ocfs2: Fix max offset calculations

ocfs2_max_file_offset() was over-estimating the largest file size for
several cases. This wasn't really a problem before, but now that we support
sparse files, it needs to be more accurate.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>

diff --git a/fs/ocfs2/super.c b/fs/ocfs2/super.c
index a100b488533e00dcd01a2d4c8aa78e1fd6aed24c..c3c89e26567ca9ec4c980cc3305223701182b42f 100644 (file)
--- a/fs/ocfs2/super.c
+++ b/fs/ocfs2/super.c
@@ -316,39 +316,51 @@ static void ocfs2_destroy_inode(struct inode *inode)
        kmem_cache_free(ocfs2_inode_cachep, OCFS2_I(inode));
 }
 
-/* From xfs_super.c:xfs_max_file_offset
- * Copyright (c) 2000-2004 Silicon Graphics, Inc.
- */
-static unsigned long long ocfs2_max_file_offset(unsigned int blockshift)
+static unsigned long long ocfs2_max_file_offset(unsigned int bbits,
+                                               unsigned int cbits)
 {
-       unsigned int pagefactor = 1;
-       unsigned int bitshift = BITS_PER_LONG - 1;
-
-       /* Figure out maximum filesize, on Linux this can depend on
-        * the filesystem blocksize (on 32 bit platforms).
-        * __block_prepare_write does this in an [unsigned] long...
-        *      page->index << (PAGE_CACHE_SHIFT - bbits)
-        * So, for page sized blocks (4K on 32 bit platforms),
-        * this wraps at around 8Tb (hence MAX_LFS_FILESIZE which is
-        *      (((u64)PAGE_CACHE_SIZE << (BITS_PER_LONG-1))-1)
-        * but for smaller blocksizes it is less (bbits = log2 bsize).
-        * Note1: get_block_t takes a long (implicit cast from above)
-        * Note2: The Large Block Device (LBD and HAVE_SECTOR_T) patch
-        * can optionally convert the [unsigned] long from above into
-        * an [unsigned] long long.
+       unsigned int bytes = 1 << cbits;
+       unsigned int trim = bytes;
+       unsigned int bitshift = 32;
+
+       /*
+        * i_size and all block offsets in ocfs2 are always 64 bits
+        * wide. i_clusters is 32 bits, in cluster-sized units. So on
+        * 64 bit platforms, cluster size will be the limiting factor.
         */
 
 #if BITS_PER_LONG == 32
 # if defined(CONFIG_LBD)
        BUILD_BUG_ON(sizeof(sector_t) != 8);
-       pagefactor = PAGE_CACHE_SIZE;
-       bitshift = BITS_PER_LONG;
+       /*
+        * We might be limited by page cache size.
+        */
+       if (bytes > PAGE_CACHE_SIZE) {
+               bytes = PAGE_CACHE_SIZE;
+               trim = 1;
+               /*
+                * Shift by 31 here so that we don't get larger than
+                * MAX_LFS_FILESIZE
+                */
+               bitshift = 31;
+       }
 # else
-       pagefactor = PAGE_CACHE_SIZE >> (PAGE_CACHE_SHIFT - blockshift);
+       /*
+        * We are limited by the size of sector_t. Use block size, as
+        * that's what we expose to the VFS.
+        */
+       bytes = 1 << bbits;
+       trim = 1;
+       bitshift = 31;
 # endif
 #endif
 
-       return (((unsigned long long)pagefactor) << bitshift) - 1;
+       /*
+        * Trim by a whole cluster when we can actually approach the
+        * on-disk limits. Otherwise we can overflow i_clusters when
+        * an extent start is at the max offset.
+        */
+       return (((unsigned long long)bytes) << bitshift) - trim;
 }
 
 static int ocfs2_remount(struct super_block *sb, int *flags, char *data)
@@ -1259,8 +1271,8 @@ static int ocfs2_initialize_super(struct super_block *sb,
                                  int sector_size)
 {
        int status = 0;
-       int i;
-       struct ocfs2_dinode *di = NULL;
+       int i, cbits, bbits;
+       struct ocfs2_dinode *di = (struct ocfs2_dinode *)bh->b_data;
        struct inode *inode = NULL;
        struct buffer_head *bitmap_bh = NULL;
        struct ocfs2_journal *journal;
@@ -1281,7 +1293,9 @@ static int ocfs2_initialize_super(struct super_block *sb,
        sb->s_export_op = &ocfs2_export_ops;
        sb->s_flags |= MS_NOATIME;
        /* this is needed to support O_LARGEFILE */
-       sb->s_maxbytes = ocfs2_max_file_offset(sb->s_blocksize_bits);
+       cbits = le32_to_cpu(di->id2.i_super.s_clustersize_bits);
+       bbits = le32_to_cpu(di->id2.i_super.s_blocksize_bits);
+       sb->s_maxbytes = ocfs2_max_file_offset(bbits, cbits);
 
        osb->sb = sb;
        /* Save off for ocfs2_rw_direct */
@@ -1341,8 +1355,6 @@ static int ocfs2_initialize_super(struct super_block *sb,
                goto bail;
        }
 
-       di = (struct ocfs2_dinode *)bh->b_data;
-
        osb->max_slots = le16_to_cpu(di->id2.i_super.s_max_slots);
        if (osb->max_slots > OCFS2_MAX_SLOTS || osb->max_slots == 0) {
                mlog(ML_ERROR, "Invalid number of node slots (%u)\n",