_userns, struct inode *inode,
>>>>
>>>> if (default_acl) {
>>>> err = ntfs_set_acl_ex(mnt_userns, inode, default_acl,
>>>> - ACL_TYPE_DEFAULT, 1);
>>>> + ACL_TYPE_DEFAULT);
>>>> posix_acl_release(default_acl);
>>>> } else {
>>>> inode->i_default_acl = NULL;
>>>> @@ -704,7 +702,7 @@ int ntfs_init_acl(struct user_namespace *mnt_userns, struct inode *inode,
>>>> else {
>>>> if (!err)
>>>> err = ntfs_set_acl_ex(mnt_userns, inode, acl,
>>>> - ACL_TYPE_ACCESS, 1);
>>>> + ACL_TYPE_ACCESS);
>>>> posix_acl_release(acl);
>>>> }
>>>>
>>>> @@ -988,7 +986,7 @@ static noinline int ntfs_setxattr(const struct xattr_handler *handler,
>>>> }
>>>> #endif
>>>> /* Deal with NTFS extended attribute. */
>>>> - err = ntfs_set_ea(inode, name, name_len, value, size, flags, 0);
>>>> + err = ntfs_set_ea(inode, name, name_len, value, size, flags);
>>>>
>>>> out:
>>>> return err;
>>>> @@ -1006,26 +1004,26 @@ int ntfs_save_wsl_perm(struct inode *inode)
>>>>
>
> do lock here and ...
>
>>>> value = cpu_to_le32(i_uid_read(inode));
>>>> err = ntfs_set_ea(inode, "$LXUID", sizeof("$LXUID") - 1, &value,
>>>> - sizeof(value), 0, 0);
>>>> + sizeof(value), 0);
>>>> if (err)
>>>> goto out;
>>>>
>>>> value = cpu_to_le32(i_gid_read(inode));
>>>> err = ntfs_set_ea(inode, "$LXGID", sizeof("$LXGID") - 1, &value,
>>>> - sizeof(value), 0, 0);
>>>> + sizeof(value), 0);
>>>> if (err)
>>>> goto out;
>>>>
>>>> value = cpu_to_le32(inode->i_mode);
>>>> err = ntfs_set_ea(inode, "$LXMOD", sizeof("$LXMOD") - 1, &value,
>>>> - sizeof(value), 0, 0);
>>>> + sizeof(value), 0);
>>>> if (err)
>>>> goto out;
>>>>
>>>> if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode)) {
>>>> value = cpu_to_le32(inode->i_rdev);
>>>> err = ntfs_set_ea(inode, "$LXDEV", sizeof("$LXDEV") - 1, &value,
>>>> - sizeof(value), 0, 0);
>>>> + sizeof(value), 0);
>
> unlock here. Of course unlock also in error path.
>
>>>
>>> Is this really that we can lock/unlock same lock 4 times in a row in a
>>> ntfs_set_ea? This does not feel correct.
>>>
>>> Argillander
>>>
>>
>> How it was working before d562e901f25d
>> "fs/ntfs3: Move ni_lock_dir and ni_unlock into ntfs_create_inode":
>>
>> ntfs_create (lock mutex) =>
>> ntfs_create_inode =>
>> ntfs_save_wsl_perm (we are under lock here) =>
>> return to ntfs_create and unlock
>>
>> How it works with d562e901f25d:
>>
>> ntfs_create =>
>> ntfs_create_inode (lock in line 1201 file fs/ntfs3/inode.c
>> and unlock in line 1557) =>
>> ntfs_save_wsl_perm (we aren't under lock here in line 1605)
>>
>> So we need to lock 4 times because there are 4 ntfs_set_ea calls.
>> But now there can be done more work between those calls
>> in other threads, locks became more granular.
>
> Yeah but locking and locking 4 times when we can do it just ones is
> quite waste. Please consider my suggestion above or tell what is wrong
> with it.
>
> Argillander
>
If I've understood correctly, you want to lock once in start of function
ntfs_save_wsl_perm and unlock at the end of it.
It takes care of locks for those 4 calls to ntfs_set_ea.
But there are still other calls to ntfs_set_ea, that aren't protected
in this case:
function ntfs_set_acl_ex (line 603 file fs/ntfs3/xattr.c)
err = ntfs_set_ea(inode, name, name_len, value, size, flags, locked);
This function called there:
- function ntfs_set_acl (line 621 file fs/ntfs3/xattr.c)
return ntfs_set_acl_ex(mnt_userns, inode, acl, type);
- function ntfs_init_acl (line 701 file fs/ntfs3/xattr.c)
err = ntfs_set_acl_ex(mnt_userns, inode, default_acl,
- function ntfs_init_acl (line 712 file fs/ntfs3/xattr.c)
err = ntfs_set_acl_ex(mnt_userns, inode, acl,
So there are many entry points to ntfs_set_ea (and can be added more).
Of course we can let int locked remain for these situations,
but in my opinion it makes code a lot less readable
(that was the reason to start looking into locking).
I'm not sure, that winning some lock/unlocking
in one specific scenario is worth it.
>>
>>>> if (err)
>>>> goto out;
>>>> }
>>>> --
>>>> 2.33.0
>>>>
>>>>
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