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    Subject[PATCH 09/11] vfs: add fcheck tracepoint
    Date
    All file accesses from userland go through fcheck to map fd to struct
    file, making it a very good location for peeking at what files
    userland is accessing. Add a tracepoint there.

    This is part of tracepoint additions to improve visiblity into
    dirtying / writeback operations for io tracer and userland.

    Signed-off-by: Tejun Heo <tj@kernel.org>
    ---
    fs/super.c | 2 ++
    include/linux/fdtable.h | 3 +++
    include/trace/events/vfs.h | 40 ++++++++++++++++++++++++++++++++++++++++
    3 files changed, 45 insertions(+), 0 deletions(-)
    create mode 100644 include/trace/events/vfs.h

    diff --git a/fs/super.c b/fs/super.c
    index afd0f1a..7b70a2e 100644
    --- a/fs/super.c
    +++ b/fs/super.c
    @@ -34,6 +34,8 @@
    #include <linux/cleancache.h>
    #include "internal.h"

    +#define CREATE_TRACE_POINTS
    +#include <trace/events/vfs.h>

    LIST_HEAD(super_blocks);
    DEFINE_SPINLOCK(sb_lock);
    diff --git a/include/linux/fdtable.h b/include/linux/fdtable.h
    index 82163c4..72df04b 100644
    --- a/include/linux/fdtable.h
    +++ b/include/linux/fdtable.h
    @@ -12,6 +12,7 @@
    #include <linux/types.h>
    #include <linux/init.h>
    #include <linux/fs.h>
    +#include <trace/events/vfs.h>

    #include <linux/atomic.h>

    @@ -87,6 +88,8 @@ static inline struct file * fcheck_files(struct files_struct *files, unsigned in

    if (fd < fdt->max_fds)
    file = rcu_dereference_check_fdtable(files, fdt->fd[fd]);
    +
    + trace_vfs_fcheck(files, fd, file);
    return file;
    }

    diff --git a/include/trace/events/vfs.h b/include/trace/events/vfs.h
    new file mode 100644
    index 0000000..9a9bae4
    --- /dev/null
    +++ b/include/trace/events/vfs.h
    @@ -0,0 +1,40 @@
    +#undef TRACE_SYSTEM
    +#define TRACE_SYSTEM vfs
    +
    +#if !defined(_TRACE_VFS_H) || defined(TRACE_HEADER_MULTI_READ)
    +#define _TRACE_VFS_H
    +
    +#include <linux/tracepoint.h>
    +#include <linux/fs.h>
    +
    +TRACE_EVENT(vfs_fcheck,
    +
    + TP_PROTO(struct files_struct *files, unsigned int fd,
    + struct file *file),
    +
    + TP_ARGS(files, fd, file),
    +
    + TP_STRUCT__entry(
    + __field(unsigned int, fd)
    + __field(umode_t, mode)
    + __field(dev_t, dev)
    + __field(ino_t, ino)
    + ),
    +
    + TP_fast_assign(
    + __entry->fd = fd;
    + __entry->mode = file ? file->f_path.dentry->d_inode->i_mode : 0;
    + __entry->dev = file ? file->f_path.dentry->d_inode->i_sb->s_dev : 0;
    + __entry->ino = file ? file->f_path.dentry->d_inode->i_ino : 0;
    + ),
    +
    + TP_printk("fd %u mode 0x%x dev %d,%d ino %lu",
    + __entry->fd, __entry->mode,
    + MAJOR(__entry->dev), MINOR(__entry->dev),
    + (unsigned long)__entry->ino)
    +);
    +
    +#endif /* _TRACE_VFS_H */
    +
    +/* This part must be outside protection */
    +#include <trace/define_trace.h>
    --
    1.7.3.1


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