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Commit 06705bff authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

ext4: Regularize mount options 



Add support for using the mount options "barrier" and "nobarrier", and
"auto_da_alloc" and "noauto_da_alloc", which is more consistent than
"barrier=<0|1>" or "auto_da_alloc=<0|1>".  Most other ext3/ext4 mount
options use the foo/nofoo naming convention.  We allow the old forms
of these mount options for backwards compatibility.

Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent e7c9e3e9

Documentation/filesystems/ext4.txt

+23 −2
Original line number Diff line number Diff line
@@ -183,8 +183,8 @@ commit=nrsec (*) Ext4 can be told to sync all its data and metadata 
			performance.



barrier=<0|1(*)>	This enables/disables the use of write barriers in

			the jbd code.  barrier=0 disables, barrier=1 enables.

			This also requires an IO stack which can support

barrier(*)		the jbd code.  barrier=0 disables, barrier=1 enables.

nobarrier		This also requires an IO stack which can support

			barriers, and if jbd gets an error on a barrier

			write, it will disable again with a warning.

			Write barriers enforce proper on-disk ordering
@@ -192,6 +192,9 @@ barrier=<0|1(*)> This enables/disables the use of write barriers in 
			safe to use, at some performance penalty.  If

			your disks are battery-backed in one way or another,

			disabling barriers may safely improve performance.

			The mount options "barrier" and "nobarrier" can

			also be used to enable or disable barriers, for

			consistency with other ext4 mount options.



inode_readahead=n	This tuning parameter controls the maximum

			number of inode table blocks that ext4's inode
@@ -313,6 +316,24 @@ journal_ioprio=prio The I/O priority (from 0 to 7, where 0 is the 
			a slightly higher priority than the default I/O

			priority.



auto_da_alloc(*)	Many broken applications don't use fsync() when 

noauto_da_alloc		replacing existing files via patterns such as

			fd = open("foo.new")/write(fd,..)/close(fd)/

			rename("foo.new", "foo"), or worse yet,

			fd = open("foo", O_TRUNC)/write(fd,..)/close(fd).

			If auto_da_alloc is enabled, ext4 will detect

			the replace-via-rename and replace-via-truncate

			patterns and force that any delayed allocation

			blocks are allocated such that at the next

			journal commit, in the default data=ordered

			mode, the data blocks of the new file are forced

			to disk before the rename() operation is

			commited.  This provides roughly the same level

			of guarantees as ext3, and avoids the

			"zero-length" problem that can happen when a

			system crashes before the delayed allocation

			blocks are forced to disk.



Data Mode

=========

There are 3 different data modes:

fs/ext4/super.c

+22 −8
Original line number Diff line number Diff line
@@ -867,7 +867,7 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs) 
		seq_puts(seq, ",data_err=abort");



	if (test_opt(sb, NO_AUTO_DA_ALLOC))

		seq_puts(seq, ",auto_da_alloc=0");

		seq_puts(seq, ",noauto_da_alloc");



	ext4_show_quota_options(seq, sb);

	return 0;
@@ -1018,7 +1018,7 @@ enum { 
	Opt_resgid, Opt_resuid, Opt_sb, Opt_err_cont, Opt_err_panic, Opt_err_ro,

	Opt_nouid32, Opt_debug, Opt_oldalloc, Opt_orlov,

	Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl,

	Opt_auto_da_alloc, Opt_noload, Opt_nobh, Opt_bh,

	Opt_auto_da_alloc, Opt_noauto_da_alloc, Opt_noload, Opt_nobh, Opt_bh,

	Opt_commit, Opt_min_batch_time, Opt_max_batch_time,

	Opt_journal_update, Opt_journal_dev,

	Opt_journal_checksum, Opt_journal_async_commit,
@@ -1026,8 +1026,8 @@ enum { 
	Opt_data_err_abort, Opt_data_err_ignore,

	Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,

	Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,

	Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota,

	Opt_grpquota, Opt_i_version,

	Opt_ignore, Opt_barrier, Opt_nobarrier, Opt_err, Opt_resize,

	Opt_usrquota, Opt_grpquota, Opt_i_version,

	Opt_stripe, Opt_delalloc, Opt_nodelalloc,

	Opt_inode_readahead_blks, Opt_journal_ioprio

};
@@ -1080,6 +1080,8 @@ static const match_table_t tokens = { 
	{Opt_quota, "quota"},

	{Opt_usrquota, "usrquota"},

	{Opt_barrier, "barrier=%u"},

	{Opt_barrier, "barrier"},

	{Opt_nobarrier, "nobarrier"},

	{Opt_i_version, "i_version"},

	{Opt_stripe, "stripe=%u"},

	{Opt_resize, "resize"},
@@ -1088,6 +1090,8 @@ static const match_table_t tokens = { 
	{Opt_inode_readahead_blks, "inode_readahead_blks=%u"},

	{Opt_journal_ioprio, "journal_ioprio=%u"},

	{Opt_auto_da_alloc, "auto_da_alloc=%u"},

	{Opt_auto_da_alloc, "auto_da_alloc"},

	{Opt_noauto_da_alloc, "noauto_da_alloc"},

	{Opt_err, NULL},

};
@@ -1422,9 +1426,14 @@ static int parse_options(char *options, struct super_block *sb, 
		case Opt_abort:

			set_opt(sbi->s_mount_opt, ABORT);

			break;

		case Opt_nobarrier:

			clear_opt(sbi->s_mount_opt, BARRIER);

			break;

		case Opt_barrier:

			if (match_int(&args[0], &option))

				return 0;

			if (match_int(&args[0], &option)) {

				set_opt(sbi->s_mount_opt, BARRIER);

				break;

			}

			if (option)

				set_opt(sbi->s_mount_opt, BARRIER);

			else
@@ -1485,9 +1494,14 @@ static int parse_options(char *options, struct super_block *sb, 
			*journal_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE,

							    option);

			break;

		case Opt_noauto_da_alloc:

			set_opt(sbi->s_mount_opt,NO_AUTO_DA_ALLOC);

			break;

		case Opt_auto_da_alloc:

			if (match_int(&args[0], &option))

				return 0;

			if (match_int(&args[0], &option)) {

				clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC);

				break;

			}

			if (option)

				clear_opt(sbi->s_mount_opt, NO_AUTO_DA_ALLOC);

			else