filesystems/iomap/operations.rst

23 Buffered I/O is the default file I/O path in Linux.
81     If this function is not provided, iomap will call
89     If this function is not provided, iomap will ``folio_unlock`` and
99     If a file's space mapping data are mutable, it is possible that the
115     ``->iomap_valid`` function to decide if the mapping is still valid.
116     If the mapping is not valid, the mapping will be sampled again.
121     A simple validation cookie implementation is a sequence counter.
125     If the value in the cookie is found to be different to the value
126     the filesystem holds when the mapping is passed back to
139 If the fsblock size matches the size of a pagecache folio, it is assumed
145 If the fsblock size is less than the size of a pagecache folio, iomap
162    folio is dirty.
166 This structure is much lighter weight than ``struct buffer_head``
167 because there is only one per folio, and the per-fsblock overhead is two
275 This is to prevent dirty folio clots when storage devices fail; an
276 ``-EIO`` is recorded for userspace to collect via ``fsync``.
278 The ``ops`` structure must be specified and is as follows:
306     This revalidation must be open-coded by the filesystem; it is
313     This might include pre-write space accounting updates, or installing
317     This function is optional.
329     This function is optional.
336 wrap the ``bio`` that is used to write pagecache data to disk.
364  * ``iomap_ioend_try_merge``: Given an ioend that is not in any list and
365    a separate list of sorted ioends, merge as many of the ioends from
369    write I/O outcome is the same.
378 In Linux, direct I/O is defined as file I/O that is issued directly to
392 extra work before or after the I/O is issued to storage.
395 It is used to continue a request asynchronously when `part of the
402 The direction of the I/O is determined from the ``iocb`` passed in.
408    kiocb is not synchronous.
415    other I/Os to the same filesystem block(s) is unnecessary as there is
424    is required to do it `correctly
455 They should not set ``->direct_IO``, which is deprecated.
459 If its return value is not an error pointer or a NULL pointer, the
503 The pagecache is invalidated both before and after the write io.
510    blocks is not allowed.
514    if the mapping is unwritten and the filesystem cannot handle zeroing
517  * ``IOMAP_ATOMIC``: This write is being issued with torn-write
542    write covers multiple extents, meaning that it is not possible to issue
567     If no function is provided, ``submit_bio`` will be called directly.
571   - ``end_io``: This is called after the ``struct bio`` completes.
587     If this field is NULL, generic ``struct bio`` objects will be used.
716 Callers must hold ``i_rwsem`` in exclusive mode; this is already
739 This function is only provided to maintain compatibility for filesystems
741 This ioctl is deprecated; do **not** add a FIBMAP implementation to
744 this function, but this is unclear.