[34-longterm 011/260] ext4: stop issuing discards if not supported by device

From: Paul Gortmaker
Date: Sun Jan 02 2011 - 03:13:47 EST

From: Eric Sandeen <sandeen@xxxxxxxxxx>

commit a30eec2a8650a77f754e84b2e15f062fe652baa7 upstream.

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 <sandeen@xxxxxxxxxx>
Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
Signed-off-by: Paul Gortmaker <paul.gortmaker@xxxxxxxxxxxxx>
fs/ext4/mballoc.c | 8 +++++++-
1 files changed, 7 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 8639d5a6..4f2d3a9 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -2534,6 +2534,7 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)
entry->count, entry->group, entry);

if (test_opt(sb, DISCARD)) {
+ int ret;
ext4_fsblk_t discard_block;

discard_block = entry->start_blk +
@@ -2541,7 +2542,12 @@ static void release_blocks_on_commit(journal_t *journal, transaction_t *txn)
(unsigned long long)discard_block,
- 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);
+ }

err = ext4_mb_load_buddy(sb, entry->group, &e4b);

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