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    Subject[Patch] cpusets: fix race in cpuset_add_file()


    Hi,

    This patch fixes a missing down()/up() pair in cpuset_add_file().

    Without this patch, sometimes it is possible to have two duplicate
    dentries for a single file of a cpuset, with one of them being invalid,
    and thus the file is present but cannot be opened...

    Something like:

    # cd /dev/cpuset/foo
    # ls
    ls: cpus: No such file or directory



    The patch also removes comments that
    1/are now bogus with this fix applied
    2/were not respected anyway



    Signed-off-by: Simon Derr <simon.derr@bull.net>

    Index: mm4/kernel/cpuset.c
    ===================================================================
    --- mm4.orig/kernel/cpuset.c 2004-09-13 09:43:02.000000000 +0200
    +++ mm4/kernel/cpuset.c 2004-09-16 15:46:21.847401360 +0200
    @@ -956,13 +956,12 @@ static int cpuset_create_dir(struct cpus
    return error;
    }

    -/* MUST be called with dir->d_inode->i_sem held */
    -
    static int cpuset_add_file(struct dentry *dir, const struct cftype *cft)
    {
    struct dentry *dentry;
    int error;

    + down(&dir->d_inode->i_sem);
    dentry = cpuset_get_dentry(dir, cft->name);
    if (!IS_ERR(dentry)) {
    error = cpuset_create_file(dentry, 0644 | S_IFREG);
    @@ -971,6 +970,7 @@ static int cpuset_add_file(struct dentry
    dput(dentry);
    } else
    error = PTR_ERR(dentry);
    + up(&dir->d_inode->i_sem);
    return error;
    }

    @@ -1162,7 +1162,6 @@ static struct cftype cft_notify_on_relea
    .private = FILE_NOTIFY_ON_RELEASE,
    };

    -/* MUST be called with ->d_inode->i_sem held */
    static int cpuset_populate_dir(struct dentry *cs_dentry)
    {
    int err;
    -
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