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Commit 5328e635 authored by Eric Sandeen's avatar Eric Sandeen Committed by Theodore Ts'o
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ext4: make trim/discard optional (and off by default) 



It is anticipated that when sb_issue_discard starts doing
real work on trim-capable devices, we may see issues.  Make
this mount-time optional, and default it to off until we know
that things are working out OK.

Signed-off-by: default avatarEric Sandeen <sandeen@redhat.com>
Signed-off-by: default avatar"Theodore Ts'o" <tytso@mit.edu>
parent 2bba702d

Documentation/filesystems/ext4.txt

+6 −0
Original line number Diff line number Diff line
@@ -353,6 +353,12 @@ noauto_da_alloc replacing existing files via patterns such as 
			system crashes before the delayed allocation

			blocks are forced to disk.



discard		Controls whether ext4 should issue discard/TRIM

nodiscard(*)		commands to the underlying block device when

			blocks are freed.  This is useful for SSD devices

			and sparse/thinly-provisioned LUNs, but it is off

			by default until sufficient testing has been done.



Data Mode

=========

There are 3 different data modes:

fs/ext4/ext4.h

+1 −0
Original line number Diff line number Diff line
@@ -750,6 +750,7 @@ struct ext4_inode_info { 
#define EXT4_MOUNT_DELALLOC		0x8000000 /* Delalloc support */

#define EXT4_MOUNT_DATA_ERR_ABORT	0x10000000 /* Abort on file data write */

#define EXT4_MOUNT_BLOCK_VALIDITY	0x20000000 /* Block validity checking */

#define EXT4_MOUNT_DISCARD		0x40000000 /* Issue DISCARD requests */



#define clear_opt(o, opt)		o &= ~EXT4_MOUNT_##opt

#define set_opt(o, opt)			o |= EXT4_MOUNT_##opt

fs/ext4/mballoc.c

+13 −8
Original line number Diff line number Diff line
@@ -2529,7 +2529,6 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn) 
	struct ext4_group_info *db;

	int err, count = 0, count2 = 0;

	struct ext4_free_data *entry;

	ext4_fsblk_t discard_block;

	struct list_head *l, *ltmp;



	list_for_each_safe(l, ltmp, &txn->t_private_list) {
@@ -2559,13 +2558,19 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn) 
			page_cache_release(e4b.bd_bitmap_page);

		}

		ext4_unlock_group(sb, entry->group);

		discard_block = (ext4_fsblk_t) entry->group * EXT4_BLOCKS_PER_GROUP(sb)

		if (test_opt(sb, DISCARD)) {

			ext4_fsblk_t discard_block;

			struct ext4_super_block *es = EXT4_SB(sb)->s_es;



			discard_block = (ext4_fsblk_t)entry->group *

						EXT4_BLOCKS_PER_GROUP(sb)

					+ entry->start_blk

			+ le32_to_cpu(EXT4_SB(sb)->s_es->s_first_data_block);

		trace_ext4_discard_blocks(sb, (unsigned long long)discard_block,

					+ le32_to_cpu(es->s_first_data_block);

			trace_ext4_discard_blocks(sb,

					(unsigned long long)discard_block,

					entry->count);

			sb_issue_discard(sb, discard_block, entry->count);



		}

		kmem_cache_free(ext4_free_ext_cachep, entry);

		ext4_mb_release_desc(&e4b);

	}

fs/ext4/super.c

+13 −1
Original line number Diff line number Diff line
@@ -899,6 +899,9 @@ static int ext4_show_options(struct seq_file *seq, struct vfsmount *vfs) 
	if (test_opt(sb, NO_AUTO_DA_ALLOC))

		seq_puts(seq, ",noauto_da_alloc");



	if (test_opt(sb, DISCARD))

		seq_puts(seq, ",discard");



	ext4_show_quota_options(seq, sb);



	return 0;
@@ -1079,7 +1082,8 @@ enum { 
	Opt_usrquota, Opt_grpquota, Opt_i_version,

	Opt_stripe, Opt_delalloc, Opt_nodelalloc,

	Opt_block_validity, Opt_noblock_validity,

	Opt_inode_readahead_blks, Opt_journal_ioprio

	Opt_inode_readahead_blks, Opt_journal_ioprio,

	Opt_discard, Opt_nodiscard,

};



static const match_table_t tokens = {
@@ -1144,6 +1148,8 @@ static const match_table_t tokens = { 
	{Opt_auto_da_alloc, "auto_da_alloc=%u"},

	{Opt_auto_da_alloc, "auto_da_alloc"},

	{Opt_noauto_da_alloc, "noauto_da_alloc"},

	{Opt_discard, "discard"},

	{Opt_nodiscard, "nodiscard"},

	{Opt_err, NULL},

};
@@ -1565,6 +1571,12 @@ static int parse_options(char *options, struct super_block *sb, 
			else

				set_opt(sbi->s_mount_opt,NO_AUTO_DA_ALLOC);

			break;

		case Opt_discard:

			set_opt(sbi->s_mount_opt, DISCARD);

			break;

		case Opt_nodiscard:

			clear_opt(sbi->s_mount_opt, DISCARD);

			break;

		default:

			ext4_msg(sb, KERN_ERR,

			       "Unrecognized mount option \"%s\" "