UBIFS: add the fixup function

This patch adds the 'ubifs_fixup_free_space()' function which scans all
LEBs in the filesystem for those that are in-use but have one or more
empty pages, then re-maps the LEBs in order to erase the empty portions.
Afterward it removes the "space_fixup" flag from the UBIFS superblock.

Artem: massaged the patch

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

2 files changed, 150 insertions, 0 deletions

diff --git a/fs/ubifs/sb.c b/fs/ubifs/sb.c
index 93d69289d6f4..c606f010e8df 100644
--- a/fs/ubifs/sb.c
+++ b/fs/ubifs/sb.c
@@ -652,3 +652,152 @@ out:
         kfree(sup);
         return err;
 }
+
+/**
+ * fixup_leb - fixup/unmap an LEB containing free space.
+ * @c: UBIFS file-system description object
+ * @lnum: the LEB number to fix up
+ * @len: number of used bytes in LEB (starting at offset 0)
+ *
+ * This function reads the contents of the given LEB number @lnum, then fixes
+ * it up, so that empty min. I/O units in the end of LEB are actually erased on
+ * flash (rather than being just all-0xff real data). If the LEB is completely
+ * empty, it is simply unmapped.
+ */
+static int fixup_leb(struct ubifs_info *c, int lnum, int len)
+{
+        int err;
+
+        ubifs_assert(len >= 0);
+        ubifs_assert(len % c->min_io_size == 0);
+        ubifs_assert(len < c->leb_size);
+
+        if (len == 0) {
+                dbg_mnt("unmap empty LEB %d", lnum);
+                return ubi_leb_unmap(c->ubi, lnum);
+        }
+
+        dbg_mnt("fixup LEB %d, data len %d", lnum, len);
+        err = ubi_read(c->ubi, lnum, c->sbuf, 0, len);
+        if (err)
+                return err;
+
+        return ubi_leb_change(c->ubi, lnum, c->sbuf, len, UBI_UNKNOWN);
+}
+
+/**
+ * fixup_free_space - find & remap all LEBs containing free space.
+ * @c: UBIFS file-system description object
+ *
+ * This function walks through all LEBs in the filesystem and fiexes up those
+ * containing free/empty space.
+ */
+static int fixup_free_space(struct ubifs_info *c)
+{
+        int lnum, err = 0;
+        struct ubifs_lprops *lprops;
+
+        ubifs_get_lprops(c);
+
+        /* Fixup LEBs in the master area */
+        for (lnum = UBIFS_MST_LNUM; lnum < UBIFS_LOG_LNUM; lnum++) {
+                err = fixup_leb(c, lnum, c->mst_offs + c->mst_node_alsz);
+                if (err)
+                        goto out;
+        }
+
+        /* Unmap unused log LEBs */
+        lnum = ubifs_next_log_lnum(c, c->lhead_lnum);
+        while (lnum != c->ltail_lnum) {
+                err = fixup_leb(c, lnum, 0);
+                if (err)
+                        goto out;
+                lnum = ubifs_next_log_lnum(c, lnum);
+        }
+
+        /* Fixup the current log head */
+        err = fixup_leb(c, c->lhead_lnum, c->lhead_offs);
+        if (err)
+                goto out;
+
+        /* Fixup LEBs in the LPT area */
+        for (lnum = c->lpt_first; lnum <= c->lpt_last; lnum++) {
+                int free = c->ltab[lnum - c->lpt_first].free;
+
+                if (free > 0) {
+                        err = fixup_leb(c, lnum, c->leb_size - free);
+                        if (err)
+                                goto out;
+                }
+        }
+
+        /* Unmap LEBs in the orphans area */
+        for (lnum = c->orph_first; lnum <= c->orph_last; lnum++) {
+                err = fixup_leb(c, lnum, 0);
+                if (err)
+                        goto out;
+        }
+
+        /* Fixup LEBs in the main area */
+        for (lnum = c->main_first; lnum < c->leb_cnt; lnum++) {
+                lprops = ubifs_lpt_lookup(c, lnum);
+                if (IS_ERR(lprops)) {
+                        err = PTR_ERR(lprops);
+                        goto out;
+                }
+
+                if (lprops->free > 0) {
+                        err = fixup_leb(c, lnum, c->leb_size - lprops->free);
+                        if (err)
+                                goto out;
+                }
+        }
+
+out:
+        ubifs_release_lprops(c);
+        return err;
+}
+
+/**
+ * ubifs_fixup_free_space - find & fix all LEBs with free space.
+ * @c: UBIFS file-system description object
+ *
+ * This function fixes up LEBs containing free space on first mount, if the
+ * appropriate flag was set when the FS was created. Each LEB with one or more
+ * empty min. I/O unit (i.e. free-space-count > 0) is re-written, to make sure
+ * the free space is actually erased. E.g., this is necessary for some NAND
+ * chips, since the free space may have been programmed like real "0xff" data
+ * (generating a non-0xff ECC), causing future writes to the not-really-erased
+ * NAND pages to behave badly. After the space is fixed up, the superblock flag
+ * is cleared, so that this is skipped for all future mounts.
+ */
+int ubifs_fixup_free_space(struct ubifs_info *c)
+{
+        int err;
+        struct ubifs_sb_node *sup;
+
+        ubifs_assert(c->space_fixup);
+        ubifs_assert(!c->ro_mount);
+
+        ubifs_msg("start fixing up free space");
+
+        err = fixup_free_space(c);
+        if (err)
+                return err;
+
+        sup = ubifs_read_sb_node(c);
+        if (IS_ERR(sup))
+                return PTR_ERR(sup);
+
+        /* Free-space fixup is no longer required */
+        c->space_fixup = 0;
+        sup->flags &= cpu_to_le32(~UBIFS_FLG_SPACE_FIXUP);
+
+        err = ubifs_write_sb_node(c, sup);
+        kfree(sup);
+        if (err)
+                return err;
+
+        ubifs_msg("free space fixup complete");
+        return err;
+}
diff --git a/fs/ubifs/ubifs.h b/fs/ubifs/ubifs.h
index 8e27553e9655..93d1412a06f0 100644
--- a/fs/ubifs/ubifs.h
+++ b/fs/ubifs/ubifs.h
@@ -1633,6 +1633,7 @@ int ubifs_write_master(struct ubifs_info *c);
 int ubifs_read_superblock(struct ubifs_info *c);
 struct ubifs_sb_node *ubifs_read_sb_node(struct ubifs_info *c);
 int ubifs_write_sb_node(struct ubifs_info *c, struct ubifs_sb_node *sup);
+int ubifs_fixup_free_space(struct ubifs_info *c);
 
 /* replay.c */
 int ubifs_validate_entry(struct ubifs_info *c,