lkml.org 
[lkml]   [2022]   [Jun]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 5.17 766/772] fs: add two trivial lookup helpers
    Date
    From: Christian Brauner <brauner@kernel.org>

    commit 00675017e0aeba5305665c52ded4ddce6a4c0231 upstream.

    Similar to the addition of lookup_one() add a version of
    lookup_one_unlocked() and lookup_one_positive_unlocked() that take
    idmapped mounts into account. This is required to port overlay to
    support idmapped base layers.

    Cc: <linux-fsdevel@vger.kernel.org>
    Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
    Reviewed-by: Amir Goldstein <amir73il@gmail.com>
    Reviewed-by: Christoph Hellwig <hch@lst.de>
    Signed-off-by: Christian Brauner (Microsoft) <brauner@kernel.org>
    Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    ---
    fs/namei.c | 70 ++++++++++++++++++++++++++++++++++++++++++--------
    include/linux/namei.h | 6 ++++
    2 files changed, 66 insertions(+), 10 deletions(-)

    --- a/fs/namei.c
    +++ b/fs/namei.c
    @@ -2768,7 +2768,8 @@ struct dentry *lookup_one(struct user_na
    EXPORT_SYMBOL(lookup_one);

    /**
    - * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
    + * lookup_one_unlocked - filesystem helper to lookup single pathname component
    + * @mnt_userns: idmapping of the mount the lookup is performed from
    * @name: pathname component to lookup
    * @base: base directory to lookup from
    * @len: maximum length @len should be interpreted to
    @@ -2779,14 +2780,15 @@ EXPORT_SYMBOL(lookup_one);
    * Unlike lookup_one_len, it should be called without the parent
    * i_mutex held, and will take the i_mutex itself if necessary.
    */
    -struct dentry *lookup_one_len_unlocked(const char *name,
    - struct dentry *base, int len)
    +struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns,
    + const char *name, struct dentry *base,
    + int len)
    {
    struct qstr this;
    int err;
    struct dentry *ret;

    - err = lookup_one_common(&init_user_ns, name, base, len, &this);
    + err = lookup_one_common(mnt_userns, name, base, len, &this);
    if (err)
    return ERR_PTR(err);

    @@ -2795,6 +2797,59 @@ struct dentry *lookup_one_len_unlocked(c
    ret = lookup_slow(&this, base, 0);
    return ret;
    }
    +EXPORT_SYMBOL(lookup_one_unlocked);
    +
    +/**
    + * lookup_one_positive_unlocked - filesystem helper to lookup single
    + * pathname component
    + * @mnt_userns: idmapping of the mount the lookup is performed from
    + * @name: pathname component to lookup
    + * @base: base directory to lookup from
    + * @len: maximum length @len should be interpreted to
    + *
    + * This helper will yield ERR_PTR(-ENOENT) on negatives. The helper returns
    + * known positive or ERR_PTR(). This is what most of the users want.
    + *
    + * Note that pinned negative with unlocked parent _can_ become positive at any
    + * time, so callers of lookup_one_unlocked() need to be very careful; pinned
    + * positives have >d_inode stable, so this one avoids such problems.
    + *
    + * Note that this routine is purely a helper for filesystem usage and should
    + * not be called by generic code.
    + *
    + * The helper should be called without i_mutex held.
    + */
    +struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
    + const char *name,
    + struct dentry *base, int len)
    +{
    + struct dentry *ret = lookup_one_unlocked(mnt_userns, name, base, len);
    +
    + if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
    + dput(ret);
    + ret = ERR_PTR(-ENOENT);
    + }
    + return ret;
    +}
    +EXPORT_SYMBOL(lookup_one_positive_unlocked);
    +
    +/**
    + * lookup_one_len_unlocked - filesystem helper to lookup single pathname component
    + * @name: pathname component to lookup
    + * @base: base directory to lookup from
    + * @len: maximum length @len should be interpreted to
    + *
    + * Note that this routine is purely a helper for filesystem usage and should
    + * not be called by generic code.
    + *
    + * Unlike lookup_one_len, it should be called without the parent
    + * i_mutex held, and will take the i_mutex itself if necessary.
    + */
    +struct dentry *lookup_one_len_unlocked(const char *name,
    + struct dentry *base, int len)
    +{
    + return lookup_one_unlocked(&init_user_ns, name, base, len);
    +}
    EXPORT_SYMBOL(lookup_one_len_unlocked);

    /*
    @@ -2808,12 +2863,7 @@ EXPORT_SYMBOL(lookup_one_len_unlocked);
    struct dentry *lookup_positive_unlocked(const char *name,
    struct dentry *base, int len)
    {
    - struct dentry *ret = lookup_one_len_unlocked(name, base, len);
    - if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) {
    - dput(ret);
    - ret = ERR_PTR(-ENOENT);
    - }
    - return ret;
    + return lookup_one_positive_unlocked(&init_user_ns, name, base, len);
    }
    EXPORT_SYMBOL(lookup_positive_unlocked);

    --- a/include/linux/namei.h
    +++ b/include/linux/namei.h
    @@ -69,6 +69,12 @@ extern struct dentry *lookup_one_len(con
    extern struct dentry *lookup_one_len_unlocked(const char *, struct dentry *, int);
    extern struct dentry *lookup_positive_unlocked(const char *, struct dentry *, int);
    struct dentry *lookup_one(struct user_namespace *, const char *, struct dentry *, int);
    +struct dentry *lookup_one_unlocked(struct user_namespace *mnt_userns,
    + const char *name, struct dentry *base,
    + int len);
    +struct dentry *lookup_one_positive_unlocked(struct user_namespace *mnt_userns,
    + const char *name,
    + struct dentry *base, int len);

    extern int follow_down_one(struct path *);
    extern int follow_down(struct path *);

    \
     
     \ /
      Last update: 2022-06-07 23:59    [W:2.673 / U:0.612 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site