libext2fs: make read_bitmaps() more efficient when using direct I/O

Read in a full block for each allocation bitmap, to avoid using a
kernel bounce buffer when using direct I/O.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

diff --git a/lib/ext2fs/rw_bitmaps.c b/lib/ext2fs/rw_bitmaps.c
index 1d5f7b2..81e09c0 100644 (file)
--- a/lib/ext2fs/rw_bitmaps.c
+++ b/lib/ext2fs/rw_bitmaps.c
@@ -166,6 +166,9 @@ static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
 
        EXT2_CHECK_MAGIC(fs, EXT2_ET_MAGIC_EXT2FS_FILSYS);
 
+       if ((block_nbytes > fs->blocksize) || (inode_nbytes > fs->blocksize))
+               return EXT2_ET_CORRUPT_SUPERBLOCK;
+
        fs->write_bitmaps = ext2fs_write_bitmaps;
 
        if (EXT2_HAS_RO_COMPAT_FEATURE(fs->super,
@@ -186,7 +189,7 @@ static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
                if (do_image)
                        retval = ext2fs_get_mem(fs->blocksize, &block_bitmap);
                else
-                       retval = ext2fs_get_memalign((unsigned) block_nbytes,
+                       retval = ext2fs_get_memalign(fs->blocksize,
                                                     fs->blocksize,
                                                     &block_bitmap);
                        
@@ -202,8 +205,7 @@ static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
                retval = ext2fs_allocate_inode_bitmap(fs, buf, &fs->inode_map);
                if (retval)
                        goto cleanup;
-               retval = ext2fs_get_mem(do_image ? fs->blocksize :
-                                       (unsigned) inode_nbytes, &inode_bitmap);
+               retval = ext2fs_get_mem(fs->blocksize, &inode_bitmap);
                if (retval)
                        goto cleanup;
        } else
@@ -261,7 +263,7 @@ static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
                                blk = 0;
                        if (blk) {
                                retval = io_channel_read_blk64(fs->io, blk,
-                                            -block_nbytes, block_bitmap);
+                                                              1, block_bitmap);
                                if (retval) {
                                        retval = EXT2_ET_BLOCK_BITMAP_READ;
                                        goto cleanup;
@@ -283,7 +285,7 @@ static errcode_t read_bitmaps(ext2_filsys fs, int do_inode, int do_block)
                                blk = 0;
                        if (blk) {
                                retval = io_channel_read_blk64(fs->io, blk,
-                                            -inode_nbytes, inode_bitmap);
+                                                              1, inode_bitmap);
                                if (retval) {
                                        retval = EXT2_ET_INODE_BITMAP_READ;
                                        goto cleanup;