diff options
Diffstat (limited to 'Documentation/filesystems/ext4.txt')
| -rw-r--r-- | Documentation/filesystems/ext4.txt | 61 |
1 files changed, 41 insertions, 20 deletions
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt index 10ec4639f15..919a3293aaa 100644 --- a/Documentation/filesystems/ext4.txt +++ b/Documentation/filesystems/ext4.txt @@ -2,7 +2,7 @@ Ext4 Filesystem =============== -Ext4 is an an advanced level of the ext3 filesystem which incorporates +Ext4 is an advanced level of the ext3 filesystem which incorporates scalability and reliability enhancements for supporting large filesystems (64 bit) in keeping with increasing disk capacities and state-of-the-art feature requirements. @@ -144,14 +144,12 @@ journal_async_commit Commit block can be written to disk without waiting mount the device. This will enable 'journal_checksum' internally. -journal=update Update the ext4 file system's journal to the current - format. - +journal_path=path journal_dev=devnum When the external journal device's major/minor numbers - have changed, this option allows the user to specify + have changed, these options allow the user to specify the new journal location. The journal device is - identified through its new major/minor numbers encoded - in devnum. + identified through either its new major/minor numbers + encoded in devnum, or via a path to the device. norecovery Don't load the journal on mounting. Note that noload if the filesystem was not unmounted cleanly, @@ -203,12 +201,9 @@ inode_readahead_blks=n This tuning parameter controls the maximum table readahead algorithm will pre-read into the buffer cache. The default value is 32 blocks. -nouser_xattr Disables Extended User Attributes. If you have extended - attribute support enabled in the kernel configuration - (CONFIG_EXT4_FS_XATTR), extended attribute support - is enabled by default on mount. See the attr(5) manual - page and http://acl.bestbits.at/ for more information - about extended attributes. +nouser_xattr Disables Extended User Attributes. See the + attr(5) manual page and http://acl.bestbits.at/ + for more information about extended attributes. noacl This option disables POSIX Access Control List support. If ACL support is enabled in the kernel @@ -308,7 +303,7 @@ min_batch_time=usec This parameter sets the commit time (as fast disks, at the cost of increasing latency. journal_ioprio=prio The I/O priority (from 0 to 7, where 0 is the - highest priorty) which should be used for I/O + highest priority) which should be used for I/O operations submitted by kjournald2 during a commit operation. This defaults to 3, which is a slightly higher priority than the default I/O @@ -343,7 +338,7 @@ noinit_itable Do not initialize any uninitialized inode table init_itable=n The lazy itable init code will wait n times the number of milliseconds it took to zero out the previous block group's inode table. This - minimizes the impact on the systme performance + minimizes the impact on the system performance while file system's inode table is being initialized. discard Controls whether ext4 should issue discard/TRIM @@ -356,11 +351,6 @@ nouid32 Disables 32-bit UIDs and GIDs. This is for interoperability with older kernels which only store and expect 16-bit values. -resize Allows to resize filesystem to the end of the last - existing block group, further resize has to be done - with resize2fs either online, or offline. It can be - used only with conjunction with remount. - block_validity This options allows to enables/disables the in-kernel noblock_validity facility for tracking filesystem metadata blocks within internal data structures. This allows multi- @@ -383,6 +373,16 @@ dioread_nolock locking. If the dioread_nolock option is specified Because of the restrictions this options comprises it is off by default (e.g. dioread_lock). +max_dir_size_kb=n This limits the size of directories so that any + attempt to expand them beyond the specified + limit in kilobytes will cause an ENOSPC error. + This is useful in memory constrained + environments, where a very large directory can + cause severe performance problems or even + provoke the Out Of Memory killer. (For example, + if there is only 512mb memory available, a 176mb + directory may seriously cramp the system's style.) + i_version Enable 64-bit inode version support. This option is off by default. @@ -495,6 +495,17 @@ Files in /sys/fs/ext4/<devname> session_write_kbytes This file is read-only and shows the number of kilobytes of data that have been written to this filesystem since it was mounted. + + reserved_clusters This is RW file and contains number of reserved + clusters in the file system which will be used + in the specific situations to avoid costly + zeroout, unexpected ENOSPC, or possible data + loss. The default is 2% or 4096 clusters, + whichever is smaller and this can be changed + however it can never exceed number of clusters + in the file system. If there is not enough space + for the reserved space when mounting the file + mount will _not_ fail. .............................................................................. Ioctls @@ -588,6 +599,16 @@ Table of Ext4 specific ioctls bitmaps and inode table, the userspace tool thus just passes the new number of blocks. +EXT4_IOC_SWAP_BOOT Swap i_blocks and associated attributes + (like i_blocks, i_size, i_flags, ...) from + the specified inode with inode + EXT4_BOOT_LOADER_INO (#5). This is typically + used to store a boot loader in a secure part of + the filesystem, where it can't be changed by a + normal user by accident. + The data blocks of the previous boot loader + will be associated with the given inode. + .............................................................................. References |