diff options
| author | Jan Kara <jack@suse.cz> | 2016-11-20 20:48:36 -0500 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2016-11-20 20:48:36 -0500 |
| commit | dd936e4313fa3f60abd6e67abb3cb66fc9a018d1 (patch) | |
| tree | fd9b89b7922a9c28bdb614ae2d49853d94772093 /Documentation/filesystems/dax.txt | |
| parent | 00697eed386d57c5267aad5b8343f027b10da0c0 (diff) | |
dax: rip out get_block based IO support
No one uses functions using the get_block callback anymore. Rip them
out and update documentation.
Reviewed-by: Ross Zwisler <ross.zwisler@linux.intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Diffstat (limited to 'Documentation/filesystems/dax.txt')
| -rw-r--r-- | Documentation/filesystems/dax.txt | 22 |
1 files changed, 11 insertions, 11 deletions
diff --git a/Documentation/filesystems/dax.txt b/Documentation/filesystems/dax.txt index 23d18b8a49d5..a7e6e14aeb08 100644 --- a/Documentation/filesystems/dax.txt +++ b/Documentation/filesystems/dax.txt @@ -58,22 +58,22 @@ Implementation Tips for Filesystem Writers Filesystem support consists of - adding support to mark inodes as being DAX by setting the S_DAX flag in i_flags -- implementing the direct_IO address space operation, and calling - dax_do_io() instead of blockdev_direct_IO() if S_DAX is set +- implementing ->read_iter and ->write_iter operations which use dax_iomap_rw() + when inode has S_DAX flag set - implementing an mmap file operation for DAX files which sets the VM_MIXEDMAP and VM_HUGEPAGE flags on the VMA, and setting the vm_ops to - include handlers for fault, pmd_fault and page_mkwrite (which should - probably call dax_fault(), dax_pmd_fault() and dax_mkwrite(), passing the - appropriate get_block() callback) -- calling dax_truncate_page() instead of block_truncate_page() for DAX files -- calling dax_zero_page_range() instead of zero_user() for DAX files + include handlers for fault, pmd_fault, page_mkwrite, pfn_mkwrite. These + handlers should probably call dax_iomap_fault() (for fault and page_mkwrite + handlers), dax_iomap_pmd_fault(), dax_pfn_mkwrite() passing the appropriate + iomap operations. +- calling iomap_zero_range() passing appropriate iomap operations instead of + block_truncate_page() for DAX files - ensuring that there is sufficient locking between reads, writes, truncates and page faults -The get_block() callback passed to the DAX functions may return -uninitialised extents. If it does, it must ensure that simultaneous -calls to get_block() (for example by a page-fault racing with a read() -or a write()) work correctly. +The iomap handlers for allocating blocks must make sure that allocated blocks +are zeroed out and converted to written extents before being returned to avoid +exposure of uninitialized data through mmap. These filesystems may be used for inspiration: - ext2: see Documentation/filesystems/ext2.txt |