UBIFS: do not allocate too much

Bulk-read allocates 128KiB or more using kmalloc. The allocation
starts failing often when the memory gets fragmented. UBIFS still
works fine in this case, because it falls-back to standard
(non-optimized) read method, though. This patch teaches bulk-read
to allocate exactly the amount of memory it needs, instead of
allocating 128KiB every time.

This patch is also a preparation to the further fix where we'll
have a pre-allocated bulk-read buffer as well. For example, now
the @bu object is prepared in 'ubifs_bulk_read()', so we could
path either pre-allocated or allocated information to
'ubifs_do_bulk_read()' later. Or teaching 'ubifs_do_bulk_read()'
not to allocate 'bu->buf' if it is already there.

Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/ubifs/tnc.c b/fs/ubifs/tnc.c
index 99e9a74..6eef534 100644
--- a/fs/ubifs/tnc.c
+++ b/fs/ubifs/tnc.c
@@ -1501,7 +1501,12 @@ out:
  * @bu: bulk-read parameters and results
  *
  * Lookup consecutive data node keys for the same inode that reside
- * consecutively in the same LEB.
+ * consecutively in the same LEB. This function returns zero in case of success
+ * and a negative error code in case of failure.
+ *
+ * Note, if the bulk-read buffer length (@bu->buf_len) is known, this function
+ * makes sure bulk-read nodes fit the buffer. Otherwise, this function prepares
+ * maxumum possible amount of nodes for bulk-read.
  */
 int ubifs_tnc_get_bu_keys(struct ubifs_info *c, struct bu_info *bu)
 {