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Subject[PATCH 019/106] ext4: don't allow ext4_free_blocks() to fail due to ENOMEM
Date
3.5.7.18 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Theodore Ts'o <tytso@mit.edu>

commit e7676a704ee0a1ef71a6b23760b5a8f6896cb1a1 upstream.

The filesystem should not be marked inconsistent if ext4_free_blocks()
is not able to allocate memory. Unfortunately some callers (most
notably ext4_truncate) don't have a way to reflect an error back up to
the VFS. And even if we did, most userspace applications won't deal
with most system calls returning ENOMEM anyway.

Reported-by: Nagachandra P <nagachandra@gmail.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
---
fs/ext4/mballoc.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 4986dd3..aaece99 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4636,11 +4636,16 @@ do_more:
* blocks being freed are metadata. these blocks shouldn't
* be used until this transaction is committed
*/
+ retry:
new_entry = kmem_cache_alloc(ext4_free_data_cachep, GFP_NOFS);
if (!new_entry) {
- ext4_mb_unload_buddy(&e4b);
- err = -ENOMEM;
- goto error_return;
+ /*
+ * We use a retry loop because
+ * ext4_free_blocks() is not allowed to fail.
+ */
+ cond_resched();
+ congestion_wait(BLK_RW_ASYNC, HZ/50);
+ goto retry;
}
new_entry->efd_start_cluster = bit;
new_entry->efd_group = block_group;
--
1.8.3.2


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