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ext4: make trim/discard optional (and off by default)

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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: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
This commit is contained in:
Eric Sandeen 2009-11-19 14:25:42 -05:00 committed by Theodore Ts'o
parent 2bba702d4f
commit 5328e63531
4 changed files with 32 additions and 8 deletions
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6
Documentation/filesystems/ext4.txt
View file

@ -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:

1
fs/ext4/ext4.h
View file

@ -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

15
fs/ext4/mballoc.c
View file

@ -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);
}

14
fs/ext4/super.c
View file

@ -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\" "