[71/90] ext4: make trim/discard optional (and off by default)

Greg KH
2009-12-11T04:45:59Z

[-- Attachment #1: 0071-ext4-make-trim-discard-optional-and-off-by-default.patch --]
[-- Type: text/plain, Size: 4375 bytes --]

2.6.31-stable review patch. If anyone has any objections, please let us know.

------------------
(cherry picked from commit 5328e635315734d42080de9a5a1ee87bf4cae0a4)

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
Documentation/filesystems/ext4.txt | 6 ++++++
fs/ext4/ext4.h | 1 +
fs/ext4/mballoc.c | 21 +++++++++++++--------
fs/ext4/super.c | 14 +++++++++++++-
4 files changed, 33 insertions(+), 9 deletions(-)

--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -338,6 +338,12 @@ noauto_da_alloc replacing existing file
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:
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -747,6 +747,7 @@ 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
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2810,7 +2810,6 @@ static void release_blocks_on_commit(jou
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) {
@@ -2840,13 +2839,19 @@ static void release_blocks_on_commit(jou
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)
- + 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,
- entry->count);
- sb_issue_discard(sb, discard_block, entry->count);
-
+ 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(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);
}
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -906,6 +906,9 @@ static int ext4_show_options(struct seq_
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;
@@ -1086,7 +1089,8 @@ 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 = {
@@ -1152,6 +1156,8 @@ 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},
};

@@ -1580,6 +1586,12 @@ set_qf_format:
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\" "