2010-03-10 16:54:11

by Eric Sandeen

Subject: [PATCH] ext4: stop issuing discards if not supported by device

Turn off issuance of discard requests if the device does
not support it - similar to the action we take for barriers.
This will save a little computation time if a non-discardable
device is mounted with -o discard, and also makes it obvious
that it's not doing what was asked at mount time ...

Signed-off-by: Eric Sandeen <[email protected]>
---

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 506713a..6ee4cac 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2556,6 +2556,7 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)
}
ext4_unlock_group(sb, entry->group);
if (test_opt(sb, DISCARD)) {
+ int ret;
ext4_fsblk_t discard_block;

discard_block = entry->start_blk +
@@ -2563,7 +2564,12 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)
trace_ext4_discard_blocks(sb,
(unsigned long long)discard_block,
entry->count);
- sb_issue_discard(sb, discard_block, entry->count);
+ ret = sb_issue_discard(sb, discard_block, entry->count);
+ if (ret == EOPNOTSUPP) {
+ ext4_warning(sb,
+ "discard not supported, disabling");
+ clear_opt(EXT4_SB(sb)->s_mount_opt, DISCARD);
+ }
}
kmem_cache_free(ext4_free_ext_cachep, entry);
ext4_mb_release_desc(&e4b);

2010-04-08 00:58:14

by Theodore Ts'o

Subject: Re: [PATCH] ext4: stop issuing discards if not supported by device

On Wed, Mar 10, 2010 at 10:54:03AM -0600, Eric Sandeen wrote:
> Turn off issuance of discard requests if the device does
> not support it - similar to the action we take for barriers.
> This will save a little computation time if a non-discardable
> device is mounted with -o discard, and also makes it obvious
> that it's not doing what was asked at mount time ...
>
> Signed-off-by: Eric Sandeen <[email protected]>

Added to the ext4 patch queue, thanks.

- Ted