logfs: handle powerfail on NAND flash

The write buffer may not have been written and may no longer be written
due to an interrupted write in the affected page.

Signed-off-by: Joern Engel <joern@logfs.org>

1 files changed, 23 insertions, 1 deletions

diff --git a/fs/logfs/dev_mtd.c b/fs/logfs/dev_mtd.c
index b02a4020241a..a85d47d13e4b 100644
--- a/fs/logfs/dev_mtd.c
+++ b/fs/logfs/dev_mtd.c
@@ -9,6 +9,7 @@
 #include <linux/completion.h>
 #include <linux/mount.h>
 #include <linux/sched.h>
+#include <linux/slab.h>
 
 #define PAGE_OFS(ofs) ((ofs) & (PAGE_SIZE-1))
 
@@ -126,7 +127,8 @@ static int mtd_readpage(void *_sb, struct page *page)
 
         err = mtd_read(sb, page->index << PAGE_SHIFT, PAGE_SIZE,
                         page_address(page));
-        if (err == -EUCLEAN) {
+        if (err == -EUCLEAN || err == -EBADMSG) {
+                /* -EBADMSG happens regularly on power failures */
                 err = 0;
                 /* FIXME: force GC this segment */
         }
@@ -233,12 +235,32 @@ static void mtd_put_device(struct super_block *sb)
         put_mtd_device(logfs_super(sb)->s_mtd);
 }
 
+static int mtd_can_write_buf(struct super_block *sb, u64 ofs)
+{
+        struct logfs_super *super = logfs_super(sb);
+        void *buf;
+        int err;
+
+        buf = kmalloc(super->s_writesize, GFP_KERNEL);
+        if (!buf)
+                return -ENOMEM;
+        err = mtd_read(sb, ofs, super->s_writesize, buf);
+        if (err)
+                goto out;
+        if (memchr_inv(buf, 0xff, super->s_writesize))
+                err = -EIO;
+        kfree(buf);
+out:
+        return err;
+}
+
 static const struct logfs_device_ops mtd_devops = {
         .find_first_sb  = mtd_find_first_sb,
         .find_last_sb   = mtd_find_last_sb,
         .readpage       = mtd_readpage,
         .writeseg       = mtd_writeseg,
         .erase          = mtd_erase,
+        .can_write_buf  = mtd_can_write_buf,
         .sync           = mtd_sync,
         .put_device     = mtd_put_device,
 };