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, 21 insertions, 28 deletions

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;
 }