Documentation/admin-guide/ext4.rst

4 ext4 General Information
12 Mailing list:	linux-ext4@vger.kernel.org
13 Web site:	http://ext4.wiki.kernel.org
19 Note: More extensive information for getting started with ext4 can be
20 found at the ext4 wiki site at the URL:
21 http://ext4.wiki.kernel.org/index.php/Ext4_Howto
35   - Create a new filesystem using the ext4 filesystem type:
37         # mke2fs -t ext4 /dev/hda1
50 	# mount -t ext4 /dev/hda1 /wherever
56     note that ext4 enables write barriers by default, while ext3 does
59     '-o barriers=[0|1]' mount option for both ext3 and ext4 filesystems
92 * efficient new ordered mode in JBD2 and ext4 (avoid using buffer head to force
141 When mounting an ext4 filesystem, the following option are accepted:
145         Mount filesystem read only. Note that ext4 will replay the journal (and
208         ext4 mount options.
212         that ext4's inode table readahead algorithm will pre-read into the
279         Defer block allocation until just before ext4 writes out the block(s)
280         in question.  This allows ext4 to better allocation decisions more
290         Maximum amount of time ext4 should wait for additional filesystem
300         time, ext4 will try sleeping for the commit time to see if other
321         O_TRUNC)/write(fd,..)/close(fd).  If auto_da_alloc is enabled, ext4
344         Controls whether ext4 should issue discard/TRIM commands to the
361         Controls whether or not ext4 should use the DIO read locking. If the
362         dioread_nolock option is specified ext4 will allocate uninitialized
364         IO completes. This approach allows ext4 code to avoid using inode
400   In data=writeback mode, ext4 does not journal data at all.  This mode provides
404   typically provide the best ext4 performance.
408   In data=ordered mode, ext4 only officially journals metadata, but it logically
428 Information about mounted ext4 file systems can be found in
429 /proc/fs/ext4.  Each mounted filesystem will have a directory in
430 /proc/fs/ext4 based on its device name (i.e., /proc/fs/ext4/hdc or
431 /proc/fs/ext4/dm-0).   The files in each per-device directory are shown
434 Files in /proc/fs/ext4/<devname>
442 Information about mounted ext4 file systems can be found in
443 /sys/fs/ext4.  Each mounted filesystem will have a directory in
444 /sys/fs/ext4 based on its device name (i.e., /sys/fs/ext4/hdc or
445 /sys/fs/ext4/dm-0).   The files in each per-device directory are shown
448 Files in /sys/fs/ext4/<devname>:
450 (see also Documentation/ABI/testing/sysfs-fs-ext4)
465         blocks that ext4's inode table readahead algorithm will pre-read into
479         ext4 superblock
522 ext4-specific functionality. An incomplete list of these ioctls is shown in the
523 table below. This list includes truly ext4-specific ioctls (``EXT4_IOC_*``) as
524 well as ioctls that may have been ext4-specific originally but are now supported
531         an integer bitfield, with bit values described in ext4.h.
535         an integer bitfield, with bit values described in ext4.h.
573         ext3 indirect block mapped inode to ext4 extent mapped inode by walking
575         contiguous block ranges into ext4 extents of the temporary inode. Then,
577         ext4 filesystem, however suggestion is to create fresh ext4 filesystem
605 kernel source:	<file:fs/ext4/>
611 		http://www.bullopensource.org/ext4/
612 		http://ext4.wiki.kernel.org/index.php/Main_Page