[PATCH] ufs: not usual amounts of fragments per block

The writing to UFS file system with block/fragment!=8 may cause bogus
behaviour.  The problem in "ufs_bitmap_search" function, which doesn't work
correctly in "block/fragment!=8" case.  The idea is stolen from BSD code.

Signed-off-by: Evgeniy Dushistov <dushistov@mail.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 87 insertions, 45 deletions

diff --git a/fs/ufs/balloc.c b/fs/ufs/balloc.c
index 68de1312e4b6..343eaf4542f8 100644
--- a/fs/ufs/balloc.c
+++ b/fs/ufs/balloc.c
@@ -726,18 +726,63 @@ gotit:
         return result;
 }
 
-static unsigned ufs_bitmap_search (struct super_block * sb,
-        struct ufs_cg_private_info * ucpi, unsigned goal, unsigned count)
+static unsigned ubh_scanc(struct ufs_sb_private_info *uspi,
+                          struct ufs_buffer_head *ubh,
+                          unsigned begin, unsigned size,
+                          unsigned char *table, unsigned char mask)
 {
-        struct ufs_sb_private_info * uspi;
-        struct ufs_super_block_first * usb1;
-        struct ufs_cylinder_group * ucg;
-        unsigned start, length, location, result;
-        unsigned possition, fragsize, blockmap, mask;
-        
-        UFSD(("ENTER, cg %u, goal %u, count %u\n", ucpi->c_cgx, goal, count))
+        unsigned rest, offset;
+        unsigned char *cp;
+        
+
+        offset = begin & ~uspi->s_fmask;
+        begin >>= uspi->s_fshift;
+        for (;;) {
+                if ((offset + size) < uspi->s_fsize)
+                        rest = size;
+                else
+                        rest = uspi->s_fsize - offset;
+                size -= rest;
+                cp = ubh->bh[begin]->b_data + offset;
+                while ((table[*cp++] & mask) == 0 && --rest)
+                        ;
+                if (rest || !size)
+                        break;
+                begin++;
+                offset = 0;
+        }
+        return (size + rest);
+}
+
+/*
+ * Find a block of the specified size in the specified cylinder group.
+ * @sp: pointer to super block
+ * @ucpi: pointer to cylinder group info
+ * @goal: near which block we want find new one
+ * @count: specified size
+ */
+static unsigned ufs_bitmap_search(struct super_block *sb,
+                                  struct ufs_cg_private_info *ucpi,
+                                  unsigned goal, unsigned count)
+{
+        /*
+         * Bit patterns for identifying fragments in the block map
+         * used as ((map & mask_arr) == want_arr)
+         */
+        static const int mask_arr[9] = {
+                0x3, 0x7, 0xf, 0x1f, 0x3f, 0x7f, 0xff, 0x1ff, 0x3ff
+        };
+        static const int want_arr[9] = {
+                0x0, 0x2, 0x6, 0xe, 0x1e, 0x3e, 0x7e, 0xfe, 0x1fe
+        };
+        struct ufs_sb_private_info *uspi = UFS_SB(sb)->s_uspi;
+        struct ufs_super_block_first *usb1;
+        struct ufs_cylinder_group *ucg;
+        unsigned start, length, loc, result;
+        unsigned pos, want, blockmap, mask, end;
+
+        UFSD(("ENTER, cg %u, goal %u, count %u\n", ucpi->c_cgx, goal, count));
 
-        uspi = UFS_SB(sb)->s_uspi;
         usb1 = ubh_get_usb_first (uspi);
         ucg = ubh_get_ucg(UCPI_UBH(ucpi));
 
@@ -747,53 +792,50 @@ static unsigned ufs_bitmap_search (struct super_block * sb,
                 start = ucpi->c_frotor >> 3;
                 
         length = ((uspi->s_fpg + 7) >> 3) - start;
-        location = ubh_scanc(UCPI_UBH(ucpi), ucpi->c_freeoff + start, length,
+        loc = ubh_scanc(uspi, UCPI_UBH(ucpi), ucpi->c_freeoff + start, length,
                 (uspi->s_fpb == 8) ? ufs_fragtable_8fpb : ufs_fragtable_other,
                 1 << (count - 1 + (uspi->s_fpb & 7))); 
-        if (location == 0) {
+        if (loc == 0) {
                 length = start + 1;
-                location = ubh_scanc(UCPI_UBH(ucpi), ucpi->c_freeoff, length,
-                        (uspi->s_fpb == 8) ? ufs_fragtable_8fpb : ufs_fragtable_other,
-                        1 << (count - 1 + (uspi->s_fpb & 7)));
-                if (location == 0) {
-                        ufs_error (sb, "ufs_bitmap_search",
-                        "bitmap corrupted on cg %u, start %u, length %u, count %u, freeoff %u\n",
-                        ucpi->c_cgx, start, length, count, ucpi->c_freeoff);
+                loc = ubh_scanc(uspi, UCPI_UBH(ucpi), ucpi->c_freeoff, length,
+                                (uspi->s_fpb == 8) ? ufs_fragtable_8fpb :
+                                ufs_fragtable_other,
+                                1 << (count - 1 + (uspi->s_fpb & 7)));
+                if (loc == 0) {
+                        ufs_error(sb, "ufs_bitmap_search",
+                                  "bitmap corrupted on cg %u, start %u,"
+                                  " length %u, count %u, freeoff %u\n",
+                                  ucpi->c_cgx, start, length, count,
+                                  ucpi->c_freeoff);
                         return (unsigned)-1;
                 }
                 start = 0;
         }
-        result = (start + length - location) << 3;
+        result = (start + length - loc) << 3;
         ucpi->c_frotor = result;
 
         /*
          * found the byte in the map
          */
-        blockmap = ubh_blkmap(UCPI_UBH(ucpi), ucpi->c_freeoff, result);
-        fragsize = 0;
-        for (possition = 0, mask = 1; possition < 8; possition++, mask <<= 1) {
-                if (blockmap & mask) {
-                        if (!(possition & uspi->s_fpbmask))
-                                fragsize = 1;
-                        else 
-                                fragsize++;
-                }
-                else {
-                        if (fragsize == count) {
-                                result += possition - count;
-                                UFSD(("EXIT, result %u\n", result))
-                                return result;
-                        }
-                        fragsize = 0;
-                }
-        }
-        if (fragsize == count) {
-                result += possition - count;
-                UFSD(("EXIT, result %u\n", result))
-                return result;
-        }
-        ufs_error (sb, "ufs_bitmap_search", "block not in map on cg %u\n", ucpi->c_cgx);
-        UFSD(("EXIT (FAILED)\n"))
+
+        for (end = result + 8; result < end; result += uspi->s_fpb) {
+                blockmap = ubh_blkmap(UCPI_UBH(ucpi), ucpi->c_freeoff, result);
+                blockmap <<= 1;
+                mask = mask_arr[count];
+                want = want_arr[count];
+                for (pos = 0; pos <= uspi->s_fpb - count; pos++) {
+                        if ((blockmap & mask) == want) {
+                                UFSD(("EXIT, result %u\n", result));
+                                return result + pos;
+                        }
+                        mask <<= 1;
+                        want <<= 1;
+                }
+        }
+
+        ufs_error(sb, "ufs_bitmap_search", "block not in map on cg %u\n",
+                  ucpi->c_cgx);
+        UFSD(("EXIT (FAILED)\n"));
         return (unsigned)-1;
 }