src/common/fs-handle.h

   1 /*
   2  * Copyright (C) 2020 Jérémie Galarneau <jeremie.galarneau@efficios.com>
   3  *
   4  * SPDX-License-Identifier: LGPL-2.1-only
   5  *
   6  */
   7
   8 #ifndef FS_HANDLE_H
   9 #define FS_HANDLE_H
  10
  11 #include <common/macros.h>
  12 #include <stdio.h>
  13
  14 struct fs_handle;
  15
  16 /*
  17  * Marks the handle as the most recently used and marks the 'fd' as
  18  * "in-use". This prevents the tracker from recycling the underlying
  19  * file descriptor while it is actively being used by a thread.
  20  *
  21  * Don't forget that the tracker may be initiating an fd 'suspension'
  22  * from another thread as the need to free an fd slot may arise from any
  23  * thread within the daemon.
  24  *
  25  * Note that a restorable fd should never be held for longer than
  26  * strictly necessary (e.g. the duration of a syscall()).
  27  *
  28  * Returns the fd on success, otherwise a negative value may be returned
  29  * if the restoration of the fd failed.
  30  */
  31 LTTNG_HIDDEN
  32 int fs_handle_get_fd(struct fs_handle *handle);
  33
  34 /*
  35  * Used by the caller to signal that it is no longer using the underlying fd and
  36  * that it may be safely suspended.
  37  */
  38 LTTNG_HIDDEN
  39 void fs_handle_put_fd(struct fs_handle *handle);
  40
  41 /*
  42  * Unlink the file associated to an fs_handle. Note that the unlink
  43  * operation will not be performed immediately. It will only be performed
  44  * once all references to the underlying file (through other fs_handle objects)
  45  * have been released.
  46  *
  47  * However, note that the file will be renamed so as to provide the observable
  48  * effect of an unlink(), that is removing a name from the filesystem.
  49  *
  50  * Returns 0 on success, otherwise a negative value will be returned
  51  * if the operation failed.
  52  */
  53 LTTNG_HIDDEN
  54 int fs_handle_unlink(struct fs_handle *handle);
  55
  56 /*
  57  * Frees the handle and discards the underlying fd.
  58  */
  59 LTTNG_HIDDEN
  60 int fs_handle_close(struct fs_handle *handle);
  61
  62 LTTNG_HIDDEN
  63 ssize_t fs_handle_read(struct fs_handle *handle, void *buf, size_t count);
  64
  65 LTTNG_HIDDEN
  66 ssize_t fs_handle_write(struct fs_handle *handle, const void *buf, size_t count);
  67
  68 LTTNG_HIDDEN
  69 int fs_handle_truncate(struct fs_handle *handle, off_t offset);
  70
  71 LTTNG_HIDDEN
  72 int fs_handle_seek(struct fs_handle *handle, off_t offset, int whence);
  73
  74 #endif /* FS_HANDLE_H */