UBIFS: add a superblock flag for free space fix-up

The 'space_fixup' flag can be set in the superblock of a new filesystem by
mkfs.ubifs to indicate that any eraseblocks with free space remaining should be
fixed-up the first time it's mounted (after which the flag is un-set). This
means that the UBIFS image has been flashed by a "dumb" flasher and the free
space has been actually programmed (writing all 0xFFs), so this free space
cannot be used. UBIFS fixes the free space up by re-writing the contents of all
LEBs with free space using the atomic LEB change UBI operation.

Artem: improved commit message, add some more commentaries to the code.

Signed-off-by: Matthew L. Creech <mlcreech@gmail.com>
Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>

4 files changed, 7 insertions, 0 deletions

diff --git a/fs/ubifs/debug.c b/fs/ubifs/debug.c
index b5ba2ea5b626..f46d77e9f031 100644
--- a/fs/ubifs/debug.c
+++ b/fs/ubifs/debug.c
@@ -316,6 +316,8 @@ void dbg_dump_node(const struct ubifs_info *c, const void *node)
                 printk(KERN_DEBUG "\tflags          %#x\n", sup_flags);
                 printk(KERN_DEBUG "\t  big_lpt      %u\n",
                        !!(sup_flags & UBIFS_FLG_BIGLPT));
+                printk(KERN_DEBUG "\t  space_fixup  %u\n",
+                       !!(sup_flags & UBIFS_FLG_SPACE_FIXUP));
                 printk(KERN_DEBUG "\tmin_io_size    %u\n",
                        le32_to_cpu(sup->min_io_size));
                 printk(KERN_DEBUG "\tleb_size       %u\n",
diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
index cad60b51f7c4..93d69289d6f4 100644
--- a/fs/ubifs/sb.c
+++ b/fs/ubifs/sb.c
@@ -617,6 +617,7 @@ int ubifs_read_superblock(struct ubifs_info *c)
         c->vfs_sb->s_time_gran = le32_to_cpu(sup->time_gran);
         memcpy(&c->uuid, &sup->uuid, 16);
         c->big_lpt = !!(sup_flags & UBIFS_FLG_BIGLPT);
+        c->space_fixup = !!(sup_flags & UBIFS_FLG_SPACE_FIXUP);
 
         /* Automatically increase file system size to the maximum size */
         c->old_leb_cnt = c->leb_cnt;
diff --git a/fs/ubifs/ubifs-media.h b/fs/ubifs/ubifs-media.h
index b922f03c31ae..e24380cf46ed 100644
--- a/fs/ubifs/ubifs-media.h
+++ b/fs/ubifs/ubifs-media.h
@@ -408,9 +408,11 @@ enum {
  * Superblock flags.
  *
  * UBIFS_FLG_BIGLPT: if "big" LPT model is used if set
+ * UBIFS_FLG_SPACE_FIXUP: first-mount "fixup" of free space within LEBs needed
  */
 enum {
         UBIFS_FLG_BIGLPT = 0x02,
+        UBIFS_FLG_SPACE_FIXUP = 0x04,
 };
 
 /**
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index a2f9d4e3519f..8e27553e9655 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1014,6 +1014,7 @@ struct ubifs_debug_info;
  * @cmt_wq: wait queue to sleep on if the log is full and a commit is running
  *
  * @big_lpt: flag that LPT is too big to write whole during commit
+ * @space_fixup: flag indicating that free space in LEBs needs to be cleaned up
  * @no_chk_data_crc: do not check CRCs when reading data nodes (except during
  *                   recovery)
  * @bulk_read: enable bulk-reads
@@ -1253,6 +1254,7 @@ struct ubifs_info {
         wait_queue_head_t cmt_wq;
 
         unsigned int big_lpt:1;
+        unsigned int space_fixup:1;
         unsigned int no_chk_data_crc:1;
         unsigned int bulk_read:1;
         unsigned int default_compr:2;