From: Eric Sandeen <[email protected]>

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 <[email protected]>
Signed-off-by: "Theodore Ts'o" <[email protected]>
Signed-off-by: Paul Gortmaker <[email protected]>
---
 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)
                        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);
+                       }
                }
 
                err = ext4_mb_load_buddy(sb, entry->group, &e4b);
-- 
1.7.3.3

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