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    Subject[PATCH 4/4] vfs: prevent remount read-only if pending removes
    Date
    From: Miklos Szeredi <mszeredi@suse.cz>

    If there are any inodes on the super block that have been unlinked
    (i_nlink == 0) but have not yet been deleted then prevent the
    remounting the super block read-only.

    Reported-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
    Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
    Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
    ---
    fs/file_table.c | 23 -----------------------
    fs/namespace.c | 7 +++++++
    fs/super.c | 4 ----
    include/linux/fs.h | 2 --
    4 files changed, 7 insertions(+), 29 deletions(-)

    diff --git a/fs/file_table.c b/fs/file_table.c
    index c322794..20002e3 100644
    --- a/fs/file_table.c
    +++ b/fs/file_table.c
    @@ -474,29 +474,6 @@ void file_sb_list_del(struct file *file)

    #endif

    -int fs_may_remount_ro(struct super_block *sb)
    -{
    - struct file *file;
    - /* Check that no files are currently opened for writing. */
    - lg_global_lock(files_lglock);
    - do_file_list_for_each_entry(sb, file) {
    - struct inode *inode = file->f_path.dentry->d_inode;
    -
    - /* File with pending delete? */
    - if (inode->i_nlink == 0)
    - goto too_bad;
    -
    - /* Writeable file? */
    - if (S_ISREG(inode->i_mode) && (file->f_mode & FMODE_WRITE))
    - goto too_bad;
    - } while_file_list_for_each_entry;
    - lg_global_unlock(files_lglock);
    - return 1; /* Tis' cool bro. */
    -too_bad:
    - lg_global_unlock(files_lglock);
    - return 0;
    -}
    -
    /**
    * mark_files_ro - mark all files read-only
    * @sb: superblock in question
    diff --git a/fs/namespace.c b/fs/namespace.c
    index f296790..62684d3 100644
    --- a/fs/namespace.c
    +++ b/fs/namespace.c
    @@ -480,6 +480,10 @@ int sb_prepare_remount_readonly(struct super_block *sb)
    struct vfsmount *mnt;
    int err = 0;

    + /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */
    + if (atomic_long_read(&sb->s_remove_count))
    + return -EBUSY;
    +
    br_write_lock(vfsmount_lock);
    list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) {
    if (!(mnt->mnt_flags & MNT_READONLY)) {
    @@ -491,6 +495,9 @@ int sb_prepare_remount_readonly(struct super_block *sb)
    }
    }
    }
    + if (!err && atomic_long_read(&sb->s_remove_count))
    + err = -EBUSY;
    +
    if (!err) {
    sb->s_readonly_remount = 1;
    smp_wmb();
    diff --git a/fs/super.c b/fs/super.c
    index 027e02d..e81baed 100644
    --- a/fs/super.c
    +++ b/fs/super.c
    @@ -727,10 +727,6 @@ int do_remount_sb(struct super_block *sb, int flags, void *data, int force)
    retval = sb_prepare_remount_readonly(sb);
    if (retval)
    return retval;
    -
    - retval = -EBUSY;
    - if (!fs_may_remount_ro(sb))
    - goto cancel_readonly;
    }
    }

    diff --git a/include/linux/fs.h b/include/linux/fs.h
    index f4636c3..963dd2a 100644
    --- a/include/linux/fs.h
    +++ b/include/linux/fs.h
    @@ -2146,8 +2146,6 @@ extern const struct file_operations read_pipefifo_fops;
    extern const struct file_operations write_pipefifo_fops;
    extern const struct file_operations rdwr_pipefifo_fops;

    -extern int fs_may_remount_ro(struct super_block *);
    -
    #ifdef CONFIG_BLOCK
    /*
    * return READ, READA, or WRITE
    --
    1.7.7


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