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>

4 files changed, 52 insertions, 29 deletions

diff --git a/fs/logfs/dev_bdev.c b/fs/logfs/dev_bdev.c
index 243c00071f76..9bd2ce2a3040 100644
--- a/fs/logfs/dev_bdev.c
+++ b/fs/logfs/dev_bdev.c
@@ -303,6 +303,11 @@ static void bdev_put_device(struct super_block *sb)
         close_bdev_exclusive(logfs_super(sb)->s_bdev, FMODE_READ|FMODE_WRITE);
 }
 
+static int bdev_can_write_buf(struct super_block *sb, u64 ofs)
+{
+        return 0;
+}
+
 static const struct logfs_device_ops bd_devops = {
         .find_first_sb  = bdev_find_first_sb,
         .find_last_sb   = bdev_find_last_sb,
@@ -310,6 +315,7 @@ static const struct logfs_device_ops bd_devops = {
         .readpage       = bdev_readpage,
         .writeseg       = bdev_writeseg,
         .erase          = bdev_erase,
+        .can_write_buf  = bdev_can_write_buf,
         .sync           = bdev_sync,
         .put_device     = bdev_put_device,
 };
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,
 };
diff --git a/fs/logfs/gc.c b/fs/logfs/gc.c
index 76c242fbe1b0..caa4419285dc 100644
--- a/fs/logfs/gc.c
+++ b/fs/logfs/gc.c
@@ -122,7 +122,7 @@ static void logfs_cleanse_block(struct super_block *sb, u64 ofs, u64 ino,
         logfs_safe_iput(inode, cookie);
 }
 
-static u32 logfs_gc_segment(struct super_block *sb, u32 segno, u8 dist)
+static u32 logfs_gc_segment(struct super_block *sb, u32 segno)
 {
         struct logfs_super *super = logfs_super(sb);
         struct logfs_segment_header sh;
@@ -401,7 +401,7 @@ static int __logfs_gc_once(struct super_block *sb, struct gc_candidate *cand)
                         segno, (u64)segno << super->s_segshift,
                         dist, no_free_segments(sb), valid,
                         super->s_free_bytes);
-        cleaned = logfs_gc_segment(sb, segno, dist);
+        cleaned = logfs_gc_segment(sb, segno);
         log_gc("GC segment #%02x complete - now %x valid\n", segno,
                         valid - cleaned);
         BUG_ON(cleaned != valid);
@@ -632,38 +632,31 @@ static int check_area(struct super_block *sb, int i)
 {
         struct logfs_super *super = logfs_super(sb);
         struct logfs_area *area = super->s_area[i];
-        struct logfs_object_header oh;
+        gc_level_t gc_level;
+        u32 cleaned, valid, ec;
         u32 segno = area->a_segno;
-        u32 ofs = area->a_used_bytes;
-        __be32 crc;
-        int err;
+        u64 ofs = dev_ofs(sb, area->a_segno, area->a_written_bytes);
 
         if (!area->a_is_open)
                 return 0;
 
-        for (ofs = area->a_used_bytes;
-             ofs <= super->s_segsize - sizeof(oh);
-             ofs += (u32)be16_to_cpu(oh.len) + sizeof(oh)) {
-                err = wbuf_read(sb, dev_ofs(sb, segno, ofs), sizeof(oh), &oh);
-                if (err)
-                        return err;
-
-                if (!memchr_inv(&oh, 0xff, sizeof(oh)))
-                        break;
+        if (super->s_devops->can_write_buf(sb, ofs) == 0)
+                return 0;
 
-                crc = logfs_crc32(&oh, sizeof(oh) - 4, 4);
-                if (crc != oh.crc) {
-                        printk(KERN_INFO "interrupted header at %llx\n",
-                                        dev_ofs(sb, segno, ofs));
-                        return 0;
-                }
-        }
-        if (ofs != area->a_used_bytes) {
-                printk(KERN_INFO "%x bytes unaccounted data found at %llx\n",
-                                ofs - area->a_used_bytes,
-                                dev_ofs(sb, segno, area->a_used_bytes));
-                area->a_used_bytes = ofs;
-        }
+        printk(KERN_INFO"LogFS: Possibly incomplete write at %llx\n", ofs);
+        /*
+         * The device cannot write back the write buffer.  Most likely the
+         * wbuf was already written out and the system crashed at some point
+         * before the journal commit happened.  In that case we wouldn't have
+         * to do anything.  But if the crash happened before the wbuf was
+         * written out correctly, we must GC this segment.  So assume the
+         * worst and always do the GC run.
+         */
+        area->a_is_open = 0;
+        valid = logfs_valid_bytes(sb, segno, &ec, &gc_level);
+        cleaned = logfs_gc_segment(sb, segno);
+        if (cleaned != valid)
+                return -EIO;
         return 0;
 }
 
diff --git a/fs/logfs/logfs.h b/fs/logfs/logfs.h
index 26a9458e6b13..93b55f337245 100644
--- a/fs/logfs/logfs.h
+++ b/fs/logfs/logfs.h
@@ -144,6 +144,7 @@ struct logfs_area_ops {
  * @erase:                      erase one segment
  * @read:                       read from the device
  * @erase:                      erase part of the device
+ * @can_write_buf:              decide whether wbuf can be written to ofs
  */
 struct logfs_device_ops {
         struct page *(*find_first_sb)(struct super_block *sb, u64 *ofs);
@@ -153,6 +154,7 @@ struct logfs_device_ops {
         void (*writeseg)(struct super_block *sb, u64 ofs, size_t len);
         int (*erase)(struct super_block *sb, loff_t ofs, size_t len,
                         int ensure_write);
+        int (*can_write_buf)(struct super_block *sb, u64 ofs);
         void (*sync)(struct super_block *sb);
         void (*put_device)(struct super_block *sb);
 };