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    Subject[PATCH 144/145] ext4: don't allow ext4_free_blocks() to fail due to ENOMEM
    Date
    3.8.13.5 -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: Kamal Mostafa <kamal@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 1206682..c8003a1 100644
    --- a/fs/ext4/mballoc.c
    +++ b/fs/ext4/mballoc.c
    @@ -4652,11 +4652,16 @@ 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;
    --
    1.8.1.2


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