ext4: Retry block reservation

During block reservation if we don't have enough blocks left, retry
block reservation with smaller block counts.  This makes sure we try
fallocate and DIO with smaller request size and don't fail early.  The
delayed allocation reservation cannot try with smaller block count. So
retry block reservation to handle temporary disk full conditions.  Also
print free blocks details if we fail block allocation during writepages.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 7 insertions, 1 deletions

diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
index 1707850301d6..57909882c084 100644
--- a/fs/ext4/balloc.c
+++ b/fs/ext4/balloc.c
@@ -1738,10 +1738,16 @@ ext4_fsblk_t ext4_old_new_blocks(handle_t *handle, struct inode *inode,
                 /*
                  * With delalloc we already reserved the blocks
                  */
-                if (ext4_claim_free_blocks(sbi, *count)) {
+                while (*count && ext4_claim_free_blocks(sbi, *count)) {
+                        /* let others to free the space */
+                        yield();
+                        *count = *count >> 1;
+                }
+                if (!*count) {
                         *errp = -ENOSPC;
                         return 0;       /*return with ENOSPC error */
                 }
+                num = *count;
         }
         /*
          * Check quota for allocation of this block.